[Development] Losing keyboard events after sheet appears in Mac OS

[Chris Meyer]

In my window, if I have a QGraphicsView. I then display a dialog in
the form of a sheet attached to the window. After the sheet closes, I
lose all keyboard events directed towards the window, although menu
keyboard shortcuts still work.

This bug did not occur in 4.7 and it does occur in 4.8. It is 100%
reproducible within my application, but I have not isolated it to a
small test case yet.

If I remove the QGraphicsView, everything works fine.

Before I dive into the Qt source code or isolate it to file a bug, I'm
wondering if this rings any bells with any of the Mac developers? Has
anyone seen anything like this? Has anyone made changes since 4.7
which might result in this behavior?