Version 1.01.0.0

1 files changed, 900 insertions, 0 deletions

diff --git a/src/backend/gl/blur.c b/src/backend/gl/blur.c
new file mode 100644
index 0000000..41022f5
--- /dev/null
+++ b/src/backend/gl/blur.c
@@ -0,0 +1,900 @@
+#include <locale.h>
+#include <stdbool.h>
+
+#include <backend/backend.h>
+#include <backend/backend_common.h>
+
+#include "gl_common.h"
+
+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;
+};
+
+/**
+ * Blur contents in a particular region.
+ */
+bool gl_kernel_blur(double opacity, struct gl_blur_context *bctx, const rect_t *extent,
+                    struct backend_image *mask, coord_t mask_dst, const GLuint vao[2],
+                    const int vao_nelems[2], GLuint source_texture,
+                    geometry_t source_size, GLuint target_fbo, GLuint default_mask) {
+	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 = source_texture;
+			tex_width = source_size.width;
+			tex_height = source_size.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;
+		}
+
+		glActiveTexture(GL_TEXTURE0);
+		glBindTexture(GL_TEXTURE_2D, src_texture);
+		glUseProgram(p->prog);
+		glUniform2f(p->uniform_pixel_norm, 1.0F / (GLfloat)tex_width,
+		            1.0F / (GLfloat)tex_height);
+
+		glActiveTexture(GL_TEXTURE1);
+		glBindTexture(GL_TEXTURE_2D, default_mask);
+
+		glUniform1i(p->uniform_mask_tex, 1);
+		glUniform2f(p->uniform_mask_offset, 0.0F, 0.0F);
+		glUniform1i(p->uniform_mask_inverted, 0);
+		glUniform1f(p->uniform_mask_corner_radius, 0.0F);
+
+		// 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->uniform_opacity, 1.0F);
+		} else {
+			// last pass, draw directly into the back buffer, with origin
+			// regions. And apply mask if requested
+			if (mask) {
+				auto inner = (struct gl_texture *)mask->inner;
+				glActiveTexture(GL_TEXTURE1);
+				glBindTexture(GL_TEXTURE_2D, inner->texture);
+				glUniform1i(p->uniform_mask_inverted, mask->color_inverted);
+				glUniform1f(p->uniform_mask_corner_radius,
+				            (float)mask->corner_radius);
+				glUniform2f(
+				    p->uniform_mask_offset, (float)(mask_dst.x),
+				    (float)(bctx->fb_height - mask_dst.y - inner->height));
+			}
+			glBindVertexArray(vao[0]);
+			nelems = vao_nelems[0];
+			glBindFramebuffer(GL_FRAMEBUFFER, target_fbo);
+
+			glUniform1f(p->uniform_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(double opacity, struct gl_blur_context *bctx, const rect_t *extent,
+                         struct backend_image *mask, coord_t mask_dst, const GLuint vao[2],
+                         const int vao_nelems[2], GLuint source_texture,
+                         geometry_t source_size, GLuint target_fbo, GLuint default_mask) {
+	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 = source_texture;
+			tex_width = source_size.width;
+			tex_height = source_size.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->uniform_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;
+
+		glActiveTexture(GL_TEXTURE0);
+		glBindTexture(GL_TEXTURE_2D, src_texture);
+		glActiveTexture(GL_TEXTURE1);
+		glBindTexture(GL_TEXTURE_2D, default_mask);
+
+		glUniform1i(up_pass->uniform_mask_tex, 1);
+		glUniform2f(up_pass->uniform_mask_offset, 0.0F, 0.0F);
+		glUniform1i(up_pass->uniform_mask_inverted, 0);
+		glUniform1f(up_pass->uniform_mask_corner_radius, 0.0F);
+		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->uniform_opacity, (GLfloat)1);
+		} else {
+			// last pass, draw directly into the back buffer
+			if (mask) {
+				auto inner = (struct gl_texture *)mask->inner;
+				glActiveTexture(GL_TEXTURE1);
+				glBindTexture(GL_TEXTURE_2D, inner->texture);
+				glUniform1i(up_pass->uniform_mask_inverted,
+				            mask->color_inverted);
+				glUniform1f(up_pass->uniform_mask_corner_radius,
+				            (float)mask->corner_radius);
+				glUniform2f(
+				    up_pass->uniform_mask_offset, (float)(mask_dst.x),
+				    (float)(bctx->fb_height - mask_dst.y - inner->height));
+			}
+			glBindVertexArray(vao[0]);
+			nelems = vao_nelems[0];
+			glBindFramebuffer(GL_DRAW_FRAMEBUFFER, target_fbo);
+
+			glUniform1f(up_pass->uniform_opacity, (GLfloat)opacity);
+		}
+
+		glUniform1f(up_pass->scale_loc, (GLfloat)scale_factor);
+		glUniform2f(up_pass->uniform_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_impl(double opacity, struct gl_blur_context *bctx, void *mask,
+                  coord_t mask_dst, const region_t *reg_blur,
+                  const region_t *reg_visible attr_unused, GLuint source_texture,
+                  geometry_t source_size, GLuint target_fbo, GLuint default_mask) {
+	bool ret = false;
+
+	if (source_size.width != bctx->fb_width || source_size.height != bctx->fb_height) {
+		// Resize the temporary textures used for blur in case the root
+		// size changed
+		bctx->fb_width = source_size.width;
+		bctx->fb_height = source_size.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);
+	auto extent_height = extent_resized->y2 - extent_resized->y1;
+	x_rect_to_coords(
+	    nrects, rects, (coord_t){.x = extent_resized->x1, .y = extent_resized->y1},
+	    extent_height, bctx->fb_height, source_size.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,
+	                 (coord_t){.x = extent_resized->x1, .y = extent_resized->y1},
+	                 extent_height, 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(opacity, bctx, extent_resized, mask, mask_dst,
+		                          vao, vao_nelems, source_texture, source_size,
+		                          target_fbo, default_mask);
+	} else {
+		ret = gl_kernel_blur(opacity, bctx, extent_resized, mask, mask_dst, vao,
+		                     vao_nelems, source_texture, source_size, target_fbo,
+		                     default_mask);
+	}
+
+	glBindFramebuffer(GL_FRAMEBUFFER, 0);
+	glActiveTexture(GL_TEXTURE1);
+	glBindTexture(GL_TEXTURE_2D, 0);
+	glActiveTexture(GL_TEXTURE0);
+	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;
+}
+
+bool gl_blur(backend_t *base, double opacity, void *ctx, void *mask, coord_t mask_dst,
+             const region_t *reg_blur, const region_t *reg_visible attr_unused) {
+	auto gd = (struct gl_data *)base;
+	auto bctx = (struct gl_blur_context *)ctx;
+	return gl_blur_impl(opacity, bctx, mask, mask_dst, reg_blur, reg_visible,
+	                    gd->back_texture,
+	                    (geometry_t){.width = gd->width, .height = gd->height},
+	                    gd->back_fbo, gd->default_mask_texture);
+}
+
+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;
+		float mask_factor();
+		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 * mask_factor();
+		}
+	);
+	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_strv(
+		    (const char *[]){vertex_shader, NULL},
+		    (const char *[]){shader_str, masking_glsl, NULL});
+		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
+		bind_uniform(pass, pixel_norm);
+		bind_uniform(pass, opacity);
+
+		bind_uniform(pass, mask_tex);
+		bind_uniform(pass, mask_offset);
+		bind_uniform(pass, mask_inverted);
+		bind_uniform(pass, mask_corner_radius);
+		log_info("Uniform locations: %d %d %d %d %d", pass->uniform_mask_tex,
+		         pass->uniform_mask_offset, pass->uniform_mask_inverted,
+		         pass->uniform_mask_corner_radius, pass->uniform_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_strv(
+		    (const char *[]){vertex_shader, NULL},
+		    (const char *[]){copy_with_mask_frag, masking_glsl, NULL});
+		pass->uniform_pixel_norm = -1;
+		pass->uniform_opacity = -1;
+		pass->texorig_loc = glGetUniformLocationChecked(pass->prog, "texorig");
+		bind_uniform(pass, mask_tex);
+		bind_uniform(pass, mask_offset);
+		bind_uniform(pass, mask_inverted);
+		bind_uniform(pass, mask_corner_radius);
+
+		// 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
+		bind_uniform(down_pass, 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;
+			float mask_factor();
+			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 * mask_factor();
+			}
+		);
+		// 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_strv(
+		    (const char *[]){vertex_shader, NULL},
+		    (const char *[]){shader_str, masking_glsl, NULL});
+		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
+		bind_uniform(up_pass, pixel_norm);
+		bind_uniform(up_pass, opacity);
+
+		bind_uniform(up_pass, mask_tex);
+		bind_uniform(up_pass, mask_offset);
+		bind_uniform(up_pass, mask_inverted);
+		bind_uniform(up_pass, mask_corner_radius);
+
+		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;
+}