[Qt-interest] Off-screen render with QGraphicsView; focus issues?

[Penn Taylor]

Summary: Hidden instances of QGraphicsView cannot be treated as focused 
and active in Qt 4.6 but (apparently) could be in Qt 4.5.3. How can this 
behavior be mimicked in Qt 4.6?

Detailed explanation:
I'm using a hidden QGraphicsView that contains a QGraphicsProxyWidget to 
render to texture and use this directly in an OpenGL app. This is done 
with a hidden QGraphicsView because user interaction takes place through 
a GL context (and window) owned and managed by another library.

I can get keyboard focus and tab events to propagate correctly, but some 
aspects aren't quite right. For example, clicking on a slider in my app 
allows the slider to be moved, but does not place the little "selected" 
border around the widget as it should. Ditto for tab traversal. This 
makes keyboard navigation difficult, because you can never tell which 
widget is selected.

I noticed that scene->hasFocus() and view->hasFocus() always return 
false, even if I explicitly call setFocus() just before hasFocus().  It 
appears calls to setFocus() and activateWindow() do nothing as long as 
the window is hidden. I suspect this to be the root of my problem. 
So...how can I make the QGraphicsView, scene, etc. act as though they 
are visible, active, and focused even when technically they are not?

This all worked fine in Qt 4.5.3 with a very simple event forwarding 
mechanism. Tab traversal, selection highlights, etc. all worked with no 
trouble and I never bothered to look at activateWindow(), hasFocus() and 
the like because everything "just worked". Qt 4.6 has made the event 
forwarding trickier, and has introduced the problems mentioned in the 
third paragraph. I'm working under the assumption that things worked 
with 4.5.3 because I was unknowingly exploiting a bug. Now I need to 
know the right way to do it. Or confirmation that Qt 4.6 contains a 
regression on this functionality.

Perhaps there needs to be a 
Qt::WA_DontShowOnScreenButTreatAsVisibleAndActive attribute that can be 
  set on windows?

-Penn Taylor