PySide6.QtQuickControls2.QQuickAttachedPropertyPropagator¶

class QQuickAttachedPropertyPropagator¶

The QQuickAttachedPropertyPropagator class provides a way to propagate attached properties. More…

Synopsis¶

Methods¶

def __init__()
def attachedChildren()
def attachedParent()
def initialize()

Virtual methods¶

def attachedParentChange()

Note

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Detailed Description¶

In QML, it is possible to attach properties and signal handlers to objects. Providing Attached Properties goes into more detail about how to expose your own C++ attached types.

QQuickAttachedPropertyPropagator provides an API to propagate attached properties from a parent object to its children, similar to font and palette propagation. It supports propagation through items, popups , and windows.

If propagation of properties is not important, consider using a C++ or QML singleton instead, as it is better suited for that use case, and is more efficient in that it only requires one QObject.

To use QQuickAttachedPropertyPropagator :

Derive from it

Call initialize() in the constructor

Define set/inherit/propagate/reset functions for each property as needed

Reimplement attachedParentChange() to handle property inheritance

Implement a static qmlAttachedProperties function and declare the type as an attached QML type with QML_ELEMENT and QML_ATTACHED, as detailed in Providing Attached Properties

For an example that demonstrates this in depth, see Qt Quick Controls - Attached Style Properties Example .

See also

Styling Qt Quick Controls

__init__([parent=None])¶

Parameters:: parent – QObject

Constructs a QQuickAttachedPropertyPropagator with the given parent.

The parent will be used to find this object’s attached parent .

Derived classes should call initialize() in their constructor.

attachedChildren()¶

Return type:: .list of QQuickAttachedPropertyPropagator

This function returns the attached children of this attached object.

The attached children are used when propagating property values:

attachedParent()¶

Return type:: QQuickAttachedPropertyPropagator

This function returns the attached parent of this attached object.

The attached parent is used when inheriting property values:

attachedParentChange(newParent, oldParent)¶

Parameters:

newParent – QQuickAttachedPropertyPropagator
oldParent – QQuickAttachedPropertyPropagator

This function is called whenever the attached parent of this QQuickAttachedPropertyPropagator changes from oldParent to newParent.

Subclasses should reimplement this function to inherit attached properties from newParent.

initialize()¶

Finds and sets the attached parent for this attached object, and then does the same for its children. This must be called upon construction of the attached object in order for propagation to work.

It can be useful to read global/default values before calling this function. For example, before calling initialize(), the Imagine style checks a static “globalsInitialized” flag to see if it should read default values from QSettings. The values from that file form the basis for any attached property values that have not been explicitly set.