A rubber band is often used to show a new bounding area (as in a
QDockWidgetthat is undocking). Historically this has been implemented using a
QPainterand XOR, but this approach doesn’t always work properly since rendering can happen in the window below the rubber band, but before the rubber band has been “erased”.
You can create a
QRubberBandwhenever you need to render a rubber band around a given area (or to represent a single line), then call
resize()to position and size it. A common pattern is to do this in conjunction with mouse events. For example:class Widget: def mousePressEvent(self, event): origin = event.pos() if not self.rubberBand: self.rubberBand = QRubberBand(QRubberBand.Rectangle, self) rubberBand.setGeometry(QRect(origin, QSize())) rubberBand.show() def mouseMoveEvent(self, event): rubberBand.setGeometry(QRect(origin, event.pos()).normalized()) def mouseReleaseEvent(self, event): rubberBand.hide() # determine selection, for example using QRect.intersects() # and QRect.contains().
If you pass a parent to
QRubberBand‘s constructor, the rubber band will display only inside its parent, but stays on top of other child widgets. If no parent is passed,
QRubberBandwill act as a top-level widget.
show()to make the rubber band visible; also when the rubber band is not a top-level. Hiding or destroying the widget will make the rubber band disappear. The rubber band can be a
Line(vertical or horizontal), depending on the
shape()it was given when constructed.
Constructs a rubber band of shape
s, with parent
By default a rectangular rubber band (
Rectangle) will use a mask, so that a small border of the rectangle is all that is visible. Some styles (e.g., native macOS) will change this and call
setWindowOpacity()to make a semi-transparent filled selection rectangle.
QRubberBandcan represent a rectangle. Some styles will interpret this as a filled (often semi-transparent) rectangle, or a rectangular outline.
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