The Oxygen window decoration (optionally, on by default) animates window title changes with a transition animation. This usually works fine, but when the window has been resized prior to a title change, the transition is not smooth but rather flashes briefly. I've observed this with the Firefox download manager window, which shows the completion percentage of the running downloads in the window title.
Version is 4.8.2 BTW.
Git commit b59658743ff4b32239f66c9b87ab3c583e8a4ce9 by Hugo Pereira Da Costa. Committed on 20/04/2012 at 11:20. Pushed by hpereiradacosta into branch 'master'. mark title transition as dirty when resizing client, to avoid flicker. M +5 -0 kwin/clients/oxygen/oxygenclient.cpp http://commits.kde.org/kde-workspace/b59658743ff4b32239f66c9b87ab3c583e8a4ce9
Git commit 05ad4cbc3b954af14113149bf07eda9c0c7aca79 by Hugo Pereira Da Costa. Committed on 20/04/2012 at 11:20. Pushed by hpereiradacosta into branch 'KDE/4.8'. mark title transition as dirty when resizing client, to avoid flicker. M +4 -0 kwin/clients/oxygen/oxygenclient.cpp http://commits.kde.org/kde-workspace/05ad4cbc3b954af14113149bf07eda9c0c7aca79
That fixes it, as far as I can tell.
Thanks!