Re: cairo x11 surfaces

[Niels Grewe]

Hi Eric,

Am 13.10.2011 23:26, schrieb Eric Wasylishen:
> I had a look at implementing it today, and it turned out to be easier than 
> expected so I finished & committed it.
> 
> If we run in to problems we can switch back to XGCairoXImageSurface before 
> the next release, but it looks promising. In particular, I tried X forwarding 
> to Apple's X11.app, which only supports 24-bit windows, and the new surface 
> is significantly faster than XGCairoXImageSurface, and the alpha channel of 
> images is correctly preserved (unlike XGCairoSurface).

This is a nice change; things seem a lot faster now in the normal case.
But (at least for me) it seems to have quite the opposite effect once I
turn on compositing in the window manager (kwin, in this case). I'm
guessing that is because the compositing manager does its own
double-buffering, though the effects are a bit more servere than I would
expect from just that.
A possible workaround would be to check whether a compositing manager
has taken the _NET_WM_CM_S${ScreenNum} [0] selection and avoid the
double buffering in that case. But then we'd also have to keep track of
when compositing is enabled and disabled.

Cheers,

Niels

[0] http://standards.freedesktop.org/wm-spec/wm-spec-latest.html#id2552745