Composite and bit gravity

[Keith Packard]

Around 23 o'clock on Nov 12, Soeren Sandmann wrote:

> When a redirected window is resized, a new pixmap is allocated, but
> currently the old bits are not copied to the new pixmap until they are
> needed by CopyWindow. This breaks bit gravity, which at least GTK+,
> and I'd assume other toolkits, rely on.

Is it that CopyWindow isn't getting called?  I can see how that might 
happen when the bits don't move on the screen.

If you look in xserver CVS, you'll see the following comment for compint.h:

Revision 1.7
date: 2003-11-20 03:31:29 +0000;  author: keithp;  state: Exp;  lines: +31 -2
        * composite/compalloc.c: (compFreePixmap), (compReallocPixmap):
        * composite/compext.c:
        * composite/compinit.c: (compCloseScreen), (compScreenInit):
        * composite/compint.h:
        * composite/compwindow.c: (compCheckRedirect),
        (compPositionWindow), (compMoveWindow), (compResizeWindow),
        (compChangeBorderWidth), (compCopyWindow):
        * dix/window.c:
        (Yes, these are all related changes).  Rework window manipulation
        while Composite is enabled.  The basic problem was when the
        window was resized, the offscreen pixmap would get resized and if
        that shrunk, the eventual CopyWindow call would not be able to get
        bits.  Now, all resizes are managed by allocating a new pixmap
        and hanging on to the old one until after all of the CopyWindow
        calls are done.
        A related change was to reset the borderClip back to the
        parent-limited version when removing redirection from a window
        so that the UnmapWindow operation within that uses the correct
        value

There's also the problem that WindowGravity copies need access to the old 
bits, so you really can't just copy the bits during the resize.

-keith


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