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Internal/Contributor docs for the Qt SDK. Note: These are NOT official API docs; those are found at https://doc.qt.io/
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QVkBuffer Struct Reference

#include <qrhivulkan_p.h>

Inheritance diagram for QVkBuffer:
Collaboration diagram for QVkBuffer:

Classes

struct  DynamicUpdate
struct  UsageState

Public Member Functions

 QVkBuffer (QRhiImplementation *rhi, Type type, UsageFlags usage, quint32 size)
 ~QVkBuffer ()
void destroy () override
 Releases (or requests deferred releasing of) the underlying native graphics resources.
bool create () override
 Creates the corresponding native graphics resources.
QRhiBuffer::NativeBuffer nativeBuffer () override
char * beginFullDynamicBufferUpdateForCurrentFrame () override
void endFullDynamicBufferUpdateForCurrentFrame () override
 To be called when the entire contents of the buffer data has been updated in the memory block returned from beginFullDynamicBufferUpdateForCurrentFrame().
Public Member Functions inherited from QRhiBuffer
QRhiResource::Type resourceType () const override
Type type () const
void setType (Type t)
 Sets the buffer's type to t.
UsageFlags usage () const
void setUsage (UsageFlags u)
 Sets the buffer's usage flags to u.
quint32 size () const
void setSize (quint32 sz)
 Sets the size of the buffer in bytes.
virtual void fullDynamicBufferUpdateForCurrentFrame (const void *data, quint32 size=0)
Public Member Functions inherited from QRhiResource
virtual ~QRhiResource ()
 Destructor.
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

Public Attributes

VkBuffer buffers [QVK_FRAMES_IN_FLIGHT]
QVkAlloc allocations [QVK_FRAMES_IN_FLIGHT]
QVarLengthArray< DynamicUpdate, 16 > pendingDynamicUpdates [QVK_FRAMES_IN_FLIGHT]
VkBuffer stagingBuffers [QVK_FRAMES_IN_FLIGHT]
QVkAlloc stagingAllocations [QVK_FRAMES_IN_FLIGHT]
UsageState usageState [QVK_FRAMES_IN_FLIGHT]
int lastActiveFrameSlot = -1
uint generation = 0

Friends

class QRhiVulkan

Additional Inherited Members

Public Types inherited from QRhiBuffer
enum  Type { Immutable , Static , Dynamic }
 Specifies storage type of buffer resource. More...
enum  UsageFlag { VertexBuffer = 1 << 0 , IndexBuffer = 1 << 1 , UniformBuffer = 1 << 2 , StorageBuffer = 1 << 3 }
 Flag values to specify how the buffer is going to be used. More...
Public Types inherited from QRhiResource
enum  Type {
  Buffer , Texture , Sampler , RenderBuffer ,
  RenderPassDescriptor , SwapChainRenderTarget , TextureRenderTarget , ShaderResourceBindings ,
  GraphicsPipeline , SwapChain , ComputePipeline , CommandBuffer ,
  ShadingRateMap
}
 Specifies type of the resource. More...
Protected Member Functions inherited from QRhiBuffer
 QRhiBuffer (QRhiImplementation *rhi, Type type_, UsageFlags usage_, quint32 size_)
 \variable QRhiBuffer::NativeBuffer::objects
Protected Member Functions inherited from QRhiResource
 QRhiResource (QRhiImplementation *rhi)
Protected Attributes inherited from QRhiBuffer
Type m_type
UsageFlags m_usage
quint32 m_size
Protected Attributes inherited from QRhiResource
QRhiImplementation * m_rhi = nullptr
quint64 m_id
QByteArray m_objectName

Detailed Description

Definition at line 43 of file qrhivulkan_p.h.

Constructor & Destructor Documentation

◆ QVkBuffer()

QVkBuffer::QVkBuffer ( QRhiImplementation * rhi,
Type type,
UsageFlags usage,
quint32 size )

Definition at line 6763 of file qrhivulkan.cpp.

References QVkBuffer(), allocations, QVK_FRAMES_IN_FLIGHT, and stagingAllocations.

Referenced by QVkBuffer().

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◆ ~QVkBuffer()

QVkBuffer::~QVkBuffer ( )

Definition at line 6772 of file qrhivulkan.cpp.

References destroy().

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Member Function Documentation

◆ beginFullDynamicBufferUpdateForCurrentFrame()

char * QVkBuffer::beginFullDynamicBufferUpdateForCurrentFrame ( )
overridevirtual
Returns
a pointer to a memory block with the host visible buffer data.

This is a shortcut for medium-to-large dynamic uniform buffers that have their entire contents (or at least all regions that are read by the shaders in the current frame) changed {in every frame} and the QRhiResourceUpdateBatch-based update mechanism is seen too heavy due to the amount of data copying involved.

The call to this function must be eventually followed by a call to endFullDynamicUniformBufferUpdateForCurrentFrame(), before recording any render or compute pass that relies on this buffer.

Warning
Updating data via this method is not compatible with QRhiResourceUpdateBatch-based updates and readbacks. Unexpected behavior may occur when attempting to combine the two update models for the same buffer. Similarly, the data updated this direct way may not be visible to \l{QRhiResourceUpdateBatch::readBackBuffer()}{readBackBuffer operations}, depending on the backend.
When updating buffer data via this method, the update must be done in every frame, otherwise backends that perform double or triple buffering of resources may end up in unexpected behavior.
Partial updates are not possible with this approach since some backends may choose a strategy where the previous contents of the buffer is lost upon calling this function. Data must be written to all regions that are read by shaders in the frame currently being prepared.
This function can only be called when recording a frame, so between QRhi::beginFrame() and QRhi::endFrame().
This function can only be called on Dynamic buffers.

Reimplemented from QRhiBuffer.

Definition at line 6888 of file qrhivulkan.cpp.

◆ create()

bool QVkBuffer::create ( )
overridevirtual

Creates the corresponding native graphics resources.

If there are already resources present due to an earlier create() with no corresponding destroy(), then destroy() is called implicitly first.

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

Implements QRhiBuffer.

Definition at line 6809 of file qrhivulkan.cpp.

References allocations, destroy(), lastActiveFrameSlot, and QVK_FRAMES_IN_FLIGHT.

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◆ destroy()

void QVkBuffer::destroy ( )
overridevirtual

Releases (or requests deferred releasing of) the underlying native graphics resources.

Safe to call multiple times, subsequent invocations will be a no-op then.

Once destroy() is called, the QRhiResource instance can be reused, by calling create() again. That will then result in creating new native graphics resources underneath.

Note
Resources referenced by commands for the current frame should not be released until the frame is submitted by QRhi::endFrame().

The QRhiResource destructor also performs the same task, so calling this function is not necessary before deleting a QRhiResource.

See also
deleteLater()

Implements QRhiResource.

Definition at line 6777 of file qrhivulkan.cpp.

References allocations, QRhiVulkan::DeferredReleaseEntry::Buffer, QRhiVulkan::DeferredReleaseEntry::lastActiveFrameSlot, lastActiveFrameSlot, QVK_FRAMES_IN_FLIGHT, stagingAllocations, and QRhiVulkan::DeferredReleaseEntry::type.

Referenced by ~QVkBuffer(), and create().

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◆ endFullDynamicBufferUpdateForCurrentFrame()

void QVkBuffer::endFullDynamicBufferUpdateForCurrentFrame ( )
overridevirtual

To be called when the entire contents of the buffer data has been updated in the memory block returned from beginFullDynamicBufferUpdateForCurrentFrame().

Reimplemented from QRhiBuffer.

Definition at line 6909 of file qrhivulkan.cpp.

◆ nativeBuffer()

QRhiBuffer::NativeBuffer QVkBuffer::nativeBuffer ( )
overridevirtual
Returns
the underlying native resources for this buffer. The returned value will be empty if exposing the underlying native resources is not supported by the backend.

A QRhiBuffer may be backed by multiple native buffer objects, depending on the type() and the QRhi backend in use. When this is the case, all of them are returned in the objects array in the returned struct, with slotCount specifying the number of native buffer objects. While \l{QRhi::beginFrame()}{recording a frame}, QRhi::currentFrameSlot() can be used to determine which of the native buffers QRhi is using for operations that read or write from this QRhiBuffer within the frame being recorded.

In some cases a QRhiBuffer will not be backed by a native buffer object at all. In this case slotCount will be set to 0 and no valid native objects are returned. This is not an error, and is perfectly valid when a given backend does not use native buffers for QRhiBuffers with certain types or usages.

Note
Be aware that QRhi backends may employ various buffer update strategies. Unlike textures, where uploading image data always means recording a buffer-to-image (or similar) copy command on the command buffer, buffers, in particular Dynamic and UniformBuffer ones, can operate in many different ways. For example, a QRhiBuffer with usage type UniformBuffer may not even be backed by a native buffer object at all if uniform buffers are not used or supported by a given backend and graphics API. There are also differences to how data is written to the buffer and the type of backing memory used. For buffers backed by host visible memory, calling this function guarantees that pending host writes are executed for all the returned native buffers.
See also
QRhi::currentFrameSlot(), QRhi::FramesInFlight

Reimplemented from QRhiBuffer.

Definition at line 6872 of file qrhivulkan.cpp.

References QRhiVulkan::executeBufferHostWritesForSlot(), and QVK_FRAMES_IN_FLIGHT.

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◆ QRhiVulkan

friend class QRhiVulkan
friend

Definition at line 69 of file qrhivulkan_p.h.

Member Data Documentation

◆ allocations

QVkAlloc QVkBuffer::allocations[QVK_FRAMES_IN_FLIGHT]

Definition at line 54 of file qrhivulkan_p.h.

Referenced by QVkBuffer(), create(), and destroy().

◆ buffers

VkBuffer QVkBuffer::buffers[QVK_FRAMES_IN_FLIGHT]

Definition at line 53 of file qrhivulkan_p.h.

◆ generation

uint QVkBuffer::generation = 0

Definition at line 68 of file qrhivulkan_p.h.

◆ lastActiveFrameSlot

int QVkBuffer::lastActiveFrameSlot = -1

Definition at line 67 of file qrhivulkan_p.h.

Referenced by create(), and destroy().

◆ pendingDynamicUpdates

QVarLengthArray<DynamicUpdate, 16> QVkBuffer::pendingDynamicUpdates[QVK_FRAMES_IN_FLIGHT]

Definition at line 59 of file qrhivulkan_p.h.

◆ stagingAllocations

QVkAlloc QVkBuffer::stagingAllocations[QVK_FRAMES_IN_FLIGHT]

Definition at line 61 of file qrhivulkan_p.h.

Referenced by QVkBuffer(), and destroy().

◆ stagingBuffers

VkBuffer QVkBuffer::stagingBuffers[QVK_FRAMES_IN_FLIGHT]

Definition at line 60 of file qrhivulkan_p.h.

◆ usageState

UsageState QVkBuffer::usageState[QVK_FRAMES_IN_FLIGHT]

Definition at line 66 of file qrhivulkan_p.h.

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