To see this, do a build with double-buffering turned off (#define NO_DOUBLE_BUFFER in mozilla/view/src/nsViewManager.cpp). I was seeing this on Mac; it may happen on other platforms (not tested). Load a simple, text-only web page in apprunner. Note how, once loaded, the throbber animated GIF keeps flickering. It's not advancing through frames, just continuously redrawing one frame. Breakpoints in nsViewManager show that there are some invalidation problems. Break on nsViewManager::UpdateView(nsIView *aView, const nsRect &aRect, PRUint32 aUpdateFlags). This is being called alternatly from two places: 1. il_pixmap_update_notify() 2. il_frame_complete_notify() these two calls are passing in different rects, whose x and y coordinates differ by 40 twips. But RenderViews does seem to be redrawing the union of these two rects? There are 2 issues here: 1. Why is the idle throbber continuously sending update notifications? 2. Why do the 2 calls have different rects?

this happens XP, so marking it as such.

Simon, Would you test to see if fix for bug#3853 fixed this? (ie, its duplicate of bug#3853). -pn

Whatever it was, this bug seems to be fixed now.

*** This bug has been marked as a duplicate of 3853 ***

Simon says it's fixed; I dub this verified.