[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 #25 from Austin Lund <austin.lund at gmail.com>  2010-06-22 06:22:52 ---
(In reply to comment #21)
> There are cases where it's appropriate for a ConfigureNotify event to result in
> another ConfigureWindow request. Namely, if an application handles a
> WM_WINDOWPOSCHANGING event by supplying a new size/position.

But isn't the way to do the WM_WINDOWPOSCHANGING to adjust the WINDOWPOS passed
in the lParam and not to call SetWindowPos()?

The one case I can think of where this makes sense is when a non-wine based
movement of the window occurs.  My guess is that either X or the window manager
will do this and a ConfigureNotify event will occur because of it.  But surely
this is a reason to update the x11drv information (and send appropriate window
messages) rather than calling SetWindowPos (unless you change the WINDOWPOS
structure as above, which could be handled by checking if the WndProc did
that).

The heart of the issue is when this occurs:

SetWindowPos(100,100,100,100) <- from application
SetWindowPos(200,200,100,100) <- from application, no ConfigureNotify
ConfigureNotify(100,100,100,100) <- from first call 
  SetWindowPos(100,100,100,100) <- from wine ConfigureNotify handler
ConfigureNotify(200,200,100,100) <- from second call
  SetWindowPos(200,200,100,100)
#Two ConfigureNotifys are joined
ConfigureNotify(200,200,100,100) 
#Done as things are consistent.

But this will make things jump around before being done.  The issue is that
SetWindowPos will return then another call to SetWindowPos can be made before
the window is actually moved and the ConfigureNotify event is sent.  If there
was a lock which blocked the second SetWindowPos call until a configure notify
event occurs between the first and second SetWindowPos calls then the jumping
cannot occur.  And if an external ConfigureWindow call happens then this is not
blocked as it's only calling SetWindowPos that takes the lock and
ConfigureNotify which releases it.  If the external ConfigureWindow call occurs
between the two SetWindowPos calls then it will jump around, but that would
happen anyway.

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