reset

13 files changed, 0 insertions, 5313 deletions

diff --git a/src/backend/backend.c b/src/backend/backend.c
deleted file mode 100644
index b0e562a..0000000
--- a/src/backend/backend.c
+++ /dev/null
@@ -1,494 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) Yuxuan Shui <[email protected]>
-#include <xcb/sync.h>
-#include <xcb/xcb.h>
-
-#include "backend/backend.h"
-#include "common.h"
-#include "compiler.h"
-#include "config.h"
-#include "log.h"
-#include "region.h"
-#include "types.h"
-#include "win.h"
-#include "x.h"
-
-extern struct backend_operations xrender_ops, dummy_ops;
-#ifdef CONFIG_OPENGL
-extern struct backend_operations glx_ops;
-#endif
-
-struct backend_operations *backend_list[NUM_BKEND] = {
-    [BKEND_XRENDER] = &xrender_ops,
-    [BKEND_DUMMY] = &dummy_ops,
-#ifdef CONFIG_OPENGL
-    [BKEND_GLX] = &glx_ops,
-#endif
-};
-
-/**
- * @param all_damage if true ignore damage and repaint the whole screen
- */
-region_t get_damage(session_t *ps, bool all_damage) {
-	region_t region;
-	auto buffer_age_fn = ps->backend_data->ops->buffer_age;
-	int buffer_age = buffer_age_fn ? buffer_age_fn(ps->backend_data) : -1;
-
-	if (all_damage) {
-		buffer_age = -1;
-	}
-
-	pixman_region32_init(&region);
-	if (buffer_age == -1 || buffer_age > ps->ndamage) {
-		pixman_region32_copy(&region, &ps->screen_reg);
-	} else {
-		for (int i = 0; i < buffer_age; i++) {
-			auto curr = ((ps->damage - ps->damage_ring) + i) % ps->ndamage;
-			log_trace("damage index: %d, damage ring offset: %ld", i, curr);
-			dump_region(&ps->damage_ring[curr]);
-			pixman_region32_union(&region, &region, &ps->damage_ring[curr]);
-		}
-		pixman_region32_intersect(&region, &region, &ps->screen_reg);
-	}
-	return region;
-}
-
-static void process_window_for_painting(session_t *ps, struct managed_win* w, void* win_image,
-					double additional_alpha,
-					region_t* reg_bound, region_t* reg_visible,
-					region_t* reg_paint, region_t* reg_paint_in_bound) {
-	// For window image processing, we don't have to limit the process
-	// region to damage for correctness. (see <damager-note> for
-	// details)
-
-	// The visible region, in window local coordinates Although we
-	// don't limit process region to damage, we provide that info in
-	// reg_visible as a hint. Since window image data outside of the
-	// damage region won't be painted onto target
-	region_t reg_visible_local;
-	{
-		// The bounding shape, in window local coordinates
-		region_t reg_bound_local;
-		pixman_region32_init(&reg_bound_local);
-		pixman_region32_copy(&reg_bound_local, reg_bound);
-		pixman_region32_translate(&reg_bound_local, -w->g.x, -w->g.y);
-
-		pixman_region32_init(&reg_visible_local);
-		pixman_region32_intersect(&reg_visible_local,
-					  reg_visible, reg_paint);
-		pixman_region32_translate(&reg_visible_local, -w->g.x,
-					  -w->g.y);
-		// Data outside of the bounding shape won't be visible,
-		// but it is not necessary to limit the image operations
-		// to the bounding shape yet. So pass that as the visible
-		// region, not the clip region.
-		pixman_region32_intersect(
-		    &reg_visible_local, &reg_visible_local, &reg_bound_local);
-		pixman_region32_fini(&reg_bound_local);
-	}
-
-	auto new_img = ps->backend_data->ops->clone_image(
-	    ps->backend_data, win_image, &reg_visible_local);
-	auto reg_frame = win_get_region_frame_local_by_val(w);
-	double alpha = additional_alpha*w->opacity;
-	ps->backend_data->ops->set_image_property(
-	    ps->backend_data, IMAGE_PROPERTY_OPACITY, new_img, &alpha);
-	ps->backend_data->ops->image_op(
-	    ps->backend_data, IMAGE_OP_APPLY_ALPHA, new_img, &reg_frame,
-	    &reg_visible_local, (double[]){w->frame_opacity});
-	pixman_region32_fini(&reg_frame);
-	ps->backend_data->ops->compose(ps->backend_data, new_img,
-				       w->g.x, w->g.y,
-				       w->g.x + w->widthb, w->g.y + w->heightb,
-				       reg_paint_in_bound, reg_visible);
-	ps->backend_data->ops->release_image(ps->backend_data, new_img);
-	pixman_region32_fini(&reg_visible_local);
-}
-
-/// paint all windows
-void paint_all_new(session_t *ps, struct managed_win *t, bool ignore_damage) {
-	if (ps->o.xrender_sync_fence) {
-		if (ps->xsync_exists && !x_fence_sync(ps->c, ps->sync_fence)) {
-			log_error("x_fence_sync failed, xrender-sync-fence will be "
-			          "disabled from now on.");
-			xcb_sync_destroy_fence(ps->c, ps->sync_fence);
-			ps->sync_fence = XCB_NONE;
-			ps->o.xrender_sync_fence = false;
-			ps->xsync_exists = false;
-		}
-	}
-	// All painting will be limited to the damage, if _some_ of
-	// the paints bleed out of the damage region, it will destroy
-	// part of the image we want to reuse
-	region_t reg_damage;
-	if (!ignore_damage) {
-		reg_damage = get_damage(ps, ps->o.monitor_repaint || !ps->o.use_damage);
-	} else {
-		pixman_region32_init(&reg_damage);
-		pixman_region32_copy(&reg_damage, &ps->screen_reg);
-	}
-
-	if (!pixman_region32_not_empty(&reg_damage)) {
-		pixman_region32_fini(&reg_damage);
-		return;
-	}
-
-#ifdef DEBUG_REPAINT
-	static struct timespec last_paint = {0};
-#endif
-
-	// <damage-note>
-	// If use_damage is enabled, we MUST make sure only the damaged regions of the
-	// screen are ever touched by the compositor. The reason is that at the beginning
-	// of each render, we clear the damaged regions with the wallpaper, and nothing
-	// else. If later during the render we changed anything outside the damaged
-	// region, that won't be cleared by the next render, and will thus accumulate.
-	// (e.g. if shadow is drawn outside the damaged region, it will become thicker and
-	// thicker over time.)
-
-	/// The adjusted damaged regions
-	region_t reg_paint;
-	assert(ps->o.blur_method != BLUR_METHOD_INVALID);
-	if (ps->o.blur_method != BLUR_METHOD_NONE && ps->backend_data->ops->get_blur_size) {
-		int blur_width, blur_height;
-		ps->backend_data->ops->get_blur_size(ps->backend_blur_context,
-		                                     &blur_width, &blur_height);
-
-		// The region of screen a given window influences will be smeared
-		// out by blur. With more windows on top of the given window, the
-		// influences region will be smeared out more.
-		//
-		// Also, blurring requires data slightly outside the area that needs
-		// to be blurred. The more semi-transparent windows are stacked on top
-		// of each other, the larger the area will be.
-		//
-		// Instead of accurately calculate how much bigger the damage
-		// region will be because of blur, we assume the worst case here.
-		// That is, the damaged window is at the bottom of the stack, and
-		// all other windows have semi-transparent background
-		int resize_factor = 1;
-		if (t) {
-			resize_factor = t->stacking_rank;
-		}
-		resize_region_in_place(&reg_damage, blur_width * resize_factor,
-		                       blur_height * resize_factor);
-		reg_paint = resize_region(&reg_damage, blur_width * resize_factor,
-		                          blur_height * resize_factor);
-		pixman_region32_intersect(&reg_paint, &reg_paint, &ps->screen_reg);
-		pixman_region32_intersect(&reg_damage, &reg_damage, &ps->screen_reg);
-	} else {
-		pixman_region32_init(&reg_paint);
-		pixman_region32_copy(&reg_paint, &reg_damage);
-	}
-
-	// A hint to backend, the region that will be visible on screen
-	// backend can optimize based on this info
-	region_t reg_visible;
-	pixman_region32_init(&reg_visible);
-	pixman_region32_copy(&reg_visible, &ps->screen_reg);
-	if (t && !ps->o.transparent_clipping) {
-		// Calculate the region upon which the root window (wallpaper) is to be
-		// painted based on the ignore region of the lowest window, if available
-		//
-		// NOTE If transparent_clipping is enabled, transparent windows are
-		// included in the reg_ignore, but we still want to have the wallpaper
-		// beneath them, so we don't use reg_ignore for wallpaper in that case.
-		pixman_region32_subtract(&reg_visible, &reg_visible, t->reg_ignore);
-	}
-
-	// Region on screen we don't want any shadows on
-	region_t reg_shadow_clip;
-	pixman_region32_init(&reg_shadow_clip);
-
-	if (ps->backend_data->ops->prepare) {
-		ps->backend_data->ops->prepare(ps->backend_data, &reg_paint);
-	}
-
-	if (ps->root_image) {
-		ps->backend_data->ops->compose(ps->backend_data, ps->root_image,
-					       0, 0, ps->root_width, ps->root_height,
-		                               &reg_paint, &reg_visible);
-	} else {
-		ps->backend_data->ops->fill(ps->backend_data, (struct color){0, 0, 0, 1},
-		                            &reg_paint);
-	}
-
-	// Windows are sorted from bottom to top
-	// Each window has a reg_ignore, which is the region obscured by all the windows
-	// on top of that window. This is used to reduce the number of pixels painted.
-	//
-	// Whether this is beneficial is to be determined XXX
-	for (auto w = t; w; w = w->prev_trans) {
-		pixman_region32_subtract(&reg_visible, &ps->screen_reg, w->reg_ignore);
-		assert(!(w->flags & WIN_FLAGS_IMAGE_ERROR));
-		assert(!(w->flags & WIN_FLAGS_PIXMAP_STALE));
-		assert(!(w->flags & WIN_FLAGS_PIXMAP_NONE));
-
-		// The bounding shape of the window, in global/target coordinates
-		// reminder: bounding shape contains the WM frame
-		auto reg_bound = win_get_bounding_shape_global_by_val(w);
-
-		// The clip region for the current window, in global/target coordinates
-		// reg_paint_in_bound \in reg_paint
-		region_t reg_paint_in_bound;
-		pixman_region32_init(&reg_paint_in_bound);
-		pixman_region32_intersect(&reg_paint_in_bound, &reg_bound, &reg_paint);
-		if (ps->o.transparent_clipping) {
-			// <transparent-clipping-note>
-			// If transparent_clipping is enabled, we need to be SURE that
-			// things are not drawn inside reg_ignore, because otherwise they
-			// will appear underneath transparent windows.
-			// So here we have make sure reg_paint_in_bound \in reg_visible
-			// There are a few other places below where this is needed as
-			// well.
-			pixman_region32_intersect(&reg_paint_in_bound,
-			                          &reg_paint_in_bound, &reg_visible);
-		}
-
-		// Blur window background
-		/* TODO(yshui) since the backend might change the content of the window
-		 * (e.g. with shaders), we should consult the backend whether the window
-		 * is transparent or not. for now we will just rely on the force_win_blend
-		 * option */
-		auto real_win_mode = w->mode;
-
-		if (w->blur_background &&
-		    (ps->o.force_win_blend || real_win_mode == WMODE_TRANS ||
-		     (ps->o.blur_background_frame && real_win_mode == WMODE_FRAME_TRANS))) {
-			// Minimize the region we try to blur, if the window
-			// itself is not opaque, only the frame is.
-
-			double blur_opacity = 1;
-			if (w->opacity < (1.0 / MAX_ALPHA)) {
-				// Hide blur for fully transparent windows.
-				blur_opacity = 0;
-			} else if (w->state == WSTATE_MAPPING) {
-				// Gradually increase the blur intensity during
-				// fading in.
-				assert(w->opacity <= w->opacity_target);
-				blur_opacity = w->opacity / w->opacity_target;
-			} else if (w->state == WSTATE_UNMAPPING ||
-			           w->state == WSTATE_DESTROYING) {
-				// Gradually decrease the blur intensity during
-				// fading out.
-				assert(w->opacity <= w->opacity_target_old);
-				blur_opacity = w->opacity / w->opacity_target_old;
-			} else if (w->state == WSTATE_FADING) {
-				if (w->opacity < w->opacity_target &&
-				    w->opacity_target_old < (1.0 / MAX_ALPHA)) {
-					// Gradually increase the blur intensity during
-					// fading in.
-					assert(w->opacity <= w->opacity_target);
-					blur_opacity = w->opacity / w->opacity_target;
-				} else if (w->opacity > w->opacity_target &&
-				           w->opacity_target < (1.0 / MAX_ALPHA)) {
-					// Gradually decrease the blur intensity during
-					// fading out.
-					assert(w->opacity <= w->opacity_target_old);
-					blur_opacity = w->opacity / w->opacity_target_old;
-				}
-			}
-			assert(blur_opacity >= 0 && blur_opacity <= 1);
-
-			if (real_win_mode == WMODE_TRANS || ps->o.force_win_blend) {
-				// We need to blur the bounding shape of the window
-				// (reg_paint_in_bound = reg_bound \cap reg_paint)
-				ps->backend_data->ops->blur(
-				    ps->backend_data, blur_opacity, ps->backend_blur_context,
-				    &reg_paint_in_bound, &reg_visible);
-			} else {
-				// Window itself is solid, we only need to blur the frame
-				// region
-
-				// Readability assertions
-				assert(ps->o.blur_background_frame);
-				assert(real_win_mode == WMODE_FRAME_TRANS);
-
-				auto reg_blur = win_get_region_frame_local_by_val(w);
-				pixman_region32_translate(&reg_blur, w->g.x, w->g.y);
-				// make sure reg_blur \in reg_paint
-				pixman_region32_intersect(&reg_blur, &reg_blur, &reg_paint);
-				if (ps->o.transparent_clipping) {
-					// ref: <transparent-clipping-note>
-					pixman_region32_intersect(&reg_blur, &reg_blur,
-					                          &reg_visible);
-				}
-				ps->backend_data->ops->blur(ps->backend_data, blur_opacity,
-				                            ps->backend_blur_context,
-				                            &reg_blur, &reg_visible);
-				pixman_region32_fini(&reg_blur);
-			}
-		}
-
-		// Draw shadow on target
-		if (w->shadow) {
-			assert(!(w->flags & WIN_FLAGS_SHADOW_NONE));
-			// Clip region for the shadow
-			// reg_shadow \in reg_paint
-			auto reg_shadow = win_extents_by_val(w);
-			pixman_region32_intersect(&reg_shadow, &reg_shadow, &reg_paint);
-			if (!ps->o.wintype_option[w->window_type].full_shadow) {
-				pixman_region32_subtract(&reg_shadow, &reg_shadow, &reg_bound);
-			}
-
-			// Mask out the region we don't want shadow on
-			if (pixman_region32_not_empty(&ps->shadow_exclude_reg)) {
-				pixman_region32_subtract(&reg_shadow, &reg_shadow,
-				                         &ps->shadow_exclude_reg);
-			}
-			if (pixman_region32_not_empty(&reg_shadow_clip)) {
-				pixman_region32_subtract(&reg_shadow, &reg_shadow,
-				                         &reg_shadow_clip);
-			}
-
-			if (ps->o.xinerama_shadow_crop && w->xinerama_scr >= 0 &&
-			    w->xinerama_scr < ps->xinerama_nscrs) {
-				// There can be a window where number of screens is
-				// updated, but the screen number attached to the windows
-				// have not.
-				//
-				// Window screen number will be updated eventually, so
-				// here we just check to make sure we don't access out of
-				// bounds.
-				pixman_region32_intersect(
-				    &reg_shadow, &reg_shadow,
-				    &ps->xinerama_scr_regs[w->xinerama_scr]);
-			}
-
-			if (ps->o.transparent_clipping) {
-				// ref: <transparent-clipping-note>
-				pixman_region32_intersect(&reg_shadow, &reg_shadow,
-				                          &reg_visible);
-			}
-
-			assert(w->shadow_image);
-			ps->backend_data->ops->set_image_property(
-			    ps->backend_data, IMAGE_PROPERTY_OPACITY, w->shadow_image,
-			    &w->opacity);
-			ps->backend_data->ops->compose(
-			    ps->backend_data, w->shadow_image,
-			    w->g.x + w->shadow_dx, w->g.y + w->shadow_dy,
-			    w->g.x + w->shadow_dx + w->shadow_width,
-			    w->g.y + w->shadow_dy + w->shadow_height,
-			    &reg_shadow, &reg_visible);
-			pixman_region32_fini(&reg_shadow);
-		}
-
-		// Update image properties
-		{
-			double dim_opacity = 0.0;
-			if (w->dim) {
-				dim_opacity = ps->o.inactive_dim;
-				if (!ps->o.inactive_dim_fixed) {
-					dim_opacity *= w->opacity;
-				}
-			}
-
-			ps->backend_data->ops->set_image_property(
-			    ps->backend_data, IMAGE_PROPERTY_MAX_BRIGHTNESS, w->win_image,
-			    &ps->o.max_brightness);
-			ps->backend_data->ops->set_image_property(
-			    ps->backend_data, IMAGE_PROPERTY_INVERTED, w->win_image,
-			    &w->invert_color);
-			ps->backend_data->ops->set_image_property(
-			    ps->backend_data, IMAGE_PROPERTY_DIM_LEVEL, w->win_image,
-			    &dim_opacity);
-			ps->backend_data->ops->set_image_property(
-			    ps->backend_data, IMAGE_PROPERTY_OPACITY, w->win_image, &w->opacity);
-		}
-
-		if (w->opacity * MAX_ALPHA < 1) {
-			// We don't need to paint the window body itself if it's
-			// completely transparent.
-			goto skip;
-		}
-
-		if (w->clip_shadow_above) {
-			// Add window bounds to shadow-clip region
-			pixman_region32_union(&reg_shadow_clip, &reg_shadow_clip, &reg_bound);
-		} else {
-			// Remove overlapping window bounds from shadow-clip region
-			pixman_region32_subtract(&reg_shadow_clip, &reg_shadow_clip, &reg_bound);
-		}
-
-		// Draw window on target
-		bool is_animating = 0 <= w->animation_progress && w->animation_progress < 1.0;
-		if (w->frame_opacity == 1 && !is_animating) {
-			ps->backend_data->ops->compose(ps->backend_data, w->win_image,
-									w->g.x, w->g.y,
-									w->g.x + w->widthb, w->g.y + w->heightb,
-									&reg_paint_in_bound, &reg_visible);
-		} else {
-			if (is_animating && w->old_win_image) {
-				assert(w->old_win_image);
-
-				bool resizing =
-					w->g.width != w->pending_g.width ||
-					w->g.height != w->pending_g.height;
-
-				// Only animate opacity here if we are resizing
-				// a transparent window
-				process_window_for_painting(ps, w, w->win_image,
-								1,
-								&reg_bound, &reg_visible,
-								&reg_paint, &reg_paint_in_bound);
-
-				// Only do this if size changes as otherwise moving 
-				// transparent windows will flicker and if you just
-				// move so slightly they will keep flickering
-				if (resizing) {
-					process_window_for_painting(ps, w, w->old_win_image,
-									1.0 - w->animation_progress,
-									&reg_bound, &reg_visible,
-									&reg_paint, &reg_paint_in_bound);
-				}
-
-			} else {
-				process_window_for_painting(ps, w, w->win_image,
-								1,
-								&reg_bound, &reg_visible,
-								&reg_paint, &reg_paint_in_bound);
-			}
-		}
-	skip:
-		pixman_region32_fini(&reg_bound);
-		pixman_region32_fini(&reg_paint_in_bound);
-	}
-	pixman_region32_fini(&reg_paint);
-	pixman_region32_fini(&reg_shadow_clip);
-
-	if (ps->o.monitor_repaint) {
-		const struct color DEBUG_COLOR = {0.5, 0, 0, 0.5};
-		auto reg_damage_debug = get_damage(ps, false);
-		ps->backend_data->ops->fill(ps->backend_data, DEBUG_COLOR, &reg_damage_debug);
-		pixman_region32_fini(&reg_damage_debug);
-	}
-
-	// Move the head of the damage ring
-	ps->damage = ps->damage - 1;
-	if (ps->damage < ps->damage_ring) {
-		ps->damage = ps->damage_ring + ps->ndamage - 1;
-	}
-	pixman_region32_clear(ps->damage);
-
-	if (ps->backend_data->ops->present) {
-		// Present the rendered scene
-		// Vsync is done here
-		ps->backend_data->ops->present(ps->backend_data, &reg_damage);
-	}
-
-	pixman_region32_fini(&reg_damage);
-
-#ifdef DEBUG_REPAINT
-	struct timespec now = get_time_timespec();
-	struct timespec diff = {0};
-	timespec_subtract(&diff, &now, &last_paint);
-	log_trace("[ %5ld:%09ld ] ", diff.tv_sec, diff.tv_nsec);
-	last_paint = now;
-	log_trace("paint:");
-	for (win *w = t; w; w = w->prev_trans)
-		log_trace(" %#010lx", w->id);
-#endif
-}
-
-// vim: set noet sw=8 ts=8 :
diff --git a/src/backend/backend.h b/src/backend/backend.h
deleted file mode 100644
index ae107d3..0000000
--- a/src/backend/backend.h
+++ /dev/null
@@ -1,290 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) 2018, Yuxuan Shui <[email protected]>
-
-#pragma once
-
-#include <stdbool.h>
-
-#include "compiler.h"
-#include "config.h"
-#include "driver.h"
-#include "kernel.h"
-#include "region.h"
-#include "types.h"
-#include "x.h"
-
-typedef struct session session_t;
-struct managed_win;
-
-struct ev_loop;
-struct backend_operations;
-
-typedef struct backend_base {
-	struct backend_operations *ops;
-	xcb_connection_t *c;
-	xcb_window_t root;
-	struct ev_loop *loop;
-
-	/// Whether the backend can accept new render request at the moment
-	bool busy;
-	// ...
-} backend_t;
-
-typedef void (*backend_ready_callback_t)(void *);
-
-// When image properties are actually applied to the image, they are applied in a
-// particular order:
-//
-// Color inversion -> Dimming -> Opacity multiply -> Limit maximum brightness
-enum image_properties {
-	// Whether the color of the image is inverted
-	// 1 boolean, default: false
-	IMAGE_PROPERTY_INVERTED,
-	// How much the image is dimmed
-	// 1 double, default: 0
-	IMAGE_PROPERTY_DIM_LEVEL,
-	// Image opacity, i.e. an alpha value multiplied to the alpha channel
-	// 1 double, default: 1
-	IMAGE_PROPERTY_OPACITY,
-	// The effective size of the image, the image will be tiled to fit.
-	// 2 int, default: the actual size of the image
-	IMAGE_PROPERTY_EFFECTIVE_SIZE,
-	// Limit how bright image can be. The image brightness is estimated by averaging
-	// the pixels in the image, and dimming will be applied to scale the average
-	// brightness down to the max brightness value.
-	// 1 double, default: 1
-	IMAGE_PROPERTY_MAX_BRIGHTNESS,
-};
-
-enum image_operations {
-	// Multiply the alpha channel by the argument
-	IMAGE_OP_APPLY_ALPHA,
-};
-
-struct gaussian_blur_args {
-	int size;
-	double deviation;
-};
-
-struct box_blur_args {
-	int size;
-};
-
-struct kernel_blur_args {
-	struct conv **kernels;
-	int kernel_count;
-};
-
-struct dual_kawase_blur_args {
-	int size;
-	int strength;
-};
-
-struct backend_operations {
-	// ===========    Initialization    ===========
-
-	/// Initialize the backend, prepare for rendering to the target window.
-	/// Here is how you should choose target window:
-	///    1) if ps->overlay is not XCB_NONE, use that
-	///    2) use ps->root otherwise
-	// TODO(yshui) make the target window a parameter
-	backend_t *(*init)(session_t *)attr_nonnull(1);
-	void (*deinit)(backend_t *backend_data) attr_nonnull(1);
-
-	/// Called when rendering will be stopped for an unknown amount of
-	/// time (e.g. when screen is unredirected). Free some resources.
-	///
-	/// Optional, not yet used
-	void (*pause)(backend_t *backend_data, session_t *ps);
-
-	/// Called before rendering is resumed
-	///
-	/// Optional, not yet used
-	void (*resume)(backend_t *backend_data, session_t *ps);
-
-	/// Called when root property changed, returns the new
-	/// backend_data. Even if the backend_data changed, all
-	/// the existing image data returned by this backend should
-	/// remain valid.
-	///
-	/// Optional
-	void *(*root_change)(backend_t *backend_data, session_t *ps);
-
-	// ===========      Rendering      ============
-
-	// NOTE: general idea about reg_paint/reg_op vs reg_visible is that reg_visible is
-	// merely a hint. Ignoring reg_visible entirely don't affect the correctness of
-	// the operation performed. OTOH reg_paint/reg_op is part of the parameters of the
-	// operation, and must be honored in order to complete the operation correctly.
-
-	// NOTE: due to complications introduced by use-damage and blur, the rendering API
-	// is a bit weird. The idea is, `compose` and `blur` have to update a temporary
-	// buffer, because `blur` requires data from an area slightly larger than the area
-	// that will be visible. So the area outside the visible area has to be rendered,
-	// but we have to discard the result (because the result of blurring that area
-	// will be wrong). That's why we cannot render into the back buffer directly.
-	// After rendering is done, `present` is called to update a portion of the actual
-	// back buffer, then present it to the target (or update the target directly,
-	// if not back buffered).
-
-	/// Called before when a new frame starts.
-	///
-	/// Optional
-	void (*prepare)(backend_t *backend_data, const region_t *reg_damage);
-
-	/**
-	 * Paint the content of an image onto the rendering buffer
-	 *
-	 * @param backend_data   the backend data
-	 * @param image_data     the image to paint
-	 * @param dst_x1, dst_y1 the top left corner of the image in the target
-	 * @param dst_x2, dst_y2 the top right corner of the image in the target
-	 * @param reg_paint      the clip region, in target coordinates
-	 * @param reg_visible    the visible region, in target coordinates
-	 */
-	void (*compose)(backend_t *backend_data, void *image_data,
-	                int dst_x1, int dst_y1, int dst_x2, int dst_y2,
-	                const region_t *reg_paint, const region_t *reg_visible);
-
-	/// Fill rectangle of the rendering buffer, mostly for debug purposes, optional.
-	void (*fill)(backend_t *backend_data, struct color, const region_t *clip);
-
-	/// Blur a given region of the rendering buffer.
-	bool (*blur)(backend_t *backend_data, double opacity, void *blur_ctx,
-	             const region_t *reg_blur, const region_t *reg_visible)
-	    attr_nonnull(1, 3, 4, 5);
-
-	/// Update part of the back buffer with the rendering buffer, then present the
-	/// back buffer onto the target window (if not back buffered, update part of the
-	/// target window directly).
-	///
-	/// Optional, if NULL, indicates the backend doesn't have render output
-	///
-	/// @param region part of the target that should be updated
-	void (*present)(backend_t *backend_data, const region_t *region) attr_nonnull(1, 2);
-
-	/**
-	 * Bind a X pixmap to the backend's internal image data structure.
-	 *
-	 * @param backend_data backend data
-	 * @param pixmap X pixmap to bind
-	 * @param fmt information of the pixmap's visual
-	 * @param owned whether the ownership of the pixmap is transfered to the backend
-	 * @return backend internal data structure bound with this pixmap
-	 */
-	void *(*bind_pixmap)(backend_t *backend_data, xcb_pixmap_t pixmap,
-	                     struct xvisual_info fmt, bool owned);
-
-	/// Create a shadow image based on the parameters
-	/// Default implementation: default_backend_render_shadow
-	void *(*render_shadow)(backend_t *backend_data, int width, int height,
-	                       const conv *kernel, double r, double g, double b, double a);
-
-	// ============ Resource management ===========
-
-	/// Free resources associated with an image data structure
-	void (*release_image)(backend_t *backend_data, void *img_data) attr_nonnull(1, 2);
-
-	// ===========        Query         ===========
-
-	/// Return if image is not completely opaque.
-	///
-	/// This function is needed because some backend might change the content of the
-	/// window (e.g. when using a custom shader with the glx backend), so only the
-	/// backend knows if an image is transparent.
-	bool (*is_image_transparent)(backend_t *backend_data, void *image_data)
-	    attr_nonnull(1, 2);
-
-	/// Get the age of the buffer content we are currently rendering ontop
-	/// of. The buffer that has just been `present`ed has a buffer age of 1.
-	/// Everytime `present` is called, buffers get older. Return -1 if the
-	/// buffer is empty.
-	///
-	/// Optional
-	int (*buffer_age)(backend_t *backend_data);
-
-	/// The maximum number buffer_age might return.
-	int max_buffer_age;
-
-	// ===========    Post-processing   ============
-
-	/* TODO(yshui) Consider preserving the order of image ops.
-	 * Currently in both backends, the image ops are applied lazily when needed.
-	 * However neither backends preserve the order of image ops, they just applied all
-	 * pending lazy ops in a pre-determined fixed order, regardless in which order
-	 * they were originally applied. This might lead to inconsistencies.*/
-
-	/**
-	 * Change image properties
-	 *
-	 * @param backend_data backend data
-	 * @param prop         the property to change
-	 * @param image_data   an image data structure returned by the backend
-	 * @param args         property value
-	 * @return whether the operation is successful
-	 */
-	bool (*set_image_property)(backend_t *backend_data, enum image_properties prop,
-	                           void *image_data, void *args);
-
-	/**
-	 * Manipulate an image. Image properties are untouched.
-	 *
-	 * @param backend_data backend data
-	 * @param op           the operation to perform
-	 * @param image_data   an image data structure returned by the backend
-	 * @param reg_op       the clip region, define the part of the image to be
-	 *                     operated on.
-	 * @param reg_visible  define the part of the image that will eventually
-	 *                     be visible on target. this is a hint to the backend
-	 *                     for optimization purposes.
-	 * @param args         extra arguments, operation specific
-	 * @return whether the operation is successful
-	 */
-	bool (*image_op)(backend_t *backend_data, enum image_operations op, void *image_data,
-	                 const region_t *reg_op, const region_t *reg_visible, void *args);
-
-	/**
-	 * Read the color of the pixel at given position of the given image. Image
-	 * properties have no effect.
-	 *
-	 * @param      backend_data backend_data
-	 * @param      image_data   an image data structure previously returned by the
-	 *                          backend. the image to read pixel from.
-	 * @param      x, y         coordinate of the pixel to read
-	 * @param[out] color        the color of the pixel
-	 * @return whether the operation is successful
-	 */
-	bool (*read_pixel)(backend_t *backend_data, void *image_data, int x, int y,
-	                   struct color *output);
-
-	/// Create another instance of the `image_data`. All `image_op` and
-	/// `set_image_property` calls on the returned image should not affect the
-	/// original image
-	void *(*clone_image)(backend_t *base, const void *image_data,
-	                     const region_t *reg_visible);
-
-	/// Create a blur context that can be used to call `blur`
-	void *(*create_blur_context)(backend_t *base, enum blur_method, void *args);
-	/// Destroy a blur context
-	void (*destroy_blur_context)(backend_t *base, void *ctx);
-	/// Get how many pixels outside of the blur area is needed for blur
-	void (*get_blur_size)(void *blur_context, int *width, int *height);
-
-	// ===========         Hooks        ============
-	/// Let the backend hook into the event handling queue
-	/// Not implemented yet
-	void (*set_ready_callback)(backend_t *, backend_ready_callback_t cb);
-	/// Called right after the core has handled its events.
-	/// Not implemented yet
-	void (*handle_events)(backend_t *);
-	// ===========         Misc         ============
-	/// Return the driver that is been used by the backend
-	enum driver (*detect_driver)(backend_t *backend_data);
-
-	void (*diagnostics)(backend_t *backend_data);
-};
-
-extern struct backend_operations *backend_list[];
-
-void paint_all_new(session_t *ps, struct managed_win *const t, bool ignore_damage)
-    attr_nonnull(1);
diff --git a/src/backend/backend_common.c b/src/backend/backend_common.c
deleted file mode 100644
index c0377d3..0000000
--- a/src/backend/backend_common.c
+++ /dev/null
@@ -1,480 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) Yuxuan Shui <[email protected]>
-#include <math.h>
-#include <string.h>
-#include <xcb/render.h>
-#include <xcb/xcb_image.h>
-#include <xcb/xcb_renderutil.h>
-
-#include "backend/backend.h"
-#include "backend/backend_common.h"
-#include "common.h"
-#include "config.h"
-#include "kernel.h"
-#include "log.h"
-#include "utils.h"
-#include "win.h"
-#include "x.h"
-
-/**
- * Generate a 1x1 <code>Picture</code> of a particular color.
- */
-xcb_render_picture_t solid_picture(xcb_connection_t *c, xcb_drawable_t d, bool argb,
-                                   double a, double r, double g, double b) {
-	xcb_pixmap_t pixmap;
-	xcb_render_picture_t picture;
-	xcb_render_create_picture_value_list_t pa;
-	xcb_render_color_t col;
-	xcb_rectangle_t rect;
-
-	pixmap = x_create_pixmap(c, argb ? 32 : 8, d, 1, 1);
-	if (!pixmap)
-		return XCB_NONE;
-
-	pa.repeat = 1;
-	picture = x_create_picture_with_standard_and_pixmap(
-	    c, argb ? XCB_PICT_STANDARD_ARGB_32 : XCB_PICT_STANDARD_A_8, pixmap,
-	    XCB_RENDER_CP_REPEAT, &pa);
-
-	if (!picture) {
-		xcb_free_pixmap(c, pixmap);
-		return XCB_NONE;
-	}
-
-	col.alpha = (uint16_t)(a * 0xffff);
-	col.red = (uint16_t)(r * 0xffff);
-	col.green = (uint16_t)(g * 0xffff);
-	col.blue = (uint16_t)(b * 0xffff);
-
-	rect.x = 0;
-	rect.y = 0;
-	rect.width = 1;
-	rect.height = 1;
-
-	xcb_render_fill_rectangles(c, XCB_RENDER_PICT_OP_SRC, picture, col, 1, &rect);
-	xcb_free_pixmap(c, pixmap);
-
-	return picture;
-}
-
-xcb_image_t *
-make_shadow(xcb_connection_t *c, const conv *kernel, double opacity, int width, int height) {
-	/*
-	 * We classify shadows into 4 kinds of regions
-	 *    r = shadow radius
-	 * (0, 0) is the top left of the window itself
-	 *         -r     r      width-r  width+r
-	 *       -r +-----+---------+-----+
-	 *          |  1  |    2    |  1  |
-	 *        r +-----+---------+-----+
-	 *          |  2  |    3    |  2  |
-	 * height-r +-----+---------+-----+
-	 *          |  1  |    2    |  1  |
-	 * height+r +-----+---------+-----+
-	 */
-	xcb_image_t *ximage;
-	const double *shadow_sum = kernel->rsum;
-	assert(shadow_sum);
-	// We only support square kernels for shadow
-	assert(kernel->w == kernel->h);
-	int d = kernel->w;
-	int r = d / 2;
-	int swidth = width + r * 2, sheight = height + r * 2;
-
-	assert(d % 2 == 1);
-	assert(d > 0);
-
-	ximage = xcb_image_create_native(c, to_u16_checked(swidth), to_u16_checked(sheight),
-	                                 XCB_IMAGE_FORMAT_Z_PIXMAP, 8, 0, 0, NULL);
-	if (!ximage) {
-		log_error("failed to create an X image");
-		return 0;
-	}
-
-	unsigned char *data = ximage->data;
-	long sstride = ximage->stride;
-
-	// If the window body is smaller than the kernel, we do convolution directly
-	if (width < r * 2 && height < r * 2) {
-		for (int y = 0; y < sheight; y++) {
-			for (int x = 0; x < swidth; x++) {
-				double sum = sum_kernel_normalized(
-				    kernel, d - x - 1, d - y - 1, width, height);
-				data[y * sstride + x] = (uint8_t)(sum * 255.0);
-			}
-		}
-		return ximage;
-	}
-
-	if (height < r * 2) {
-		// Implies width >= r * 2
-		// If the window height is smaller than the kernel, we divide
-		// the window like this:
-		// -r     r         width-r  width+r
-		// +------+-------------+------+
-		// |      |             |      |
-		// +------+-------------+------+
-		for (int y = 0; y < sheight; y++) {
-			for (int x = 0; x < r * 2; x++) {
-				double sum = sum_kernel_normalized(kernel, d - x - 1,
-				                                   d - y - 1, d, height) *
-				             255.0;
-				data[y * sstride + x] = (uint8_t)sum;
-				data[y * sstride + swidth - x - 1] = (uint8_t)sum;
-			}
-		}
-		for (int y = 0; y < sheight; y++) {
-			double sum =
-			    sum_kernel_normalized(kernel, 0, d - y - 1, d, height) * 255.0;
-			memset(&data[y * sstride + r * 2], (uint8_t)sum,
-			       (size_t)(width - 2 * r));
-		}
-		return ximage;
-	}
-	if (width < r * 2) {
-		// Similarly, for width smaller than kernel
-		for (int y = 0; y < r * 2; y++) {
-			for (int x = 0; x < swidth; x++) {
-				double sum = sum_kernel_normalized(kernel, d - x - 1,
-				                                   d - y - 1, width, d) *
-				             255.0;
-				data[y * sstride + x] = (uint8_t)sum;
-				data[(sheight - y - 1) * sstride + x] = (uint8_t)sum;
-			}
-		}
-		for (int x = 0; x < swidth; x++) {
-			double sum =
-			    sum_kernel_normalized(kernel, d - x - 1, 0, width, d) * 255.0;
-			for (int y = r * 2; y < height; y++) {
-				data[y * sstride + x] = (uint8_t)sum;
-			}
-		}
-		return ximage;
-	}
-
-	// Implies: width >= r * 2 && height >= r * 2
-
-	// Fill part 3
-	for (int y = r; y < height + r; y++) {
-		memset(data + sstride * y + r, (uint8_t)(255 * opacity), (size_t)width);
-	}
-
-	// Part 1
-	for (int y = 0; y < r * 2; y++) {
-		for (int x = 0; x < r * 2; x++) {
-			double tmpsum = shadow_sum[y * d + x] * opacity * 255.0;
-			data[y * sstride + x] = (uint8_t)tmpsum;
-			data[(sheight - y - 1) * sstride + x] = (uint8_t)tmpsum;
-			data[(sheight - y - 1) * sstride + (swidth - x - 1)] = (uint8_t)tmpsum;
-			data[y * sstride + (swidth - x - 1)] = (uint8_t)tmpsum;
-		}
-	}
-
-	// Part 2, top/bottom
-	for (int y = 0; y < r * 2; y++) {
-		double tmpsum = shadow_sum[d * y + d - 1] * opacity * 255.0;
-		memset(&data[y * sstride + r * 2], (uint8_t)tmpsum, (size_t)(width - r * 2));
-		memset(&data[(sheight - y - 1) * sstride + r * 2], (uint8_t)tmpsum,
-		       (size_t)(width - r * 2));
-	}
-
-	// Part 2, left/right
-	for (int x = 0; x < r * 2; x++) {
-		double tmpsum = shadow_sum[d * (d - 1) + x] * opacity * 255.0;
-		for (int y = r * 2; y < height; y++) {
-			data[y * sstride + x] = (uint8_t)tmpsum;
-			data[y * sstride + (swidth - x - 1)] = (uint8_t)tmpsum;
-		}
-	}
-
-	return ximage;
-}
-
-/**
- * Generate shadow <code>Picture</code> for a window.
- */
-bool build_shadow(xcb_connection_t *c, xcb_drawable_t d, double opacity, const int width,
-                  const int height, const conv *kernel, xcb_render_picture_t shadow_pixel,
-                  xcb_pixmap_t *pixmap, xcb_render_picture_t *pict) {
-	xcb_image_t *shadow_image = NULL;
-	xcb_pixmap_t shadow_pixmap = XCB_NONE, shadow_pixmap_argb = XCB_NONE;
-	xcb_render_picture_t shadow_picture = XCB_NONE, shadow_picture_argb = XCB_NONE;
-	xcb_gcontext_t gc = XCB_NONE;
-
-	shadow_image = make_shadow(c, kernel, opacity, width, height);
-	if (!shadow_image) {
-		log_error("Failed to make shadow");
-		return false;
-	}
-
-	shadow_pixmap = x_create_pixmap(c, 8, d, shadow_image->width, shadow_image->height);
-	shadow_pixmap_argb =
-	    x_create_pixmap(c, 32, d, shadow_image->width, shadow_image->height);
-
-	if (!shadow_pixmap || !shadow_pixmap_argb) {
-		log_error("Failed to create shadow pixmaps");
-		goto shadow_picture_err;
-	}
-
-	shadow_picture = x_create_picture_with_standard_and_pixmap(
-	    c, XCB_PICT_STANDARD_A_8, shadow_pixmap, 0, NULL);
-	shadow_picture_argb = x_create_picture_with_standard_and_pixmap(
-	    c, XCB_PICT_STANDARD_ARGB_32, shadow_pixmap_argb, 0, NULL);
-	if (!shadow_picture || !shadow_picture_argb) {
-		goto shadow_picture_err;
-	}
-
-	gc = x_new_id(c);
-	xcb_create_gc(c, gc, shadow_pixmap, 0, NULL);
-
-	// We need to make room for protocol metadata in the request. The metadata should
-	// be 24 bytes plus padding, let's be generous and give it 1kb
-	auto maximum_image_size = xcb_get_maximum_request_length(c) * 4 - 1024;
-	auto maximum_row =
-	    to_u16_checked(clamp(maximum_image_size / shadow_image->stride, 0, UINT16_MAX));
-	if (maximum_row <= 0) {
-		// TODO(yshui) Upload image with XShm
-		log_error("X server request size limit is too restrictive, or the shadow "
-		          "image is too wide for us to send a single row of the shadow "
-		          "image. Shadow size: %dx%d",
-		          width, height);
-		goto shadow_picture_err;
-	}
-
-	for (uint32_t row = 0; row < shadow_image->height; row += maximum_row) {
-		auto batch_height = maximum_row;
-		if (batch_height > shadow_image->height - row) {
-			batch_height = to_u16_checked(shadow_image->height - row);
-		}
-
-		uint32_t offset = row * shadow_image->stride / sizeof(*shadow_image->data);
-		xcb_put_image(c, (uint8_t)shadow_image->format, shadow_pixmap, gc,
-		              shadow_image->width, batch_height, 0, to_i16_checked(row),
-		              0, shadow_image->depth, shadow_image->stride * batch_height,
-		              shadow_image->data + offset);
-	}
-
-	xcb_render_composite(c, XCB_RENDER_PICT_OP_SRC, shadow_pixel, shadow_picture,
-	                     shadow_picture_argb, 0, 0, 0, 0, 0, 0, shadow_image->width,
-	                     shadow_image->height);
-
-	*pixmap = shadow_pixmap_argb;
-	*pict = shadow_picture_argb;
-
-	xcb_free_gc(c, gc);
-	xcb_image_destroy(shadow_image);
-	xcb_free_pixmap(c, shadow_pixmap);
-	xcb_render_free_picture(c, shadow_picture);
-
-	return true;
-
-shadow_picture_err:
-	if (shadow_image) {
-		xcb_image_destroy(shadow_image);
-	}
-	if (shadow_pixmap) {
-		xcb_free_pixmap(c, shadow_pixmap);
-	}
-	if (shadow_pixmap_argb) {
-		xcb_free_pixmap(c, shadow_pixmap_argb);
-	}
-	if (shadow_picture) {
-		xcb_render_free_picture(c, shadow_picture);
-	}
-	if (shadow_picture_argb) {
-		xcb_render_free_picture(c, shadow_picture_argb);
-	}
-	if (gc) {
-		xcb_free_gc(c, gc);
-	}
-
-	return false;
-}
-
-void *
-default_backend_render_shadow(backend_t *backend_data, int width, int height,
-                              const conv *kernel, double r, double g, double b, double a) {
-	xcb_pixmap_t shadow_pixel = solid_picture(backend_data->c, backend_data->root,
-	                                          true, 1, r, g, b),
-	             shadow = XCB_NONE;
-	xcb_render_picture_t pict = XCB_NONE;
-
-	if (!build_shadow(backend_data->c, backend_data->root, a, width, height, kernel,
-	                  shadow_pixel, &shadow, &pict)) {
-		return NULL;
-	}
-
-	auto visual = x_get_visual_for_standard(backend_data->c, XCB_PICT_STANDARD_ARGB_32);
-	void *ret = backend_data->ops->bind_pixmap(
-	    backend_data, shadow, x_get_visual_info(backend_data->c, visual), true);
-	xcb_render_free_picture(backend_data->c, pict);
-	return ret;
-}
-
-static struct conv **generate_box_blur_kernel(struct box_blur_args *args, int *kernel_count) {
-	int r = args->size * 2 + 1;
-	assert(r > 0);
-	auto ret = ccalloc(2, struct conv *);
-	ret[0] = cvalloc(sizeof(struct conv) + sizeof(double) * (size_t)r);
-	ret[1] = cvalloc(sizeof(struct conv) + sizeof(double) * (size_t)r);
-	ret[0]->w = r;
-	ret[0]->h = 1;
-	ret[1]->w = 1;
-	ret[1]->h = r;
-	for (int i = 0; i < r; i++) {
-		ret[0]->data[i] = 1;
-		ret[1]->data[i] = 1;
-	}
-	*kernel_count = 2;
-	return ret;
-}
-
-static struct conv **
-generate_gaussian_blur_kernel(struct gaussian_blur_args *args, int *kernel_count) {
-	int r = args->size * 2 + 1;
-	assert(r > 0);
-	auto ret = ccalloc(2, struct conv *);
-	ret[0] = cvalloc(sizeof(struct conv) + sizeof(double) * (size_t)r);
-	ret[1] = cvalloc(sizeof(struct conv) + sizeof(double) * (size_t)r);
-	ret[0]->w = r;
-	ret[0]->h = 1;
-	ret[1]->w = 1;
-	ret[1]->h = r;
-	for (int i = 0; i <= args->size; i++) {
-		ret[0]->data[i] = ret[0]->data[r - i - 1] =
-		    1.0 / (sqrt(2.0 * M_PI) * args->deviation) *
-		    exp(-(args->size - i) * (args->size - i) /
-		        (2 * args->deviation * args->deviation));
-		ret[1]->data[i] = ret[1]->data[r - i - 1] = ret[0]->data[i];
-	}
-	*kernel_count = 2;
-	return ret;
-}
-
-/// Generate blur kernels for gaussian and box blur methods. Generated kernel is not
-/// normalized, and the center element will always be 1.
-struct conv **generate_blur_kernel(enum blur_method method, void *args, int *kernel_count) {
-	switch (method) {
-	case BLUR_METHOD_BOX: return generate_box_blur_kernel(args, kernel_count);
-	case BLUR_METHOD_GAUSSIAN:
-		return generate_gaussian_blur_kernel(args, kernel_count);
-	default: break;
-	}
-	return NULL;
-}
-
-/// Generate kernel parameters for dual-kawase blur method. Falls back on approximating
-/// standard gauss radius if strength is zero or below.
-struct dual_kawase_params *generate_dual_kawase_params(void *args) {
-	struct dual_kawase_blur_args *blur_args = args;
-	static const struct {
-		int iterations;        /// Number of down- and upsample iterations
-		float offset;          /// Sample offset in half-pixels
-		int min_radius;        /// Approximate gauss-blur with at least this
-		                       /// radius and std-deviation
-	} strength_levels[20] = {
-	    {.iterations = 1, .offset = 1.25f, .min_radius = 1},          // LVL  1
-	    {.iterations = 1, .offset = 2.25f, .min_radius = 6},          // LVL  2
-	    {.iterations = 2, .offset = 2.00f, .min_radius = 11},         // LVL  3
-	    {.iterations = 2, .offset = 3.00f, .min_radius = 17},         // LVL  4
-	    {.iterations = 2, .offset = 4.25f, .min_radius = 24},         // LVL  5
-	    {.iterations = 3, .offset = 2.50f, .min_radius = 32},         // LVL  6
-	    {.iterations = 3, .offset = 3.25f, .min_radius = 40},         // LVL  7
-	    {.iterations = 3, .offset = 4.25f, .min_radius = 51},         // LVL  8
-	    {.iterations = 3, .offset = 5.50f, .min_radius = 67},         // LVL  9
-	    {.iterations = 4, .offset = 3.25f, .min_radius = 83},         // LVL 10
-	    {.iterations = 4, .offset = 4.00f, .min_radius = 101},        // LVL 11
-	    {.iterations = 4, .offset = 5.00f, .min_radius = 123},        // LVL 12
-	    {.iterations = 4, .offset = 6.00f, .min_radius = 148},        // LVL 13
-	    {.iterations = 4, .offset = 7.25f, .min_radius = 178},        // LVL 14
-	    {.iterations = 4, .offset = 8.25f, .min_radius = 208},        // LVL 15
-	    {.iterations = 5, .offset = 4.50f, .min_radius = 236},        // LVL 16
-	    {.iterations = 5, .offset = 5.25f, .min_radius = 269},        // LVL 17
-	    {.iterations = 5, .offset = 6.25f, .min_radius = 309},        // LVL 18
-	    {.iterations = 5, .offset = 7.25f, .min_radius = 357},        // LVL 19
-	    {.iterations = 5, .offset = 8.50f, .min_radius = 417},        // LVL 20
-	};
-
-	auto params = ccalloc(1, struct dual_kawase_params);
-	params->iterations = 0;
-	params->offset = 1.0f;
-
-	if (blur_args->strength <= 0 && blur_args->size) {
-		// find highest level that approximates blur-strength with the selected
-		// gaussian blur-radius
-		int lvl = 1;
-		while (strength_levels[lvl - 1].min_radius < blur_args->size && lvl < 20) {
-			++lvl;
-		}
-		blur_args->strength = lvl;
-	}
-	if (blur_args->strength <= 0) {
-		// default value
-		blur_args->strength = 5;
-	}
-
-	assert(blur_args->strength > 0 && blur_args->strength <= 20);
-	params->iterations = strength_levels[blur_args->strength - 1].iterations;
-	params->offset = strength_levels[blur_args->strength - 1].offset;
-
-	// Expand sample area to cover the smallest texture / highest selected iteration:
-	// - Smallest texture dimensions are halved `iterations`-times
-	// - Upsample needs pixels two-times `offset` away from the border
-	// - Plus one for interpolation differences
-	params->expand = (1 << params->iterations) * 2 * (int)ceil(params->offset) + 1;
-
-	return params;
-}
-
-void *default_clone_image(backend_t *base attr_unused, const void *image_data,
-                          const region_t *reg_visible attr_unused) {
-	auto new_img = ccalloc(1, struct backend_image);
-	*new_img = *(struct backend_image *)image_data;
-	new_img->inner->refcount++;
-	return new_img;
-}
-
-bool default_set_image_property(backend_t *base attr_unused, enum image_properties op,
-                                void *image_data, void *arg) {
-	struct backend_image *tex = image_data;
-	int *iargs = arg;
-	bool *bargs = arg;
-	double *dargs = arg;
-	switch (op) {
-	case IMAGE_PROPERTY_INVERTED: tex->color_inverted = bargs[0]; break;
-	case IMAGE_PROPERTY_DIM_LEVEL: tex->dim = dargs[0]; break;
-	case IMAGE_PROPERTY_OPACITY: tex->opacity = dargs[0]; break;
-	case IMAGE_PROPERTY_EFFECTIVE_SIZE:
-		// texture is already set to repeat, so nothing else we need to do
-		tex->ewidth = iargs[0];
-		tex->eheight = iargs[1];
-		break;
-	case IMAGE_PROPERTY_MAX_BRIGHTNESS: tex->max_brightness = dargs[0]; break;
-	}
-
-	return true;
-}
-
-bool default_is_image_transparent(backend_t *base attr_unused, void *image_data) {
-	struct backend_image *img = image_data;
-	return img->opacity < 1 || img->inner->has_alpha;
-}
-
-struct backend_image *default_new_backend_image(int w, int h) {
-	auto ret = ccalloc(1, struct backend_image);
-	ret->opacity = 1;
-	ret->dim = 0;
-	ret->max_brightness = 1;
-	ret->eheight = h;
-	ret->ewidth = w;
-	ret->color_inverted = false;
-	return ret;
-}
-
-void init_backend_base(struct backend_base *base, session_t *ps) {
-	base->c = ps->c;
-	base->loop = ps->loop;
-	base->root = ps->root;
-	base->busy = false;
-	base->ops = NULL;
-}
diff --git a/src/backend/backend_common.h b/src/backend/backend_common.h
deleted file mode 100644
index 5c9c806..0000000
--- a/src/backend/backend_common.h
+++ /dev/null
@@ -1,78 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) Yuxuan Shui <[email protected]>
-#pragma once
-
-#include <xcb/render.h>
-#include <xcb/xcb_image.h>
-
-#include <stdbool.h>
-
-#include "backend.h"
-#include "config.h"
-#include "region.h"
-
-typedef struct session session_t;
-typedef struct win win;
-typedef struct conv conv;
-typedef struct backend_base backend_t;
-struct backend_operations;
-
-struct dual_kawase_params {
-	/// Number of downsample passes
-	int iterations;
-	/// Pixel offset for down- and upsample
-	float offset;
-	/// Save area around blur target (@ref resize_width, @ref resize_height)
-	int expand;
-};
-
-struct backend_image_inner_base {
-	int refcount;
-	bool has_alpha;
-};
-
-struct backend_image {
-	// Backend dependent inner image data
-	struct backend_image_inner_base *inner;
-	double opacity;
-	double dim;
-	double max_brightness;
-	// Effective size of the image
-	int ewidth, eheight;
-	bool color_inverted;
-};
-
-bool build_shadow(xcb_connection_t *, xcb_drawable_t, double opacity, int width,
-                  int height, const conv *kernel, xcb_render_picture_t shadow_pixel,
-                  xcb_pixmap_t *pixmap, xcb_render_picture_t *pict);
-
-xcb_render_picture_t solid_picture(xcb_connection_t *, xcb_drawable_t, bool argb,
-                                   double a, double r, double g, double b);
-
-xcb_image_t *
-make_shadow(xcb_connection_t *c, const conv *kernel, double opacity, int width, int height);
-
-/// The default implementation of `is_win_transparent`, it simply looks at win::mode. So
-/// this is not suitable for backends that alter the content of windows
-bool default_is_win_transparent(void *, win *, void *);
-
-/// The default implementation of `is_frame_transparent`, it uses win::frame_opacity. Same
-/// caveat as `default_is_win_transparent` applies.
-bool default_is_frame_transparent(void *, win *, void *);
-
-void *
-default_backend_render_shadow(backend_t *backend_data, int width, int height,
-                              const conv *kernel, double r, double g, double b, double a);
-
-void init_backend_base(struct backend_base *base, session_t *ps);
-
-struct conv **generate_blur_kernel(enum blur_method method, void *args, int *kernel_count);
-struct dual_kawase_params *generate_dual_kawase_params(void *args);
-
-void *default_clone_image(backend_t *base, const void *image_data, const region_t *reg);
-void *default_resize_image(backend_t *base, const void *image_data, uint16_t desired_width,
-			   uint16_t desired_height, const region_t *reg);
-bool default_is_image_transparent(backend_t *base attr_unused, void *image_data);
-bool default_set_image_property(backend_t *base attr_unused, enum image_properties op,
-                                void *image_data, void *arg);
-struct backend_image *default_new_backend_image(int w, int h);
diff --git a/src/backend/driver.c b/src/backend/driver.c
deleted file mode 100644
index a41d2fd..0000000
--- a/src/backend/driver.c
+++ /dev/null
@@ -1,82 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) Yuxuan Shui <[email protected]>
-#include <stdlib.h>
-#include <string.h>
-
-#include <xcb/randr.h>
-#include <xcb/xcb.h>
-
-#include "backend/backend.h"
-#include "backend/driver.h"
-#include "common.h"
-#include "compiler.h"
-#include "log.h"
-
-/// Apply driver specified global workarounds. It's safe to call this multiple times.
-void apply_driver_workarounds(struct session *ps, enum driver driver) {
-	if (driver & DRIVER_NVIDIA) {
-		// setenv("__GL_YIELD", "usleep", true);
-		setenv("__GL_MaxFramesAllowed", "1", true);
-		ps->o.xrender_sync_fence = true;
-	}
-}
-
-enum driver detect_driver(xcb_connection_t *c, backend_t *backend_data, xcb_window_t window) {
-	enum driver ret = 0;
-	// First we try doing backend agnostic detection using RANDR
-	// There's no way to query the X server about what driver is loaded, so RANDR is
-	// our best shot.
-	auto randr_version = xcb_randr_query_version_reply(
-	    c, xcb_randr_query_version(c, XCB_RANDR_MAJOR_VERSION, XCB_RANDR_MINOR_VERSION),
-	    NULL);
-	if (randr_version &&
-	    (randr_version->major_version > 1 || randr_version->minor_version >= 4)) {
-		auto r = xcb_randr_get_providers_reply(
-		    c, xcb_randr_get_providers(c, window), NULL);
-		if (r == NULL) {
-			log_warn("Failed to get RANDR providers");
-			free(randr_version);
-			return 0;
-		}
-
-		auto providers = xcb_randr_get_providers_providers(r);
-		for (auto i = 0; i < xcb_randr_get_providers_providers_length(r); i++) {
-			auto r2 = xcb_randr_get_provider_info_reply(
-			    c, xcb_randr_get_provider_info(c, providers[i], r->timestamp), NULL);
-			if (r2 == NULL) {
-				continue;
-			}
-			if (r2->num_outputs == 0) {
-				free(r2);
-				continue;
-			}
-
-			auto name_len = xcb_randr_get_provider_info_name_length(r2);
-			assert(name_len >= 0);
-			auto name =
-			    strndup(xcb_randr_get_provider_info_name(r2), (size_t)name_len);
-			if (strcasestr(name, "modesetting") != NULL) {
-				ret |= DRIVER_MODESETTING;
-			} else if (strcasestr(name, "Radeon") != NULL) {
-				// Be conservative, add both radeon drivers
-				ret |= DRIVER_AMDGPU | DRIVER_RADEON;
-			} else if (strcasestr(name, "NVIDIA") != NULL) {
-				ret |= DRIVER_NVIDIA;
-			} else if (strcasestr(name, "nouveau") != NULL) {
-				ret |= DRIVER_NOUVEAU;
-			} else if (strcasestr(name, "Intel") != NULL) {
-				ret |= DRIVER_INTEL;
-			}
-			free(name);
-			free(r2);
-		}
-		free(r);
-	}
-	free(randr_version);
-
-	// If the backend supports driver detection, use that as well
-	if (backend_data && backend_data->ops->detect_driver) {
-		ret |= backend_data->ops->detect_driver(backend_data);
-	}
-	return ret;
-}
diff --git a/src/backend/driver.h b/src/backend/driver.h
deleted file mode 100644
index a37cda3..0000000
--- a/src/backend/driver.h
+++ /dev/null
@@ -1,62 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) Yuxuan Shui <[email protected]>
-
-#pragma once
-
-#include <stddef.h>
-#include <stdio.h>
-#include <xcb/xcb.h>
-
-#include "utils.h"
-
-struct session;
-struct backend_base;
-
-// A list of known driver quirks:
-// *  NVIDIA driver doesn't like seeing the same pixmap under different
-//    ids, so avoid naming the pixmap again when it didn't actually change.
-
-/// A list of possible drivers.
-/// The driver situation is a bit complicated. There are two drivers we care about: the
-/// DDX, and the OpenGL driver. They are usually paired, but not always, since there is
-/// also the generic modesetting driver.
-/// This enum represents _both_ drivers.
-enum driver {
-	DRIVER_AMDGPU = 1,        // AMDGPU for DDX, radeonsi for OpenGL
-	DRIVER_RADEON = 2,        // ATI for DDX, mesa r600 for OpenGL
-	DRIVER_FGLRX = 4,
-	DRIVER_NVIDIA = 8,
-	DRIVER_NOUVEAU = 16,
-	DRIVER_INTEL = 32,
-	DRIVER_MODESETTING = 64,
-};
-
-static const char *driver_names[] = {
-    "AMDGPU", "Radeon", "fglrx", "NVIDIA", "nouveau", "Intel", "modesetting",
-};
-
-/// Return a list of all drivers currently in use by the X server.
-/// Note, this is a best-effort test, so no guarantee all drivers will be detected.
-enum driver detect_driver(xcb_connection_t *, struct backend_base *, xcb_window_t);
-
-/// Apply driver specified global workarounds. It's safe to call this multiple times.
-void apply_driver_workarounds(struct session *ps, enum driver);
-
-// Print driver names to stdout, for diagnostics
-static inline void print_drivers(enum driver drivers) {
-	const char *seen_drivers[ARR_SIZE(driver_names)];
-	int driver_count = 0;
-	for (size_t i = 0; i < ARR_SIZE(driver_names); i++) {
-		if (drivers & (1ul << i)) {
-			seen_drivers[driver_count++] = driver_names[i];
-		}
-	}
-
-	if (driver_count > 0) {
-		printf("%s", seen_drivers[0]);
-		for (int i = 1; i < driver_count; i++) {
-			printf(", %s", seen_drivers[i]);
-		}
-	}
-	printf("\n");
-}
diff --git a/src/backend/dummy/dummy.c b/src/backend/dummy/dummy.c
deleted file mode 100644
index a057b97..0000000
--- a/src/backend/dummy/dummy.c
+++ /dev/null
@@ -1,174 +0,0 @@
-#include <uthash.h>
-#include <xcb/xcb.h>
-
-#include "backend/backend.h"
-#include "backend/backend_common.h"
-#include "common.h"
-#include "compiler.h"
-#include "config.h"
-#include "log.h"
-#include "region.h"
-#include "types.h"
-#include "uthash_extra.h"
-#include "utils.h"
-#include "x.h"
-
-struct dummy_image {
-	xcb_pixmap_t pixmap;
-	bool transparent;
-	int *refcount;
-	UT_hash_handle hh;
-};
-
-struct dummy_data {
-	struct backend_base base;
-	struct dummy_image *images;
-};
-
-struct backend_base *dummy_init(struct session *ps attr_unused) {
-	auto ret = (struct backend_base *)ccalloc(1, struct dummy_data);
-	ret->c = ps->c;
-	ret->loop = ps->loop;
-	ret->root = ps->root;
-	ret->busy = false;
-	return ret;
-}
-
-void dummy_deinit(struct backend_base *data) {
-	auto dummy = (struct dummy_data *)data;
-	HASH_ITER2(dummy->images, img) {
-		log_warn("Backend image for pixmap %#010x is not freed", img->pixmap);
-		HASH_DEL(dummy->images, img);
-		free(img->refcount);
-		free(img);
-	}
-	free(dummy);
-}
-
-static void dummy_check_image(struct backend_base *base, const struct dummy_image *img) {
-	auto dummy = (struct dummy_data *)base;
-	struct dummy_image *tmp = NULL;
-	HASH_FIND_INT(dummy->images, &img->pixmap, tmp);
-	if (!tmp) {
-		log_warn("Using an invalid (possibly freed) image");
-		assert(false);
-	}
-	assert(*tmp->refcount > 0);
-}
-
-void dummy_compose(struct backend_base *base, void *image, int dst_x1 attr_unused,
-                   int dst_y1 attr_unused, int dst_x2 attr_unused, int dst_y2 attr_unused,
-		   const region_t *reg_paint attr_unused, const region_t *reg_visible attr_unused) {
-	dummy_check_image(base, image);
-}
-
-void dummy_fill(struct backend_base *backend_data attr_unused, struct color c attr_unused,
-                const region_t *clip attr_unused) {
-}
-
-bool dummy_blur(struct backend_base *backend_data attr_unused, double opacity attr_unused,
-                void *blur_ctx attr_unused, const region_t *reg_blur attr_unused,
-                const region_t *reg_visible attr_unused) {
-	return true;
-}
-
-void *dummy_bind_pixmap(struct backend_base *base, xcb_pixmap_t pixmap,
-                        struct xvisual_info fmt, bool owned attr_unused) {
-	auto dummy = (struct dummy_data *)base;
-	struct dummy_image *img = NULL;
-	HASH_FIND_INT(dummy->images, &pixmap, img);
-	if (img) {
-		(*img->refcount)++;
-		return img;
-	}
-
-	img = ccalloc(1, struct dummy_image);
-	img->pixmap = pixmap;
-	img->transparent = fmt.alpha_size != 0;
-	img->refcount = ccalloc(1, int);
-	*img->refcount = 1;
-
-	HASH_ADD_INT(dummy->images, pixmap, img);
-	return (void *)img;
-}
-
-void dummy_release_image(backend_t *base, void *image) {
-	auto dummy = (struct dummy_data *)base;
-	auto img = (struct dummy_image *)image;
-	assert(*img->refcount > 0);
-	(*img->refcount)--;
-	if (*img->refcount == 0) {
-		HASH_DEL(dummy->images, img);
-		free(img->refcount);
-		free(img);
-	}
-}
-
-bool dummy_is_image_transparent(struct backend_base *base, void *image) {
-	auto img = (struct dummy_image *)image;
-	dummy_check_image(base, img);
-	return img->transparent;
-}
-
-int dummy_buffer_age(struct backend_base *base attr_unused) {
-	return 2;
-}
-
-bool dummy_image_op(struct backend_base *base, enum image_operations op attr_unused,
-                    void *image, const region_t *reg_op attr_unused,
-                    const region_t *reg_visible attr_unused, void *args attr_unused) {
-	dummy_check_image(base, image);
-	return true;
-}
-
-bool dummy_set_image_property(struct backend_base *base, enum image_properties prop attr_unused,
-                              void *image, void *arg attr_unused) {
-	dummy_check_image(base, image);
-	return true;
-}
-
-void *dummy_clone_image(struct backend_base *base, const void *image,
-                        const region_t *reg_visible attr_unused) {
-	auto img = (const struct dummy_image *)image;
-	dummy_check_image(base, img);
-	(*img->refcount)++;
-	return (void *)img;
-}
-
-void *dummy_create_blur_context(struct backend_base *base attr_unused,
-                                enum blur_method method attr_unused, void *args attr_unused) {
-	static int dummy_context;
-	return &dummy_context;
-}
-
-void dummy_destroy_blur_context(struct backend_base *base attr_unused, void *ctx attr_unused) {
-}
-
-void dummy_get_blur_size(void *ctx attr_unused, int *width, int *height) {
-	// These numbers are arbitrary, to make sure the reisze_region code path is
-	// covered.
-	*width = 5;
-	*height = 5;
-}
-
-struct backend_operations dummy_ops = {
-    .init = dummy_init,
-    .deinit = dummy_deinit,
-    .compose = dummy_compose,
-    .fill = dummy_fill,
-    .blur = dummy_blur,
-    .bind_pixmap = dummy_bind_pixmap,
-    .render_shadow = default_backend_render_shadow,
-    .release_image = dummy_release_image,
-    .is_image_transparent = dummy_is_image_transparent,
-    .buffer_age = dummy_buffer_age,
-    .max_buffer_age = 5,
-
-    .image_op = dummy_image_op,
-    .clone_image = dummy_clone_image,
-    .set_image_property = dummy_set_image_property,
-    .create_blur_context = dummy_create_blur_context,
-    .destroy_blur_context = dummy_destroy_blur_context,
-    .get_blur_size = dummy_get_blur_size,
-
-};
diff --git a/src/backend/gl/gl_common.c b/src/backend/gl/gl_common.c
deleted file mode 100644
index 8cc5a05..0000000
--- a/src/backend/gl/gl_common.c
+++ /dev/null
@@ -1,1922 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) Yuxuan Shui <[email protected]>
-#include <GL/gl.h>
-#include <GL/glext.h>
-#include <locale.h>
-#include <stdbool.h>
-#include <stdio.h>
-#include <string.h>
-#include <xcb/render.h>        // for xcb_render_fixed_t, XXX
-
-#include "backend/backend.h"
-#include "common.h"
-#include "compiler.h"
-#include "config.h"
-#include "kernel.h"
-#include "log.h"
-#include "region.h"
-#include "string_utils.h"
-#include "types.h"
-#include "utils.h"
-
-#include "backend/backend_common.h"
-#include "backend/gl/gl_common.h"
-
-#define GLSL(version, ...) "#version " #version "\n" #__VA_ARGS__
-#define QUOTE(...) #__VA_ARGS__
-
-static const GLuint vert_coord_loc = 0;
-static const GLuint vert_in_texcoord_loc = 1;
-
-struct gl_blur_context {
-	enum blur_method method;
-	gl_blur_shader_t *blur_shader;
-
-	/// Temporary textures used for blurring
-	GLuint *blur_textures;
-	int blur_texture_count;
-	/// Temporary fbos used for blurring
-	GLuint *blur_fbos;
-	int blur_fbo_count;
-
-	/// Cached dimensions of each blur_texture. They are the same size as the target,
-	/// so they are always big enough without resizing.
-	/// Turns out calling glTexImage to resize is expensive, so we avoid that.
-	struct texture_size {
-		int width;
-		int height;
-	} * texture_sizes;
-
-	/// Cached dimensions of the offscreen framebuffer. It's the same size as the
-	/// target but is expanded in either direction by resize_width / resize_height.
-	int fb_width, fb_height;
-
-	/// How much do we need to resize the damaged region for blurring.
-	int resize_width, resize_height;
-
-	int npasses;
-};
-
-static GLint glGetUniformLocationChecked(GLuint p, const char *name) {
-	auto ret = glGetUniformLocation(p, name);
-	if (ret < 0) {
-		log_info("Failed to get location of uniform '%s'. This is normal when "
-		         "using custom shaders.",
-		         name);
-	}
-	return ret;
-}
-
-GLuint gl_create_shader(GLenum shader_type, const char *shader_str) {
-	log_trace("===\n%s\n===", shader_str);
-
-	bool success = false;
-	GLuint shader = glCreateShader(shader_type);
-	if (!shader) {
-		log_error("Failed to create shader with type %#x.", shader_type);
-		goto end;
-	}
-	glShaderSource(shader, 1, &shader_str, NULL);
-	glCompileShader(shader);
-
-	// Get shader status
-	{
-		GLint status = GL_FALSE;
-		glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
-		if (GL_FALSE == status) {
-			GLint log_len = 0;
-			glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &log_len);
-			if (log_len) {
-				char log[log_len + 1];
-				glGetShaderInfoLog(shader, log_len, NULL, log);
-				log_error("Failed to compile shader with type %d: %s",
-				          shader_type, log);
-			}
-			goto end;
-		}
-	}
-
-	success = true;
-
-end:
-	if (shader && !success) {
-		glDeleteShader(shader);
-		shader = 0;
-	}
-
-	return shader;
-}
-
-GLuint gl_create_program(const GLuint *const shaders, int nshaders) {
-	bool success = false;
-	GLuint program = glCreateProgram();
-	if (!program) {
-		log_error("Failed to create program.");
-		goto end;
-	}
-
-	for (int i = 0; i < nshaders; ++i)
-		glAttachShader(program, shaders[i]);
-	glLinkProgram(program);
-
-	// Get program status
-	{
-		GLint status = GL_FALSE;
-		glGetProgramiv(program, GL_LINK_STATUS, &status);
-		if (GL_FALSE == status) {
-			GLint log_len = 0;
-			glGetProgramiv(program, GL_INFO_LOG_LENGTH, &log_len);
-			if (log_len) {
-				char log[log_len + 1];
-				glGetProgramInfoLog(program, log_len, NULL, log);
-				log_error("Failed to link program: %s", log);
-			}
-			goto end;
-		}
-	}
-	success = true;
-
-end:
-	if (program) {
-		for (int i = 0; i < nshaders; ++i)
-			glDetachShader(program, shaders[i]);
-	}
-	if (program && !success) {
-		glDeleteProgram(program);
-		program = 0;
-	}
-
-	return program;
-}
-
-/**
- * @brief Create a program from vertex and fragment shader strings.
- */
-GLuint gl_create_program_from_str(const char *vert_shader_str, const char *frag_shader_str) {
-	GLuint vert_shader = 0;
-	GLuint frag_shader = 0;
-	GLuint prog = 0;
-
-	if (vert_shader_str)
-		vert_shader = gl_create_shader(GL_VERTEX_SHADER, vert_shader_str);
-	if (frag_shader_str)
-		frag_shader = gl_create_shader(GL_FRAGMENT_SHADER, frag_shader_str);
-
-	{
-		GLuint shaders[2];
-		int count = 0;
-		if (vert_shader) {
-			shaders[count++] = vert_shader;
-		}
-		if (frag_shader) {
-			shaders[count++] = frag_shader;
-		}
-		if (count) {
-			prog = gl_create_program(shaders, count);
-		}
-	}
-
-	if (vert_shader)
-		glDeleteShader(vert_shader);
-	if (frag_shader)
-		glDeleteShader(frag_shader);
-
-	return prog;
-}
-
-static void gl_free_prog_main(gl_win_shader_t *pprogram) {
-	if (!pprogram)
-		return;
-	if (pprogram->prog) {
-		glDeleteProgram(pprogram->prog);
-		pprogram->prog = 0;
-	}
-}
-
-/*
- * @brief Implements recursive part of gl_average_texture_color.
- *
- * @note In order to reduce number of textures which needs to be
- * allocated and deleted during this recursive render
- * we reuse the same two textures for render source and
- * destination simply by alterating between them.
- * Unfortunately on first iteration source_texture might
- * be read-only. In this case we will select auxiliary_texture as
- * destination_texture in order not to touch that read-only source
- * texture in following render iteration.
- * Otherwise we simply will switch source and destination textures
- * between each other on each render iteration.
- */
-static GLuint
-_gl_average_texture_color(backend_t *base, GLuint source_texture, GLuint destination_texture,
-                          GLuint auxiliary_texture, GLuint fbo, int width, int height) {
-	const int max_width = 1;
-	const int max_height = 1;
-	const int from_width = next_power_of_two(width);
-	const int from_height = next_power_of_two(height);
-	const int to_width = from_width > max_width ? from_width / 2 : from_width;
-	const int to_height = from_height > max_height ? from_height / 2 : from_height;
-
-	// Prepare coordinates
-	GLint coord[] = {
-	    // top left
-	    0, 0,        // vertex coord
-	    0, 0,        // texture coord
-
-	    // top right
-	    to_width, 0,        // vertex coord
-	    width, 0,           // texture coord
-
-	    // bottom right
-	    to_width, to_height,        // vertex coord
-	    width, height,              // texture coord
-
-	    // bottom left
-	    0, to_height,        // vertex coord
-	    0, height,           // texture coord
-	};
-	glBufferSubData(GL_ARRAY_BUFFER, 0, (long)sizeof(*coord) * 16, coord);
-
-	// Prepare framebuffer for new render iteration
-	glBindTexture(GL_TEXTURE_2D, destination_texture);
-	glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
-	                       destination_texture, 0);
-	gl_check_fb_complete(GL_FRAMEBUFFER);
-
-	// Bind source texture as downscaling shader uniform input
-	glBindTexture(GL_TEXTURE_2D, source_texture);
-
-	// Render into framebuffer
-	glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, NULL);
-
-	// Have we downscaled enough?
-	GLuint result;
-	if (to_width > max_width || to_height > max_height) {
-		GLuint new_source_texture = destination_texture;
-		GLuint new_destination_texture =
-		    auxiliary_texture != 0 ? auxiliary_texture : source_texture;
-		result = _gl_average_texture_color(base, new_source_texture,
-		                                   new_destination_texture, 0, fbo,
-		                                   to_width, to_height);
-	} else {
-		result = destination_texture;
-	}
-
-	return result;
-}
-
-/*
- * @brief Builds a 1x1 texture which has color corresponding to the average of all
- * pixels of img by recursively rendering into texture of quorter the size (half
- * width and half height).
- * Returned texture must not be deleted, since it's owned by the gl_image. It will be
- * deleted when the gl_image is released.
- */
-static GLuint gl_average_texture_color(backend_t *base, struct backend_image *img) {
-	auto gd = (struct gl_data *)base;
-	auto inner = (struct gl_texture *)img->inner;
-
-	// Prepare textures which will be used for destination and source of rendering
-	// during downscaling.
-	const int texture_count = ARR_SIZE(inner->auxiliary_texture);
-	if (!inner->auxiliary_texture[0]) {
-		assert(!inner->auxiliary_texture[1]);
-		glGenTextures(texture_count, inner->auxiliary_texture);
-		glActiveTexture(GL_TEXTURE0);
-		for (int i = 0; i < texture_count; i++) {
-			glBindTexture(GL_TEXTURE_2D, inner->auxiliary_texture[i]);
-			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
-			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
-			glTexParameteriv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR,
-			                 (GLint[]){0, 0, 0, 0});
-			glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, inner->width,
-			             inner->height, 0, GL_BGR, GL_UNSIGNED_BYTE, NULL);
-		}
-	}
-
-	// Prepare framebuffer used for rendering and bind it
-	GLuint fbo;
-	glGenFramebuffers(1, &fbo);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
-	glDrawBuffer(GL_COLOR_ATTACHMENT0);
-
-	// Enable shaders
-	glUseProgram(gd->brightness_shader.prog);
-	glUniform2f(glGetUniformLocationChecked(gd->brightness_shader.prog, "texsize"),
-	            (GLfloat)inner->width, (GLfloat)inner->height);
-
-	// Prepare vertex attributes
-	GLuint vao;
-	glGenVertexArrays(1, &vao);
-	glBindVertexArray(vao);
-	GLuint bo[2];
-	glGenBuffers(2, bo);
-	glBindBuffer(GL_ARRAY_BUFFER, bo[0]);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bo[1]);
-	glEnableVertexAttribArray(vert_coord_loc);
-	glEnableVertexAttribArray(vert_in_texcoord_loc);
-	glVertexAttribPointer(vert_coord_loc, 2, GL_INT, GL_FALSE, sizeof(GLint) * 4, NULL);
-	glVertexAttribPointer(vert_in_texcoord_loc, 2, GL_INT, GL_FALSE,
-	                      sizeof(GLint) * 4, (void *)(sizeof(GLint) * 2));
-
-	// Allocate buffers for render input
-	GLint coord[16] = {0};
-	GLuint indices[] = {0, 1, 2, 2, 3, 0};
-	glBufferData(GL_ARRAY_BUFFER, (long)sizeof(*coord) * 16, coord, GL_DYNAMIC_DRAW);
-	glBufferData(GL_ELEMENT_ARRAY_BUFFER, (long)sizeof(*indices) * 6, indices,
-	             GL_STATIC_DRAW);
-
-	// Do actual recursive render to 1x1 texture
-	GLuint result_texture = _gl_average_texture_color(
-	    base, inner->texture, inner->auxiliary_texture[0],
-	    inner->auxiliary_texture[1], fbo, inner->width, inner->height);
-
-	// Cleanup vertex attributes
-	glDisableVertexAttribArray(vert_coord_loc);
-	glDisableVertexAttribArray(vert_in_texcoord_loc);
-	glBindBuffer(GL_ARRAY_BUFFER, 0);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
-	glDeleteBuffers(2, bo);
-	glBindVertexArray(0);
-	glDeleteVertexArrays(1, &vao);
-
-	// Cleanup shaders
-	glUseProgram(0);
-
-	// Cleanup framebuffers
-	glDeleteFramebuffers(1, &fbo);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-	glDrawBuffer(GL_BACK);
-
-	// Cleanup render textures
-	glBindTexture(GL_TEXTURE_2D, 0);
-
-	gl_check_err();
-
-	return result_texture;
-}
-
-/**
- * Render a region with texture data.
- *
- * @param ptex the texture
- * @param target the framebuffer to render into
- * @param dst_x,dst_y the top left corner of region where this texture
- *                    should go. In OpenGL coordinate system (important!).
- * @param reg_tgt     the clip region, in Xorg coordinate system
- * @param reg_visible ignored
- */
-static void _gl_compose(backend_t *base, struct backend_image *img, GLuint target,
-                        GLint *coord, GLuint *indices, int nrects) {
-	auto gd = (struct gl_data *)base;
-	auto inner = (struct gl_texture *)img->inner;
-	if (!img || !inner->texture) {
-		log_error("Missing texture.");
-		return;
-	}
-
-	GLuint brightness = 0;
-	if (img->max_brightness < 1.0) {
-		brightness = gl_average_texture_color(base, img);
-	}
-
-	assert(gd->win_shader.prog);
-	glUseProgram(gd->win_shader.prog);
-	if (gd->win_shader.unifm_opacity >= 0) {
-		glUniform1f(gd->win_shader.unifm_opacity, (float)img->opacity);
-	}
-	if (gd->win_shader.unifm_invert_color >= 0) {
-		glUniform1i(gd->win_shader.unifm_invert_color, img->color_inverted);
-	}
-	if (gd->win_shader.unifm_tex >= 0) {
-		glUniform1i(gd->win_shader.unifm_tex, 0);
-	}
-	if (gd->win_shader.unifm_dim >= 0) {
-		glUniform1f(gd->win_shader.unifm_dim, (float)img->dim);
-	}
-	if (gd->win_shader.unifm_brightness >= 0) {
-		glUniform1i(gd->win_shader.unifm_brightness, 1);
-	}
-	if (gd->win_shader.unifm_max_brightness >= 0) {
-		glUniform1f(gd->win_shader.unifm_max_brightness, (float)img->max_brightness);
-	}
-
-	// log_trace("Draw: %d, %d, %d, %d -> %d, %d (%d, %d) z %d\n",
-	//          x, y, width, height, dx, dy, ptex->width, ptex->height, z);
-
-	// Bind texture
-	glActiveTexture(GL_TEXTURE1);
-	glBindTexture(GL_TEXTURE_2D, brightness);
-	glActiveTexture(GL_TEXTURE0);
-	glBindTexture(GL_TEXTURE_2D, inner->texture);
-
-	GLuint vao;
-	glGenVertexArrays(1, &vao);
-	glBindVertexArray(vao);
-
-	GLuint bo[2];
-	glGenBuffers(2, bo);
-	glBindBuffer(GL_ARRAY_BUFFER, bo[0]);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bo[1]);
-	glBufferData(GL_ARRAY_BUFFER, (long)sizeof(*coord) * nrects * 16, coord, GL_STATIC_DRAW);
-	glBufferData(GL_ELEMENT_ARRAY_BUFFER, (long)sizeof(*indices) * nrects * 6,
-	             indices, GL_STATIC_DRAW);
-
-	glEnableVertexAttribArray(vert_coord_loc);
-	glEnableVertexAttribArray(vert_in_texcoord_loc);
-	glVertexAttribPointer(vert_coord_loc, 2, GL_INT, GL_FALSE, sizeof(GLint) * 4, NULL);
-	glVertexAttribPointer(vert_in_texcoord_loc, 2, GL_INT, GL_FALSE,
-	                      sizeof(GLint) * 4, (void *)(sizeof(GLint) * 2));
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, target);
-	glDrawElements(GL_TRIANGLES, nrects * 6, GL_UNSIGNED_INT, NULL);
-
-	glDisableVertexAttribArray(vert_coord_loc);
-	glDisableVertexAttribArray(vert_in_texcoord_loc);
-	glBindVertexArray(0);
-	glDeleteVertexArrays(1, &vao);
-
-	// Cleanup
-	glBindTexture(GL_TEXTURE_2D, 0);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-	glDrawBuffer(GL_BACK);
-
-	glBindBuffer(GL_ARRAY_BUFFER, 0);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
-	glDeleteBuffers(2, bo);
-
-	glUseProgram(0);
-
-	gl_check_err();
-
-	return;
-}
-
-/// Convert rectangles in X coordinates to OpenGL vertex and texture coordinates
-/// @param[in] nrects, rects   rectangles
-/// @param[in] dst_x, dst_y    origin of the OpenGL texture, affect the calculated texture
-///                            coordinates
-/// @param[in] texture_height  height of the OpenGL texture
-/// @param[in] root_height     height of the back buffer
-/// @param[in] y_inverted      whether the texture is y inverted
-/// @param[out] coord, indices output
-static void
-x_rect_to_coords(int nrects, const rect_t *rects, int dst_x, int dst_y, int texture_height,
-                 int root_height, bool y_inverted, GLint *coord, GLuint *indices) {
-	dst_y = root_height - dst_y;
-	if (y_inverted) {
-		dst_y -= texture_height;
-	}
-
-	for (int i = 0; i < nrects; i++) {
-		// Y-flip. Note after this, crect.y1 > crect.y2
-		rect_t crect = rects[i];
-		crect.y1 = root_height - crect.y1;
-		crect.y2 = root_height - crect.y2;
-
-		// Calculate texture coordinates
-		// (texture_x1, texture_y1), texture coord for the _bottom left_ corner
-		GLint texture_x1 = crect.x1 - dst_x, texture_y1 = crect.y2 - dst_y,
-		      texture_x2 = texture_x1 + (crect.x2 - crect.x1),
-		      texture_y2 = texture_y1 + (crect.y1 - crect.y2);
-
-		// X pixmaps might be Y inverted, invert the texture coordinates
-		if (y_inverted) {
-			texture_y1 = texture_height - texture_y1;
-			texture_y2 = texture_height - texture_y2;
-		}
-
-		// Vertex coordinates
-		auto vx1 = crect.x1;
-		auto vy1 = crect.y2;
-		auto vx2 = crect.x2;
-		auto vy2 = crect.y1;
-
-		// log_trace("Rect %d: %f, %f, %f, %f -> %d, %d, %d, %d",
-		//          ri, rx, ry, rxe, rye, rdx, rdy, rdxe, rdye);
-
-		memcpy(&coord[i * 16],
-		       ((GLint[][2]){
-		           {vx1, vy1},
-		           {texture_x1, texture_y1},
-		           {vx2, vy1},
-		           {texture_x2, texture_y1},
-		           {vx2, vy2},
-		           {texture_x2, texture_y2},
-		           {vx1, vy2},
-		           {texture_x1, texture_y2},
-		       }),
-		       sizeof(GLint[2]) * 8);
-
-		GLuint u = (GLuint)(i * 4);
-		memcpy(&indices[i * 6],
-		       ((GLuint[]){u + 0, u + 1, u + 2, u + 2, u + 3, u + 0}),
-		       sizeof(GLuint) * 6);
-	}
-}
-
-// TODO(yshui) make use of reg_visible
-void gl_compose(backend_t *base, void *image_data,
-		int dst_x1, int dst_y1, int dst_x2, int dst_y2,
-                const region_t *reg_tgt, const region_t *reg_visible attr_unused) {
-	auto gd = (struct gl_data *)base;
-	struct backend_image *img = image_data;
-	auto inner = (struct gl_texture *)img->inner;
-
-	// Painting
-	int nrects;
-	const rect_t *rects;
-	rects = pixman_region32_rectangles((region_t *)reg_tgt, &nrects);
-	if (!nrects) {
-		// Nothing to paint
-		return;
-	}
-
-	// Until we start to use glClipControl, reg_tgt, dst_x and dst_y and
-	// in a different coordinate system than the one OpenGL uses.
-	// OpenGL window coordinate (or NDC) has the origin at the lower left of the
-	// screen, with y axis pointing up; Xorg has the origin at the upper left of the
-	// screen, with y axis pointing down. We have to do some coordinate conversion in
-	// this function
-
-	auto coord = ccalloc(nrects * 16, GLint);
-	auto indices = ccalloc(nrects * 6, GLuint);
-	x_rect_to_coords(nrects, rects, dst_x1, dst_y1, inner->height, gd->height,
-	                 inner->y_inverted, coord, indices);
-
-	// Interpolate the texture coordinates into the specified range
-	for (unsigned int i = 2; i < 16; i+=4) {
-		coord[i+0] = lerp_range(0, dst_x2 - dst_x1, 0, inner->width, coord[i+0]);
-		coord[i+1] = lerp_range(0, dst_y2 - dst_y1, 0, inner->height, coord[i+1]);
-	}
-
-	_gl_compose(base, img, gd->back_fbo, coord, indices, nrects);
-
-	free(indices);
-	free(coord);
-}
-
-/**
- * Blur contents in a particular region.
- */
-bool gl_kernel_blur(backend_t *base, double opacity, void *ctx, const rect_t *extent,
-                    const GLuint vao[2], const int vao_nelems[2]) {
-	auto bctx = (struct gl_blur_context *)ctx;
-	auto gd = (struct gl_data *)base;
-
-	int dst_y_fb_coord = bctx->fb_height - extent->y2;
-
-	int curr = 0;
-	for (int i = 0; i < bctx->npasses; ++i) {
-		const gl_blur_shader_t *p = &bctx->blur_shader[i];
-		assert(p->prog);
-
-		assert(bctx->blur_textures[curr]);
-
-		// The origin to use when sampling from the source texture
-		GLint texorig_x = extent->x1, texorig_y = dst_y_fb_coord;
-		GLint tex_width, tex_height;
-		GLuint src_texture;
-
-		if (i == 0) {
-			src_texture = gd->back_texture;
-			tex_width = gd->width;
-			tex_height = gd->height;
-		} else {
-			src_texture = bctx->blur_textures[curr];
-			auto src_size = bctx->texture_sizes[curr];
-			tex_width = src_size.width;
-			tex_height = src_size.height;
-		}
-
-		glBindTexture(GL_TEXTURE_2D, src_texture);
-		glUseProgram(p->prog);
-		glUniform2f(p->unifm_pixel_norm, 1.0f / (GLfloat)tex_width,
-		            1.0f / (GLfloat)tex_height);
-
-		// The number of indices in the selected vertex array
-		GLsizei nelems;
-
-		if (i < bctx->npasses - 1) {
-			assert(bctx->blur_fbos[0]);
-			assert(bctx->blur_textures[!curr]);
-
-			// not last pass, draw into framebuffer, with resized regions
-			glBindVertexArray(vao[1]);
-			nelems = vao_nelems[1];
-			glBindFramebuffer(GL_DRAW_FRAMEBUFFER, bctx->blur_fbos[0]);
-
-			glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
-			                       GL_TEXTURE_2D, bctx->blur_textures[!curr], 0);
-			glDrawBuffer(GL_COLOR_ATTACHMENT0);
-			if (!gl_check_fb_complete(GL_FRAMEBUFFER)) {
-				return false;
-			}
-
-			glUniform1f(p->unifm_opacity, 1.0);
-		} else {
-			// last pass, draw directly into the back buffer, with origin
-			// regions
-			glBindVertexArray(vao[0]);
-			nelems = vao_nelems[0];
-			glBindFramebuffer(GL_FRAMEBUFFER, gd->back_fbo);
-
-			glUniform1f(p->unifm_opacity, (float)opacity);
-		}
-
-		glUniform2f(p->texorig_loc, (GLfloat)texorig_x, (GLfloat)texorig_y);
-		glDrawElements(GL_TRIANGLES, nelems, GL_UNSIGNED_INT, NULL);
-
-		// XXX use multiple draw calls is probably going to be slow than
-		//     just simply blur the whole area.
-
-		curr = !curr;
-	}
-
-	return true;
-}
-
-bool gl_dual_kawase_blur(backend_t *base, double opacity, void *ctx, const rect_t *extent,
-                         const GLuint vao[2], const int vao_nelems[2]) {
-	auto bctx = (struct gl_blur_context *)ctx;
-	auto gd = (struct gl_data *)base;
-
-	int dst_y_fb_coord = bctx->fb_height - extent->y2;
-
-	int iterations = bctx->blur_texture_count;
-	int scale_factor = 1;
-
-	// Kawase downsample pass
-	const gl_blur_shader_t *down_pass = &bctx->blur_shader[0];
-	assert(down_pass->prog);
-	glUseProgram(down_pass->prog);
-
-	glUniform2f(down_pass->texorig_loc, (GLfloat)extent->x1, (GLfloat)dst_y_fb_coord);
-
-	for (int i = 0; i < iterations; ++i) {
-		// Scale output width / height by half in each iteration
-		scale_factor <<= 1;
-
-		GLuint src_texture;
-		int tex_width, tex_height;
-
-		if (i == 0) {
-			// first pass: copy from back buffer
-			src_texture = gd->back_texture;
-			tex_width = gd->width;
-			tex_height = gd->height;
-		} else {
-			// copy from previous pass
-			src_texture = bctx->blur_textures[i - 1];
-			auto src_size = bctx->texture_sizes[i - 1];
-			tex_width = src_size.width;
-			tex_height = src_size.height;
-		}
-
-		assert(src_texture);
-		assert(bctx->blur_fbos[i]);
-
-		glBindTexture(GL_TEXTURE_2D, src_texture);
-		glBindVertexArray(vao[1]);
-		auto nelems = vao_nelems[1];
-		glBindFramebuffer(GL_DRAW_FRAMEBUFFER, bctx->blur_fbos[i]);
-		glDrawBuffer(GL_COLOR_ATTACHMENT0);
-
-		glUniform1f(down_pass->scale_loc, (GLfloat)scale_factor);
-
-		glUniform2f(down_pass->unifm_pixel_norm, 1.0f / (GLfloat)tex_width,
-		            1.0f / (GLfloat)tex_height);
-
-		glDrawElements(GL_TRIANGLES, nelems, GL_UNSIGNED_INT, NULL);
-	}
-
-	// Kawase upsample pass
-	const gl_blur_shader_t *up_pass = &bctx->blur_shader[1];
-	assert(up_pass->prog);
-	glUseProgram(up_pass->prog);
-
-	glUniform2f(up_pass->texorig_loc, (GLfloat)extent->x1, (GLfloat)dst_y_fb_coord);
-
-	for (int i = iterations - 1; i >= 0; --i) {
-		// Scale output width / height back by two in each iteration
-		scale_factor >>= 1;
-
-		const GLuint src_texture = bctx->blur_textures[i];
-		assert(src_texture);
-
-		// Calculate normalized half-width/-height of a src pixel
-		auto src_size = bctx->texture_sizes[i];
-		int tex_width = src_size.width;
-		int tex_height = src_size.height;
-
-		// The number of indices in the selected vertex array
-		GLsizei nelems;
-
-		glBindTexture(GL_TEXTURE_2D, src_texture);
-		if (i > 0) {
-			assert(bctx->blur_fbos[i - 1]);
-
-			// not last pass, draw into next framebuffer
-			glBindVertexArray(vao[1]);
-			nelems = vao_nelems[1];
-			glBindFramebuffer(GL_DRAW_FRAMEBUFFER, bctx->blur_fbos[i - 1]);
-			glDrawBuffer(GL_COLOR_ATTACHMENT0);
-
-			glUniform1f(up_pass->unifm_opacity, (GLfloat)1);
-		} else {
-			// last pass, draw directly into the back buffer
-			glBindVertexArray(vao[0]);
-			nelems = vao_nelems[0];
-			glBindFramebuffer(GL_FRAMEBUFFER, gd->back_fbo);
-
-			glUniform1f(up_pass->unifm_opacity, (GLfloat)opacity);
-		}
-
-		glUniform1f(up_pass->scale_loc, (GLfloat)scale_factor);
-		glUniform2f(up_pass->unifm_pixel_norm, 1.0f / (GLfloat)tex_width,
-		            1.0f / (GLfloat)tex_height);
-
-		glDrawElements(GL_TRIANGLES, nelems, GL_UNSIGNED_INT, NULL);
-	}
-
-	return true;
-}
-
-bool gl_blur(backend_t *base, double opacity, void *ctx, const region_t *reg_blur,
-             const region_t *reg_visible attr_unused) {
-	auto bctx = (struct gl_blur_context *)ctx;
-	auto gd = (struct gl_data *)base;
-
-	bool ret = false;
-
-	if (gd->width != bctx->fb_width || gd->height != bctx->fb_height) {
-		// Resize the temporary textures used for blur in case the root
-		// size changed
-		bctx->fb_width = gd->width;
-		bctx->fb_height = gd->height;
-
-		for (int i = 0; i < bctx->blur_texture_count; ++i) {
-			auto tex_size = bctx->texture_sizes + i;
-			if (bctx->method == BLUR_METHOD_DUAL_KAWASE) {
-				// Use smaller textures for each iteration (quarter of the
-				// previous texture)
-				tex_size->width = 1 + ((bctx->fb_width - 1) >> (i + 1));
-				tex_size->height = 1 + ((bctx->fb_height - 1) >> (i + 1));
-			} else {
-				tex_size->width = bctx->fb_width;
-				tex_size->height = bctx->fb_height;
-			}
-
-			glBindTexture(GL_TEXTURE_2D, bctx->blur_textures[i]);
-			glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, tex_size->width,
-			             tex_size->height, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL);
-
-			if (bctx->method == BLUR_METHOD_DUAL_KAWASE) {
-				// Attach texture to FBO target
-				glBindFramebuffer(GL_DRAW_FRAMEBUFFER, bctx->blur_fbos[i]);
-				glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER,
-				                       GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
-				                       bctx->blur_textures[i], 0);
-				if (!gl_check_fb_complete(GL_FRAMEBUFFER)) {
-					glBindFramebuffer(GL_FRAMEBUFFER, 0);
-					return false;
-				}
-			}
-		}
-		glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-	}
-
-	// Remainder: regions are in Xorg coordinates
-	auto reg_blur_resized =
-	    resize_region(reg_blur, bctx->resize_width, bctx->resize_height);
-	const rect_t *extent = pixman_region32_extents((region_t *)reg_blur),
-	             *extent_resized = pixman_region32_extents(&reg_blur_resized);
-	int width = extent->x2 - extent->x1, height = extent->y2 - extent->y1;
-	if (width == 0 || height == 0) {
-		return true;
-	}
-
-	int nrects, nrects_resized;
-	const rect_t *rects = pixman_region32_rectangles((region_t *)reg_blur, &nrects),
-	             *rects_resized =
-	                 pixman_region32_rectangles(&reg_blur_resized, &nrects_resized);
-	if (!nrects || !nrects_resized) {
-		return true;
-	}
-
-	auto coord = ccalloc(nrects * 16, GLint);
-	auto indices = ccalloc(nrects * 6, GLuint);
-	x_rect_to_coords(nrects, rects, extent_resized->x1, extent_resized->y2,
-	                 bctx->fb_height, gd->height, false, coord, indices);
-
-	auto coord_resized = ccalloc(nrects_resized * 16, GLint);
-	auto indices_resized = ccalloc(nrects_resized * 6, GLuint);
-	x_rect_to_coords(nrects_resized, rects_resized, extent_resized->x1,
-	                 extent_resized->y2, bctx->fb_height, bctx->fb_height, false,
-	                 coord_resized, indices_resized);
-	pixman_region32_fini(&reg_blur_resized);
-
-	GLuint vao[2];
-	glGenVertexArrays(2, vao);
-	GLuint bo[4];
-	glGenBuffers(4, bo);
-
-	glBindVertexArray(vao[0]);
-	glBindBuffer(GL_ARRAY_BUFFER, bo[0]);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bo[1]);
-	glBufferData(GL_ARRAY_BUFFER, (long)sizeof(*coord) * nrects * 16, coord, GL_STATIC_DRAW);
-	glBufferData(GL_ELEMENT_ARRAY_BUFFER, (long)sizeof(*indices) * nrects * 6,
-	             indices, GL_STATIC_DRAW);
-	glEnableVertexAttribArray(vert_coord_loc);
-	glEnableVertexAttribArray(vert_in_texcoord_loc);
-	glVertexAttribPointer(vert_coord_loc, 2, GL_INT, GL_FALSE, sizeof(GLint) * 4, NULL);
-	glVertexAttribPointer(vert_in_texcoord_loc, 2, GL_INT, GL_FALSE,
-	                      sizeof(GLint) * 4, (void *)(sizeof(GLint) * 2));
-
-	glBindVertexArray(vao[1]);
-	glBindBuffer(GL_ARRAY_BUFFER, bo[2]);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bo[3]);
-	glBufferData(GL_ARRAY_BUFFER, (long)sizeof(*coord_resized) * nrects_resized * 16,
-	             coord_resized, GL_STATIC_DRAW);
-	glBufferData(GL_ELEMENT_ARRAY_BUFFER,
-	             (long)sizeof(*indices_resized) * nrects_resized * 6, indices_resized,
-	             GL_STATIC_DRAW);
-	glEnableVertexAttribArray(vert_coord_loc);
-	glEnableVertexAttribArray(vert_in_texcoord_loc);
-	glVertexAttribPointer(vert_coord_loc, 2, GL_INT, GL_FALSE, sizeof(GLint) * 4, NULL);
-	glVertexAttribPointer(vert_in_texcoord_loc, 2, GL_INT, GL_FALSE,
-	                      sizeof(GLint) * 4, (void *)(sizeof(GLint) * 2));
-
-	int vao_nelems[2] = {nrects * 6, nrects_resized * 6};
-
-	if (bctx->method == BLUR_METHOD_DUAL_KAWASE) {
-		ret = gl_dual_kawase_blur(base, opacity, ctx, extent_resized, vao, vao_nelems);
-	} else {
-		ret = gl_kernel_blur(base, opacity, ctx, extent_resized, vao, vao_nelems);
-	}
-
-	glBindFramebuffer(GL_FRAMEBUFFER, 0);
-	glBindTexture(GL_TEXTURE_2D, 0);
-	glBindBuffer(GL_ARRAY_BUFFER, 0);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
-	glDeleteBuffers(4, bo);
-	glBindVertexArray(0);
-	glDeleteVertexArrays(2, vao);
-	glUseProgram(0);
-
-	free(indices);
-	free(coord);
-	free(indices_resized);
-	free(coord_resized);
-
-	gl_check_err();
-	return ret;
-}
-
-// clang-format off
-const char *vertex_shader = GLSL(330,
-	uniform mat4 projection;
-	uniform float scale = 1.0;
-	uniform vec2 texorig;
-	layout(location = 0) in vec2 coord;
-	layout(location = 1) in vec2 in_texcoord;
-	out vec2 texcoord;
-	void main() {
-		gl_Position = projection * vec4(coord, 0, scale);
-		texcoord = in_texcoord + texorig;
-	}
-);
-// clang-format on
-
-/**
- * Load a GLSL main program from shader strings.
- */
-static int gl_win_shader_from_string(const char *vshader_str, const char *fshader_str,
-                                     gl_win_shader_t *ret) {
-	// Build program
-	ret->prog = gl_create_program_from_str(vshader_str, fshader_str);
-	if (!ret->prog) {
-		log_error("Failed to create GLSL program.");
-		return -1;
-	}
-
-	// Get uniform addresses
-	ret->unifm_opacity = glGetUniformLocationChecked(ret->prog, "opacity");
-	ret->unifm_invert_color = glGetUniformLocationChecked(ret->prog, "invert_color");
-	ret->unifm_tex = glGetUniformLocationChecked(ret->prog, "tex");
-	ret->unifm_dim = glGetUniformLocationChecked(ret->prog, "dim");
-	ret->unifm_brightness = glGetUniformLocationChecked(ret->prog, "brightness");
-	ret->unifm_max_brightness =
-	    glGetUniformLocationChecked(ret->prog, "max_brightness");
-
-	gl_check_err();
-
-	return true;
-}
-
-/**
- * Callback to run on root window size change.
- */
-void gl_resize(struct gl_data *gd, int width, int height) {
-	GLint viewport_dimensions[2];
-	glGetIntegerv(GL_MAX_VIEWPORT_DIMS, viewport_dimensions);
-
-	gd->height = height;
-	gd->width = width;
-
-	assert(viewport_dimensions[0] >= gd->width);
-	assert(viewport_dimensions[1] >= gd->height);
-
-	glBindTexture(GL_TEXTURE_2D, gd->back_texture);
-	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, width, height, 0, GL_BGR,
-	             GL_UNSIGNED_BYTE, NULL);
-
-	gl_check_err();
-}
-
-// clang-format off
-static const char dummy_frag[] = GLSL(330,
-	uniform sampler2D tex;
-	in vec2 texcoord;
-	void main() {
-		gl_FragColor = texelFetch(tex, ivec2(texcoord.xy), 0);
-	}
-);
-
-static const char fill_frag[] = GLSL(330,
-	uniform vec4 color;
-	void main() {
-		gl_FragColor = color;
-	}
-);
-
-static const char fill_vert[] = GLSL(330,
-	layout(location = 0) in vec2 in_coord;
-	uniform mat4 projection;
-	void main() {
-		gl_Position = projection * vec4(in_coord, 0, 1);
-	}
-);
-
-static const char interpolating_frag[] = GLSL(330,
-	uniform sampler2D tex;
-	in vec2 texcoord;
-	void main() {
-		gl_FragColor = vec4(texture2D(tex, vec2(texcoord.xy), 0).rgb, 1);
-	}
-);
-
-static const char interpolating_vert[] = GLSL(330,
-	uniform mat4 projection;
-	uniform vec2 texsize;
-	layout(location = 0) in vec2 in_coord;
-	layout(location = 1) in vec2 in_texcoord;
-	out vec2 texcoord;
-	void main() {
-		gl_Position = projection * vec4(in_coord, 0, 1);
-		texcoord = in_texcoord / texsize;
-	}
-);
-// clang-format on
-
-/// Fill a given region in bound framebuffer.
-/// @param[in] y_inverted whether the y coordinates in `clip` should be inverted
-static void _gl_fill(backend_t *base, struct color c, const region_t *clip, GLuint target,
-                     int height, bool y_inverted) {
-	static const GLuint fill_vert_in_coord_loc = 0;
-	int nrects;
-	const rect_t *rect = pixman_region32_rectangles((region_t *)clip, &nrects);
-	auto gd = (struct gl_data *)base;
-
-	GLuint vao;
-	glGenVertexArrays(1, &vao);
-	glBindVertexArray(vao);
-
-	GLuint bo[2];
-	glGenBuffers(2, bo);
-	glUseProgram(gd->fill_shader.prog);
-	glUniform4f(gd->fill_shader.color_loc, (GLfloat)c.red, (GLfloat)c.green,
-	            (GLfloat)c.blue, (GLfloat)c.alpha);
-	glEnableVertexAttribArray(fill_vert_in_coord_loc);
-	glBindBuffer(GL_ARRAY_BUFFER, bo[0]);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bo[1]);
-
-	auto coord = ccalloc(nrects * 8, GLint);
-	auto indices = ccalloc(nrects * 6, GLuint);
-	for (int i = 0; i < nrects; i++) {
-		GLint y1 = y_inverted ? height - rect[i].y2 : rect[i].y1,
-		      y2 = y_inverted ? height - rect[i].y1 : rect[i].y2;
-		// clang-format off
-		memcpy(&coord[i * 8],
-		       ((GLint[][2]){
-		           {rect[i].x1, y1}, {rect[i].x2, y1},
-		           {rect[i].x2, y2}, {rect[i].x1, y2}}),
-		       sizeof(GLint[2]) * 4);
-		// clang-format on
-		indices[i * 6 + 0] = (GLuint)i * 4 + 0;
-		indices[i * 6 + 1] = (GLuint)i * 4 + 1;
-		indices[i * 6 + 2] = (GLuint)i * 4 + 2;
-		indices[i * 6 + 3] = (GLuint)i * 4 + 2;
-		indices[i * 6 + 4] = (GLuint)i * 4 + 3;
-		indices[i * 6 + 5] = (GLuint)i * 4 + 0;
-	}
-	glBufferData(GL_ARRAY_BUFFER, nrects * 8 * (long)sizeof(*coord), coord, GL_STREAM_DRAW);
-	glBufferData(GL_ELEMENT_ARRAY_BUFFER, nrects * 6 * (long)sizeof(*indices),
-	             indices, GL_STREAM_DRAW);
-
-	glVertexAttribPointer(fill_vert_in_coord_loc, 2, GL_INT, GL_FALSE,
-	                      sizeof(*coord) * 2, (void *)0);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, target);
-	glDrawElements(GL_TRIANGLES, nrects * 6, GL_UNSIGNED_INT, NULL);
-
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-	glBindBuffer(GL_ARRAY_BUFFER, 0);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
-	glDisableVertexAttribArray(fill_vert_in_coord_loc);
-	glBindVertexArray(0);
-	glDeleteVertexArrays(1, &vao);
-
-	glDeleteBuffers(2, bo);
-	free(indices);
-	free(coord);
-
-	gl_check_err();
-}
-
-void gl_fill(backend_t *base, struct color c, const region_t *clip) {
-	auto gd = (struct gl_data *)base;
-	return _gl_fill(base, c, clip, gd->back_fbo, gd->height, true);
-}
-
-static void gl_release_image_inner(backend_t *base, struct gl_texture *inner) {
-	auto gd = (struct gl_data *)base;
-	gd->release_user_data(base, inner);
-	assert(inner->user_data == NULL);
-
-	glDeleteTextures(1, &inner->texture);
-	glDeleteTextures(2, inner->auxiliary_texture);
-	free(inner);
-	gl_check_err();
-}
-
-void gl_release_image(backend_t *base, void *image_data) {
-	struct backend_image *wd = image_data;
-	auto inner = (struct gl_texture *)wd->inner;
-	inner->refcount--;
-	assert(inner->refcount >= 0);
-	if (inner->refcount == 0) {
-		gl_release_image_inner(base, inner);
-	}
-	free(wd);
-}
-
-static inline void gl_free_blur_shader(gl_blur_shader_t *shader) {
-	if (shader->prog) {
-		glDeleteProgram(shader->prog);
-	}
-
-	shader->prog = 0;
-}
-
-void gl_destroy_blur_context(backend_t *base attr_unused, void *ctx) {
-	auto bctx = (struct gl_blur_context *)ctx;
-	// Free GLSL shaders/programs
-	for (int i = 0; i < bctx->npasses; ++i) {
-		gl_free_blur_shader(&bctx->blur_shader[i]);
-	}
-	free(bctx->blur_shader);
-
-	if (bctx->blur_texture_count && bctx->blur_textures) {
-		glDeleteTextures(bctx->blur_texture_count, bctx->blur_textures);
-		free(bctx->blur_textures);
-	}
-	if (bctx->blur_texture_count && bctx->texture_sizes) {
-		free(bctx->texture_sizes);
-	}
-	if (bctx->blur_fbo_count && bctx->blur_fbos) {
-		glDeleteFramebuffers(bctx->blur_fbo_count, bctx->blur_fbos);
-		free(bctx->blur_fbos);
-	}
-
-	bctx->blur_texture_count = 0;
-	bctx->blur_fbo_count = 0;
-
-	free(bctx);
-
-	gl_check_err();
-}
-
-/**
- * Initialize GL blur filters.
- */
-bool gl_create_kernel_blur_context(void *blur_context, GLfloat *projection,
-                                   enum blur_method method, void *args) {
-	bool success = false;
-	auto ctx = (struct gl_blur_context *)blur_context;
-
-	struct conv **kernels;
-
-	int nkernels;
-	ctx->method = BLUR_METHOD_KERNEL;
-	if (method == BLUR_METHOD_KERNEL) {
-		nkernels = ((struct kernel_blur_args *)args)->kernel_count;
-		kernels = ((struct kernel_blur_args *)args)->kernels;
-	} else {
-		kernels = generate_blur_kernel(method, args, &nkernels);
-	}
-
-	if (!nkernels) {
-		ctx->method = BLUR_METHOD_NONE;
-		return true;
-	}
-
-	// Specify required textures and FBOs
-	ctx->blur_texture_count = 2;
-	ctx->blur_fbo_count = 1;
-
-	ctx->blur_shader = ccalloc(max2(2, nkernels), gl_blur_shader_t);
-
-	char *lc_numeric_old = strdup(setlocale(LC_NUMERIC, NULL));
-	// Enforce LC_NUMERIC locale "C" here to make sure decimal point is sane
-	// Thanks to hiciu for reporting.
-	setlocale(LC_NUMERIC, "C");
-
-	// clang-format off
-	static const char *FRAG_SHADER_BLUR = GLSL(330,
-		%s\n // other extension pragmas
-		uniform sampler2D tex_src;
-		uniform vec2 pixel_norm;
-		uniform float opacity;
-		in vec2 texcoord;
-		out vec4 out_color;
-		void main() {
-			vec2 uv = texcoord * pixel_norm;
-			vec4 sum = vec4(0.0, 0.0, 0.0, 0.0);
-			%s //body of the convolution
-			out_color = sum / float(%.7g) * opacity;
-		}
-	);
-	static const char *FRAG_SHADER_BLUR_ADD = QUOTE(
-		sum += float(%.7g) * texture2D(tex_src, uv + pixel_norm * vec2(%.7g, %.7g));
-	);
-	// clang-format on
-
-	const char *shader_add = FRAG_SHADER_BLUR_ADD;
-	char *extension = strdup("");
-
-	for (int i = 0; i < nkernels; i++) {
-		auto kern = kernels[i];
-		// Build shader
-		int width = kern->w, height = kern->h;
-		int nele = width * height;
-		// '%.7g' is at most 14 characters, inserted 3 times
-		size_t body_len = (strlen(shader_add) + 42) * (uint)nele;
-		char *shader_body = ccalloc(body_len, char);
-		char *pc = shader_body;
-
-		// Make use of the linear interpolation hardware by sampling 2 pixels with
-		// one texture access by sampling between both pixels based on their
-		// relative weight. Easiest done in a single dimension as 2D bilinear
-		// filtering would raise additional constraints on the kernels. Therefore
-		// only use interpolation along the larger dimension.
-		double sum = 0.0;
-		if (width > height) {
-			// use interpolation in x dimension (width)
-			for (int j = 0; j < height; ++j) {
-				for (int k = 0; k < width; k += 2) {
-					double val1, val2;
-					val1 = kern->data[j * width + k];
-					val2 = (k + 1 < width)
-					           ? kern->data[j * width + k + 1]
-					           : 0;
-
-					double combined_weight = val1 + val2;
-					if (combined_weight == 0) {
-						continue;
-					}
-					sum += combined_weight;
-
-					double offset_x =
-					    k + (val2 / combined_weight) - (width / 2);
-					double offset_y = j - (height / 2);
-					pc += snprintf(
-					    pc, body_len - (ulong)(pc - shader_body),
-					    shader_add, combined_weight, offset_x, offset_y);
-					assert(pc < shader_body + body_len);
-				}
-			}
-		} else {
-			// use interpolation in y dimension (height)
-			for (int j = 0; j < height; j += 2) {
-				for (int k = 0; k < width; ++k) {
-					double val1, val2;
-					val1 = kern->data[j * width + k];
-					val2 = (j + 1 < height)
-					           ? kern->data[(j + 1) * width + k]
-					           : 0;
-
-					double combined_weight = val1 + val2;
-					if (combined_weight == 0) {
-						continue;
-					}
-					sum += combined_weight;
-
-					double offset_x = k - (width / 2);
-					double offset_y =
-					    j + (val2 / combined_weight) - (height / 2);
-					pc += snprintf(
-					    pc, body_len - (ulong)(pc - shader_body),
-					    shader_add, combined_weight, offset_x, offset_y);
-					assert(pc < shader_body + body_len);
-				}
-			}
-		}
-
-		auto pass = ctx->blur_shader + i;
-		size_t shader_len = strlen(FRAG_SHADER_BLUR) + strlen(extension) +
-		                    strlen(shader_body) + 10 /* sum */ +
-		                    1 /* null terminator */;
-		char *shader_str = ccalloc(shader_len, char);
-		auto real_shader_len = snprintf(shader_str, shader_len, FRAG_SHADER_BLUR,
-		                                extension, shader_body, sum);
-		CHECK(real_shader_len >= 0);
-		CHECK((size_t)real_shader_len < shader_len);
-		free(shader_body);
-
-		// Build program
-		pass->prog = gl_create_program_from_str(vertex_shader, shader_str);
-		free(shader_str);
-		if (!pass->prog) {
-			log_error("Failed to create GLSL program.");
-			success = false;
-			goto out;
-		}
-		glBindFragDataLocation(pass->prog, 0, "out_color");
-
-		// Get uniform addresses
-		pass->unifm_pixel_norm =
-		    glGetUniformLocationChecked(pass->prog, "pixel_norm");
-		pass->unifm_opacity = glGetUniformLocationChecked(pass->prog, "opacity");
-		pass->texorig_loc = glGetUniformLocationChecked(pass->prog, "texorig");
-
-		// Setup projection matrix
-		glUseProgram(pass->prog);
-		int pml = glGetUniformLocationChecked(pass->prog, "projection");
-		glUniformMatrix4fv(pml, 1, false, projection);
-		glUseProgram(0);
-
-		ctx->resize_width += kern->w / 2;
-		ctx->resize_height += kern->h / 2;
-	}
-
-	if (nkernels == 1) {
-		// Generate an extra null pass so we don't need special code path for
-		// the single pass case
-		auto pass = &ctx->blur_shader[1];
-		pass->prog = gl_create_program_from_str(vertex_shader, dummy_frag);
-		pass->unifm_pixel_norm = -1;
-		pass->unifm_opacity = -1;
-		pass->texorig_loc = glGetUniformLocationChecked(pass->prog, "texorig");
-
-		// Setup projection matrix
-		glUseProgram(pass->prog);
-		int pml = glGetUniformLocationChecked(pass->prog, "projection");
-		glUniformMatrix4fv(pml, 1, false, projection);
-		glUseProgram(0);
-
-		ctx->npasses = 2;
-	} else {
-		ctx->npasses = nkernels;
-	}
-
-	success = true;
-out:
-	if (method != BLUR_METHOD_KERNEL) {
-		// We generated the blur kernels, so we need to free them
-		for (int i = 0; i < nkernels; i++) {
-			free(kernels[i]);
-		}
-		free(kernels);
-	}
-
-	free(extension);
-	// Restore LC_NUMERIC
-	setlocale(LC_NUMERIC, lc_numeric_old);
-	free(lc_numeric_old);
-
-	return success;
-}
-
-bool gl_create_dual_kawase_blur_context(void *blur_context, GLfloat *projection,
-                                        enum blur_method method, void *args) {
-	bool success = false;
-	auto ctx = (struct gl_blur_context *)blur_context;
-
-	ctx->method = method;
-
-	auto blur_params = generate_dual_kawase_params(args);
-
-	// Specify required textures and FBOs
-	ctx->blur_texture_count = blur_params->iterations;
-	ctx->blur_fbo_count = blur_params->iterations;
-
-	ctx->resize_width += blur_params->expand;
-	ctx->resize_height += blur_params->expand;
-
-	ctx->npasses = 2;
-	ctx->blur_shader = ccalloc(ctx->npasses, gl_blur_shader_t);
-
-	char *lc_numeric_old = strdup(setlocale(LC_NUMERIC, NULL));
-	// Enforce LC_NUMERIC locale "C" here to make sure decimal point is sane
-	// Thanks to hiciu for reporting.
-	setlocale(LC_NUMERIC, "C");
-
-	// Dual-kawase downsample shader / program
-	auto down_pass = ctx->blur_shader;
-	{
-		// clang-format off
-		static const char *FRAG_SHADER_DOWN = GLSL(330,
-			uniform sampler2D tex_src;
-			uniform float scale = 1.0;
-			uniform vec2 pixel_norm;
-			in vec2 texcoord;
-			out vec4 out_color;
-			void main() {
-				vec2 offset = %.7g * pixel_norm;
-				vec2 uv = texcoord * pixel_norm * (2.0 / scale);
-				vec4 sum = texture2D(tex_src, uv) * 4.0;
-				sum += texture2D(tex_src, uv - vec2(0.5, 0.5) * offset);
-				sum += texture2D(tex_src, uv + vec2(0.5, 0.5) * offset);
-				sum += texture2D(tex_src, uv + vec2(0.5, -0.5) * offset);
-				sum += texture2D(tex_src, uv - vec2(0.5, -0.5) * offset);
-				out_color = sum / 8.0;
-			}
-		);
-		// clang-format on
-
-		// Build shader
-		size_t shader_len =
-		    strlen(FRAG_SHADER_DOWN) + 10 /* offset */ + 1 /* null terminator */;
-		char *shader_str = ccalloc(shader_len, char);
-		auto real_shader_len =
-		    snprintf(shader_str, shader_len, FRAG_SHADER_DOWN, blur_params->offset);
-		CHECK(real_shader_len >= 0);
-		CHECK((size_t)real_shader_len < shader_len);
-
-		// Build program
-		down_pass->prog = gl_create_program_from_str(vertex_shader, shader_str);
-		free(shader_str);
-		if (!down_pass->prog) {
-			log_error("Failed to create GLSL program.");
-			success = false;
-			goto out;
-		}
-		glBindFragDataLocation(down_pass->prog, 0, "out_color");
-
-		// Get uniform addresses
-		down_pass->unifm_pixel_norm =
-		    glGetUniformLocationChecked(down_pass->prog, "pixel_norm");
-		down_pass->texorig_loc =
-		    glGetUniformLocationChecked(down_pass->prog, "texorig");
-		down_pass->scale_loc =
-		    glGetUniformLocationChecked(down_pass->prog, "scale");
-
-		// Setup projection matrix
-		glUseProgram(down_pass->prog);
-		int pml = glGetUniformLocationChecked(down_pass->prog, "projection");
-		glUniformMatrix4fv(pml, 1, false, projection);
-		glUseProgram(0);
-	}
-
-	// Dual-kawase upsample shader / program
-	auto up_pass = ctx->blur_shader + 1;
-	{
-		// clang-format off
-		static const char *FRAG_SHADER_UP = GLSL(330,
-			uniform sampler2D tex_src;
-			uniform float scale = 1.0;
-			uniform vec2 pixel_norm;
-			uniform float opacity;
-			in vec2 texcoord;
-			out vec4 out_color;
-			void main() {
-				vec2 offset = %.7g * pixel_norm;
-				vec2 uv = texcoord * pixel_norm / (2 * scale);
-				vec4 sum = texture2D(tex_src, uv + vec2(-1.0, 0.0) * offset);
-				sum += texture2D(tex_src, uv + vec2(-0.5, 0.5) * offset) * 2.0;
-				sum += texture2D(tex_src, uv + vec2(0.0, 1.0) * offset);
-				sum += texture2D(tex_src, uv + vec2(0.5, 0.5) * offset) * 2.0;
-				sum += texture2D(tex_src, uv + vec2(1.0, 0.0) * offset);
-				sum += texture2D(tex_src, uv + vec2(0.5, -0.5) * offset) * 2.0;
-				sum += texture2D(tex_src, uv + vec2(0.0, -1.0) * offset);
-				sum += texture2D(tex_src, uv + vec2(-0.5, -0.5) * offset) * 2.0;
-				out_color = sum / 12.0 * opacity;
-			}
-		);
-		// clang-format on
-
-		// Build shader
-		size_t shader_len =
-		    strlen(FRAG_SHADER_UP) + 10 /* offset */ + 1 /* null terminator */;
-		char *shader_str = ccalloc(shader_len, char);
-		auto real_shader_len =
-		    snprintf(shader_str, shader_len, FRAG_SHADER_UP, blur_params->offset);
-		CHECK(real_shader_len >= 0);
-		CHECK((size_t)real_shader_len < shader_len);
-
-		// Build program
-		up_pass->prog = gl_create_program_from_str(vertex_shader, shader_str);
-		free(shader_str);
-		if (!up_pass->prog) {
-			log_error("Failed to create GLSL program.");
-			success = false;
-			goto out;
-		}
-		glBindFragDataLocation(up_pass->prog, 0, "out_color");
-
-		// Get uniform addresses
-		up_pass->unifm_pixel_norm =
-		    glGetUniformLocationChecked(up_pass->prog, "pixel_norm");
-		up_pass->unifm_opacity =
-		    glGetUniformLocationChecked(up_pass->prog, "opacity");
-		up_pass->texorig_loc =
-		    glGetUniformLocationChecked(up_pass->prog, "texorig");
-		up_pass->scale_loc = glGetUniformLocationChecked(up_pass->prog, "scale");
-
-		// Setup projection matrix
-		glUseProgram(up_pass->prog);
-		int pml = glGetUniformLocationChecked(up_pass->prog, "projection");
-		glUniformMatrix4fv(pml, 1, false, projection);
-		glUseProgram(0);
-	}
-
-	success = true;
-out:
-	free(blur_params);
-
-	if (!success) {
-		ctx = NULL;
-	}
-
-	// Restore LC_NUMERIC
-	setlocale(LC_NUMERIC, lc_numeric_old);
-	free(lc_numeric_old);
-
-	return success;
-}
-
-void *gl_create_blur_context(backend_t *base, enum blur_method method, void *args) {
-	bool success;
-	auto gd = (struct gl_data *)base;
-
-	auto ctx = ccalloc(1, struct gl_blur_context);
-
-	if (!method || method >= BLUR_METHOD_INVALID) {
-		ctx->method = BLUR_METHOD_NONE;
-		return ctx;
-	}
-
-	// Set projection matrix to gl viewport dimensions so we can use screen
-	// coordinates for all vertices
-	// Note: OpenGL matrices are column major
-	GLint viewport_dimensions[2];
-	glGetIntegerv(GL_MAX_VIEWPORT_DIMS, viewport_dimensions);
-	GLfloat projection_matrix[4][4] = {{2.0f / (GLfloat)viewport_dimensions[0], 0, 0, 0},
-	                                   {0, 2.0f / (GLfloat)viewport_dimensions[1], 0, 0},
-	                                   {0, 0, 0, 0},
-	                                   {-1, -1, 0, 1}};
-
-	if (method == BLUR_METHOD_DUAL_KAWASE) {
-		success = gl_create_dual_kawase_blur_context(ctx, projection_matrix[0],
-		                                             method, args);
-	} else {
-		success =
-		    gl_create_kernel_blur_context(ctx, projection_matrix[0], method, args);
-	}
-	if (!success || ctx->method == BLUR_METHOD_NONE) {
-		goto out;
-	}
-
-	// Texture size will be defined by gl_blur
-	ctx->blur_textures = ccalloc(ctx->blur_texture_count, GLuint);
-	ctx->texture_sizes = ccalloc(ctx->blur_texture_count, struct texture_size);
-	glGenTextures(ctx->blur_texture_count, ctx->blur_textures);
-
-	for (int i = 0; i < ctx->blur_texture_count; ++i) {
-		glBindTexture(GL_TEXTURE_2D, ctx->blur_textures[i]);
-		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
-		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-	}
-
-	// Generate FBO and textures when needed
-	ctx->blur_fbos = ccalloc(ctx->blur_fbo_count, GLuint);
-	glGenFramebuffers(ctx->blur_fbo_count, ctx->blur_fbos);
-
-	for (int i = 0; i < ctx->blur_fbo_count; ++i) {
-		if (!ctx->blur_fbos[i]) {
-			log_error("Failed to generate framebuffer objects for blur");
-			success = false;
-			goto out;
-		}
-	}
-
-out:
-	if (!success) {
-		gl_destroy_blur_context(&gd->base, ctx);
-		ctx = NULL;
-	}
-
-	gl_check_err();
-	return ctx;
-}
-
-void gl_get_blur_size(void *blur_context, int *width, int *height) {
-	auto ctx = (struct gl_blur_context *)blur_context;
-	*width = ctx->resize_width;
-	*height = ctx->resize_height;
-}
-
-// clang-format off
-const char *win_shader_glsl = GLSL(330,
-	uniform float opacity;
-	uniform float dim;
-	uniform bool invert_color;
-	in vec2 texcoord;
-	uniform sampler2D tex;
-	uniform sampler2D brightness;
-	uniform float max_brightness;
-
-	void main() {
-		vec4 c = texelFetch(tex, ivec2(texcoord), 0);
-		if (invert_color) {
-			c = vec4(c.aaa - c.rgb, c.a);
-		}
-		c = vec4(c.rgb * (1.0 - dim), c.a) * opacity;
-
-		vec3 rgb_brightness = texelFetch(brightness, ivec2(0, 0), 0).rgb;
-		// Ref: https://en.wikipedia.org/wiki/Relative_luminance
-		float brightness = rgb_brightness.r * 0.21 +
-		                   rgb_brightness.g * 0.72 +
-		                   rgb_brightness.b * 0.07;
-		if (brightness > max_brightness)
-			c.rgb = c.rgb * (max_brightness / brightness);
-
-		gl_FragColor = c;
-	}
-);
-
-const char *present_vertex_shader = GLSL(330,
-	uniform mat4 projection;
-	layout(location = 0) in vec2 coord;
-	out vec2 texcoord;
-	void main() {
-		gl_Position = projection * vec4(coord, 0, 1);
-		texcoord = coord;
-	}
-);
-// clang-format on
-
-bool gl_init(struct gl_data *gd, session_t *ps) {
-	// Initialize GLX data structure
-	glDisable(GL_DEPTH_TEST);
-	glDepthMask(GL_FALSE);
-
-	glEnable(GL_BLEND);
-	// X pixmap is in premultiplied alpha, so we might just as well use it too.
-	// Thanks to derhass for help.
-	glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
-
-	// Initialize stencil buffer
-	glDisable(GL_STENCIL_TEST);
-	glStencilMask(0x1);
-	glStencilFunc(GL_EQUAL, 0x1, 0x1);
-
-	// Set gl viewport to the maximum supported size so we won't have to worry about
-	// it later on when the screen is resized. The corresponding projection matrix can
-	// be set now and won't have to be updated. Since fragments outside the target
-	// buffer are skipped anyways, this should have no impact on performance.
-	GLint viewport_dimensions[2];
-	glGetIntegerv(GL_MAX_VIEWPORT_DIMS, viewport_dimensions);
-	glViewport(0, 0, viewport_dimensions[0], viewport_dimensions[1]);
-
-	// Clear screen
-	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
-	glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
-
-	glGenFramebuffers(1, &gd->back_fbo);
-	glGenTextures(1, &gd->back_texture);
-	if (!gd->back_fbo || !gd->back_texture) {
-		log_error("Failed to generate a framebuffer object");
-		return false;
-	}
-
-	glBindTexture(GL_TEXTURE_2D, gd->back_texture);
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-	glBindTexture(GL_TEXTURE_2D, 0);
-
-	// Set projection matrix to gl viewport dimensions so we can use screen
-	// coordinates for all vertices
-	// Note: OpenGL matrices are column major
-	GLfloat projection_matrix[4][4] = {{2.0f / (GLfloat)viewport_dimensions[0], 0, 0, 0},
-	                                   {0, 2.0f / (GLfloat)viewport_dimensions[1], 0, 0},
-	                                   {0, 0, 0, 0},
-	                                   {-1, -1, 0, 1}};
-
-	// Initialize shaders
-	gl_win_shader_from_string(vertex_shader, win_shader_glsl, &gd->win_shader);
-	int pml = glGetUniformLocationChecked(gd->win_shader.prog, "projection");
-	glUseProgram(gd->win_shader.prog);
-	glUniformMatrix4fv(pml, 1, false, projection_matrix[0]);
-	glUseProgram(0);
-
-	gd->fill_shader.prog = gl_create_program_from_str(fill_vert, fill_frag);
-	gd->fill_shader.color_loc = glGetUniformLocation(gd->fill_shader.prog, "color");
-	pml = glGetUniformLocationChecked(gd->fill_shader.prog, "projection");
-	glUseProgram(gd->fill_shader.prog);
-	glUniformMatrix4fv(pml, 1, false, projection_matrix[0]);
-	glUseProgram(0);
-
-	gd->present_prog = gl_create_program_from_str(present_vertex_shader, dummy_frag);
-	if (!gd->present_prog) {
-		log_error("Failed to create the present shader");
-		return false;
-	}
-	pml = glGetUniformLocationChecked(gd->present_prog, "projection");
-	glUseProgram(gd->present_prog);
-	glUniform1i(glGetUniformLocationChecked(gd->present_prog, "tex"), 0);
-	glUniformMatrix4fv(pml, 1, false, projection_matrix[0]);
-	glUseProgram(0);
-
-	gd->brightness_shader.prog =
-	    gl_create_program_from_str(interpolating_vert, interpolating_frag);
-	if (!gd->brightness_shader.prog) {
-		log_error("Failed to create the brightness shader");
-		return false;
-	}
-	pml = glGetUniformLocationChecked(gd->brightness_shader.prog, "projection");
-	glUseProgram(gd->brightness_shader.prog);
-	glUniform1i(glGetUniformLocationChecked(gd->brightness_shader.prog, "tex"), 0);
-	glUniformMatrix4fv(pml, 1, false, projection_matrix[0]);
-	glUseProgram(0);
-
-	// Set up the size of the back texture
-	gl_resize(gd, ps->root_width, ps->root_height);
-
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, gd->back_fbo);
-	glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
-	                       gd->back_texture, 0);
-	glDrawBuffer(GL_COLOR_ATTACHMENT0);
-	if (!gl_check_fb_complete(GL_FRAMEBUFFER)) {
-		return false;
-	}
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-
-	gd->logger = gl_string_marker_logger_new();
-	if (gd->logger) {
-		log_add_target_tls(gd->logger);
-	}
-
-	const char *vendor = (const char *)glGetString(GL_VENDOR);
-	log_debug("GL_VENDOR = %s", vendor);
-	if (strcmp(vendor, "NVIDIA Corporation") == 0) {
-		log_info("GL vendor is NVIDIA, don't use glFinish");
-		gd->is_nvidia = true;
-	} else {
-		gd->is_nvidia = false;
-	}
-
-	return true;
-}
-
-void gl_deinit(struct gl_data *gd) {
-	gl_free_prog_main(&gd->win_shader);
-
-	if (gd->logger) {
-		log_remove_target_tls(gd->logger);
-		gd->logger = NULL;
-	}
-
-	gl_check_err();
-}
-
-GLuint gl_new_texture(GLenum target) {
-	GLuint texture;
-	glGenTextures(1, &texture);
-	if (!texture) {
-		log_error("Failed to generate texture");
-		return 0;
-	}
-
-	glBindTexture(target, texture);
-	glTexParameteri(target, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
-	glTexParameteri(target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
-	glTexParameteri(target, GL_TEXTURE_WRAP_S, GL_REPEAT);
-	glTexParameteri(target, GL_TEXTURE_WRAP_T, GL_REPEAT);
-	glBindTexture(target, 0);
-
-	return texture;
-}
-
-/// Actually duplicate a texture into a new one, if this texture is shared
-static inline void gl_image_decouple(backend_t *base, struct backend_image *img) {
-	if (img->inner->refcount == 1) {
-		return;
-	}
-	auto gd = (struct gl_data *)base;
-	auto inner = (struct gl_texture *)img->inner;
-	auto new_tex = ccalloc(1, struct gl_texture);
-
-	new_tex->texture = gl_new_texture(GL_TEXTURE_2D);
-	new_tex->y_inverted = true;
-	new_tex->height = inner->height;
-	new_tex->width = inner->width;
-	new_tex->refcount = 1;
-	new_tex->user_data = gd->decouple_texture_user_data(base, inner->user_data);
-
-	glBindTexture(GL_TEXTURE_2D, new_tex->texture);
-	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, new_tex->width, new_tex->height, 0,
-	             GL_BGRA, GL_UNSIGNED_BYTE, NULL);
-	glBindTexture(GL_TEXTURE_2D, 0);
-
-	assert(gd->present_prog);
-	glUseProgram(gd->present_prog);
-	glBindTexture(GL_TEXTURE_2D, inner->texture);
-
-	GLuint fbo;
-	glGenFramebuffers(1, &fbo);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
-	glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
-	                       new_tex->texture, 0);
-	glDrawBuffer(GL_COLOR_ATTACHMENT0);
-	gl_check_fb_complete(GL_DRAW_FRAMEBUFFER);
-
-	glClearColor(0, 0, 0, 0);
-	glClear(GL_COLOR_BUFFER_BIT);
-
-	// clang-format off
-	GLint coord[] = {
-		// top left
-		0, 0,                 // vertex coord
-		0, 0,                 // texture coord
-
-		// top right
-		new_tex->width, 0, // vertex coord
-		new_tex->width, 0, // texture coord
-
-		// bottom right
-		new_tex->width, new_tex->height,
-		new_tex->width, new_tex->height,
-
-		// bottom left
-		0, new_tex->height,
-		0, new_tex->height,
-	};
-	// clang-format on
-	GLuint indices[] = {0, 1, 2, 2, 3, 0};
-
-	GLuint vao;
-	glGenVertexArrays(1, &vao);
-	glBindVertexArray(vao);
-
-	GLuint bo[2];
-	glGenBuffers(2, bo);
-	glBindBuffer(GL_ARRAY_BUFFER, bo[0]);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bo[1]);
-	glBufferData(GL_ARRAY_BUFFER, (long)sizeof(*coord) * 16, coord, GL_STATIC_DRAW);
-	glBufferData(GL_ELEMENT_ARRAY_BUFFER, (long)sizeof(*indices) * 6, indices,
-	             GL_STATIC_DRAW);
-
-	glEnableVertexAttribArray(vert_coord_loc);
-	glEnableVertexAttribArray(vert_in_texcoord_loc);
-	glVertexAttribPointer(vert_coord_loc, 2, GL_INT, GL_FALSE, sizeof(GLint) * 4, NULL);
-	glVertexAttribPointer(vert_in_texcoord_loc, 2, GL_INT, GL_FALSE,
-	                      sizeof(GLint) * 4, (void *)(sizeof(GLint) * 2));
-
-	glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, NULL);
-
-	glDisableVertexAttribArray(vert_coord_loc);
-	glDisableVertexAttribArray(vert_in_texcoord_loc);
-	glBindVertexArray(0);
-	glDeleteVertexArrays(1, &vao);
-
-	glBindBuffer(GL_ARRAY_BUFFER, 0);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
-	glDeleteBuffers(2, bo);
-
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-	glDeleteFramebuffers(1, &fbo);
-
-	glBindTexture(GL_TEXTURE_2D, 0);
-	glUseProgram(0);
-
-	gl_check_err();
-
-	img->inner = (struct backend_image_inner_base *)new_tex;
-	inner->refcount--;
-}
-
-static void gl_image_apply_alpha(backend_t *base, struct backend_image *img,
-                                 const region_t *reg_op, double alpha) {
-	// Result color = 0 (GL_ZERO) + alpha (GL_CONSTANT_ALPHA) * original color
-	auto inner = (struct gl_texture *)img->inner;
-	glBlendFunc(GL_ZERO, GL_CONSTANT_ALPHA);
-	glBlendColor(0, 0, 0, (GLclampf)alpha);
-	GLuint fbo;
-	glGenFramebuffers(1, &fbo);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo);
-	glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
-	                       inner->texture, 0);
-	glDrawBuffer(GL_COLOR_ATTACHMENT0);
-	_gl_fill(base, (struct color){0, 0, 0, 0}, reg_op, fbo, 0, false);
-	glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-	glDeleteFramebuffers(1, &fbo);
-}
-
-void gl_present(backend_t *base, const region_t *region) {
-	auto gd = (struct gl_data *)base;
-
-	int nrects;
-	const rect_t *rect = pixman_region32_rectangles((region_t *)region, &nrects);
-	auto coord = ccalloc(nrects * 8, GLint);
-	auto indices = ccalloc(nrects * 6, GLuint);
-	for (int i = 0; i < nrects; i++) {
-		// clang-format off
-		memcpy(&coord[i * 8],
-		       ((GLint[]){rect[i].x1, gd->height - rect[i].y2,
-		                 rect[i].x2, gd->height - rect[i].y2,
-		                 rect[i].x2, gd->height - rect[i].y1,
-		                 rect[i].x1, gd->height - rect[i].y1}),
-		       sizeof(GLint) * 8);
-		// clang-format on
-
-		GLuint u = (GLuint)(i * 4);
-		memcpy(&indices[i * 6],
-		       ((GLuint[]){u + 0, u + 1, u + 2, u + 2, u + 3, u + 0}),
-		       sizeof(GLuint) * 6);
-	}
-
-	glUseProgram(gd->present_prog);
-	glBindTexture(GL_TEXTURE_2D, gd->back_texture);
-
-	GLuint vao;
-	glGenVertexArrays(1, &vao);
-	glBindVertexArray(vao);
-
-	GLuint bo[2];
-	glGenBuffers(2, bo);
-	glEnableVertexAttribArray(vert_coord_loc);
-	glBindBuffer(GL_ARRAY_BUFFER, bo[0]);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bo[1]);
-	glBufferData(GL_ARRAY_BUFFER, (long)sizeof(GLint) * nrects * 8, coord, GL_STREAM_DRAW);
-	glBufferData(GL_ELEMENT_ARRAY_BUFFER, (long)sizeof(GLuint) * nrects * 6, indices,
-	             GL_STREAM_DRAW);
-
-	glVertexAttribPointer(vert_coord_loc, 2, GL_INT, GL_FALSE, sizeof(GLint) * 2, NULL);
-	glDrawElements(GL_TRIANGLES, nrects * 6, GL_UNSIGNED_INT, NULL);
-
-	glBindBuffer(GL_ARRAY_BUFFER, 0);
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
-	glBindVertexArray(0);
-	glDeleteBuffers(2, bo);
-	glDeleteVertexArrays(1, &vao);
-
-	free(coord);
-	free(indices);
-}
-
-bool gl_image_op(backend_t *base, enum image_operations op, void *image_data,
-                 const region_t *reg_op, const region_t *reg_visible attr_unused, void *arg) {
-	struct backend_image *tex = image_data;
-	switch (op) {
-	case IMAGE_OP_APPLY_ALPHA:
-		gl_image_decouple(base, tex);
-		assert(tex->inner->refcount == 1);
-		gl_image_apply_alpha(base, tex, reg_op, *(double *)arg);
-		break;
-	}
-
-	return true;
-}
-
-bool gl_read_pixel(backend_t *base attr_unused, void *image_data, int x, int y,
-                   struct color *output) {
-	struct backend_image *tex = image_data;
-	auto inner = (struct gl_texture *)tex->inner;
-	GLfloat color[4];
-	glReadPixels(x, inner->y_inverted ? inner->height - y : y, 1, 1, GL_RGBA,
-	             GL_FLOAT, color);
-	output->alpha = color[3];
-	output->red = color[0];
-	output->green = color[1];
-	output->blue = color[2];
-
-	bool ret = glGetError() == GL_NO_ERROR;
-	gl_clear_err();
-	return ret;
-}
diff --git a/src/backend/gl/gl_common.h b/src/backend/gl/gl_common.h
deleted file mode 100644
index b1d93b0..0000000
--- a/src/backend/gl/gl_common.h
+++ /dev/null
@@ -1,220 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) Yuxuan Shui <[email protected]>
-#pragma once
-#include <GL/gl.h>
-#include <GL/glext.h>
-#include <stdbool.h>
-#include <string.h>
-
-#include "backend/backend.h"
-#include "log.h"
-#include "region.h"
-
-#define CASESTRRET(s)                                                                    \
-	case s: return #s
-
-// Program and uniforms for window shader
-typedef struct {
-	GLuint prog;
-	GLint unifm_opacity;
-	GLint unifm_invert_color;
-	GLint unifm_tex;
-	GLint unifm_dim;
-	GLint unifm_brightness;
-	GLint unifm_max_brightness;
-} gl_win_shader_t;
-
-// Program and uniforms for brightness shader
-typedef struct {
-	GLuint prog;
-} gl_brightness_shader_t;
-
-// Program and uniforms for blur shader
-typedef struct {
-	GLuint prog;
-	GLint unifm_pixel_norm;
-	GLint unifm_opacity;
-	GLint texorig_loc;
-	GLint scale_loc;
-} gl_blur_shader_t;
-
-typedef struct {
-	GLuint prog;
-	GLint color_loc;
-} gl_fill_shader_t;
-
-/// @brief Wrapper of a binded GLX texture.
-struct gl_texture {
-	int refcount;
-	bool has_alpha;
-	GLuint texture;
-	int width, height;
-	bool y_inverted;
-
-	// Textures for auxiliary uses.
-	GLuint auxiliary_texture[2];
-	void *user_data;
-};
-
-struct gl_data {
-	backend_t base;
-	// If we are using proprietary NVIDIA driver
-	bool is_nvidia;
-	// Height and width of the root window
-	int height, width;
-	gl_win_shader_t win_shader;
-	gl_brightness_shader_t brightness_shader;
-	gl_fill_shader_t fill_shader;
-	GLuint back_texture, back_fbo;
-	GLuint present_prog;
-
-	/// Called when an gl_texture is decoupled from the texture it refers. Returns
-	/// the decoupled user_data
-	void *(*decouple_texture_user_data)(backend_t *base, void *user_data);
-
-	/// Release the user data attached to a gl_texture
-	void (*release_user_data)(backend_t *base, struct gl_texture *);
-
-	struct log_target *logger;
-};
-
-typedef struct session session_t;
-
-#define GL_PROG_MAIN_INIT                                                                \
-	{ .prog = 0, .unifm_opacity = -1, .unifm_invert_color = -1, .unifm_tex = -1, }
-
-GLuint gl_create_shader(GLenum shader_type, const char *shader_str);
-GLuint gl_create_program(const GLuint *const shaders, int nshaders);
-GLuint gl_create_program_from_str(const char *vert_shader_str, const char *frag_shader_str);
-
-/**
- * @brief Render a region with texture data.
- */
-void gl_compose(backend_t *, void *ptex,
-		int dst_x1, int dst_y1, int dst_x2, int dst_y2,
-		const region_t *reg_tgt, const region_t *reg_visible);
-
-void gl_resize(struct gl_data *, int width, int height);
-
-bool gl_init(struct gl_data *gd, session_t *);
-void gl_deinit(struct gl_data *gd);
-
-GLuint gl_new_texture(GLenum target);
-
-bool gl_image_op(backend_t *base, enum image_operations op, void *image_data,
-                 const region_t *reg_op, const region_t *reg_visible, void *arg);
-
-void gl_release_image(backend_t *base, void *image_data);
-
-void *gl_clone(backend_t *base, const void *image_data, const region_t *reg_visible);
-
-bool gl_blur(backend_t *base, double opacity, void *, const region_t *reg_blur,
-             const region_t *reg_visible);
-void *gl_create_blur_context(backend_t *base, enum blur_method, void *args);
-void gl_destroy_blur_context(backend_t *base, void *ctx);
-void gl_get_blur_size(void *blur_context, int *width, int *height);
-
-void gl_fill(backend_t *base, struct color, const region_t *clip);
-
-void gl_present(backend_t *base, const region_t *);
-bool gl_read_pixel(backend_t *base, void *image_data, int x, int y, struct color *output);
-
-static inline void gl_delete_texture(GLuint texture) {
-	glDeleteTextures(1, &texture);
-}
-
-/**
- * Get a textual representation of an OpenGL error.
- */
-static inline const char *gl_get_err_str(GLenum err) {
-	switch (err) {
-		CASESTRRET(GL_NO_ERROR);
-		CASESTRRET(GL_INVALID_ENUM);
-		CASESTRRET(GL_INVALID_VALUE);
-		CASESTRRET(GL_INVALID_OPERATION);
-		CASESTRRET(GL_INVALID_FRAMEBUFFER_OPERATION);
-		CASESTRRET(GL_OUT_OF_MEMORY);
-		CASESTRRET(GL_STACK_UNDERFLOW);
-		CASESTRRET(GL_STACK_OVERFLOW);
-		CASESTRRET(GL_FRAMEBUFFER_UNDEFINED);
-		CASESTRRET(GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT);
-		CASESTRRET(GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT);
-		CASESTRRET(GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER);
-		CASESTRRET(GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER);
-		CASESTRRET(GL_FRAMEBUFFER_UNSUPPORTED);
-		CASESTRRET(GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE);
-		CASESTRRET(GL_FRAMEBUFFER_INCOMPLETE_LAYER_TARGETS);
-	}
-	return NULL;
-}
-
-/**
- * Check for GLX error.
- *
- * http://blog.nobel-joergensen.com/2013/01/29/debugging-opengl-using-glgeterror/
- */
-static inline void gl_check_err_(const char *func, int line) {
-	GLenum err = GL_NO_ERROR;
-
-	while (GL_NO_ERROR != (err = glGetError())) {
-		const char *errtext = gl_get_err_str(err);
-		if (errtext) {
-			log_printf(tls_logger, LOG_LEVEL_ERROR, func,
-			           "GLX error at line %d: %s", line, errtext);
-		} else {
-			log_printf(tls_logger, LOG_LEVEL_ERROR, func,
-			           "GLX error at line %d: %d", line, err);
-		}
-	}
-}
-
-static inline void gl_clear_err(void) {
-	while (glGetError() != GL_NO_ERROR)
-		;
-}
-
-#define gl_check_err() gl_check_err_(__func__, __LINE__)
-
-/**
- * Check for GL framebuffer completeness.
- */
-static inline bool gl_check_fb_complete_(const char *func, int line, GLenum fb) {
-	GLenum status = glCheckFramebufferStatus(fb);
-
-	if (status == GL_FRAMEBUFFER_COMPLETE) {
-		return true;
-	}
-
-	const char *stattext = gl_get_err_str(status);
-	if (stattext) {
-		log_printf(tls_logger, LOG_LEVEL_ERROR, func,
-		           "Framebuffer attachment failed at line %d: %s", line, stattext);
-	} else {
-		log_printf(tls_logger, LOG_LEVEL_ERROR, func,
-		           "Framebuffer attachment failed at line %d: %d", line, status);
-	}
-
-	return false;
-}
-
-#define gl_check_fb_complete(fb) gl_check_fb_complete_(__func__, __LINE__, (fb))
-
-/**
- * Check if a GLX extension exists.
- */
-static inline bool gl_has_extension(const char *ext) {
-	int nexts = 0;
-	glGetIntegerv(GL_NUM_EXTENSIONS, &nexts);
-	for (int i = 0; i < nexts || !nexts; i++) {
-		const char *exti = (const char *)glGetStringi(GL_EXTENSIONS, (GLuint)i);
-		if (exti == NULL) {
-			break;
-		}
-		if (strcmp(ext, exti) == 0) {
-			return true;
-		}
-	}
-	gl_clear_err();
-	log_info("Missing GL extension %s.", ext);
-	return false;
-}
diff --git a/src/backend/gl/glx.c b/src/backend/gl/glx.c
deleted file mode 100644
index 1397d19..0000000
--- a/src/backend/gl/glx.c
+++ /dev/null
@@ -1,648 +0,0 @@
-// SPDX-License-Identifier: MIT
-/*
- * Compton - a compositor for X11
- *
- * Based on `xcompmgr` - Copyright (c) 2003, Keith Packard
- *
- * Copyright (c) 2011-2013, Christopher Jeffrey
- * Copyright (c) 2019 Yuxuan Shui <[email protected]>
- * See LICENSE-mit for more information.
- *
- */
-
-#include <X11/Xlib-xcb.h>
-#include <assert.h>
-#include <limits.h>
-#include <pixman.h>
-#include <stdbool.h>
-#include <stdlib.h>
-#include <string.h>
-#include <xcb/composite.h>
-#include <xcb/xcb.h>
-
-#include "backend/backend.h"
-#include "backend/backend_common.h"
-#include "backend/gl/gl_common.h"
-#include "backend/gl/glx.h"
-#include "common.h"
-#include "compiler.h"
-#include "config.h"
-#include "log.h"
-#include "picom.h"
-#include "region.h"
-#include "utils.h"
-#include "win.h"
-#include "x.h"
-
-struct _glx_pixmap {
-	GLXPixmap glpixmap;
-	xcb_pixmap_t pixmap;
-	bool owned;
-};
-
-struct _glx_data {
-	struct gl_data gl;
-	Display *display;
-	int screen;
-	xcb_window_t target_win;
-	GLXContext ctx;
-};
-
-#define glXGetFBConfigAttribChecked(a, b, attr, c)                                       \
-	do {                                                                             \
-		if (glXGetFBConfigAttrib(a, b, attr, c)) {                               \
-			log_info("Cannot get FBConfig attribute " #attr);                \
-			continue;                                                        \
-		}                                                                        \
-	} while (0)
-
-struct glx_fbconfig_info *glx_find_fbconfig(Display *dpy, int screen, struct xvisual_info m) {
-	log_debug("Looking for FBConfig for RGBA%d%d%d%d, depth %d", m.red_size,
-	          m.blue_size, m.green_size, m.alpha_size, m.visual_depth);
-
-	int ncfg;
-	// clang-format off
-	GLXFBConfig *cfg =
-	    glXChooseFBConfig(dpy, screen, (int[]){
-	                          GLX_RENDER_TYPE, GLX_RGBA_BIT,
-	                          GLX_DRAWABLE_TYPE, GLX_PIXMAP_BIT,
-	                          GLX_X_VISUAL_TYPE, GLX_TRUE_COLOR,
-	                          GLX_X_RENDERABLE, true,
-	                          GLX_FRAMEBUFFER_SRGB_CAPABLE_EXT, (GLint)GLX_DONT_CARE,
-	                          GLX_BUFFER_SIZE, m.red_size + m.green_size +
-	                                           m.blue_size + m.alpha_size,
-	                          GLX_RED_SIZE, m.red_size,
-	                          GLX_BLUE_SIZE, m.blue_size,
-	                          GLX_GREEN_SIZE, m.green_size,
-	                          GLX_ALPHA_SIZE, m.alpha_size,
-	                          GLX_STENCIL_SIZE, 0,
-	                          GLX_DEPTH_SIZE, 0,
-	                          0
-	                      }, &ncfg);
-	// clang-format on
-
-	int texture_tgts, y_inverted, texture_fmt;
-	bool found = false;
-	int min_cost = INT_MAX;
-	GLXFBConfig ret;
-	for (int i = 0; i < ncfg; i++) {
-		int depthbuf, stencil, doublebuf, bufsize;
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_BUFFER_SIZE, &bufsize);
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_DEPTH_SIZE, &depthbuf);
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_STENCIL_SIZE, &stencil);
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_DOUBLEBUFFER, &doublebuf);
-		if (depthbuf + stencil + bufsize * (doublebuf + 1) >= min_cost) {
-			continue;
-		}
-		int red, green, blue;
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_RED_SIZE, &red);
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_BLUE_SIZE, &blue);
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_GREEN_SIZE, &green);
-		if (red != m.red_size || green != m.green_size || blue != m.blue_size) {
-			// Color size doesn't match, this cannot work
-			continue;
-		}
-
-		int rgb, rgba;
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_BIND_TO_TEXTURE_RGB_EXT, &rgb);
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_BIND_TO_TEXTURE_RGBA_EXT, &rgba);
-		if (!rgb && !rgba) {
-			log_info("FBConfig is neither RGBA nor RGB, we cannot "
-			         "handle this setup.");
-			continue;
-		}
-
-		int visual;
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_VISUAL_ID, &visual);
-		if (m.visual_depth != -1 &&
-		    x_get_visual_depth(XGetXCBConnection(dpy), (xcb_visualid_t)visual) !=
-		        m.visual_depth) {
-			// FBConfig and the correspondent X Visual might not have the same
-			// depth. (e.g. 32 bit FBConfig with a 24 bit Visual). This is
-			// quite common, seen in both open source and proprietary drivers.
-			//
-			// If the FBConfig has a matching depth but its visual doesn't, we
-			// still cannot use it.
-			continue;
-		}
-
-		// All check passed, we are using this one.
-		found = true;
-		ret = cfg[i];
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_BIND_TO_TEXTURE_TARGETS_EXT,
-		                            &texture_tgts);
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_Y_INVERTED_EXT, &y_inverted);
-
-		// Prefer the texture format with matching alpha, with the other one as
-		// fallback
-		if (m.alpha_size) {
-			texture_fmt = rgba ? GLX_TEXTURE_FORMAT_RGBA_EXT
-			                   : GLX_TEXTURE_FORMAT_RGB_EXT;
-		} else {
-			texture_fmt =
-			    rgb ? GLX_TEXTURE_FORMAT_RGB_EXT : GLX_TEXTURE_FORMAT_RGBA_EXT;
-		}
-		min_cost = depthbuf + stencil + bufsize * (doublebuf + 1);
-	}
-	free(cfg);
-	if (!found) {
-		return NULL;
-	}
-
-	auto info = cmalloc(struct glx_fbconfig_info);
-	info->cfg = ret;
-	info->texture_tgts = texture_tgts;
-	info->texture_fmt = texture_fmt;
-	info->y_inverted = y_inverted;
-	return info;
-}
-
-/**
- * Free a glx_texture_t.
- */
-static void glx_release_image(backend_t *base, struct gl_texture *tex) {
-	struct _glx_data *gd = (void *)base;
-
-	struct _glx_pixmap *p = tex->user_data;
-	// Release binding
-	if (p->glpixmap && tex->texture) {
-		glBindTexture(GL_TEXTURE_2D, tex->texture);
-		glXReleaseTexImageEXT(gd->display, p->glpixmap, GLX_FRONT_LEFT_EXT);
-		glBindTexture(GL_TEXTURE_2D, 0);
-	}
-
-	// Free GLX Pixmap
-	if (p->glpixmap) {
-		glXDestroyPixmap(gd->display, p->glpixmap);
-		p->glpixmap = 0;
-	}
-
-	if (p->owned) {
-		xcb_free_pixmap(base->c, p->pixmap);
-		p->pixmap = XCB_NONE;
-	}
-
-	free(p);
-	tex->user_data = NULL;
-}
-
-/**
- * Destroy GLX related resources.
- */
-void glx_deinit(backend_t *base) {
-	struct _glx_data *gd = (void *)base;
-
-	gl_deinit(&gd->gl);
-
-	// Destroy GLX context
-	if (gd->ctx) {
-		glXMakeCurrent(gd->display, None, NULL);
-		glXDestroyContext(gd->display, gd->ctx);
-		gd->ctx = 0;
-	}
-
-	free(gd);
-}
-
-static void *glx_decouple_user_data(backend_t *base attr_unused, void *ud attr_unused) {
-	auto ret = cmalloc(struct _glx_pixmap);
-	ret->owned = false;
-	ret->glpixmap = 0;
-	ret->pixmap = 0;
-	return ret;
-}
-
-static bool glx_set_swap_interval(int interval, Display *dpy, GLXDrawable drawable) {
-	bool vsync_enabled = false;
-	if (glxext.has_GLX_MESA_swap_control) {
-		vsync_enabled = (glXSwapIntervalMESA((uint)interval) == 0);
-	}
-	if (!vsync_enabled && glxext.has_GLX_SGI_swap_control) {
-		vsync_enabled = (glXSwapIntervalSGI(interval) == 0);
-	}
-	if (!vsync_enabled && glxext.has_GLX_EXT_swap_control) {
-		// glXSwapIntervalEXT doesn't return if it's successful
-		glXSwapIntervalEXT(dpy, drawable, interval);
-		vsync_enabled = true;
-	}
-	return vsync_enabled;
-}
-
-/**
- * Initialize OpenGL.
- */
-static backend_t *glx_init(session_t *ps) {
-	bool success = false;
-	glxext_init(ps->dpy, ps->scr);
-	auto gd = ccalloc(1, struct _glx_data);
-	init_backend_base(&gd->gl.base, ps);
-
-	gd->display = ps->dpy;
-	gd->screen = ps->scr;
-	gd->target_win = session_get_target_window(ps);
-
-	XVisualInfo *pvis = NULL;
-
-	// Check for GLX extension
-	if (!ps->glx_exists) {
-		log_error("No GLX extension.");
-		goto end;
-	}
-
-	// Get XVisualInfo
-	int nitems = 0;
-	XVisualInfo vreq = {.visualid = ps->vis};
-	pvis = XGetVisualInfo(ps->dpy, VisualIDMask, &vreq, &nitems);
-	if (!pvis) {
-		log_error("Failed to acquire XVisualInfo for current visual.");
-		goto end;
-	}
-
-	// Ensure the visual is double-buffered
-	int value = 0;
-	if (glXGetConfig(ps->dpy, pvis, GLX_USE_GL, &value) || !value) {
-		log_error("Root visual is not a GL visual.");
-		goto end;
-	}
-
-	if (glXGetConfig(ps->dpy, pvis, GLX_STENCIL_SIZE, &value) || !value) {
-		log_error("Root visual lacks stencil buffer.");
-		goto end;
-	}
-
-	if (glXGetConfig(ps->dpy, pvis, GLX_DOUBLEBUFFER, &value) || !value) {
-		log_error("Root visual is not a double buffered GL visual.");
-		goto end;
-	}
-
-	if (glXGetConfig(ps->dpy, pvis, GLX_RGBA, &value) || !value) {
-		log_error("Root visual is a color index visual, not supported");
-		goto end;
-	}
-
-	if (!glxext.has_GLX_EXT_texture_from_pixmap) {
-		log_error("GLX_EXT_texture_from_pixmap is not supported by your driver");
-		goto end;
-	}
-
-	if (!glxext.has_GLX_ARB_create_context) {
-		log_error("GLX_ARB_create_context is not supported by your driver");
-		goto end;
-	}
-
-	// Find a fbconfig with visualid matching the one from the target win, so we can
-	// be sure that the fbconfig is compatible with our target window.
-	int ncfgs;
-	GLXFBConfig *cfg = glXGetFBConfigs(gd->display, gd->screen, &ncfgs);
-	bool found = false;
-	for (int i = 0; i < ncfgs; i++) {
-		int visualid;
-		glXGetFBConfigAttribChecked(gd->display, cfg[i], GLX_VISUAL_ID, &visualid);
-		if ((VisualID)visualid != pvis->visualid) {
-			continue;
-		}
-
-		gd->ctx = glXCreateContextAttribsARB(ps->dpy, cfg[i], 0, true,
-		                                     (int[]){
-		                                         GLX_CONTEXT_MAJOR_VERSION_ARB,
-		                                         3,
-		                                         GLX_CONTEXT_MINOR_VERSION_ARB,
-		                                         3,
-		                                         GLX_CONTEXT_PROFILE_MASK_ARB,
-		                                         GLX_CONTEXT_CORE_PROFILE_BIT_ARB,
-		                                         0,
-		                                     });
-		free(cfg);
-
-		if (!gd->ctx) {
-			log_error("Failed to get GLX context.");
-			goto end;
-		}
-		found = true;
-		break;
-	}
-
-	if (!found) {
-		log_error("Couldn't find a suitable fbconfig for the target window");
-		goto end;
-	}
-
-	// Attach GLX context
-	GLXDrawable tgt = gd->target_win;
-	if (!glXMakeCurrent(ps->dpy, tgt, gd->ctx)) {
-		log_error("Failed to attach GLX context.");
-		goto end;
-	}
-
-	if (!gl_init(&gd->gl, ps)) {
-		log_error("Failed to setup OpenGL");
-		goto end;
-	}
-
-	gd->gl.decouple_texture_user_data = glx_decouple_user_data;
-	gd->gl.release_user_data = glx_release_image;
-
-	if (ps->o.vsync) {
-		if (!glx_set_swap_interval(1, ps->dpy, tgt)) {
-			log_error("Failed to enable vsync.");
-		}
-	} else {
-		glx_set_swap_interval(0, ps->dpy, tgt);
-	}
-
-	success = true;
-
-end:
-	if (pvis) {
-		XFree(pvis);
-	}
-
-	if (!success) {
-		glx_deinit(&gd->gl.base);
-		return NULL;
-	}
-
-	return &gd->gl.base;
-}
-
-static void *
-glx_bind_pixmap(backend_t *base, xcb_pixmap_t pixmap, struct xvisual_info fmt, bool owned) {
-	struct _glx_data *gd = (void *)base;
-	struct _glx_pixmap *glxpixmap = NULL;
-	// Retrieve pixmap parameters, if they aren't provided
-	if (fmt.visual_depth > OPENGL_MAX_DEPTH) {
-		log_error("Requested depth %d higher than max possible depth %d.",
-		          fmt.visual_depth, OPENGL_MAX_DEPTH);
-		return false;
-	}
-
-	if (fmt.visual_depth < 0) {
-		log_error("Pixmap %#010x with invalid depth %d", pixmap, fmt.visual_depth);
-		return false;
-	}
-
-	auto r = xcb_get_geometry_reply(base->c, xcb_get_geometry(base->c, pixmap), NULL);
-	if (!r) {
-		log_error("Invalid pixmap %#010x", pixmap);
-		return NULL;
-	}
-
-	log_trace("Binding pixmap %#010x", pixmap);
-	auto wd = ccalloc(1, struct backend_image);
-	wd->max_brightness = 1;
-	auto inner = ccalloc(1, struct gl_texture);
-	inner->width = wd->ewidth = r->width;
-	inner->height = wd->eheight = r->height;
-	wd->inner = (struct backend_image_inner_base *)inner;
-	free(r);
-
-	auto fbcfg = glx_find_fbconfig(gd->display, gd->screen, fmt);
-	if (!fbcfg) {
-		log_error("Couldn't find FBConfig with requested visual %x", fmt.visual);
-		goto err;
-	}
-
-	// Choose a suitable texture target for our pixmap.
-	// Refer to GLX_EXT_texture_om_pixmap spec to see what are the mean
-	// of the bits in texture_tgts
-	if (!(fbcfg->texture_tgts & GLX_TEXTURE_2D_BIT_EXT)) {
-		log_error("Cannot bind pixmap to GL_TEXTURE_2D, giving up");
-		goto err;
-	}
-
-	log_debug("depth %d, rgba %d", fmt.visual_depth,
-	          (fbcfg->texture_fmt == GLX_TEXTURE_FORMAT_RGBA_EXT));
-
-	GLint attrs[] = {
-	    GLX_TEXTURE_FORMAT_EXT,
-	    fbcfg->texture_fmt,
-	    GLX_TEXTURE_TARGET_EXT,
-	    GLX_TEXTURE_2D_EXT,
-	    0,
-	};
-
-	inner->y_inverted = fbcfg->y_inverted;
-
-	glxpixmap = cmalloc(struct _glx_pixmap);
-	glxpixmap->pixmap = pixmap;
-	glxpixmap->glpixmap = glXCreatePixmap(gd->display, fbcfg->cfg, pixmap, attrs);
-	glxpixmap->owned = owned;
-	free(fbcfg);
-
-	if (!glxpixmap->glpixmap) {
-		log_error("Failed to create glpixmap for pixmap %#010x", pixmap);
-		goto err;
-	}
-
-	log_trace("GLXPixmap %#010lx", glxpixmap->glpixmap);
-
-	// Create texture
-	inner->user_data = glxpixmap;
-	inner->texture = gl_new_texture(GL_TEXTURE_2D);
-	inner->has_alpha = fmt.alpha_size != 0;
-	wd->opacity = 1;
-	wd->color_inverted = false;
-	wd->dim = 0;
-	wd->inner->refcount = 1;
-	glBindTexture(GL_TEXTURE_2D, inner->texture);
-	glXBindTexImageEXT(gd->display, glxpixmap->glpixmap, GLX_FRONT_LEFT_EXT, NULL);
-	glBindTexture(GL_TEXTURE_2D, 0);
-
-	gl_check_err();
-	return wd;
-err:
-	if (glxpixmap && glxpixmap->glpixmap) {
-		glXDestroyPixmap(gd->display, glxpixmap->glpixmap);
-	}
-	free(glxpixmap);
-
-	if (owned) {
-		xcb_free_pixmap(base->c, pixmap);
-	}
-	free(wd);
-	return NULL;
-}
-
-static void glx_present(backend_t *base, const region_t *region attr_unused) {
-	struct _glx_data *gd = (void *)base;
-	gl_present(base, region);
-	glXSwapBuffers(gd->display, gd->target_win);
-	if (!gd->gl.is_nvidia) {
-		glFinish();
-	}
-}
-
-static int glx_buffer_age(backend_t *base) {
-	if (!glxext.has_GLX_EXT_buffer_age) {
-		return -1;
-	}
-
-	struct _glx_data *gd = (void *)base;
-	unsigned int val;
-	glXQueryDrawable(gd->display, gd->target_win, GLX_BACK_BUFFER_AGE_EXT, &val);
-	return (int)val ?: -1;
-}
-
-static void glx_diagnostics(backend_t *base) {
-	struct _glx_data *gd = (void *)base;
-	bool warn_software_rendering = false;
-	const char *software_renderer_names[] = {"llvmpipe", "SWR", "softpipe"};
-	auto glx_vendor = glXGetClientString(gd->display, GLX_VENDOR);
-	printf("* Driver vendors:\n");
-	printf(" * GLX: %s\n", glx_vendor);
-	printf(" * GL: %s\n", glGetString(GL_VENDOR));
-
-	auto gl_renderer = (const char *)glGetString(GL_RENDERER);
-	printf("* GL renderer: %s\n", gl_renderer);
-	if (strcmp(glx_vendor, "Mesa Project and SGI")) {
-		for (size_t i = 0; i < ARR_SIZE(software_renderer_names); i++) {
-			if (strstr(gl_renderer, software_renderer_names[i]) != NULL) {
-				warn_software_rendering = true;
-				break;
-			}
-		}
-	}
-
-#ifdef GLX_MESA_query_renderer
-	if (glxext.has_GLX_MESA_query_renderer) {
-		unsigned int accelerated = 0;
-		glXQueryCurrentRendererIntegerMESA(GLX_RENDERER_ACCELERATED_MESA, &accelerated);
-		printf("* Accelerated: %d\n", accelerated);
-
-		// Trust GLX_MESA_query_renderer when it's available
-		warn_software_rendering = (accelerated == 0);
-	}
-#endif
-
-	if (warn_software_rendering) {
-		printf("\n(You are using a software renderer. Unless you are doing this\n"
-		       "intentionally, this means you don't have a graphics driver\n"
-		       "properly installed. Performance will suffer. Please fix this\n"
-		       "before reporting your issue.)\n");
-	}
-}
-
-struct backend_operations glx_ops = {
-    .init = glx_init,
-    .deinit = glx_deinit,
-    .bind_pixmap = glx_bind_pixmap,
-    .release_image = gl_release_image,
-    .compose = gl_compose,
-    .image_op = gl_image_op,
-    .set_image_property = default_set_image_property,
-    .read_pixel = gl_read_pixel,
-    .clone_image = default_clone_image,
-    .blur = gl_blur,
-    .is_image_transparent = default_is_image_transparent,
-    .present = glx_present,
-    .buffer_age = glx_buffer_age,
-    .render_shadow = default_backend_render_shadow,
-    .fill = gl_fill,
-    .create_blur_context = gl_create_blur_context,
-    .destroy_blur_context = gl_destroy_blur_context,
-    .get_blur_size = gl_get_blur_size,
-    .diagnostics = glx_diagnostics,
-    .max_buffer_age = 5,        // Why?
-};
-
-/**
- * Check if a GLX extension exists.
- */
-static inline bool glx_has_extension(Display *dpy, int screen, const char *ext) {
-	const char *glx_exts = glXQueryExtensionsString(dpy, screen);
-	if (!glx_exts) {
-		log_error("Failed get GLX extension list.");
-		return false;
-	}
-
-	auto inlen = strlen(ext);
-	const char *curr = glx_exts;
-	bool match = false;
-	while (curr && !match) {
-		const char *end = strchr(curr, ' ');
-		if (!end) {
-			// Last extension string
-			match = strcmp(ext, curr) == 0;
-		} else if (curr + inlen == end) {
-			// Length match, do match string
-			match = strncmp(ext, curr, (unsigned long)(end - curr)) == 0;
-		}
-		curr = end ? end + 1 : NULL;
-	}
-
-	if (!match) {
-		log_info("Missing GLX extension %s.", ext);
-	} else {
-		log_info("Found GLX extension %s.", ext);
-	}
-
-	return match;
-}
-
-struct glxext_info glxext = {0};
-PFNGLXGETVIDEOSYNCSGIPROC glXGetVideoSyncSGI;
-PFNGLXWAITVIDEOSYNCSGIPROC glXWaitVideoSyncSGI;
-PFNGLXGETSYNCVALUESOMLPROC glXGetSyncValuesOML;
-PFNGLXWAITFORMSCOMLPROC glXWaitForMscOML;
-PFNGLXSWAPINTERVALEXTPROC glXSwapIntervalEXT;
-PFNGLXSWAPINTERVALSGIPROC glXSwapIntervalSGI;
-PFNGLXSWAPINTERVALMESAPROC glXSwapIntervalMESA;
-PFNGLXBINDTEXIMAGEEXTPROC glXBindTexImageEXT;
-PFNGLXRELEASETEXIMAGEEXTPROC glXReleaseTexImageEXT;
-PFNGLXCREATECONTEXTATTRIBSARBPROC glXCreateContextAttribsARB;
-
-#ifdef GLX_MESA_query_renderer
-PFNGLXQUERYCURRENTRENDERERINTEGERMESAPROC glXQueryCurrentRendererIntegerMESA;
-#endif
-
-void glxext_init(Display *dpy, int screen) {
-	if (glxext.initialized) {
-		return;
-	}
-	glxext.initialized = true;
-#define check_ext(name) glxext.has_##name = glx_has_extension(dpy, screen, #name)
-	check_ext(GLX_SGI_video_sync);
-	check_ext(GLX_SGI_swap_control);
-	check_ext(GLX_OML_sync_control);
-	check_ext(GLX_MESA_swap_control);
-	check_ext(GLX_EXT_swap_control);
-	check_ext(GLX_EXT_texture_from_pixmap);
-	check_ext(GLX_ARB_create_context);
-	check_ext(GLX_EXT_buffer_age);
-#ifdef GLX_MESA_query_renderer
-	check_ext(GLX_MESA_query_renderer);
-#endif
-#undef check_ext
-
-#define lookup(name) (name = (__typeof__(name))glXGetProcAddress((GLubyte *)#name))
-	// Checking if the returned function pointer is NULL is not really necessary,
-	// or maybe not even useful, since glXGetProcAddress might always return
-	// something. We are doing it just for completeness' sake.
-	if (!lookup(glXGetVideoSyncSGI) || !lookup(glXWaitVideoSyncSGI)) {
-		glxext.has_GLX_SGI_video_sync = false;
-	}
-	if (!lookup(glXSwapIntervalEXT)) {
-		glxext.has_GLX_EXT_swap_control = false;
-	}
-	if (!lookup(glXSwapIntervalMESA)) {
-		glxext.has_GLX_MESA_swap_control = false;
-	}
-	if (!lookup(glXSwapIntervalSGI)) {
-		glxext.has_GLX_SGI_swap_control = false;
-	}
-	if (!lookup(glXWaitForMscOML) || !lookup(glXGetSyncValuesOML)) {
-		glxext.has_GLX_OML_sync_control = false;
-	}
-	if (!lookup(glXBindTexImageEXT) || !lookup(glXReleaseTexImageEXT)) {
-		glxext.has_GLX_EXT_texture_from_pixmap = false;
-	}
-	if (!lookup(glXCreateContextAttribsARB)) {
-		glxext.has_GLX_ARB_create_context = false;
-	}
-#ifdef GLX_MESA_query_renderer
-	if (!lookup(glXQueryCurrentRendererIntegerMESA)) {
-		glxext.has_GLX_MESA_query_renderer = false;
-	}
-#endif
-#undef lookup
-}
diff --git a/src/backend/gl/glx.h b/src/backend/gl/glx.h
deleted file mode 100644
index 1061f0b..0000000
--- a/src/backend/gl/glx.h
+++ /dev/null
@@ -1,77 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) Yuxuan Shui <[email protected]>
-#pragma once
-#include <stdbool.h>
-// Older version of glx.h defines function prototypes for these extensions...
-// Rename them to avoid conflicts
-#define glXSwapIntervalMESA glXSwapIntervalMESA_
-#define glXBindTexImageEXT glXBindTexImageEXT_
-#define glXReleaseTexImageEXT glXReleaseTexImageEXT
-#include <GL/glx.h>
-#undef glXSwapIntervalMESA
-#undef glXBindTexImageEXT
-#undef glXReleaseTexImageEXT
-#include <X11/Xlib.h>
-#include <xcb/xcb.h>
-#include <xcb/render.h>
-
-#include "log.h"
-#include "compiler.h"
-#include "utils.h"
-#include "x.h"
-
-struct glx_fbconfig_info {
-	GLXFBConfig cfg;
-	int texture_tgts;
-	int texture_fmt;
-	int y_inverted;
-};
-
-/// The search criteria for glx_find_fbconfig
-struct glx_fbconfig_criteria {
-	/// Bit width of the red component
-	int red_size;
-	/// Bit width of the green component
-	int green_size;
-	/// Bit width of the blue component
-	int blue_size;
-	/// Bit width of the alpha component
-	int alpha_size;
-	/// The depth of X visual
-	int visual_depth;
-};
-
-struct glx_fbconfig_info *glx_find_fbconfig(Display *, int screen, struct xvisual_info);
-
-
-struct glxext_info {
-	bool initialized;
-	bool has_GLX_SGI_video_sync;
-	bool has_GLX_SGI_swap_control;
-	bool has_GLX_OML_sync_control;
-	bool has_GLX_MESA_swap_control;
-	bool has_GLX_EXT_swap_control;
-	bool has_GLX_EXT_texture_from_pixmap;
-	bool has_GLX_ARB_create_context;
-	bool has_GLX_EXT_buffer_age;
-	bool has_GLX_MESA_query_renderer;
-};
-
-extern struct glxext_info glxext;
-
-extern PFNGLXGETVIDEOSYNCSGIPROC glXGetVideoSyncSGI;
-extern PFNGLXWAITVIDEOSYNCSGIPROC glXWaitVideoSyncSGI;
-extern PFNGLXGETSYNCVALUESOMLPROC glXGetSyncValuesOML;
-extern PFNGLXWAITFORMSCOMLPROC glXWaitForMscOML;
-extern PFNGLXSWAPINTERVALEXTPROC glXSwapIntervalEXT;
-extern PFNGLXSWAPINTERVALSGIPROC glXSwapIntervalSGI;
-extern PFNGLXSWAPINTERVALMESAPROC glXSwapIntervalMESA;
-extern PFNGLXBINDTEXIMAGEEXTPROC glXBindTexImageEXT;
-extern PFNGLXRELEASETEXIMAGEEXTPROC glXReleaseTexImageEXT;
-extern PFNGLXCREATECONTEXTATTRIBSARBPROC glXCreateContextAttribsARB;
-
-#ifdef GLX_MESA_query_renderer
-extern PFNGLXQUERYCURRENTRENDERERINTEGERMESAPROC glXQueryCurrentRendererIntegerMESA;
-#endif
-
-void glxext_init(Display *, int screen);
diff --git a/src/backend/meson.build b/src/backend/meson.build
deleted file mode 100644
index b8f0ad9..0000000
--- a/src/backend/meson.build
+++ /dev/null
@@ -1,7 +0,0 @@
-# enable xrender
-srcs += [ files('backend_common.c', 'xrender/xrender.c', 'dummy/dummy.c', 'backend.c', 'driver.c') ]
-
-# enable opengl
-if get_option('opengl')
-  srcs += [ files('gl/gl_common.c', 'gl/glx.c') ]
-endif
diff --git a/src/backend/xrender/xrender.c b/src/backend/xrender/xrender.c
deleted file mode 100644
index ccf358b..0000000
--- a/src/backend/xrender/xrender.c
+++ /dev/null
@@ -1,779 +0,0 @@
-// SPDX-License-Identifier: MPL-2.0
-// Copyright (c) Yuxuan Shui <[email protected]>
-#include <assert.h>
-#include <math.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include <xcb/composite.h>
-#include <xcb/present.h>
-#include <xcb/render.h>
-#include <xcb/sync.h>
-#include <xcb/xcb.h>
-
-#include "backend/backend.h"
-#include "backend/backend_common.h"
-#include "common.h"
-#include "config.h"
-#include "kernel.h"
-#include "log.h"
-#include "picom.h"
-#include "region.h"
-#include "types.h"
-#include "utils.h"
-#include "win.h"
-#include "x.h"
-
-typedef struct _xrender_data {
-	backend_t base;
-	/// If vsync is enabled and supported by the current system
-	bool vsync;
-	xcb_visualid_t default_visual;
-	/// Target window
-	xcb_window_t target_win;
-	/// Painting target, it is either the root or the overlay
-	xcb_render_picture_t target;
-	/// Back buffers. Double buffer, with 1 for temporary render use
-	xcb_render_picture_t back[3];
-	/// The back buffer that is for temporary use
-	/// Age of each back buffer.
-	int buffer_age[3];
-	/// The back buffer we should be painting into
-	int curr_back;
-	/// The corresponding pixmap to the back buffer
-	xcb_pixmap_t back_pixmap[3];
-	/// Pictures of pixel of different alpha value, used as a mask to
-	/// paint transparent images
-	xcb_render_picture_t alpha_pict[256];
-
-	// XXX don't know if these are really needed
-
-	/// 1x1 white picture
-	xcb_render_picture_t white_pixel;
-	/// 1x1 black picture
-	xcb_render_picture_t black_pixel;
-
-	/// Width and height of the target pixmap
-	int target_width, target_height;
-
-	xcb_special_event_t *present_event;
-} xrender_data;
-
-struct _xrender_blur_context {
-	enum blur_method method;
-	/// Blur kernels converted to X format
-	struct x_convolution_kernel **x_blur_kernel;
-
-	int resize_width, resize_height;
-
-	/// Number of blur kernels
-	int x_blur_kernel_count;
-};
-
-struct _xrender_image_data_inner {
-	// struct backend_image_inner_base
-	int refcount;
-	bool has_alpha;
-
-	// Pixmap that the client window draws to,
-	// it will contain the content of client window.
-	xcb_pixmap_t pixmap;
-	// A Picture links to the Pixmap
-	xcb_render_picture_t pict;
-	int width, height;
-	xcb_visualid_t visual;
-	uint8_t depth;
-	// Whether we own this image, e.g. we allocated it;
-	// or not, e.g. this is a named pixmap of a X window.
-	bool owned;
-};
-
-static void compose_impl(struct _xrender_data *xd, const struct backend_image *img,
-                         int dst_x1, int dst_y1, int dst_x2, int dst_y2,
-			 const region_t *reg_paint, const region_t *reg_visible,
-			 xcb_render_picture_t result) {
-	auto alpha_pict = xd->alpha_pict[(int)(img->opacity * MAX_ALPHA)];
-	auto inner = (struct _xrender_image_data_inner *)img->inner;
-	region_t reg;
-
-	bool has_alpha = inner->has_alpha || img->opacity != 1;
-	const auto tmpw = to_u16_checked(dst_x2 - dst_x1);
-	const auto tmph = to_u16_checked(dst_y2 - dst_y1);
-	const auto tmpew = to_u16_checked(dst_x2 - dst_x1);
-	const auto tmpeh = to_u16_checked(dst_y2 - dst_y1);
-	const xcb_render_color_t dim_color = {
-	    .red = 0, .green = 0, .blue = 0, .alpha = (uint16_t)(0xffff * img->dim)};
-
-	// Clip region of rendered_pict might be set during rendering, clear it to
-	// make sure we get everything into the buffer
-	x_clear_picture_clip_region(xd->base.c, inner->pict);
-
-	pixman_region32_init(&reg);
-	pixman_region32_intersect(&reg, (region_t *)reg_paint, (region_t *)reg_visible);
-	x_set_picture_clip_region(xd->base.c, result, 0, 0, &reg);
-
-#define DOUBLE_TO_XFIXED(value) ((xcb_render_fixed_t)(((double)(value)) * 65536))
-		{
-			const xcb_render_transform_t transform = {
-				DOUBLE_TO_XFIXED((double)img->ewidth / (double)tmpew), DOUBLE_TO_XFIXED(0.0), DOUBLE_TO_XFIXED(0.0),
-				DOUBLE_TO_XFIXED(0.0), DOUBLE_TO_XFIXED((double)img->eheight / (double)tmpeh), DOUBLE_TO_XFIXED(0.0),
-				DOUBLE_TO_XFIXED(0.0), DOUBLE_TO_XFIXED(0.0), DOUBLE_TO_XFIXED(1.0),
-			};
-			xcb_render_set_picture_transform(xd->base.c, inner->pict, transform);
-			xcb_render_set_picture_filter(xd->base.c, inner->pict, 7, "nearest", 0, NULL);
-		}
-#undef DOUBLE_TO_XFIXED
-
-	if ((img->color_inverted || img->dim != 0) && has_alpha) {
-		// Apply image properties using a temporary image, because the source
-		// image is transparent. Otherwise the properties can be applied directly
-		// on the target image.
-		auto tmp_pict =
-		    x_create_picture_with_visual(xd->base.c, xd->base.root, inner->width,
-		                                 inner->height, inner->visual, 0, NULL);
-
-		// Set clip region translated to source coordinate
-		x_set_picture_clip_region(xd->base.c, tmp_pict, to_i16_checked(-dst_x1),
-		                          to_i16_checked(-dst_y1), &reg);
-		// Copy source -> tmp
-		xcb_render_composite(xd->base.c, XCB_RENDER_PICT_OP_OVER, inner->pict,
-		                     XCB_NONE, tmp_pict, 0, 0, 0, 0, 0, 0, tmpw, tmph);
-		if (img->color_inverted) {
-			if (inner->has_alpha) {
-				auto tmp_pict2 = x_create_picture_with_visual(
-				    xd->base.c, xd->base.root, tmpw, tmph, inner->visual,
-				    0, NULL);
-				xcb_render_composite(xd->base.c, XCB_RENDER_PICT_OP_OVER,
-				                     tmp_pict, XCB_NONE, tmp_pict2, 0, 0,
-				                     0, 0, 0, 0, tmpw, tmph);
-
-				xcb_render_composite(xd->base.c, XCB_RENDER_PICT_OP_DIFFERENCE,
-				                     xd->white_pixel, XCB_NONE, tmp_pict,
-				                     0, 0, 0, 0, 0, 0, tmpw, tmph);
-				xcb_render_composite(
-				    xd->base.c, XCB_RENDER_PICT_OP_IN_REVERSE, tmp_pict2,
-				    XCB_NONE, tmp_pict, 0, 0, 0, 0, 0, 0, tmpw, tmph);
-				xcb_render_free_picture(xd->base.c, tmp_pict2);
-			} else {
-				xcb_render_composite(xd->base.c, XCB_RENDER_PICT_OP_DIFFERENCE,
-				                     xd->white_pixel, XCB_NONE, tmp_pict,
-				                     0, 0, 0, 0, 0, 0, tmpw, tmph);
-			}
-		}
-		if (img->dim != 0) {
-			// Dim the actually content of window
-			xcb_rectangle_t rect = {
-			    .x = 0,
-			    .y = 0,
-			    .width = tmpw,
-			    .height = tmph,
-			};
-
-			xcb_render_fill_rectangles(xd->base.c, XCB_RENDER_PICT_OP_OVER,
-			                           tmp_pict, dim_color, 1, &rect);
-		}
-
-		xcb_render_composite(xd->base.c, XCB_RENDER_PICT_OP_OVER, tmp_pict,
-		                     alpha_pict, result, 0, 0, 0, 0, to_i16_checked(dst_x1),
-		                     to_i16_checked(dst_y1), tmpew, tmpeh);
-		xcb_render_free_picture(xd->base.c, tmp_pict);
-	} else {
-		uint8_t op = (has_alpha ? XCB_RENDER_PICT_OP_OVER : XCB_RENDER_PICT_OP_SRC);
-
-		xcb_render_composite(xd->base.c, op, inner->pict, alpha_pict, result, 0,
-		                     0, 0, 0, to_i16_checked(dst_x1),
-		                     to_i16_checked(dst_y1), tmpew, tmpeh);
-		if (img->dim != 0 || img->color_inverted) {
-			// Apply properties, if we reach here, then has_alpha == false
-			assert(!has_alpha);
-			if (img->color_inverted) {
-				xcb_render_composite(xd->base.c, XCB_RENDER_PICT_OP_DIFFERENCE,
-				                     xd->white_pixel, XCB_NONE, result, 0,
-				                     0, 0, 0, to_i16_checked(dst_x1),
-				                     to_i16_checked(dst_y1), tmpew, tmpeh);
-			}
-
-			if (img->dim != 0) {
-				// Dim the actually content of window
-				xcb_rectangle_t rect = {
-				    .x = to_i16_checked(dst_x1),
-				    .y = to_i16_checked(dst_y1),
-				    .width = tmpew,
-				    .height = tmpeh,
-				};
-
-				xcb_render_fill_rectangles(xd->base.c, XCB_RENDER_PICT_OP_OVER,
-				                           result, dim_color, 1, &rect);
-			}
-		}
-	}
-	pixman_region32_fini(&reg);
-}
-
-static void compose(backend_t *base, void *img_data,
-		    int dst_x1, int dst_y1, int dst_x2, int dst_y2,
-                    const region_t *reg_paint, const region_t *reg_visible) {
-	// TODO(dccsillag): use dst_{x,y}2
-	struct _xrender_data *xd = (void *)base;
-	return compose_impl(xd, img_data, dst_x1, dst_y1, dst_x2, dst_y2, reg_paint, reg_visible, xd->back[2]);
-}
-
-static void fill(backend_t *base, struct color c, const region_t *clip) {
-	struct _xrender_data *xd = (void *)base;
-	const rect_t *extent = pixman_region32_extents((region_t *)clip);
-	x_set_picture_clip_region(base->c, xd->back[2], 0, 0, clip);
-	// color is in X fixed point representation
-	xcb_render_fill_rectangles(
-	    base->c, XCB_RENDER_PICT_OP_OVER, xd->back[2],
-	    (xcb_render_color_t){.red = (uint16_t)(c.red * 0xffff),
-	                         .green = (uint16_t)(c.green * 0xffff),
-	                         .blue = (uint16_t)(c.blue * 0xffff),
-	                         .alpha = (uint16_t)(c.alpha * 0xffff)},
-	    1,
-	    (xcb_rectangle_t[]){{.x = to_i16_checked(extent->x1),
-	                         .y = to_i16_checked(extent->y1),
-	                         .width = to_u16_checked(extent->x2 - extent->x1),
-	                         .height = to_u16_checked(extent->y2 - extent->y1)}});
-}
-
-static bool blur(backend_t *backend_data, double opacity, void *ctx_,
-                 const region_t *reg_blur, const region_t *reg_visible) {
-	struct _xrender_blur_context *bctx = ctx_;
-	if (bctx->method == BLUR_METHOD_NONE) {
-		return true;
-	}
-
-	struct _xrender_data *xd = (void *)backend_data;
-	xcb_connection_t *c = xd->base.c;
-	region_t reg_op;
-	pixman_region32_init(&reg_op);
-	pixman_region32_intersect(&reg_op, (region_t *)reg_blur, (region_t *)reg_visible);
-	if (!pixman_region32_not_empty(&reg_op)) {
-		pixman_region32_fini(&reg_op);
-		return true;
-	}
-
-	region_t reg_op_resized =
-	    resize_region(&reg_op, bctx->resize_width, bctx->resize_height);
-
-	const pixman_box32_t *extent_resized = pixman_region32_extents(&reg_op_resized);
-	const auto height_resized = to_u16_checked(extent_resized->y2 - extent_resized->y1);
-	const auto width_resized = to_u16_checked(extent_resized->x2 - extent_resized->x1);
-	static const char *filter0 = "Nearest";        // The "null" filter
-	static const char *filter = "convolution";
-
-	// Create a buffer for storing blurred picture, make it just big enough
-	// for the blur region
-	const uint32_t pic_attrs_mask = XCB_RENDER_CP_REPEAT;
-	const xcb_render_create_picture_value_list_t pic_attrs = {.repeat = XCB_RENDER_REPEAT_PAD};
-	xcb_render_picture_t tmp_picture[2] = {
-	    x_create_picture_with_visual(xd->base.c, xd->base.root, width_resized, height_resized,
-	                                 xd->default_visual, pic_attrs_mask, &pic_attrs),
-	    x_create_picture_with_visual(xd->base.c, xd->base.root, width_resized, height_resized,
-	                                 xd->default_visual, pic_attrs_mask, &pic_attrs)};
-
-	if (!tmp_picture[0] || !tmp_picture[1]) {
-		log_error("Failed to build intermediate Picture.");
-		pixman_region32_fini(&reg_op);
-		pixman_region32_fini(&reg_op_resized);
-		return false;
-	}
-
-	region_t clip;
-	pixman_region32_init(&clip);
-	pixman_region32_copy(&clip, &reg_op_resized);
-	pixman_region32_translate(&clip, -extent_resized->x1, -extent_resized->y1);
-	x_set_picture_clip_region(c, tmp_picture[0], 0, 0, &clip);
-	x_set_picture_clip_region(c, tmp_picture[1], 0, 0, &clip);
-	pixman_region32_fini(&clip);
-
-	xcb_render_picture_t src_pict = xd->back[2], dst_pict = tmp_picture[0];
-	auto alpha_pict = xd->alpha_pict[(int)(opacity * MAX_ALPHA)];
-	int current = 0;
-	x_set_picture_clip_region(c, src_pict, 0, 0, &reg_op_resized);
-
-	// For more than 1 pass, we do:
-	//   back -(pass 1)-> tmp0 -(pass 2)-> tmp1 ...
-	//   -(pass n-1)-> tmp0 or tmp1 -(pass n)-> back
-	// For 1 pass, we do
-	//   back -(pass 1)-> tmp0 -(copy)-> target_buffer
-	int i;
-	for (i = 0; i < bctx->x_blur_kernel_count; i++) {
-		// Copy from source picture to destination. The filter must
-		// be applied on source picture, to get the nearby pixels outside the
-		// window.
-		xcb_render_set_picture_filter(c, src_pict, to_u16_checked(strlen(filter)),
-		                              filter,
-		                              to_u32_checked(bctx->x_blur_kernel[i]->size),
-		                              bctx->x_blur_kernel[i]->kernel);
-
-		if (i == 0) {
-			// First pass, back buffer -> tmp picture
-			// (we do this even if this is also the last pass, because we
-			// cannot do back buffer -> back buffer)
-			xcb_render_composite(c, XCB_RENDER_PICT_OP_SRC, src_pict, XCB_NONE,
-			                     dst_pict, to_i16_checked(extent_resized->x1),
-			                     to_i16_checked(extent_resized->y1), 0, 0, 0,
-			                     0, width_resized, height_resized);
-		} else if (i < bctx->x_blur_kernel_count - 1) {
-			// This is not the last pass or the first pass,
-			// tmp picture 1 -> tmp picture 2
-			xcb_render_composite(c, XCB_RENDER_PICT_OP_SRC, src_pict,
-			                     XCB_NONE, dst_pict, 0, 0, 0, 0, 0, 0,
-			                     width_resized, height_resized);
-		} else {
-			x_set_picture_clip_region(c, xd->back[2], 0, 0, &reg_op);
-			// This is the last pass, and we are doing more than 1 pass
-			xcb_render_composite(c, XCB_RENDER_PICT_OP_OVER, src_pict,
-			                     alpha_pict, xd->back[2], 0, 0, 0, 0,
-			                     to_i16_checked(extent_resized->x1),
-			                     to_i16_checked(extent_resized->y1),
-			                     width_resized, height_resized);
-		}
-
-		// reset filter
-		xcb_render_set_picture_filter(
-		    c, src_pict, to_u16_checked(strlen(filter0)), filter0, 0, NULL);
-
-		src_pict = tmp_picture[current];
-		dst_pict = tmp_picture[!current];
-		current = !current;
-	}
-
-	// There is only 1 pass
-	if (i == 1) {
-		x_set_picture_clip_region(c, xd->back[2], 0, 0, &reg_op);
-		xcb_render_composite(
-		    c, XCB_RENDER_PICT_OP_OVER, src_pict, alpha_pict, xd->back[2], 0, 0,
-		    0, 0, to_i16_checked(extent_resized->x1),
-		    to_i16_checked(extent_resized->y1), width_resized, height_resized);
-	}
-
-	xcb_render_free_picture(c, tmp_picture[0]);
-	xcb_render_free_picture(c, tmp_picture[1]);
-	pixman_region32_fini(&reg_op);
-	pixman_region32_fini(&reg_op_resized);
-	return true;
-}
-
-static void *
-bind_pixmap(backend_t *base, xcb_pixmap_t pixmap, struct xvisual_info fmt, bool owned) {
-	xcb_generic_error_t *e;
-	auto r = xcb_get_geometry_reply(base->c, xcb_get_geometry(base->c, pixmap), &e);
-	if (!r) {
-		log_error("Invalid pixmap: %#010x", pixmap);
-		x_print_error(e->full_sequence, e->major_code, e->minor_code, e->error_code);
-		return NULL;
-	}
-
-	auto img = ccalloc(1, struct backend_image);
-	auto inner = ccalloc(1, struct _xrender_image_data_inner);
-	inner->depth = (uint8_t)fmt.visual_depth;
-	inner->width = img->ewidth = r->width;
-	inner->height = img->eheight = r->height;
-	inner->pixmap = pixmap;
-	inner->has_alpha = fmt.alpha_size != 0;
-	inner->pict =
-	    x_create_picture_with_visual_and_pixmap(base->c, fmt.visual, pixmap, 0, NULL);
-	inner->owned = owned;
-	inner->visual = fmt.visual;
-	inner->refcount = 1;
-
-	img->inner = (struct backend_image_inner_base *)inner;
-	img->opacity = 1;
-	free(r);
-
-	if (inner->pict == XCB_NONE) {
-		free(inner);
-		free(img);
-		return NULL;
-	}
-	return img;
-}
-static void release_image_inner(backend_t *base, struct _xrender_image_data_inner *inner) {
-	xcb_render_free_picture(base->c, inner->pict);
-	if (inner->owned) {
-		xcb_free_pixmap(base->c, inner->pixmap);
-	}
-	free(inner);
-}
-static void release_image(backend_t *base, void *image) {
-	struct backend_image *img = image;
-	img->inner->refcount--;
-	if (img->inner->refcount == 0) {
-		release_image_inner(base, (void *)img->inner);
-	}
-	free(img);
-}
-
-static void deinit(backend_t *backend_data) {
-	struct _xrender_data *xd = (void *)backend_data;
-	for (int i = 0; i < 256; i++) {
-		xcb_render_free_picture(xd->base.c, xd->alpha_pict[i]);
-	}
-	xcb_render_free_picture(xd->base.c, xd->target);
-	for (int i = 0; i < 2; i++) {
-		xcb_render_free_picture(xd->base.c, xd->back[i]);
-		xcb_free_pixmap(xd->base.c, xd->back_pixmap[i]);
-	}
-	if (xd->present_event) {
-		xcb_unregister_for_special_event(xd->base.c, xd->present_event);
-	}
-	xcb_render_free_picture(xd->base.c, xd->white_pixel);
-	xcb_render_free_picture(xd->base.c, xd->black_pixel);
-	free(xd);
-}
-
-static void present(backend_t *base, const region_t *region) {
-	struct _xrender_data *xd = (void *)base;
-	const rect_t *extent = pixman_region32_extents((region_t *)region);
-	int16_t orig_x = to_i16_checked(extent->x1), orig_y = to_i16_checked(extent->y1);
-	uint16_t region_width = to_u16_checked(extent->x2 - extent->x1),
-	         region_height = to_u16_checked(extent->y2 - extent->y1);
-
-	// compose() sets clip region on the back buffer, so clear it first
-	x_clear_picture_clip_region(base->c, xd->back[xd->curr_back]);
-
-	// limit the region of update
-	x_set_picture_clip_region(base->c, xd->back[2], 0, 0, region);
-
-	if (xd->vsync) {
-		// Update the back buffer first, then present
-		xcb_render_composite(base->c, XCB_RENDER_PICT_OP_SRC, xd->back[2],
-		                     XCB_NONE, xd->back[xd->curr_back], orig_x, orig_y, 0,
-		                     0, orig_x, orig_y, region_width, region_height);
-
-		// Make sure we got reply from PresentPixmap before waiting for events,
-		// to avoid deadlock
-		auto e = xcb_request_check(
-		    base->c, xcb_present_pixmap_checked(
-		                 xd->base.c, xd->target_win,
-		                 xd->back_pixmap[xd->curr_back], 0, XCB_NONE, XCB_NONE, 0,
-		                 0, XCB_NONE, XCB_NONE, XCB_NONE, 0, 0, 0, 0, 0, NULL));
-		if (e) {
-			log_error("Failed to present pixmap");
-			free(e);
-			return;
-		}
-		// TODO(yshui) don't block wait for present completion
-		xcb_present_generic_event_t *pev =
-		    (void *)xcb_wait_for_special_event(base->c, xd->present_event);
-		if (!pev) {
-			// We don't know what happened, maybe X died
-			// But reset buffer age, so in case we do recover, we will
-			// render correctly.
-			xd->buffer_age[0] = xd->buffer_age[1] = -1;
-			return;
-		}
-		assert(pev->evtype == XCB_PRESENT_COMPLETE_NOTIFY);
-		xcb_present_complete_notify_event_t *pcev = (void *)pev;
-		// log_trace("Present complete: %d %ld", pcev->mode, pcev->msc);
-		xd->buffer_age[xd->curr_back] = 1;
-
-		// buffer_age < 0 means that back buffer is empty
-		if (xd->buffer_age[1 - xd->curr_back] > 0) {
-			xd->buffer_age[1 - xd->curr_back]++;
-		}
-		if (pcev->mode == XCB_PRESENT_COMPLETE_MODE_FLIP) {
-			// We cannot use the pixmap we used anymore
-			xd->curr_back = 1 - xd->curr_back;
-		}
-		free(pev);
-	} else {
-		// No vsync needed, draw into the target picture directly
-		xcb_render_composite(base->c, XCB_RENDER_PICT_OP_SRC, xd->back[2],
-		                     XCB_NONE, xd->target, orig_x, orig_y, 0, 0, orig_x,
-		                     orig_y, region_width, region_height);
-	}
-}
-
-static int buffer_age(backend_t *backend_data) {
-	struct _xrender_data *xd = (void *)backend_data;
-	if (!xd->vsync) {
-		// Only the target picture really holds the screen content, and its
-		// content is always up to date. So buffer age is always 1.
-		return 1;
-	}
-	return xd->buffer_age[xd->curr_back];
-}
-
-static struct _xrender_image_data_inner *
-new_inner(backend_t *base, int w, int h, xcb_visualid_t visual, uint8_t depth) {
-	auto new_inner = ccalloc(1, struct _xrender_image_data_inner);
-	new_inner->pixmap = x_create_pixmap(base->c, depth, base->root, w, h);
-	if (new_inner->pixmap == XCB_NONE) {
-		log_error("Failed to create pixmap for copy");
-		free(new_inner);
-		return NULL;
-	}
-	new_inner->pict = x_create_picture_with_visual_and_pixmap(
-	    base->c, visual, new_inner->pixmap, 0, NULL);
-	if (new_inner->pict == XCB_NONE) {
-		log_error("Failed to create picture for copy");
-		xcb_free_pixmap(base->c, new_inner->pixmap);
-		free(new_inner);
-		return NULL;
-	}
-	new_inner->width = w;
-	new_inner->height = h;
-	new_inner->visual = visual;
-	new_inner->depth = depth;
-	new_inner->refcount = 1;
-	new_inner->owned = true;
-	return new_inner;
-}
-
-static bool decouple_image(backend_t *base, struct backend_image *img, const region_t *reg) {
-	if (img->inner->refcount == 1) {
-		return true;
-	}
-	auto inner = (struct _xrender_image_data_inner *)img->inner;
-	// Force new pixmap to a 32-bit ARGB visual to allow for transparent frames around
-	// non-transparent windows
-	auto visual = (inner->depth == 32)
-	                  ? inner->visual
-	                  : x_get_visual_for_standard(base->c, XCB_PICT_STANDARD_ARGB_32);
-	auto inner2 = new_inner(base, inner->width, inner->height, visual, 32);
-	if (!inner2) {
-		return false;
-	}
-
-	x_set_picture_clip_region(base->c, inner->pict, 0, 0, reg);
-	xcb_render_composite(base->c, XCB_RENDER_PICT_OP_SRC, inner->pict, XCB_NONE,
-	                     inner2->pict, 0, 0, 0, 0, 0, 0, to_u16_checked(inner->width),
-	                     to_u16_checked(inner->height));
-
-	img->inner = (struct backend_image_inner_base *)inner2;
-	inner->refcount--;
-	return true;
-}
-
-static bool image_op(backend_t *base, enum image_operations op, void *image,
-                     const region_t *reg_op, const region_t *reg_visible, void *arg) {
-	struct _xrender_data *xd = (void *)base;
-	struct backend_image *img = image;
-	region_t reg;
-	double *dargs = arg;
-
-	pixman_region32_init(&reg);
-	pixman_region32_intersect(&reg, (region_t *)reg_op, (region_t *)reg_visible);
-
-	switch (op) {
-	case IMAGE_OP_APPLY_ALPHA:
-		assert(reg_op);
-
-		if (!pixman_region32_not_empty(&reg)) {
-			break;
-		}
-
-		if (dargs[0] == 1) {
-			break;
-		}
-
-		if (!decouple_image(base, img, reg_visible)) {
-			pixman_region32_fini(&reg);
-			return false;
-		}
-
-		auto inner = (struct _xrender_image_data_inner *)img->inner;
-		auto alpha_pict = xd->alpha_pict[(int)((1 - dargs[0]) * MAX_ALPHA)];
-		x_set_picture_clip_region(base->c, inner->pict, 0, 0, &reg);
-		xcb_render_composite(base->c, XCB_RENDER_PICT_OP_OUT_REVERSE, alpha_pict,
-		                     XCB_NONE, inner->pict, 0, 0, 0, 0, 0, 0,
-		                     to_u16_checked(inner->width),
-		                     to_u16_checked(inner->height));
-		inner->has_alpha = true;
-		break;
-	}
-	pixman_region32_fini(&reg);
-	return true;
-}
-
-static void *
-create_blur_context(backend_t *base attr_unused, enum blur_method method, void *args) {
-	auto ret = ccalloc(1, struct _xrender_blur_context);
-	if (!method || method >= BLUR_METHOD_INVALID) {
-		ret->method = BLUR_METHOD_NONE;
-		return ret;
-	}
-	if (method == BLUR_METHOD_DUAL_KAWASE) {
-		log_warn("Blur method 'dual_kawase' is not compatible with the 'xrender' "
-		         "backend.");
-		ret->method = BLUR_METHOD_NONE;
-		return ret;
-	}
-
-	ret->method = BLUR_METHOD_KERNEL;
-	struct conv **kernels;
-	int kernel_count;
-	if (method == BLUR_METHOD_KERNEL) {
-		kernels = ((struct kernel_blur_args *)args)->kernels;
-		kernel_count = ((struct kernel_blur_args *)args)->kernel_count;
-	} else {
-		kernels = generate_blur_kernel(method, args, &kernel_count);
-	}
-
-	ret->x_blur_kernel = ccalloc(kernel_count, struct x_convolution_kernel *);
-	for (int i = 0; i < kernel_count; i++) {
-		int center = kernels[i]->h * kernels[i]->w / 2;
-		x_create_convolution_kernel(kernels[i], kernels[i]->data[center],
-		                            &ret->x_blur_kernel[i]);
-		ret->resize_width += kernels[i]->w / 2;
-		ret->resize_height += kernels[i]->h / 2;
-	}
-	ret->x_blur_kernel_count = kernel_count;
-
-	if (method != BLUR_METHOD_KERNEL) {
-		// Kernels generated by generate_blur_kernel, so we need to free them.
-		for (int i = 0; i < kernel_count; i++) {
-			free(kernels[i]);
-		}
-		free(kernels);
-	}
-	return ret;
-}
-
-static void destroy_blur_context(backend_t *base attr_unused, void *ctx_) {
-	struct _xrender_blur_context *ctx = ctx_;
-	for (int i = 0; i < ctx->x_blur_kernel_count; i++) {
-		free(ctx->x_blur_kernel[i]);
-	}
-	free(ctx->x_blur_kernel);
-	free(ctx);
-}
-
-static void get_blur_size(void *blur_context, int *width, int *height) {
-	struct _xrender_blur_context *ctx = blur_context;
-	*width = ctx->resize_width;
-	*height = ctx->resize_height;
-}
-
-static bool
-read_pixel(backend_t *backend_data, void *image_data, int x, int y, struct color *output) {
-	auto xd = (struct _xrender_data *)backend_data;
-	auto img = (struct backend_image *)image_data;
-	auto inner = (struct _xrender_image_data_inner *)img->inner;
-
-	auto r = XCB_AWAIT(xcb_get_image, xd->base.c, XCB_IMAGE_FORMAT_XY_PIXMAP, inner->pixmap,
-	                   to_i16_checked(x), to_i16_checked(y), 1, 1, (uint32_t)-1L);
-
-	if (!r) {
-		return false;
-	}
-
-	// Color format seems to be BGRA8888, see glamor_format_for_pixmap from the
-	// Xserver codebase.
-	uint8_t *pixels = xcb_get_image_data(r);
-	output->blue = pixels[0] / 255.0;
-	output->green = pixels[1] / 255.0;
-	output->red = pixels[2] / 255.0;
-	output->alpha = pixels[3] / 255.0;
-
-	return true;
-}
-
-static backend_t *backend_xrender_init(session_t *ps) {
-	auto xd = ccalloc(1, struct _xrender_data);
-	init_backend_base(&xd->base, ps);
-
-	for (int i = 0; i <= MAX_ALPHA; ++i) {
-		double o = (double)i / (double)MAX_ALPHA;
-		xd->alpha_pict[i] = solid_picture(ps->c, ps->root, false, o, 0, 0, 0);
-		assert(xd->alpha_pict[i] != XCB_NONE);
-	}
-
-	xd->target_width = ps->root_width;
-	xd->target_height = ps->root_height;
-	xd->default_visual = ps->vis;
-	xd->black_pixel = solid_picture(ps->c, ps->root, true, 1, 0, 0, 0);
-	xd->white_pixel = solid_picture(ps->c, ps->root, true, 1, 1, 1, 1);
-
-	xd->target_win = session_get_target_window(ps);
-	xcb_render_create_picture_value_list_t pa = {
-	    .subwindowmode = XCB_SUBWINDOW_MODE_INCLUDE_INFERIORS,
-	};
-	xd->target = x_create_picture_with_visual_and_pixmap(
-	    ps->c, ps->vis, xd->target_win, XCB_RENDER_CP_SUBWINDOW_MODE, &pa);
-
-	auto pictfmt = x_get_pictform_for_visual(ps->c, ps->vis);
-	if (!pictfmt) {
-		log_fatal("Default visual is invalid");
-		abort();
-	}
-
-	xd->vsync = ps->o.vsync;
-	if (ps->present_exists) {
-		auto eid = x_new_id(ps->c);
-		auto e =
-		    xcb_request_check(ps->c, xcb_present_select_input_checked(
-		                                 ps->c, eid, xd->target_win,
-		                                 XCB_PRESENT_EVENT_MASK_COMPLETE_NOTIFY));
-		if (e) {
-			log_error("Cannot select present input, vsync will be disabled");
-			xd->vsync = false;
-			free(e);
-		}
-
-		xd->present_event =
-		    xcb_register_for_special_xge(ps->c, &xcb_present_id, eid, NULL);
-		if (!xd->present_event) {
-			log_error("Cannot register for special XGE, vsync will be "
-			          "disabled");
-			xd->vsync = false;
-		}
-	} else {
-		xd->vsync = false;
-	}
-
-	// We might need to do double buffering for vsync, and buffer 0 and 1 are for
-	// double buffering.
-	int first_buffer_index = xd->vsync ? 0 : 2;
-	for (int i = first_buffer_index; i < 3; i++) {
-		xd->back_pixmap[i] = x_create_pixmap(ps->c, pictfmt->depth, ps->root,
-		                                     to_u16_checked(ps->root_width),
-		                                     to_u16_checked(ps->root_height));
-		const uint32_t pic_attrs_mask = XCB_RENDER_CP_REPEAT;
-		const xcb_render_create_picture_value_list_t pic_attrs = {
-		    .repeat = XCB_RENDER_REPEAT_PAD};
-		xd->back[i] = x_create_picture_with_pictfmt_and_pixmap(
-		    ps->c, pictfmt, xd->back_pixmap[i], pic_attrs_mask, &pic_attrs);
-		xd->buffer_age[i] = -1;
-		if (xd->back_pixmap[i] == XCB_NONE || xd->back[i] == XCB_NONE) {
-			log_error("Cannot create pixmap for rendering");
-			goto err;
-		}
-	}
-	xd->curr_back = 0;
-
-	return &xd->base;
-err:
-	deinit(&xd->base);
-	return NULL;
-}
-
-struct backend_operations xrender_ops = {
-    .init = backend_xrender_init,
-    .deinit = deinit,
-    .blur = blur,
-    .present = present,
-    .compose = compose,
-    .fill = fill,
-    .bind_pixmap = bind_pixmap,
-    .release_image = release_image,
-    .render_shadow = default_backend_render_shadow,
-    //.prepare_win = prepare_win,
-    //.release_win = release_win,
-    .is_image_transparent = default_is_image_transparent,
-    .buffer_age = buffer_age,
-    .max_buffer_age = 2,
-
-    .image_op = image_op,
-    .read_pixel = read_pixel,
-    .clone_image = default_clone_image,
-    .set_image_property = default_set_image_property,
-    .create_blur_context = create_blur_context,
-    .destroy_blur_context = destroy_blur_context,
-    .get_blur_size = get_blur_size,
-};
-
-// vim: set noet sw=8 ts=8: