class QQuickPaintedItem

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

Inheritance diagram of PySide6.QtQuick.QQuickPaintedItem

Synopsis

Properties

Methods

Virtual methods

Signals

Note

This documentation may contain snippets that were automatically translated from C++ to Python. We always welcome contributions to the snippet translation. If you see an issue with the translation, you can also let us know by creating a ticket on https:/bugreports.qt.io/projects/PYSIDE

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 in Qt 6 is always a QImage. When the render target is a QImage, QPainter first renders into the image then the content is uploaded to 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 .

See also

Scene Graph - Painted Item Writing QML Extensions with C++

class 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

As of Qt 6.0, this value is ignored.

QQuickPaintedItem.InvertedYFramebufferObject

As of Qt 6.0, this value is ignored.

See also

setRenderTarget()

class PerformanceHint

(inherits enum.Flag) 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

As of Qt 6.0, this value is ignored.

Note

Properties can be used directly when from __feature__ import true_property is used or via accessor functions otherwise.

property contentsScaleᅟ: 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.

Access functions:
property contentsSizeᅟ: 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.

Access functions:
property fillColorᅟ: QColor

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

By default, the fill color is set to Qt::transparent.

Set the fill color to an invalid color (e.g. QColor()) to disable background filling. This may improve performance, and is safe to do if the paint() function draws to all pixels on each frame.

Access functions:
property renderTargetᅟ: QQuickPaintedItem.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 .

Access functions:
property textureSizeᅟ: 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.

Access functions:
__init__([parent=None])
Parameters:

parent – QQuickItem

Constructs a QQuickPaintedItem with the given parent item.

contentsBoundingRect()
Return type:

QRectF

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

contentsScale()
Return type:

float

See also

setContentsScale()

Getter of property contentsScaleᅟ .

contentsScaleChanged()

Notification signal of property contentsScaleᅟ .

contentsSize()
Return type:

QSize

See also

setContentsSize()

Getter of property contentsSizeᅟ .

contentsSizeChanged()

Notification signal of property contentsSizeᅟ .

fillColor()
Return type:

QColor

See also

setFillColor()

Getter of property fillColorᅟ .

fillColorChanged()

Notification signal of property fillColorᅟ .

mipmap()
Return type:

bool

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

By default, mipmapping is not enabled.

See also

setMipmap()

opaquePainting()
Return type:

bool

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

By default, painted items are not opaque.

abstract paint(painter)
Parameters:

painter – 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 issuing of graphics resource updates and the recording of draw calls. As a consequence, paint() is not called from the main GUI thread but from the GL enabled renderer thread. At the moment paint() 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.

See also

width() height() textureSize

performanceHints()
Return type:

Combination of PerformanceHint

Returns the performance hints.

By default, no performance hint is enabled.

renderTarget()
Return type:

RenderTarget

See also

setRenderTarget()

Getter of property renderTargetᅟ .

renderTargetChanged()

Notification signal of property renderTargetᅟ .

resetContentsSize()

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

setContentsScale(arg__1)
Parameters:

arg__1 – float

See also

contentsScale()

Setter of property contentsScaleᅟ .

setContentsSize(arg__1)
Parameters:

arg__1 – QSize

See also

contentsSize()

Setter of property contentsSizeᅟ .

setFillColor(arg__1)
Parameters:

arg__1 – QColor

See also

fillColor()

Setter of property fillColorᅟ .

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()

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()

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/

setPerformanceHints(hints)
Parameters:

hints – Combination of PerformanceHint

Sets the performance hints to hints

By default, no performance hint is enabled/

setRenderTarget(target)
Parameters:

target – RenderTarget

See also

renderTarget()

Setter of property renderTargetᅟ .

setTextureSize(size)
Parameters:

size – QSize

See also

textureSize()

Setter of property textureSizeᅟ .

textureSize()
Return type:

QSize

See also

setTextureSize()

Getter of property textureSizeᅟ .

textureSizeChanged()

Notification signal of property textureSizeᅟ .

update([rect=QRect()])
Parameters:

rect – 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()