I have a problem with a group of about a dozen QPushButtons inside a QScrollArea. Starting with the scroll area oriented at the top of the underlying widget, as I scroll down, some of the QPushButtons near the bottom of the area are not properly rendered as they come into view. In particular, the background is off-color and the text on the buttons is "shadowed" -- showing a light ghost of the text from the previous button in that position.
I rigged up a loop to do first update(), and when that didn't work, repaint() on the buttons as they come into view but it only helped a little -- the text is no longer shadowed but the backgrounds are still off-color.
As you can see, the buttons #19 and #20 have a coloration different from the rest. This miscoloring is even preserved if the buttons are pressed (switching to normal "pressed" coloration) and released (switching back to being miscolored).
Scrolling up and down a bit will clear it up, but that's not something we should require users to do.
Note that this is on a Nokia N97 -- I'm not set up at present to test it on a desktop.