[PATCH] composite: Optimize resizes of ForgetGravity windows

[Keith Packard]

Adam Jackson <ajax at redhat.com> writes:

> [censored] borders.  True enough.  Okay, so we can still take this
> shortcut if either:
>
> a) pixmap is resizing but border width has not changed
> b) pixmap is not resizing but border width has changed

  c) pixmap is resizing by twice the change in border width in
     both directions. This happens when you just change the border size
     of a window (as when it gets managed by the WM).

> I guess then the other problem is handling non-Forget subwindows?

Sadly, it's worse than you  think -- any children have their contents
retained as they aren't getting resized along with the parent.

> Technically we're allowed to treat any window like Forget so it's
> _legal_ to blow away subwindow content in those cases, but we'd need to
> signal that up to the caller so we know to generate exposes for bits
> dropped down the memory hole.

I'd suggest that we'd want to hack this in the original expose
computation. Ick.

-- 
keith.packard at intel.com
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