[Bug 20865] Steam login window jumps around the screen when moved

[wine-bugs at winehq.org]

http://bugs.winehq.org/show_bug.cgi?id=20865





--- Comment #8 from Vincent Povirk <madewokherd at gmail.com>  2009-12-14 00:41:57 ---
I wasn't on #wine-devel when you asked about this so I'll have to settle for
writing what I know or can easily look up on the bug. :(

Wine's windowing system is odd in that it's controlled by two different
servers: X and the wineserver. The position stored in wineserver is what
programs see, and SetWindowPos actually updates BOTH positions (see
set_window_pos and X11DRV_WindowPosChanged).

As you may have noticed, the ConfigureNotify event calls SetWindowPos (see the
X11DRV_ConfigureNotify function).

Now, here's the fun part. We get a ConfigureNotify event every time the window
moves, no matter who caused it. We ignore those events if the position we get
matches the wineserver position.

And here's the really fun part. If we are behind in processing ConfigureNotify
events, we may get a notify event for a PREVIOUS position, causing us to move
the window BACK to that position. If we get two ConfigureNotify events in a
row, for the same window, we will discard the old one (see merge_events), but
that is no guarantee that the event we are processing is the most recent.

Unfortunately, I don't think there's any way to tell whether an event is due to
Wine's configure request or something else.

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