QPlatformGraphicsBuffer Class

The QPlatformGraphicsBuffer is a windowsystem abstraction for native graphics buffers. More...

Header: #include <QPlatformGraphicsBuffer>
Inherits: QObject

Public Types

enum AccessType { None, SWReadAccess, SWWriteAccess, TextureAccess, HWCompositor }
flags AccessTypes
enum Origin { OriginTopLeft, OriginBottomLeft }

Public Functions

virtual ~QPlatformGraphicsBuffer()
virtual bool bindToTexture(const QRect &rect = QRect()) const
int byteCount() const
virtual int bytesPerLine() const
virtual const uchar *data() const
virtual uchar *data()
bool lock(AccessTypes access, const QRect &rect = QRect())
virtual Origin origin() const
void unlock()

Protected Functions

QPlatformGraphicsBuffer(const QSize &size, const QPixelFormat &format)

Detailed Description

\inmoduleQtGui \since 5.5

Different platforms have different ways of representing graphics buffers. On some platforms, it is possible to create one graphics buffer that you can bind to a texture and also get main memory access to the image bits. On the other hand, on some platforms all graphics buffer abstraction is completely hidden.

QPlatformGraphicsBuffer is an abstraction of a single Graphics Buffer.

There is no public constructor nor any public factory function.

\internal

Member Type Documentation

enum QPlatformGraphicsBuffer::AccessType
flags QPlatformGraphicsBuffer::AccessTypes

This enum describes the access that is desired or granted for the graphics buffer.

ConstantValue
QPlatformGraphicsBuffer::None0x00
QPlatformGraphicsBuffer::SWReadAccess0x01
QPlatformGraphicsBuffer::SWWriteAccess0x02
QPlatformGraphicsBuffer::TextureAccess0x04
QPlatformGraphicsBuffer::HWCompositor0x08

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

enum QPlatformGraphicsBuffer::Origin

This enum describes the origin of the content of the buffer.

ConstantValue
QPlatformGraphicsBuffer::OriginTopLeft1
QPlatformGraphicsBuffer::OriginBottomLeft0

Member Function Documentation

[protected] QPlatformGraphicsBuffer::QPlatformGraphicsBuffer(const QSize &size, const QPixelFormat &format)

Protected constructor to initialize the private members.

size is the size of the buffer. format is the format of the buffer.

See also size() and format().

[virtual noexcept] QPlatformGraphicsBuffer::~QPlatformGraphicsBuffer()

Virtual destructor.

[virtual] bool QPlatformGraphicsBuffer::bindToTexture(const QRect &rect = QRect()) const

Binds the content of this graphics buffer into the currently bound texture.

This function should fail for buffers not capable of locking to TextureAccess.

rect is the subrect which is desired to be bounded to the texture. This argument has a no less than semantic, meaning more (if not all) of the buffer can be bounded to the texture. An empty QRect is interpreted as entire buffer should be bound.

This function only supports binding buffers to the GL_TEXTURE_2D texture target.

Returns true on success, otherwise false.

int QPlatformGraphicsBuffer::byteCount() const

Accessor for the length of the data buffer. This function is a convenience function multiplying height of buffer with bytesPerLine().

See also data(), bytesPerLine(), and size().

[virtual] int QPlatformGraphicsBuffer::bytesPerLine() const

Accessor for bytes per line in the graphics buffer.

[virtual] const uchar *QPlatformGraphicsBuffer::data() const

Accessor for the bytes of the buffer. This function needs to be called on a buffer with SWReadAccess access lock. Behavior is undefined for modifying the memory returned when not having a SWWriteAccess.

[virtual] uchar *QPlatformGraphicsBuffer::data()

Accessor for the bytes of the buffer. This function needs to be called on a buffer with SWReadAccess access lock. Behavior is undefined for modifying the memory returned when not having a SWWriteAccess.

bool QPlatformGraphicsBuffer::lock(AccessTypes access, const QRect &rect = QRect())

Before the data can be retrieved or before a buffer can be bound to a texture it needs to be locked. This is a separate function call since this operation might be time consuming, and it would not be satisfactory to do it per function call.

access is the access type wanted.

rect is the subrect which is desired to be locked. This argument has a no less than semantic, meaning more (if not all) of the buffer can be locked. An empty QRect is interpreted as entire buffer should be locked.

Return true on successfully locking all AccessTypes specified access otherwise returns false and no locks have been granted.

[virtual] Origin QPlatformGraphicsBuffer::origin() const

In origin of the content of the graphics buffer.

Default implementation is OriginTopLeft, as this is the coordinate system default for Qt. However, for most regular OpenGL textures this will be OriginBottomLeft.

void QPlatformGraphicsBuffer::unlock()

Unlocks the current buffer lock.

This function calls doUnlock, and then emits the unlocked signal with the AccessTypes from before doUnlock was called.