[PyQt] Bug with QWidget masks in QGraphicsScene?

[Jeremy]

Hi Matteo,

First, thanks for your reply!  Unfortunately, I'm not sure your solution 
would work for what I'm trying to do (as is).  In essence, I'm trying to 
create a GUI with several irregularly shaped buttons, whose bounding 
boxes overlap (but not the actual shapes).  (For example, think of a 
rectangle cut across the diagonal -- each resulting triangle would be a 
button.)  I guess I could subclass QGraphicsScene, and add a method to 
register the buttons' masks with the scene, and create my own logic for 
determining which button should receive a click event when someone 
clicks on the scene (by redefining mousePressEvent, as you suggested).

I suppose that's what I'll do, until someone can determine if this is a 
bug or the proper behavior.

Thanks for the suggestion!  I wouldn't've thought of it otherwise.

 - J

Matteo Boscolo wrote:
> Hi Jeremy,
> I did some test and I notice that if you use the ..
> graphics_view.setMask(....)
> you get the get some problem.
>
> I do not why The view work in this way..I'm not so skilled in qt to help
> you.
>
> But a work around could be:
>
> graphics_scene.mousePressEvent =myMouseEvent #to get the mouse click event
> ..
>
> def myMouseEvent(event):
> 	#if event is in region:
> 		event.ignore()
>
> Regards,
> Matteo
>
> -----Original Message-----
> From: pyqt-bounces at riverbankcomputing.com
> [mailto:pyqt-bounces at riverbankcomputing.com] On Behalf Of Jeremy
> Sent: 11 June 2010 19:47
> To: pyqt at riverbankcomputing.com
> Subject: [PyQt] Bug with QWidget masks in QGraphicsScene?
>
> Hello,
>
> I have a question (which may stem from either a bug in PyQt, Qt, or just my
> understanding of how Qt is supposed to work). In particular, according to
> the Qt documentation
> (http://doc.trolltech.com/4.6/qwidget.html#setMask) masked widgets are only
> supposed to receive mouse events on their visible portions. This works fine
> on a normal widget in a GUI, but doesn't seem to be the case if I add a
> widget to a QGraphicsScene via the addWidget method.
>
> In particular, some example code is attached.  In this example I create two
> buttons, and place one in a QGraphicsScene and the other as part of a normal
> layout. I then add a simple mask so that only the left half of each button
> is visible. Then, if I click the non-visible part (right
> half) of the normal-layout-button, nothing happens (which seems like the
> correct behavior). But if I click the invisible right half of the
> QGraphicsScene button, the button still appears to be receiving the mouse
> click event.
>
> So, my question is...is this a bug in PyQt? Or does the same behavior happen
> under Qt in other languages? Or is it not a bug at all, and QWidgets are not
> supposed to respect their masks with regard to mouse events when added to
> QGraphicsScenes? Or am I just totally crazy? ;-)
>
> Any advice or suggestions anyone can provide would be very much appreciated!
>
> - Jeremy
>
>