QQuickFramebufferObject Class

The QQuickFramebufferObject class is a convenience class for integrating OpenGL rendering using a framebuffer object (FBO) with Qt Quick. 更多...

头：	#include <QQuickFramebufferObject>
qmake:	QT += quick
Since:	Qt 5.2
继承：	QQuickItem

该类在 Qt 5.2 引入。

所有成员列表，包括继承成员

公共类型

class

Renderer

特性

mirrorVertically : bool
textureFollowsItemSize : bool

公共函数

	QQuickFramebufferObject (QQuickItem * parent = nullptr)
virtual QQuickFramebufferObject::Renderer *	createRenderer () const = 0
bool	mirrorVertically () const
void	setMirrorVertically (bool enable )
void	setTextureFollowsItemSize (bool follows )
bool	textureFollowsItemSize () const

重实现公共函数

virtual bool	isTextureProvider () const override
virtual void	releaseResources () override
virtual QSGTextureProvider *	textureProvider () const override

信号

void	mirrorVerticallyChanged ( bool )
void	textureFollowsItemSizeChanged ( bool )

详细描述

On most platforms, the rendering will occur on a dedicated thread . For this reason, the QQuickFramebufferObject class enforces a strict separation between the item implementation and the FBO rendering. All item logic, such as properties and UI-related helper functions needed by QML should be located in a QQuickFramebufferObject class subclass. Everything that relates to rendering must be located in the QQuickFramebufferObject::Renderer 类。

警告： This class is only functional when Qt Quick is rendering via OpenGL, either directly or through the RHI-based rendering path . It is not compatible with other RHI backends, such as, Vulkan or Metal.

To avoid race conditions and read/write issues from two threads it is important that the renderer and the item never read or write shared variables. Communication between the item and the renderer should primarily happen via the QQuickFramebufferObject::Renderer::synchronize () function. This function will be called on the render thread while the GUI thread is blocked.

Using queued connections or events for communication between item and renderer is also possible.

Both the Renderer and the FBO are memory managed internally.

To render into the FBO, the user should subclass the Renderer class and reimplement its Renderer::render () function. The Renderer subclass is returned from createRenderer ().

The size of the FBO will by default adapt to the size of the item. If a fixed size is preferred, set textureFollowsItemSize to false and return a texture of your choosing from QQuickFramebufferObject::Renderer::createFramebufferObject ().

Starting Qt 5.4, the QQuickFramebufferObject class is a 纹理提供程序 and can be used directly in ShaderEffects and other classes that consume texture providers.

另请参阅 场景图形 - 渲染 FBO (帧缓冲对象) and 场景图形和渲染 .

特性文档编制

mirrorVertically : bool

This property controls if the size of the FBO's contents should be mirrored vertically when drawing. This allows easy integration of third-party rendering code that does not follow the standard expectations.

默认值为 false .

该特性在 Qt 5.6 引入。

访问函数：

bool	mirrorVertically () const
void	setMirrorVertically (bool enable )

通知程序信号：

void	mirrorVerticallyChanged ( bool )

textureFollowsItemSize : bool

This property controls if the size of the FBO's texture should follow the dimensions of the QQuickFramebufferObject item. When this property is false, the FBO will be created once the first time it is displayed. If it is set to true, the FBO will be recreated every time the dimensions of the item change.

默认值为 true .

访问函数：

bool	textureFollowsItemSize () const
void	setTextureFollowsItemSize (bool follows )

通知程序信号：

void	textureFollowsItemSizeChanged ( bool )

成员函数文档编制

QQuickFramebufferObject:: QQuickFramebufferObject ( QQuickItem * parent = nullptr)

Constructs a new QQuickFramebufferObject with parent parent .

`[pure virtual]` QQuickFramebufferObject::Renderer *QQuickFramebufferObject:: createRenderer () const

Reimplement this function to create a renderer used to render into the FBO.

This function will be called on the rendering thread while the GUI thread is blocked.

`[override virtual]` bool QQuickFramebufferObject:: isTextureProvider () const

重实现： QQuickItem::isTextureProvider () const.

`[override virtual]` void QQuickFramebufferObject:: releaseResources ()

重实现： QQuickItem::releaseResources ().

`[override virtual]` QSGTextureProvider *QQuickFramebufferObject:: textureProvider () const

重实现： QQuickItem::textureProvider () const.