Idea how to fix slow window resize in a composited desktop

Adam Jackson ajax at
Tue Sep 4 09:33:13 PDT 2007

On Mon, 2007-09-03 at 13:52 +0200, Dennis Kasprzyk wrote:
> Hi,
> I think that I have found a solution for the slow window resize in a 
> composited desktop environment. I don't know enough about the xserver 
> internals to say that my idea will work, but I would like to share it with 
> you.
> To prevent the need the reallocation of new window pixmaps on the xserver side 
> and it's handling on the composite manager side during a frequent window 
> resize, we could redirect the drawing of the window to a pixmap that is 
> bigger than the window:

Yeah, this idea has come up before.  We even have the internal hook for
this, in SetWindowPixmap.  There are some situations where we can even
resize "for free", since most hardware has pitch or tile alignment
constraints.  However, everything we've measured so far indicates that
the slowest part of resizing is application reflow, not pixmap

It'd certainly be interesting to implement to see what the difference is

- ajax
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