OpenGL specific initialization parameters. More...
|CMake:|| find_package(Qt6 REQUIRED COMPONENTS Gui) |
target_link_libraries(mytarget PRIVATE Qt6::Gui)
|qmake:||QT += gui|
|QOffscreenSurface *||newFallbackSurface(const QSurfaceFormat &format = QSurfaceFormat::defaultFormat())|
Note: This is a RHI API with limited compatibility guarantees, see QRhi for details.
An OpenGL-based QRhi needs an already created QSurface that can be used in combination with QOpenGLContext. Most commonly, this is a QOffscreenSurface in practice. Additionally, while optional, it is recommended that the QWindow the first QRhiSwapChain will target is passed in as well.
QOffscreenSurface *fallbackSurface = QRhiGles2InitParams::newFallbackSurface(); QRhiGles2InitParams params; params.fallbackSurface = fallbackSurface; params.window = window; rhi = QRhi::create(QRhi::OpenGLES2, ¶ms);
By default QRhi creates a QOpenGLContext on its own. This approach works well in most cases, included threaded scenarios, where there is a dedicated QRhi for each rendering thread. As there will be a QOpenGLContext for each QRhi, the OpenGL context requirements (a context can only be current on one thread) are satisfied. The implicitly created context is destroyed automatically together with the QRhi.
The QSurfaceFormat for the context is specified in
format. The constructor sets this to QSurfaceFormat::defaultFormat() so applications that call QSurfaceFormat::setDefaultFormat() with the appropriate settings before the constructor runs will not need to change value of
Note: Remember to set the depth and stencil buffer sizes to 24 and 8 when the renderer relies on depth or stencil testing, either in the global default QSurfaceFormat, or, alternatively, separately in all the involved QSurfaceFormat instances: in
format, the format argument passed to newFallbackSurface(), and on any QWindow that is used with the QRhi.
A QSurface has to be specified in
fallbackSurface. In order to prevent mistakes in threaded situations, this is never created automatically by the QRhi because, like QWindow, instances of QSurface subclasses can often be created on the gui/main thread only.
As a convenience, applications can use newFallbackSurface() which creates and returns a QOffscreenSurface that is compatible with the QOpenGLContext that is going to be created by the QRhi afterwards. Note that the ownership of the returned QOffscreenSurface is transferred to the caller and the QRhi will not destroy it.
window is optional. It is recommended to specify it whenever possible, in order to avoid problems on multi-adapter and multi-screen systems. When
window is not set, the very first QOpenGLContext::makeCurrent() happens with
fallbackSurface which may be an invisible window on some platforms (for example, Windows) and that may trigger unexpected problems in some cases.
When interoperating with another graphics engine, it may be necessary to get a QRhi instance that uses the same OpenGL context. This can be achieved by passing a pointer to a QRhiGles2NativeHandles to QRhi::create(). The
QRhiGles2NativeHandles::context must be set to a non-null value then.
Member Function Documentation
Constructs a new QRhiGles2InitParams.
[static] QOffscreenSurface *QRhiGles2InitParams::newFallbackSurface(const QSurfaceFormat &format = QSurfaceFormat::defaultFormat())
When format is not specified, its default value is the global default format settable via QSurfaceFormat::setDefaultFormat().
format is adjusted as appropriate in order to avoid having problems afterwards due to an incompatible context and surface.
Note: This function must only be called on the gui/main thread.
Member Variable Documentation
A QSurface compatible with format. Typically a QOffscreenSurface. Providing this is mandatory. Be aware of the threading implications: a QOffscreenSurface, like QWindow, must only ever be created and destroyed on the main (gui) thread, even if the QRhi is created and operates on another thread.
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