QSGRendererInterface Class

An interface providing access to some of the graphics API specific internals of the scenegraph. More...

Header: #include <QSGRendererInterface>
qmake: QT += quick
Since: Qt 5.8

Public Types

enum GraphicsApi { Unknown, Software, OpenGL, Direct3D12, OpenVG }
enum Resource { DeviceResource, CommandQueueResource, CommandListResource, PainterResource }
enum ShaderCompilationType { RuntimeCompilation, OfflineCompilation }
flags ShaderCompilationTypes
enum ShaderSourceType { ShaderSourceString, ShaderSourceFile, ShaderByteCode }
flags ShaderSourceTypes
enum ShaderType { UnknownShadingLanguage, GLSL, HLSL }

Public Functions

virtual ~QSGRendererInterface()
virtual void * getResource(QQuickWindow *window, QSGRendererInterface::Resource resource) const
virtual void * getResource(QQuickWindow *window, const char *resource) const
virtual QSGRendererInterface::GraphicsApi graphicsApi() const = 0
virtual QSGRendererInterface::ShaderCompilationTypes shaderCompilationType() const = 0
virtual QSGRendererInterface::ShaderSourceTypes shaderSourceType() const = 0
virtual QSGRendererInterface::ShaderType shaderType() const = 0

Detailed Description

An interface providing access to some of the graphics API specific internals of the scenegraph.

Renderer interfaces allow accessing graphics API specific functionality in the scenegraph. Such internals are not typically exposed. However, when integrating custom rendering via QSGRenderNode for example, it may become necessary to query certain values, for instance the graphics device (e.g. the Direct3D or Vulkan device) that is used by the scenegraph.

QSGRendererInterface's functions have varying availability. API and language queries, like graphicsApi() or shaderType() are always available, meaning it is sufficient to construct a QQuickWindow or QQuickView, and the graphics API or shading language in use can be queried right after via QQuickWindow::rendererInterface(). This guarantees that utilities like the GraphicsInfo QML type are able to report the correct values as early as possible, without having conditional property values - depending on for instance shaderType() - evaluate to unexpected values.

Engine-specific accessors, like getResource(), are however available only after the scenegraph is initialized. Additionally, there may be backend-specific limitations on when such functions can be called. The only way that is guaranteed to succeed is calling them when the rendering of a node (i.e. the preparation of the command list for the next frame) is active. In practice this typically means QSGRenderNode::render().

Member Type Documentation

enum QSGRendererInterface::GraphicsApi

Constant Value Description
QSGRendererInterface::Unknown 0 An unknown graphics API is in use
QSGRendererInterface::Software 1 The Qt Quick 2D Renderer is in use
QSGRendererInterface::OpenGL 2 OpenGL ES 2.0 or higher
QSGRendererInterface::Direct3D12 3 Direct3D 12
QSGRendererInterface::OpenVG 4 OpenVG via EGL

enum QSGRendererInterface::Resource

Constant Value Description
QSGRendererInterface::DeviceResource 0 The graphics device, when applicable.
QSGRendererInterface::CommandQueueResource 1 The graphics command queue used by the scenegraph, when applicable.
QSGRendererInterface::CommandListResource 2 The command list or buffer used by the scenegraph, when applicable.
QSGRendererInterface::PainterResource 3 The active QPainter used by the scenegraph, when running with the software backend.

enum QSGRendererInterface::ShaderCompilationType
flags QSGRendererInterface::ShaderCompilationTypes

Constant Value Description
QSGRendererInterface::RuntimeCompilation 0x01 Runtime compilation of shader source code is supported
QSGRendererInterface::OfflineCompilation 0x02 Pre-compiled bytecode supported

The ShaderCompilationTypes type is a typedef for QFlags<ShaderCompilationType>. It stores an OR combination of ShaderCompilationType values.

enum QSGRendererInterface::ShaderSourceType
flags QSGRendererInterface::ShaderSourceTypes

Constant Value Description
QSGRendererInterface::ShaderSourceString 0x01 Shader source can be provided as a string in the corresponding properties of ShaderEffect
QSGRendererInterface::ShaderSourceFile 0x02 Local or resource files containing shader source code are supported
QSGRendererInterface::ShaderByteCode 0x04 Local or resource files containing shader bytecode are supported

The ShaderSourceTypes type is a typedef for QFlags<ShaderSourceType>. It stores an OR combination of ShaderSourceType values.

enum QSGRendererInterface::ShaderType

Constant Value Description
QSGRendererInterface::UnknownShadingLanguage 0 Not yet known due to no window and scenegraph associated
QSGRendererInterface::GLSL 1 GLSL or GLSL ES
QSGRendererInterface::HLSL 2 HLSL

Member Function Documentation

[virtual] QSGRendererInterface::~QSGRendererInterface()

Destroys the instance of QSGRendererInterface. The destructor is virtual.

[virtual] void *QSGRendererInterface::getResource(QQuickWindow *window, QSGRendererInterface::Resource resource) const

Queries a graphics resource in window. Returns null when the resource in question is not supported or not available.

When successful, the returned pointer is either a direct pointer to an interface (and can be cast, for example, to ID3D12Device *) or a pointer to an opaque handle that needs to be dereferenced first (for example, VkDevice dev = *static_cast<VkDevice *>(result)). The latter is necessary since such handles may have sizes different from a pointer.

Note: The ownership of the returned pointer is never transferred to the caller.

Note: This function must only be called on the render thread.

[virtual] void *QSGRendererInterface::getResource(QQuickWindow *window, const char *resource) const

Queries a graphics resource. resource is a backend-specific key. This allows supporting any future resources that are not listed in the Resource enum.

Note: The ownership of the returned pointer is never transferred to the caller.

Note: This function must only be called on the render thread.

[pure virtual] QSGRendererInterface::GraphicsApi QSGRendererInterface::graphicsApi() const

Returns the graphics API that is in use by the Qt Quick scenegraph.

Note: This function can be called on any thread.

[pure virtual] QSGRendererInterface::ShaderCompilationTypes QSGRendererInterface::shaderCompilationType() const

Returns a bitmask of the shader compilation approaches supported by the Qt Quick backend the application is using.

Note: This function can be called on any thread.

See also QtQuick::GraphicsInfo.

[pure virtual] QSGRendererInterface::ShaderSourceTypes QSGRendererInterface::shaderSourceType() const

Returns a bitmask of the supported ways of providing shader sources in ShaderEffect items.

Note: This function can be called on any thread.

See also QtQuick::GraphicsInfo.

[pure virtual] QSGRendererInterface::ShaderType QSGRendererInterface::shaderType() const

Returns the shading language supported by the Qt Quick backend the application is using.

Note: This function can be called on any thread.

See also QtQuick::GraphicsInfo.

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