RandR 1.4 restart

Keith Packard keithp at keithp.com
Tue Mar 1 08:02:24 PST 2011

On Tue, 1 Mar 2011 15:48:51 +0200, Ville Syrjälä <ville.syrjala at nokia.com> wrote:

> So what about also allowing windows to use the scanout pixmaps as their
> backing pixmap? I'm mainly interested in something that would allow
> unredirected 32bpp windows on a 16bpp screen.

We talked about a SetWindowPixmap call a while ago. There were lots of
corner cases dealing with window configuration changes that made it look
a bit tricky and so we punted.

Scanout pixmaps get resized automatically when the associated crtc gets
a new mode. This lets a compositing manager deal with the scanout pixmap
creation while separate screen configuration applications deal with mode
setting. Of course, internally, this is done by creating a new scanout
pixmap and pointing the existing XID at the new object. (Hrm. I wonder if
there are implications for DRI2/GLX/EGL here...)

A window pixmap is freed when the window changes size and a new window
pixmap allocated. This allows compositing managers to draw consistent
frames in the face of window resize; they can sequentially draw a frame
and then check for configuration notify events, assigning new XIDs to
resized windows.

If we could nail down sensible semantics that tied these two notions
together cleanly, I can imagine this would be useful.

keith.packard at intel.com
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