QQuickPaintedItem

The QQuickPaintedItem class provides a way to use the QPainter API in the QML Scene Graph. More

Inheritance diagram of PySide2.QtQuick.QQuickPaintedItem

Synopsis

Functions

Virtual functions

Detailed Description

The QQuickPaintedItem makes it possible to use the QPainter API with the QML Scene Graph. It sets up a textured rectangle in the Scene Graph and uses a QPainter to paint onto the texture. The render target can be either a QImage or, when OpenGL is in use, a QOpenGLFramebufferObject . When the render target is a QImage , QPainter first renders into the image then the content is uploaded to the texture. When a QOpenGLFramebufferObject is used, QPainter paints directly onto the texture. Call update() to trigger a repaint.

To enable QPainter to do anti-aliased rendering, use setAntialiasing() .

To write your own painted item, you first create a subclass of QQuickPaintedItem , and then start by implementing its only pure virtual public function: paint() , which implements the actual painting. The painting will be inside the rectangle spanning from 0,0 to width() , height() .

Note

It important to understand the performance implications such items can incur. See RenderTarget and renderTarget .

class PySide2.QtQuick.QQuickPaintedItem([parent=None])

Constructs a QQuickPaintedItem with the given parent item.

PySide2.QtQuick.QQuickPaintedItem.RenderTarget

This enum describes QQuickPaintedItem ‘s render targets. The render target is the surface QPainter paints onto before the item is rendered on screen.

Constant

Description

QQuickPaintedItem.Image

The default; QPainter paints into a QImage using the raster paint engine. The image’s content needs to be uploaded to graphics memory afterward, this operation can potentially be slow if the item is large. This render target allows high quality anti-aliasing and fast item resizing.

QQuickPaintedItem.FramebufferObject

QPainter paints into a QOpenGLFramebufferObject using the GL paint engine. Painting can be faster as no texture upload is required, but anti-aliasing quality is not as good as if using an image. This render target allows faster rendering in some cases, but you should avoid using it if the item is resized often.

QQuickPaintedItem.InvertedYFramebufferObject

Exactly as for above, except once the painting is done, prior to rendering the painted image is flipped about the x-axis so that the top-most pixels are now at the bottom. Since this is done with the OpenGL texture coordinates it is a much faster way to achieve this effect than using a painter transform.

PySide2.QtQuick.QQuickPaintedItem.PerformanceHint

This enum describes flags that you can enable to improve rendering performance in QQuickPaintedItem . By default, none of these flags are set.

Constant

Description

QQuickPaintedItem.FastFBOResizing

Resizing an FBO can be a costly operation on a few OpenGL driver implementations. To work around this, one can set this flag to let the QQuickPaintedItem allocate one large framebuffer object and instead draw into a subregion of it. This saves the resize at the cost of using more memory. Please note that this is not a common problem.

PySide2.QtQuick.QQuickPaintedItem.contentsBoundingRect()
Return type

PySide2.QtCore.QRectF

This function is provided for compatibility, use size in combination with textureSize to decide the size of what you are drawing.

PySide2.QtQuick.QQuickPaintedItem.contentsScale()
Return type

float

This property holds Obsolete method for scaling the contents..

This function is provided for compatibility, use size() in combination with textureSize() to decide the size of what you are drawing.

PySide2.QtQuick.QQuickPaintedItem.contentsScaleChanged()
PySide2.QtQuick.QQuickPaintedItem.contentsSize()
Return type

PySide2.QtCore.QSize

This property holds Obsolete method for setting the contents size..

This function is provided for compatibility, use size in combination with textureSize to decide the size of what you are drawing.

PySide2.QtQuick.QQuickPaintedItem.contentsSizeChanged()
PySide2.QtQuick.QQuickPaintedItem.fillColor()
Return type

PySide2.QtGui.QColor

This property holds The item’s background fill color..

By default, the fill color is set to transparent .

PySide2.QtQuick.QQuickPaintedItem.fillColorChanged()
PySide2.QtQuick.QQuickPaintedItem.mipmap()
Return type

bool

Returns true if mipmaps are enabled; otherwise, false is returned.

By default, mipmapping is not enabled.

See also

setMipmap()

PySide2.QtQuick.QQuickPaintedItem.opaquePainting()
Return type

bool

Returns true if this item is opaque; otherwise, false is returned.

By default, painted items are not opaque.

PySide2.QtQuick.QQuickPaintedItem.paint(painter)
Parameters

painterPySide2.QtGui.QPainter

This function, which is usually called by the QML Scene Graph, paints the contents of an item in local coordinates.

The underlying texture will have a size defined by textureSize when set, or the item’s size, multiplied by the window’s device pixel ratio.

The function is called after the item has been filled with the fillColor .

Reimplement this function in a QQuickPaintedItem subclass to provide the item’s painting implementation, using painter .

Note

The QML Scene Graph uses two separate threads, the main thread does things such as processing events or updating animations while a second thread does the actual OpenGL rendering. As a consequence, is not called from the main GUI thread but from the GL enabled renderer thread. At the moment is called, the GUI thread is blocked and this is therefore thread-safe.

Warning

Extreme caution must be used when creating QObjects, emitting signals, starting timers and similar inside this function as these will have affinity to the rendering thread.

PySide2.QtQuick.QQuickPaintedItem.performanceHints()
Return type

PerformanceHints

Returns the performance hints.

By default, no performance hint is enabled.

PySide2.QtQuick.QQuickPaintedItem.renderTarget()
Return type

RenderTarget

This property holds The item’s render target..

This property defines which render target the QPainter renders into, it can be either Image , FramebufferObject or InvertedYFramebufferObject .

Each has certain benefits, typically performance versus quality. Using a framebuffer object avoids a costly upload of the image contents to the texture in graphics memory, while using an image enables high quality anti-aliasing.

Warning

Resizing a framebuffer object is a costly operation, avoid using the FramebufferObject render target if the item gets resized often.

By default, the render target is Image .

Note

Some Qt Quick backends may not support all render target options. For example, it is likely that non-OpenGL backends will lack support for FramebufferObject and InvertedYFramebufferObject . Requesting these will then be ignored.

PySide2.QtQuick.QQuickPaintedItem.renderTargetChanged()
PySide2.QtQuick.QQuickPaintedItem.resetContentsSize()

This convenience function is equivalent to calling setContentsSize (QSize()).

PySide2.QtQuick.QQuickPaintedItem.setContentsScale(arg__1)
Parameters

arg__1 – float

This property holds Obsolete method for scaling the contents..

This function is provided for compatibility, use size() in combination with textureSize() to decide the size of what you are drawing.

PySide2.QtQuick.QQuickPaintedItem.setContentsSize(arg__1)
Parameters

arg__1PySide2.QtCore.QSize

This property holds Obsolete method for setting the contents size..

This function is provided for compatibility, use size in combination with textureSize to decide the size of what you are drawing.

PySide2.QtQuick.QQuickPaintedItem.setFillColor(arg__1)
Parameters

arg__1PySide2.QtGui.QColor

This property holds The item’s background fill color..

By default, the fill color is set to transparent .

PySide2.QtQuick.QQuickPaintedItem.setMipmap(enable)
Parameters

enable – bool

If enable is true, mipmapping is enabled on the associated texture.

Mipmapping increases rendering speed and reduces aliasing artifacts when the item is scaled down.

By default, mipmapping is not enabled.

See also

mipmap()

PySide2.QtQuick.QQuickPaintedItem.setOpaquePainting(opaque)
Parameters

opaque – bool

If opaque is true, the item is opaque; otherwise, it is considered as translucent.

Opaque items are not blended with the rest of the scene, you should set this to true if the content of the item is opaque to speed up rendering.

By default, painted items are not opaque.

See also

opaquePainting()

PySide2.QtQuick.QQuickPaintedItem.setPerformanceHint(hint[, enabled=true])
Parameters

Sets the given performance hint on the item if enabled is true; otherwise clears the performance hint.

By default, no performance hint is enabled/

PySide2.QtQuick.QQuickPaintedItem.setPerformanceHints(hints)
Parameters

hintsPerformanceHints

Sets the performance hints to hints

By default, no performance hint is enabled/

PySide2.QtQuick.QQuickPaintedItem.setRenderTarget(target)
Parameters

targetRenderTarget

This property holds The item’s render target..

This property defines which render target the QPainter renders into, it can be either Image , FramebufferObject or InvertedYFramebufferObject .

Each has certain benefits, typically performance versus quality. Using a framebuffer object avoids a costly upload of the image contents to the texture in graphics memory, while using an image enables high quality anti-aliasing.

Warning

Resizing a framebuffer object is a costly operation, avoid using the FramebufferObject render target if the item gets resized often.

By default, the render target is Image .

Note

Some Qt Quick backends may not support all render target options. For example, it is likely that non-OpenGL backends will lack support for FramebufferObject and InvertedYFramebufferObject . Requesting these will then be ignored.

PySide2.QtQuick.QQuickPaintedItem.setTextureSize(size)
Parameters

sizePySide2.QtCore.QSize

This property Defines the size of the texture..

Changing the texture’s size does not affect the coordinate system used in paint() . A scale factor is instead applied so painting should still happen inside 0,0 to width() , height() .

By default, the texture size will have the same size as this item.

Note

If the item is on a window with a device pixel ratio different from 1, this scale factor will be implicitly applied to the texture size.

PySide2.QtQuick.QQuickPaintedItem.textureSize()
Return type

PySide2.QtCore.QSize

This property Defines the size of the texture..

Changing the texture’s size does not affect the coordinate system used in paint() . A scale factor is instead applied so painting should still happen inside 0,0 to width() , height() .

By default, the texture size will have the same size as this item.

Note

If the item is on a window with a device pixel ratio different from 1, this scale factor will be implicitly applied to the texture size.

PySide2.QtQuick.QQuickPaintedItem.textureSizeChanged()
PySide2.QtQuick.QQuickPaintedItem.update([rect=QRect()])
Parameters

rectPySide2.QtCore.QRect

Schedules a redraw of the area covered by rect in this item. You can call this function whenever your item needs to be redrawn, such as if it changes appearance or size.

This function does not cause an immediate paint; instead it schedules a paint request that is processed by the QML Scene Graph when the next frame is rendered. The item will only be redrawn if it is visible.

See also

paint()