[PyKDE] Trouble figuring out QCanvas and QCanvasView

Bryan O'Sullivan bos at serpentine.com
Wed Oct 6 19:47:03 BST 2004

On Wed, 2004-10-06 at 03:32 -0700, David Boddie wrote:

> That's disappointing to hear. 

Think of it as an opportunity to write an article for one of the
developerworks, onlamp and so on sites :-)

> I think that the problem is with the ownership of the QCanvas, although 
> it's very strange if that really is the case since you pass it to the 
> QCanvasView. I "fixed" your example so that it would work by giving the 
> QCanvas a parent when it is created. I've included the modified code below. 

You're right!  It was just a one-line change that was required.  Well,
four bytes really.  Thanks.  I can safely say that this would not have
occurred to me.

Armed with this knowledge, I checked Troll Tech's Qt documentation,
along with the docs in theKompany's PyQtDoc product, and sure enough,
there's no mention anywhere of the fact that a QCanvas must have a
parent in order to actually render anything.

By the way, everything also works if a QCanvasView, whose parent is a
QWidget, is the parent of the QCanvas.


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