class QGraphicsEffect#

The QGraphicsEffect class is the base class for all graphics effects. More…

Inherited by: QGraphicsOpacityEffect, QGraphicsDropShadowEffect, QGraphicsColorizeEffect, QGraphicsBlurEffect

New in version 4.6.

Synopsis#

Properties#

enabledᅟ - Whether the effect is enabled or not

Virtual methods#

def boundingRectFor()
def draw()
def sourceChanged()

Slots#

def setEnabled()
def update()

Signals#

def enabledChanged()

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#

Effects alter the appearance of elements by hooking into the rendering pipeline and operating between the source (e.g., a QGraphicsPixmapItem ) and the destination device (e.g., QGraphicsView ‘s viewport). Effects can be disabled by calling setEnabled (false). If effects are disabled, the source is rendered directly.

To add a visual effect to a QGraphicsItem , for example, you can use one of the standard effects, or alternately, create your own effect by creating a subclass of QGraphicsEffect . The effect can then be installed on the item using setGraphicsEffect() .

Qt provides the following standard effects:

QGraphicsBlurEffect - blurs the item by a given radius

QGraphicsDropShadowEffect - renders a dropshadow behind the item

QGraphicsColorizeEffect - renders the item in shades of any given color

QGraphicsOpacityEffect - renders the item with an opacity

For more information on how to use each effect, refer to the specific effect’s documentation.

To create your own custom effect, create a subclass of QGraphicsEffect (or any other existing effects) and reimplement the virtual function draw() . This function is called whenever the effect needs to redraw. The draw() function takes the painter with which to draw as an argument. For more information, refer to the documentation for draw() . In the draw() function you can call sourcePixmap() to get a pixmap of the graphics effect source which you can then process.

If your effect changes, use update() to request for a redraw. If your custom effect changes the bounding rectangle of the source, e.g., a radial glow effect may need to apply an extra margin, you can reimplement the virtual boundingRectFor() function, and call updateBoundingRect() to notify the framework whenever this rectangle changes. The virtual sourceChanged() function is called to notify the effects that the source has changed in some way - e.g., if the source is a QGraphicsRectItem and its rectangle parameters have changed.

See also

setGraphicsEffect() setGraphicsEffect()

class ChangeFlag#

(inherits enum.Flag) This enum describes what has changed in QGraphicsEffectSource.

Constant

Description

QGraphicsEffect.SourceAttached

The effect is installed on a source.

QGraphicsEffect.SourceDetached

The effect is uninstalled on a source.

QGraphicsEffect.SourceBoundingRectChanged

The bounding rect of the source has changed.

QGraphicsEffect.SourceInvalidated

The visual appearance of the source has changed.

Constant	Description
QGraphicsEffect.SourceAttached	The effect is installed on a source.
QGraphicsEffect.SourceDetached	The effect is uninstalled on a source.
QGraphicsEffect.SourceBoundingRectChanged	The bounding rect of the source has changed.
QGraphicsEffect.SourceInvalidated	The visual appearance of the source has changed.

class PixmapPadMode#

This enum describes how the pixmap returned from sourcePixmap should be padded.

Constant

Description

QGraphicsEffect.NoPad

The pixmap should not receive any additional padding.

QGraphicsEffect.PadToTransparentBorder

The pixmap should be padded to ensure it has a completely transparent border.

QGraphicsEffect.PadToEffectiveBoundingRect

The pixmap should be padded to match the effective bounding rectangle of the effect.

Constant	Description
QGraphicsEffect.NoPad	The pixmap should not receive any additional padding.
QGraphicsEffect.PadToTransparentBorder	The pixmap should be padded to ensure it has a completely transparent border.
QGraphicsEffect.PadToEffectiveBoundingRect	The pixmap should be padded to match the effective bounding rectangle of the effect.

Note

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

property enabledᅟ: bool#

This property holds whether the effect is enabled or not..

If an effect is disabled, the source will be rendered with as normal, with no interference from the effect. If the effect is enabled, the source will be rendered with the effect applied.

This property is enabled by default.

Using this property, you can disable certain effects on slow platforms, in order to ensure that the user interface is responsive.

Access functions:

isEnabled()
setEnabled()
Signal enabledChanged()

__init__([parent=None])#

Parameters:: parent – QObject

Constructs a new QGraphicsEffect instance having the specified parent.

boundingRect()#

Return type:: QRectF

Returns the effective bounding rectangle for this effect, i.e., the bounding rectangle of the source in device coordinates, adjusted by any margins applied by the effect itself.

See also

boundingRectFor() updateBoundingRect()

boundingRectFor(sourceRect)#

Parameters:: sourceRect – QRectF
Return type:: QRectF

Returns the effective bounding rectangle for this effect, given the provided rect in the device coordinates. When writing you own custom effect, you must call updateBoundingRect() whenever any parameters are changed that may cause this this function to return a different value.

See also

sourceBoundingRect()

abstract draw(painter)#

Parameters:: painter – QPainter

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

This pure virtual function draws the effect and is called whenever the source needs to be drawn.

Reimplement this function in a QGraphicsEffect subclass to provide the effect’s drawing implementation, using painter.

For example:

MyGraphicsEffect::draw(QPainter painter)

    ...
    offset = QPoint()
    if sourceIsPixmap():
        # No point in drawing in device coordinates (pixmap will be scaled anyways).
        pixmap = sourcePixmap(Qt.LogicalCoordinates, offset)
        ...
        painter.drawPixmap(offset, pixmap)
    else:
        # Draw pixmap in device coordinates to avoid pixmap scaling
        pixmap = sourcePixmap(Qt.DeviceCoordinates, offset)
        painter.setWorldTransform(QTransform())
        ...
        painter.drawPixmap(offset, pixmap)

    ...

This function should not be called explicitly by the user, since it is meant for reimplementation purposes only.

drawSource(painter)#

Parameters:: painter – QPainter

Warning

This section contains snippets that were automatically translated from C++ to Python and may contain errors.

Draws the source directly using the given painter.

This function should only be called from draw() .

For example:

MyGraphicsOpacityEffect::draw(QPainter painter)

    # Fully opaque; draw directly without going through a pixmap.
    if qFuzzyCompare(m_opacity, 1):
        drawSource(painter)
        return

    ...