Grabbing widget's background

**jpn** · 13th May 2006, 22:50

I'm doing some effects to a child widget. For performing these effects, I need to grab an image of the child widget's background. Or more correctly, grab an image of anything behind the child widget.

The problem is, that when I call QPixmap::grabWidget() for the widget's parent or window, the widget itself gets naturally drawn too. The only way I have found to avoid this is to hide the widget during the grab. This leads to a slight flickering, which is not what I want.

Qt Code:

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// QWidget* widget is the widget whose background we are insterested of
 
// map widget's rect to it's window
QRect bgRect = widget->rect();
bgRect.moveTo(widget->mapTo(widget->window(), bgRect.topLeft()));
 
// need a better solution for this to avoid flickering
widget->hide();
QImage behind = QPixmap::grabWidget(widget->window(), bgRect).toImage();
widget->show();

// QWidget* widget is the widget whose background we are insterested of

// map widget's rect to it's window
QRect bgRect = widget->rect();
bgRect.moveTo(widget->mapTo(widget->window(), bgRect.topLeft()));

// need a better solution for this to avoid flickering
widget->hide();
QImage behind = QPixmap::grabWidget(widget->window(), bgRect).toImage();
widget->show();

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Any ideas, how to achieve the same without the hide/show trick, if it's even possible?