Is it possible to set the opacity of qt widgets?

Question

I know that there is a function QWidget::setWindowOpacity(qreal level) but as written in the documentation this does only work for windows.

Is there a way to make widgets that are lying inside layouts opaque too?

What I'm trying to do is an animation where widgets are fading in. I once did that with a preferences-dialog and there it worked.

So do you think there is a way or a work-around to achieve opacity for widgets inside layouts? How would you do that?

Thanks in advance!

Answer 1

Just use QGraphicsOpacityEffect in order to achieve this effect.

• Qt4: http://doc.qt.io/qt-4.8/qgraphicsopacityeffect.html
• Qt5: http://doc.qt.io/qt-5/qgraphicsopacityeffect.html

Answer 2

Well for widgets inside mainwidow appear to have setAutoFillBackground(False) by default.

to make it fade in fadeout u need to to use QGraphicsOpacityEffect along with setAutoFillBackground(True)

a small example: write inside the widget which is called inside the mainwindow

op=QGraphicsOpacityEffect(self)
op.setOpacity(1.00) #0 to 1 will cause the fade effect to kick in
self.setGraphicsEffect(op)
self.setAutoFillBackground(True)