QRhiSwapChain Class Reference

\inmodule QtGui More...

#include <qrhi.h>

Inheritance diagram for QRhiSwapChain:

Collaboration diagram for QRhiSwapChain:

Public Types
enum	Flag {   SurfaceHasPreMulAlpha = 1 << 0 , SurfaceHasNonPreMulAlpha = 1 << 1 , sRGB = 1 << 2 , UsedAsTransferSource = 1 << 3 ,   NoVSync = 1 << 4 , MinimalBufferCount = 1 << 5 }
	Flag values to describe swapchain properties. More...
enum	Format { SDR , HDRExtendedSrgbLinear , HDR10 , HDRExtendedDisplayP3Linear }
	Describes the swapchain format. More...
enum	StereoTargetBuffer { LeftBuffer , RightBuffer }
	Selects the backbuffer to use with a stereoscopic swapchain. More...
Public Types inherited from QRhiResource
enum	Type {   Buffer , Texture , Sampler , RenderBuffer ,   RenderPassDescriptor , SwapChainRenderTarget , TextureRenderTarget , ShaderResourceBindings ,   GraphicsPipeline , SwapChain , ComputePipeline , CommandBuffer }
	Specifies type of the resource. More...

Public Member Functions
QRhiResource::Type	resourceType () const override
QWindow *	window () const
void	setWindow (QWindow *window)
	Sets the window.
QRhiSwapChainProxyData	proxyData () const
void	setProxyData (const QRhiSwapChainProxyData &d)
	Sets the proxy data d.
Flags	flags () const
void	setFlags (Flags f)
	Sets the flags f.
Format	format () const
void	setFormat (Format f)
	Sets the format f.
QRhiRenderBuffer *	depthStencil () const
void	setDepthStencil (QRhiRenderBuffer *ds)
	Sets the renderbuffer ds for use as a depth-stencil buffer.
int	sampleCount () const
void	setSampleCount (int samples)
	Sets the sample count.
QRhiRenderPassDescriptor *	renderPassDescriptor () const
void	setRenderPassDescriptor (QRhiRenderPassDescriptor *desc)
	Associates with the QRhiRenderPassDescriptor desc.
QSize	currentPixelSize () const
virtual QRhiCommandBuffer *	currentFrameCommandBuffer ()=0
virtual QRhiRenderTarget *	currentFrameRenderTarget ()=0
virtual QRhiRenderTarget *	currentFrameRenderTarget (StereoTargetBuffer targetBuffer)
virtual QSize	surfacePixelSize ()=0
virtual bool	isFormatSupported (Format f)=0
virtual QRhiRenderPassDescriptor *	newCompatibleRenderPassDescriptor ()=0
virtual bool	createOrResize ()=0
	Creates the swapchain if not already done and resizes the swapchain buffers to match the current size of the targeted surface.
virtual QRhiSwapChainHdrInfo	hdrInfo ()
	\variable QRhiSwapChainHdrInfo::limitsType
Public Member Functions inherited from QRhiResource
virtual	~QRhiResource ()
	Destructor.
virtual void	destroy ()=0
	Releases (or requests deferred releasing of) the underlying native graphics resources.
void	deleteLater ()
	When called without a frame being recorded, this function is equivalent to deleting the object.
QByteArray	name () const
void	setName (const QByteArray &name)
	Sets a name for the object.
quint64	globalResourceId () const
QRhi *	rhi () const

Protected Member Functions
	QRhiSwapChain (QRhiImplementation *rhi)
Protected Member Functions inherited from QRhiResource
	QRhiResource (QRhiImplementation *rhi)

Protected Attributes
QWindow *	m_window = nullptr
Flags	m_flags
Format	m_format = SDR
QRhiRenderBuffer *	m_depthStencil = nullptr
int	m_sampleCount = 1
QRhiRenderPassDescriptor *	m_renderPassDesc = nullptr
QSize	m_currentPixelSize
QRhiSwapChainProxyData	m_proxyData
Protected Attributes inherited from QRhiResource
QRhiImplementation *	m_rhi = nullptr
quint64	m_id
QByteArray	m_objectName

Detailed Description

\inmodule QtGui

Since

6.6

Swapchain resource.

A swapchain enables presenting rendering results to a surface. A swapchain is typically backed by a set of color buffers. Of these, one is displayed at a time.

Below is a typical pattern for creating and managing a swapchain and some associated resources in order to render onto a QWindow:

void init()
{
    sc = rhi->newSwapChain();
    ds = rhi->newRenderBuffer(QRhiRenderBuffer::DepthStencil,
                              QSize(), // no need to set the size here due to UsedWithSwapChainOnly
                              1,
                              QRhiRenderBuffer::UsedWithSwapChainOnly);
    sc->setWindow(window);
    sc->setDepthStencil(ds);
    rp = sc->newCompatibleRenderPassDescriptor();
    sc->setRenderPassDescriptor(rp);
    resizeSwapChain();
}
 
void resizeSwapChain()
{
    hasSwapChain = sc->createOrResize();
}
 
void render()
{
    if (!hasSwapChain || notExposed)
        return;
 
    if (sc->currentPixelSize() != sc->surfacePixelSize() || newlyExposed) {
        resizeSwapChain();
        if (!hasSwapChain)
            return;
        newlyExposed = false;
    }
 
    rhi->beginFrame(sc);
    // ...
    rhi->endFrame(sc);
}

Avoid relying on QWindow resize events to resize swapchains, especially considering that surface sizes may not always fully match the QWindow reported dimensions. The safe, cross-platform approach is to do the check via surfacePixelSize() whenever starting a new frame.

Releasing the swapchain must happen while the QWindow and the underlying native window is fully up and running. Building on the previous example:

void releaseSwapChain()
{
    if (hasSwapChain) {
        sc->destroy();
        hasSwapChain = false;
    }
}
 
// assuming Window is our QWindow subclass
bool Window::event(QEvent *e)
{
    switch (e->type()) {
    case QEvent::UpdateRequest: // for QWindow::requestUpdate()
        render();
        break;
    case QEvent::PlatformSurface:
        if (static_cast<QPlatformSurfaceEvent *>(e)->surfaceEventType() == QPlatformSurfaceEvent::SurfaceAboutToBeDestroyed)
            releaseSwapChain();
        break;
    default:
        break;
    }
    return QWindow::event(e);
}

Initializing the swapchain and starting to render the first frame cannot start at any time. The safe, cross-platform approach is to rely on expose events. QExposeEvent is a loosely specified event that is sent whenever a window gets mapped, obscured, and resized, depending on the platform.

void Window::exposeEvent(QExposeEvent *)
{
    // initialize and start rendering when the window becomes usable for graphics purposes
    if (isExposed() && !running) {
        running = true;
        init();
    }
 
    // stop pushing frames when not exposed or size becomes 0
    if ((!isExposed() || (hasSwapChain && sc->surfacePixelSize().isEmpty())) && running)
        notExposed = true;
 
    // continue when exposed again and the surface has a valid size
    if (isExposed() && running && notExposed && !sc->surfacePixelSize().isEmpty()) {
        notExposed = false;
        newlyExposed = true;
    }
 
    if (isExposed() && !sc->surfacePixelSize().isEmpty())
        render();
}

Once the rendering has started, a simple way to request a new frame is QWindow::requestUpdate(). While on some platforms this is merely a small timer, on others it has a specific implementation: for instance on macOS or iOS it may be backed by \l{https://developer.apple.com/documentation/corevideo/cvdisplaylink?language=objc}{CVDisplayLink}. The example above is already prepared for update requests by handling QEvent::UpdateRequest.

While acting as a QRhiRenderTarget, QRhiSwapChain also manages a QRhiCommandBuffer. Calling QRhi::endFrame() submits the recorded commands and also enqueues a present request. The default behavior is to do this with a swap interval of 1, meaning synchronizing to the display's vertical refresh is enabled. Thus the rendering thread calling beginFrame() and endFrame() will get throttled to vsync. On some backends this can be disabled by passing QRhiSwapChain:NoVSync in flags().

Multisampling (MSAA) is handled transparently to the applications when requested via setSampleCount(). Where applicable, QRhiSwapChain will take care of creating additional color buffers and issuing a multisample resolve command at the end of a frame. For OpenGL, it is necessary to request the appropriate sample count also via QSurfaceFormat, by calling QSurfaceFormat::setDefaultFormat() before initializing the QRhi.

Note

This is a RHI API with limited compatibility guarantees, see \l QRhi for details.

Definition at line 1548 of file qrhi.h.

Member Enumeration Documentation

Flag

enum QRhiSwapChain::Flag

Flag values to describe swapchain properties.

\value SurfaceHasPreMulAlpha Indicates that the target surface has transparency with premultiplied alpha. For example, this is what Qt Quick uses when the alpha channel is enabled on the target QWindow, because the scenegraph rendrerer always outputs fragments with alpha multiplied into the red, green, and blue values. To ensure identical behavior across platforms, always set QSurfaceFormat::alphaBufferSize() to a non-zero value on the target QWindow whenever this flag is set on the swapchain.

\value SurfaceHasNonPreMulAlpha Indicates the target surface has transparency with non-premultiplied alpha. Be aware that this may not be supported on some systems, if the system compositor always expects content with premultiplied alpha. In that case the behavior with this flag set is expected to be equivalent to SurfaceHasPreMulAlpha.

\value sRGB Requests to pick an sRGB format for the swapchain's color buffers and/or render target views, where applicable. Note that this implies that sRGB framebuffer update and blending will get enabled for all content targeting this swapchain, and opting out is not possible. For OpenGL, set \l{QSurfaceFormat::sRGBColorSpace}{sRGBColorSpace} on the QSurfaceFormat of the QWindow in addition. Applicable only when the swapchain format is set to QRhiSwapChain::SDR.

\value UsedAsTransferSource Indicates the swapchain will be used as the source of a readback in QRhiResourceUpdateBatch::readBackTexture().

\value NoVSync Requests disabling waiting for vertical sync, also avoiding throttling the rendering thread. The behavior is backend specific and applicable only where it is possible to control this. Some may ignore the request altogether. For OpenGL, try instead setting the swap interval to 0 on the QWindow via QSurfaceFormat::setSwapInterval().

\value MinimalBufferCount Requests creating the swapchain with the minimum number of buffers, which is in practice 2, unless the graphics implementation has a higher minimum number than that. Only applicable with backends where such control is available via the graphics API, for example, Vulkan. By default it is up to the backend to decide what number of buffers it requests (in practice this is almost always either 2 or 3), and it is not the applications' concern. However, on Vulkan for instance the backend will likely prefer the higher number (3), for example to avoid odd performance issues with some Vulkan implementations on mobile devices. It could be that on some platforms it can prove to be beneficial to force the lower buffer count (2), so this flag allows forcing that. Note that all this has no effect on the number of frames kept in flight, so the CPU (QRhi) will still prepare frames at most {N - 1} frames ahead of the GPU, even when the swapchain image buffer count larger than N. ({N} = QRhi::FramesInFlight and typically 2).

Enumerator
SurfaceHasPreMulAlpha
SurfaceHasNonPreMulAlpha
sRGB
UsedAsTransferSource
NoVSync
MinimalBufferCount

Definition at line 1551 of file qrhi.h.

Format

enum QRhiSwapChain::Format

Describes the swapchain format.

The default format is SDR.

This enum is used with \l{QRhiSwapChain::isFormatSupported()}{isFormatSupported()} to check upfront if creating the swapchain with the given format is supported by the platform and the window's associated screen, and with \l{QRhiSwapChain::setFormat()}{setFormat()} to set the requested format in the swapchain before calling \l{QRhiSwapChain::createOrResize()}{createOrResize()} for the first time.

\value SDR 8-bit RGBA or BGRA, depending on the backend and platform. With OpenGL ES in particular, it could happen that the platform provides less than 8 bits (e.g. due to EGL and the QSurfaceFormat choosing a 565 or 444 format - this is outside the control of QRhi). Standard dynamic range. May be combined with setting the QRhiSwapChain::sRGB flag.

\value HDRExtendedSrgbLinear 16-bit float RGBA, high dynamic range, extended linear sRGB (scRGB) color space. This involves Rec. 709 primaries (same as SDR/sRGB) and linear colors. Conversion to the display's native color space (such as, HDR10) is performed by the windowing system. On Windows this is the canonical color space of the system compositor, and is the recommended format for HDR swapchains in general on desktop platforms.

\value HDR10 10-bit unsigned int RGB or BGR with 2 bit alpha, high dynamic range, HDR10 (Rec. 2020) color space with an ST2084 PQ transfer function.

\value HDRExtendedDisplayP3Linear 16-bit float RGBA, high dynamic range, extended linear Display P3 color space. The primary choice for HDR on platforms such as iOS and VisionOS.

Enumerator
SDR
HDRExtendedSrgbLinear
HDR10
HDRExtendedDisplayP3Linear

Definition at line 1561 of file qrhi.h.

StereoTargetBuffer

enum QRhiSwapChain::StereoTargetBuffer

Selects the backbuffer to use with a stereoscopic swapchain.

\value LeftBuffer \value RightBuffer

Enumerator
LeftBuffer
RightBuffer

Definition at line 1568 of file qrhi.h.

Constructor & Destructor Documentation

QRhiSwapChain()

QRhiSwapChain::QRhiSwapChain ( QRhiImplementation * rhi )

protected

Definition at line 7313 of file qrhi.cpp.

Member Function Documentation

createOrResize()

bool QRhiSwapChain::createOrResize ( )

pure virtual

Creates the swapchain if not already done and resizes the swapchain buffers to match the current size of the targeted surface.

Call this whenever the size of the target surface is different than before.

Note

call destroy() only when the swapchain needs to be released completely, typically upon QPlatformSurfaceEvent::SurfaceAboutToBeDestroyed. To perform resizing, just call createOrResize().

Returns

true when successful, false when a graphics operation failed. Regardless of the return value, calling destroy() is always safe.

Implemented in QD3D11SwapChain, QGles2SwapChain, QMetalSwapChain, QNullSwapChain, and QVkSwapChain.

Referenced by QBackingStoreDefaultCompositor::flush(), QSGGuiThreadRenderLoop::renderWindow(), QBackingStoreRhiSupport::swapChainForWindow(), and QSGRenderThread::syncAndRender().

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currentFrameCommandBuffer()

QRhiCommandBuffer * QRhiSwapChain::currentFrameCommandBuffer ( )

pure virtual

Returns

a command buffer on which rendering commands and resource updates can be recorded within a \l{QRhi::beginFrame()}{beginFrame} - \l{QRhi::endFrame()}{endFrame} block, assuming beginFrame() was called with this swapchain.

Note

The returned object is valid also after endFrame(), up until the next beginFrame(), but the returned command buffer should not be used to record any commands then. Rather, it can be used to query data collected during the frame (or previous frames), for example by calling \l{QRhiCommandBuffer::lastCompletedGpuTime()}{lastCompletedGpuTime()}.

The value must not be cached and reused between frames. The caller should not hold on to the returned object once \l{QRhi::beginFrame()}{beginFrame()} is called again. Instead, the command buffer object should be queried again by calling this function.

Implemented in QD3D11SwapChain, QGles2SwapChain, QMetalSwapChain, QNullSwapChain, and QVkSwapChain.

Referenced by QSGRenderThread::event(), QBackingStoreDefaultCompositor::flush(), QSGGuiThreadRenderLoop::grab(), QQuickRhiItemNode::queryCommandBuffer(), QQuick3DSceneRenderer::renderToRhiTexture(), QSGGuiThreadRenderLoop::renderWindow(), and QSGRenderThread::syncAndRender().

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currentFrameRenderTarget() [1/2]

QRhiRenderTarget * QRhiSwapChain::currentFrameRenderTarget ( )

pure virtual

Returns

a render target that can used with beginPass() in order to render the swapchain's current backbuffer. Only valid within a QRhi::beginFrame() - QRhi::endFrame() block where beginFrame() was called with this swapchain.

Note

the value must not be cached and reused between frames

Implemented in QD3D11SwapChain, QGles2SwapChain, QMetalSwapChain, QNullSwapChain, and QVkSwapChain.

Referenced by currentFrameRenderTarget(), and QBackingStoreDefaultCompositor::flush().

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currentFrameRenderTarget() [2/2]

QRhiRenderTarget * QRhiSwapChain::currentFrameRenderTarget ( StereoTargetBuffer targetBuffer )

virtual

Returns

a render target that can be used with beginPass() in order to render to the swapchain's left or right backbuffer. This overload should be used only with stereoscopic rendering, that is, when the associated QWindow is backed by two color buffers, one for each eye, instead of just one.

When stereoscopic rendering is not supported, the return value will be the default target. It is supported by all hardware backends except for Metal, in combination with \l QSurfaceFormat::StereoBuffers, assuming it is supported by the graphics and display driver stack at run time. Metal and Null backends are going to return the default render target from this overload.

Note

the value must not be cached and reused between frames

Reimplemented in QD3D11SwapChain, QGles2SwapChain, and QVkSwapChain.

Definition at line 7471 of file qrhi.cpp.

References currentFrameRenderTarget(), and Q_UNUSED.

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currentPixelSize()

QSize QRhiSwapChain::currentPixelSize ( ) const

inline

Returns

the size with which the swapchain was last successfully built. Use this to decide if createOrResize() needs to be called again: if {currentPixelSize() != surfacePixelSize()} then the swapchain needs to be resized.

Note

Typical rendering logic will call this function to get the output size when starting to prepare a new frame, and base dependent calculations (such as, the viewport) on the size returned from this function.

While in many cases the value is the same as {QWindow::size() * QWindow::devicePixelRatio()}, relying on the QWindow-reported size is not guaranteed to be correct on all platforms and graphics API implementations. Using this function is therefore strongly recommended whenever there is a need to identify the dimensions, in pixels, of the output layer or surface.

This also has the added benefit of avoiding potential data races when QRhi is used on a dedicated rendering thread, because the need to call QWindow functions, that may then access data updated on the main thread, is avoided.

See also

surfacePixelSize()

Definition at line 1596 of file qrhi.h.

Referenced by QBackingStoreDefaultCompositor::flush(), QSGGuiThreadRenderLoop::renderWindow(), QRhiNull::resourceUpdate(), and QSGRenderThread::syncAndRender().

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depthStencil()

QRhiRenderBuffer * QRhiSwapChain::depthStencil ( ) const

inline

Returns

the currently associated renderbuffer for depth-stencil.

Definition at line 1587 of file qrhi.h.

flags()

QRhiSwapChain::Flags QRhiSwapChain::flags ( ) const

inline

Returns

the currently set flags.

Definition at line 1581 of file qrhi.h.

format()

QRhiSwapChain::Format QRhiSwapChain::format ( ) const

inline

Returns

the currently set format.

Definition at line 1584 of file qrhi.h.

Referenced by QD3D11SwapChain::newColorBuffer(), and qShouldUpdateSwapChainFormat().

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hdrInfo()

QRhiSwapChainHdrInfo QRhiSwapChain::hdrInfo ( )

virtual

\variable QRhiSwapChainHdrInfo::limitsType

With Metal on macOS/iOS, there is no luminance values exposed in the platform APIs. Instead, the maximum color component value, that would be 1.0 in a non-HDR setup, is provided. This value indicates what kind of information is available in \l limits.

See also

QRhiSwapChain::hdrInfo()

\variable QRhiSwapChainHdrInfo::limits

Contains the actual values queried from the graphics API or the platform. The type of data is indicated by \l limitsType. This is therefore a union. There are currently two options:

Luminance values in nits:

struct {
    float minLuminance;
    float maxLuminance;
} luminanceInNits;

On Windows the minimum and maximum luminance depends on the screen brightness. While not relevant for desktops, on laptops the screen brightness may change at any time. Increasing brightness implies decreased maximum luminance. In addition, the results may also be dependent on the HDR Content Brightness set in Windows Settings' System/Display/HDR view, if there is such a setting.

Note however that the changes made to the laptop screen's brightness or in the system settings while the application is running are not necessarily reflected in the returned values, meaning calling hdrInfo() again may still return the same luminance range as before for the rest of the process' lifetime. The exact behavior is up to DXGI and Qt has no control over it.

Note

The Windows compositor works in scene-referred mode for HDR content. A color component value of 1.0 corresponds to a luminance of 80 nits. When rendering non-HDR content (e.g. 2D UI elements), the correction of the white level is often necessary. (e.g., outputting the fragment color (1, 1, 1) will likely lead to showing a shade of white that is too dim on-screen) See \l sdrWhiteLevel.

For macOS/iOS, the current maximum and potential maximum color component values are provided:

struct {
    float maxColorComponentValue;
    float maxPotentialColorComponentValue;
} colorComponentValue;

The value may depend on the screen brightness, which on laptops means that the result may change in the next call to hdrInfo() if the brightness was changed in the meantime. The maximum screen brightness implies a maximum color value of 1.0.

Note

Apple's EDR is display-referred. 1.0 corresponds to a luminance level of SDR white (e.g. 200 nits), the value of which varies based on the screen brightness and possibly other settings. The exact luminance value for that, or the maximum luminance of the display, are not exposed to the applications.

It has been observed that the color component values are not set to the correct larger-than-1 value right away on startup on some macOS systems, but the values tend to change during or after the first frame.

See also

QRhiSwapChain::hdrInfo()

\variable QRhiSwapChainHdrInfo::luminanceBehavior

Describes the platform's presumed behavior with regards to color values.

See also

sdrWhiteLevel

\variable QRhiSwapChainHdrInfo::sdrWhiteLevel

On Windows this is the dynamic SDR white level in nits. The value is dependent on the screen brightness (on laptops), and the SDR or HDR Content Brightness settings in the Windows settings' System/Display/HDR view.

To perform white level correction for non-HDR (SDR) content, such as 2D UI elemenents, multiply the final color with sdrWhiteLevel / 80.0 whenever \l luminanceBehavior is SceneReferred. (assuming Windows and a linear extended sRGB (scRGB) color space)

On other platforms the value is always a pre-defined value, 200. This may not match the system's actual SDR white level, but the value of this variable is not relevant in practice when the \l luminanceBehavior is DisplayReferred, because then the color component value of 1.0 refers to the SDR white by default.

See also

luminanceBehavior

Returns

the HDR information for the associated display.

Do not assume that this is a cheap operation. Depending on the platform, this function makes various platform queries which may have a performance impact.

Note

Can be called before createOrResize() as long as the window is \l{setWindow()}{set}.

What happens when moving a window with an initialized swapchain between displays (HDR to HDR with different characteristics, HDR to SDR, etc.) is not currently well-defined and depends heavily on the windowing system and compositor, with potentially varying behavior between platforms. Currently QRhi only guarantees that hdrInfo() returns valid data, if available, for the display to which the swapchain's associated window belonged at the time of createOrResize().

See also

QRhiSwapChainHdrInfo

Reimplemented in QD3D11SwapChain, and QMetalSwapChain.

Definition at line 7797 of file qrhi.cpp.

References info, QRhiSwapChainHdrInfo::LuminanceInNits, and QRhiSwapChainHdrInfo::SceneReferred.

Referenced by QD3D11SwapChain::hdrInfo().

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isFormatSupported()

bool QRhiSwapChain::isFormatSupported ( Format f )

pure virtual

Returns

true if the given swapchain format f is supported. SDR is always supported.

Note

Can be called independently of createOrResize(), but window() must already be set. Calling without the window set may lead to unexpected results depending on the backend and platform (most likely false for any HDR format), because HDR format support is usually tied to the output (screen) to which the swapchain's associated window belongs at any given time. If the result is true for a HDR format, then creating the swapchain with that format is expected to succeed as long as the window is not moved to another screen in the meantime.

The main use of this function is to call it before the first createOrResize() after the window is already set. This allow the QRhi backends to perform platform or windowing system specific queries to determine if the window (and the screen it is on) is capable of true HDR output with the specified format.

When the format is reported as supported, call setFormat() to set the requested format and call createOrResize(). Be aware of the consequences however: successfully requesting a HDR format will involve having to deal with a different color space, possibly doing white level correction for non-HDR-aware content, adjusting tonemapping methods, adjusting offscreen render target settings, etc.

See also

setFormat()

Implemented in QD3D11SwapChain, QGles2SwapChain, QMetalSwapChain, QNullSwapChain, and QVkSwapChain.

Referenced by qShouldUpdateSwapChainFormat().

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newCompatibleRenderPassDescriptor()

QRhiRenderPassDescriptor * QRhiSwapChain::newCompatibleRenderPassDescriptor ( )

pure virtual

Returns

a new QRhiRenderPassDescriptor that is compatible with this swapchain.

The returned value is used in two ways: it can be passed to setRenderPassDescriptor() and QRhiGraphicsPipeline::setRenderPassDescriptor(). A render pass descriptor describes the attachments (color, depth/stencil) and the load/store behavior that can be affected by flags(). A QRhiGraphicsPipeline can only be used in combination with a swapchain that has a \l{QRhiRenderPassDescriptor::isCompatible()}{compatible} QRhiRenderPassDescriptor set.

See also

createOrResize()

Implemented in QD3D11SwapChain, QGles2SwapChain, QMetalSwapChain, QNullSwapChain, and QVkSwapChain.

Referenced by QSGRenderThread::ensureRhi(), QSGGuiThreadRenderLoop::ensureRhi(), and QBackingStoreRhiSupport::swapChainForWindow().

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proxyData()

QRhiSwapChainProxyData QRhiSwapChain::proxyData ( ) const

inline

Returns

the currently set proxy data.

Definition at line 1578 of file qrhi.h.

renderPassDescriptor()

QRhiRenderPassDescriptor * QRhiSwapChain::renderPassDescriptor ( ) const

inline

Returns

the currently associated QRhiRenderPassDescriptor object.

Definition at line 1593 of file qrhi.h.

Referenced by QBackingStoreDefaultCompositor::flush(), and QBackingStoreRhiSupport::swapChainForWindow().

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resourceType()

QRhiResource::Type QRhiSwapChain::resourceType ( ) const

overridevirtual

Returns

the resource type.

Implements QRhiResource.

Definition at line 7321 of file qrhi.cpp.

References QRhiResource::SwapChain.

sampleCount()

int QRhiSwapChain::sampleCount ( ) const

inline

Returns

the currently set sample count. 1 means no multisample antialiasing.

Definition at line 1590 of file qrhi.h.

setDepthStencil()

void QRhiSwapChain::setDepthStencil ( QRhiRenderBuffer * ds )

inline

Sets the renderbuffer ds for use as a depth-stencil buffer.

Definition at line 1588 of file qrhi.h.

Referenced by QSGRenderThread::ensureRhi(), and QSGGuiThreadRenderLoop::ensureRhi().

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setFlags()

void QRhiSwapChain::setFlags ( Flags f )

inline

Sets the flags f.

Definition at line 1582 of file qrhi.h.

Referenced by QSGRenderThread::ensureRhi(), QSGGuiThreadRenderLoop::ensureRhi(), and QBackingStoreRhiSupport::swapChainForWindow().

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setFormat()

void QRhiSwapChain::setFormat ( Format f )

inline

Sets the format f.

Avoid setting formats that are reported as unsupported from isFormatSupported(). Note that support for a given format may depend on the screen the swapchain's associated window is opened on. On some platforms, such as Windows and macOS, for HDR output to work it is necessary to have HDR output enabled in the display settings.

See isFormatSupported(), \l QRhiSwapChainHdrInfo, and \l Format for more information on high dynamic range output.

Definition at line 1585 of file qrhi.h.

setProxyData()

void QRhiSwapChain::setProxyData ( const QRhiSwapChainProxyData & d )

inline

Sets the proxy data d.

See also

QRhi::updateSwapChainProxyData()

Definition at line 1579 of file qrhi.h.

References d.

Referenced by QSGRenderThread::ensureRhi(), and QSGRenderThread::syncAndRender().

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setRenderPassDescriptor()

void QRhiSwapChain::setRenderPassDescriptor ( QRhiRenderPassDescriptor * desc )

inline

Associates with the QRhiRenderPassDescriptor desc.

Definition at line 1594 of file qrhi.h.

Referenced by QSGRenderThread::ensureRhi(), QSGGuiThreadRenderLoop::ensureRhi(), and QBackingStoreRhiSupport::swapChainForWindow().

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setSampleCount()

void QRhiSwapChain::setSampleCount ( int samples )

inline

Sets the sample count.

Common values for samples are 1 (no MSAA), 4 (4x MSAA), or 8 (8x MSAA).

See also

QRhi::supportedSampleCounts()

Definition at line 1591 of file qrhi.h.

Referenced by QSGRenderThread::ensureRhi(), and QSGGuiThreadRenderLoop::ensureRhi().

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setWindow()

void QRhiSwapChain::setWindow ( QWindow * window )

inline

Sets the window.

Definition at line 1576 of file qrhi.h.

References window().

Referenced by QSGRenderThread::ensureRhi(), QSGGuiThreadRenderLoop::ensureRhi(), and QBackingStoreRhiSupport::swapChainForWindow().

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surfacePixelSize()

QSize QRhiSwapChain::surfacePixelSize ( )

pure virtual

Returns

The size of the window's associated surface or layer.

Warning

Do not assume this is the same as {QWindow::size() * QWindow::devicePixelRatio()}. With some graphics APIs and windowing system interfaces (for example, Vulkan) there is a theoretical possibility for a surface to assume a size different from the associated window. To support these cases, {rendering logic must always base size-derived calculations (such as, viewports) on the size reported from QRhiSwapChain, and never on the size queried from QWindow}.

Note

{Can also be called before createOrResize(), if at least window() is already set. This in combination with currentPixelSize() allows to detect when a swapchain needs to be resized.} However, watch out for the fact that the size of the underlying native object (surface, layer, or similar) is "live", so whenever this function is called, it returns the latest value reported by the underlying implementation, without any atomicity guarantee. Therefore, using this function to determine pixel sizes for graphics resources that are used in a frame is strongly discouraged. Rely on currentPixelSize() instead which returns a size that is atomic and will not change between createOrResize() invocations.

For depth-stencil buffers used in combination with the swapchain's color buffers, it is strongly recommended to rely on the automatic sizing and rebuilding behavior provided by the QRhiRenderBuffer:UsedWithSwapChainOnly flag. Avoid querying the surface size via this function just to get a size that can be passed to QRhiRenderBuffer::setPixelSize() as that would suffer from the lack of atomicity as described above.

See also

currentPixelSize()

Implemented in QD3D11SwapChain, QGles2SwapChain, QMetalSwapChain, QNullSwapChain, and QVkSwapChain.

Referenced by QSGGuiThreadRenderLoop::exposureChanged(), QSGThreadedRenderLoop::exposureChanged(), QBackingStoreDefaultCompositor::flush(), QSGGuiThreadRenderLoop::renderWindow(), and QSGRenderThread::syncAndRender().

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window()

QWindow * QRhiSwapChain::window ( ) const

inline

Returns

the currently set window.

Definition at line 1575 of file qrhi.h.

Referenced by QBackingStoreDefaultCompositor::flush().

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Member Data Documentation

m_currentPixelSize

QSize QRhiSwapChain::m_currentPixelSize

protected

Definition at line 1615 of file qrhi.h.

Referenced by QD3D11SwapChain::createOrResize(), QGles2SwapChain::createOrResize(), QMetalSwapChain::createOrResize(), QNullSwapChain::createOrResize(), and QVkSwapChain::createOrResize().

m_depthStencil

QRhiRenderBuffer* QRhiSwapChain::m_depthStencil = nullptr

protected

Definition at line 1612 of file qrhi.h.

Referenced by QD3D11SwapChain::createOrResize(), QGles2SwapChain::createOrResize(), QMetalSwapChain::createOrResize(), QVkSwapChain::createOrResize(), QGles2SwapChain::initSwapChainRenderTarget(), QMetalSwapChain::newCompatibleRenderPassDescriptor(), and QVkSwapChain::newCompatibleRenderPassDescriptor().

m_flags

Flags QRhiSwapChain::m_flags

protected

Definition at line 1610 of file qrhi.h.

Referenced by QMetalSwapChain::chooseFormats(), QD3D11SwapChain::createOrResize(), QMetalSwapChain::createOrResize(), QVkSwapChain::ensureSurface(), and QGles2SwapChain::initSwapChainRenderTarget().

m_format

Format QRhiSwapChain::m_format = SDR

protected

Definition at line 1611 of file qrhi.h.

Referenced by QMetalSwapChain::chooseFormats(), QD3D11SwapChain::createOrResize(), QMetalSwapChain::createOrResize(), and QVkSwapChain::ensureSurface().

m_proxyData

QRhiSwapChainProxyData QRhiSwapChain::m_proxyData

protected

Definition at line 1616 of file qrhi.h.

Referenced by QMetalSwapChain::createOrResize(), QMetalSwapChain::destroy(), and QMetalSwapChain::surfacePixelSize().

m_renderPassDesc

QRhiRenderPassDescriptor* QRhiSwapChain::m_renderPassDesc = nullptr

protected

Definition at line 1614 of file qrhi.h.

Referenced by QD3D11SwapChain::createOrResize(), QMetalSwapChain::createOrResize(), QNullSwapChain::createOrResize(), QVkSwapChain::createOrResize(), and QGles2SwapChain::initSwapChainRenderTarget().

m_sampleCount

int QRhiSwapChain::m_sampleCount = 1

protected

Definition at line 1613 of file qrhi.h.

Referenced by QMetalSwapChain::chooseFormats(), QD3D11SwapChain::createOrResize(), QMetalSwapChain::createOrResize(), QVkSwapChain::createOrResize(), QVkSwapChain::ensureSurface(), and QGles2SwapChain::initSwapChainRenderTarget().

m_window

QWindow* QRhiSwapChain::m_window = nullptr

protected

Definition at line 1609 of file qrhi.h.

Referenced by QD3D11SwapChain::createOrResize(), QGles2SwapChain::createOrResize(), QMetalSwapChain::createOrResize(), QNullSwapChain::createOrResize(), QVkSwapChain::createOrResize(), QVkSwapChain::ensureSurface(), QD3D11SwapChain::hdrInfo(), QMetalSwapChain::hdrInfo(), QGles2SwapChain::initSwapChainRenderTarget(), QD3D11SwapChain::isFormatSupported(), QVkSwapChain::isFormatSupported(), QD3D11SwapChain::surfacePixelSize(), QGles2SwapChain::surfacePixelSize(), QMetalSwapChain::surfacePixelSize(), and QVkSwapChain::surfacePixelSize().

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The documentation for this class was generated from the following files:

• qtbase/src/gui/rhi/qrhi.h (e36c1a8d840ee47be0d4fbf8069fda536042a53c)
• qtbase/src/gui/rhi/qrhi.cpp (e36c1a8d840ee47be0d4fbf8069fda536042a53c)