[Interest] Drawing artifacts when scrolling QGraphicsView on OS X

[Jelmer van der Linde]

Hello,

I get drawing issues when I simultaneously scroll and track the mouse
to let a (home made) tooltip follow it. It looks as if Qt fails to
track which part of the image should be redrawn. (screenshot:
http://dl.dropbox.com/u/6635118/Screen%20Shot%202012-05-18%20at%2013.04.21.png)

Is this a bug, or is my drawing code incomplete? The artifacts only
happen on OS X, with QT 4.8 or newer. A small example program (my
original program, but stripped down to a bare minimum) can be found
here: https://gist.github.com/gists/2843603 (cmake . && make && ./dact
should do)

Currently I do have a workaround that manually invalidates parts of the
scene, but this slows scrolling tremendously. (source: https://github.com/rug-compling/dact/commit/cdbf57d8ee5bf447b838756649ab395a279efbf2)

Any input is welcome.

Thank you
~ Jelmer