path: root/README.md

# Overview #   {#mainpage}

# NVIDIA GeForce Experience SDK #   {#section_main}

* Version: 1.0.0.d2a45f0d
* Built for GFE Version: 3.9.0.37
* See [Changelog](\ref section_changelog)

## At a Glance {#section_glance}

The GeForce SDK (GfeSDK) is a means for games to integrate with ShadowPlay Highlights allowing them to capture videos
and screenshots and present the resulting highlights back to users for viewing and sharing. GfeSDK will add other features
over time that benefit from games and applications working in concert with GFE functionality.

![Shadowplay Highlights](/img/gfesdk_highlights.png)

### Software Stack {#section_stack}

![Software Stack](/img/gfesdk_block.png)

An application integrates with the GfeSDK via either the provided Unreal Engine 4 plug-in, C++ interface, or C interface. This integration, via the SDK, calls a compatible GFE 3.0 release. 

The developer (or associated publisher) distributes the application (including associated SDK libraries).

NVIDIA distributes a GfeSDK package coupled with GfeSDK-compatible GFE releases. GFE maintains backwards SDK-compatibility; games integrated with older SDKs work with newer GFE releases.

### GfeSDK Package {#section_package}

The distribution will look like the following
```
.
+-- README.md
+-- LICENSE
+-- doc
|   +-- index.html          # Points to the deeper index.html
|   +-- html
|   |   +-- index.html
|   |   ...
+-- include
|   +-- gfesdk
|   |   +-- bindings        
|   |   |   +-- cpp         # C++ bindings that sit on top of C API
|   |   +-- isdk.h
|   |   ...
+-- lib
|   +-- win32
|   |   +-- GfeSDK.lib      # x86 Import library for linking
|   +-- win64
|   |   +-- GfeSDK.lib      # x64 Import library for linking
+-- redist
|   +-- win32
|   |   +-- GfeSDK.dll      # x86 DLL to be shipped with the game
|   +-- win64
|   |   +-- GfeSDK.dll      # x64 DLL to be shipped with the game
+-- samples
```

### Compiling And Linking {#section_compiling}

To compile, add the ./include (not the ./include/gfesdk) directory to the compiler's list of includes. The import libraries
are found in the ./lib folder and can be used to link the symbols into the game's executable. The proper GfeSDK.dll file
will need to be distributed with the game in a place that the game can find it.

The C++ bindings are currently distributed in header-only form to avoid ABI incompatibilities between different compiler
versions. The linking and include steps are the same.

## Using GfeSDK ## {#section_using}

Creation and destruction of an SDK instance is a prerequisite to making calls
to the SDK. The means of creating and destroying an instance depend on which
integration mechanism the client employs:

See [Core header documentation](\ref isdk.h)

See [Highlights header documentation](\ref ihighlights.h)

### Creation and Release {#section_example_create}

#### C++ Bindings

\snippet GfeSDKDemo.cpp Creation CPP

// After using GfeSDK

\snippet GfeSDKDemo.cpp Release CPP

#### C API

\snippet GfeSDKDemo.cpp Creation

// After using GfeSDK

\snippet GfeSDKDemo.cpp Release

### Request Permissions {#section_example_permission}

The Create call will inform the app if one or more scopes require user
permission. If so, make this call. It will display the overlay UI.

#### C++ Bindings

\snippet GfeSDKDemo.cpp Permissions CPP

#### C API

\snippet GfeSDKDemo.cpp Permissions

### Configure Highlights {#section_example_highlightsconfigure}

This only needs to happen once ever. It is persistent. It could even happen
during game installation.

#### C++ Bindings

\snippet GfeSDKDemo.cpp ConfigureHighlights CPP

#### C API

\snippet GfeSDKDemo.cpp ConfigureHighlights

### Groups and Saving Highlights {#section_Example_highlights}

#### C++ Bindings

\snippet GfeSDKDemo.cpp OpenGroup CPP
\snippet GfeSDKDemo.cpp SaveVideo CPP
\snippet GfeSDKDemo.cpp CloseGroup CPP

#### C API

\snippet GfeSDKDemo.cpp OpenGroup
\snippet GfeSDKDemo.cpp SaveVideo
\snippet GfeSDKDemo.cpp CloseGroup

### Open Highlight Summary {#section_example_summary}

#### C++ Bindings

\snippet GfeSDKDemo.cpp OpenSummary CPP

#### C API

\snippet GfeSDKDemo.cpp OpenSummary

## Concepts {#section_concepts}

The GfeSDK is composed of two parts, the client/app, and the backend/server.
This distribution contains GfeSDK.dll which represents the client/app part.
The end-user downloads GFE onto their machine. The GFE package includes the
backend pieces necessary to support the calls coming from the client. See
\ref section_version for more information regarding this communication.

Calls made will be serialized. Therefore, if the app makes two consecutive
calls to NVGSDK_Highlights_OpenGroup and then either
NVGSDK_Highlights_SetVideoHighlight or NVGSDK_Highlights_SetScreenshotHighlight,
before receiving the callback from open group, the set highlight call will
function normally. If open group succeeded, then the set highlights calls will
succeed as well. If it failed, the set highlights calls will fail, as there
will be no valid group to assign them to.

### Strings {#section_strings}
All strings are to be provided in single-byte width, UTF-8 encoded.

### Versioning {#section_version}
Because there are two different parts, and the client / user's machine may
be mismatched at times, the game should be aware of the versioning system.
It's GfeSDK's goal to make this as seamless as possible, but there could still
be compatibility issues to be aware of.

The GfeSDK version contains 4 parts, MAJOR.MINOR.BUILD.HASH. The BUILD and HASH
components are descriptive and don't have any effect on functionality. The
MAJOR component identifies overall compatibility. If the client and server
mismatch on the major version number, no communication is possible. **There
are no current plans to update from 1, breaking communication**. The major
version number gives a way to show incompatibility if the fundamental
architecture of GFE ever changes. The minor version number indicates feature
compatibility. When a new feature gets added / modified on the SDK, the minor
version number will be bumped. This means that for older games / newer GFE
installations, the game is simply missing out on newer features. This will
generally not be a problem. For a game with a newer version of the GfeSDK,
and a user with an older installation of GFE, some features may not function,
and the user should be encouraged to update GFE.

With that in mind, here are the possible return values from \ref NVGSDK_Create,
with regards to versioning:
* **NVGSDK_SUCCESS** - Perfect version match
* **NVGSDK_SUCCESS_OLD_GFE** - Minor version mismatch. User has an older
version of GFE installed. Newer features distributed by the game will not
function properly until the user upgrades.
* **NVGSDK_SUCCESS_OLD_SDK** - Minor version mismatch.
Game is distributing an older version of GfeSDK.
Game could be missing out on latest features, but no compatibily issue. 
* **NVGSDK_ERR_GFE_VERSION** - Major version mismatch. User has a GFE
installation that predates the GfeSDK. User must upgrade to get functionality.
* **NVGSDK_ERR_SDK_VERSION** - Major version mismatch. GFE has changed
fundamentally. **There are no plans to do this. This is to cover all bases**

### Permissions {#section_permissions}
Certain actions require permission from the user. For example, recording video
for Highlights requires the user to agree to the recording. To achieve this,
the app must know what features it wishes to enable. It will pass these
"scopes" into the  NVGSDK_Create call via NVGSDK_CreateInputParams. Consider
the typical Highlights case as an example. The app will pass in a list of
the scopes NVGSDK_SCOPE_HIGHLIGHTS, NVGSDK_SCOPE_HIGHLIGHTS_VIDEO, and
NVGSDK_SCOPE_SCREENSHOT. The first of these is required in order for any
of the NVGSDK_Highlights_* calls to succeed and send a message to the server.
It will allocate the resources required in the DLL and on the server in order
to achieve this. The second of these permissions is required in order to
capture video of the gameplay, and the final is to capture a screenshot.

The first time the user runs the game, and the game calls NVGSDK_Create(...),
and passes in these three permissions, the game might receive back that
NVGSDK_SCOPE_HIGHLIGHTS has been granted permission implicitly, but that
NVGSDK_SCOPE_HIGHLIGHTS_VIDEO and NVGSDK_SCOPE_HIGHLIGHTS_SCREENSHOT
currently have "must ask" permission. In other words, the game must ask
GFE for permission to record video before it will succeed in doing so. To
achieve this, the game will call NVGSDK_RequestPermissionsAsync with two
scopes in the list, NVGSDK_SCOPE_HIGHLIGHTS_VIDEO and
NVGSDK_SCOPE_HIGHLIGHTS_SCREENSHOT. It's not necessary to request permission
for a scope that has implicitly been granted permission already.

The call to NVGSDK_RequestPermissions is required because it will trigger
GFE to put up an \ref section_igo. The game might not want this to occur
during NVGSDK_Create time. Once called, the user will see the overlay
pop up, asking them for permission.

![Highlights Permission](/img/permission.png)

The async callback will be triggered as soon as the message is processed
by the GFE backend. The user will be able to accept, deny, or defer the
request. If the user accepts or denies the request, the app will recieve
a \ref NVGSDK_NOTIFICATION_PERMISSIONS_CHANGED notification with the results.
If \ref NVGSDK_RequestPermissionsAsync is called again when the permission is
already granted or denied, the overlay will not be displayed a second time.
The user can reverse their decision in either case later on in GFE3 on
the games details page.

### Asynchronous Calls {#section_async}
Most of the calls to GfeSDK are asynchronous. This is due to the client/server
architecture described in \ref section_concepts. For each asynchronous call, a
callback and an opaque void* context are passed in as arguments. If the app
does not care or desire to know what happens to the call, is it fine to pass
in NULL. If the app does care, supply a callback of the proper type, and
optionally a pointer as a context to receive back during the callback.

The callbacks are properly typed. For callbacks that return nothing but the
return value and context, a \ref NVGSDK_EmptyCallback is passed in. For
versions that do return data, a typed callback is passed in, such as
\ref NVGSDK_GetUILanguageCallback.

The callback will be called on one of three threads, depending on the
situation. If NVGSDK_CreateInputParams::pollForCallbacks is set to false
during creation, the callback will always occur on a GfeSDK controller thread.
If the app desires callback to occur on their own thread, true is passed in
instead. In that case, the callback will occur on the thread that calls
\ref NVGSDK_Poll. The exception is that during \ref NVGSDK_Destroy, GfeSDK
pushes out all remaining callbacks. If the app is awaiting any callbacks
during this time, they will be called on the same thread that called
NVGSDK_Destroy. Usually, this will be the same thread that calls NVGSDK_Poll,
so it shouldn't cause any surprises, but it's something to be aware of. See
\ref section_threading for more information

**Note:** There is currently a limitation in the GfeSDK backend that depends
on game frames being rendered during certain API calls. Therefore, the game
cannot block the render loop while awaiting an asynchronous callback. Doing
so will result in a deadlock.

### Notifications ### {#section_notifications}

In addition to the async callbacks that most of the APIs accept as an argument,
the app can also register to recieve unsolicited notifications when certain
events occur. For example, the app might want to know when the user can
given / removed permission for recording video from the app, either through
the permissions dialog, or via GFE3. See \ref NVGSDK_CreateInputParams and
\ref NVGSDK_NotificationType

This notification will get called on either the GfeSDK callback thread, or
the thread that calls \ref NVGSDK_Poll, depending on params passed in to
\ref NVGSDK_Create. See \ref section_threading for more information.

### Threading {#section_threading}
There are two different threading models that may be used. The model used
depends on the value passed in to \ref NVGSDK_CreateInputParams

##### GfeSDK Controller Callback Model
In this model, all callbacks will occur as soon as they are processed on the
internal GfeSDK callback thread.

##### Polling Model
The app can choose to use this model if it wants to take action during the
callback that depend on being on the game loop. Callbacks are queued up, and
executed when the app calls \ref NVGSDK_Poll. This means that callbacks will
be blocked indefinitely if that API is never called.

The exception occurs during \ref NVGSDK_Destroy. Because the normal case is
to make NVGSDK_Destroy and NVGSDK_Poll calls from the same thread, GfeSDK
can't block and wait for another poll call. All remaining callbacks will be
executed during \ref NVGSDK_Destroy. See \ref section_async for more info.

### In Game Overlay {#section_igo}
![In Game Overlay](/img/igo.png)

The In-Game overlay can be used by the user to change Highlights settings, and
view Highlights that have been saved to the gallery. It's also used to display
the permissions dialog from \ref NVGSDK_RequestPermissionsAsync, and the
group summary from \ref NVGSDK_OpenGroupSummaryAsync. The user can open it
up by themselves using the default keybinding Alt+Z

### Logging {#section_log}
By default, GfeSDK stores its own logs for problem triage in
%LOCALAPPDATA%\NVIDIA Corporation\GfeSDK. This behavior can be adjusted by
the following calls:

* \ref NVGSDK_SetLogLevel
* \ref NVGSDK_AttachLogListener
* \ref NVGSDK_SetListenerLogLevel