Re: [dev] xinerama and dbe mutual exclusion

From: Christoph Lohmann <>
Date: Sat, 19 Jan 2013 15:03:27 +0100


On Sat, 19 Jan 2013 15:03:27 +0100 Mihail Zenkov <> wrote:
> 2013/1/19, Mihail Zenkov <>:
> > 2013/1/19, Christoph Lohmann <>:
> >> Please all report back of any performance issues in st not using xdbe.
> >> You can easily enforce Xdbe by commenting out the lines that query for
> >> the Xdbe extension and reset the xw.buf.
> >
> > With radeon-kms it show empty black screen with flickering on refresh
> > with usedbe = False and usedbe = True.
> Fix for this behavior:
> -xw.draw = XftDrawCreate(xw.dpy,, xw.vis, xw.cmap);
> +xw.draw = XftDrawCreate(xw.dpy, xw.buf, xw.vis, xw.cmap);

I pushed a patch to the st git repository which activates the XCopyArea
double buffering to st. In my first tests this is spaking the CPU usage
of X11, which is because it is not handling special cases and simply
does redraw if something new happens.

Please guys try this out. Of course I will remove this in some commits
so people having the dbe extension will use this fast drawing in the
next st release.

I still need some easy way to do the double buffering on my side without
doing too many X11 calls.

It is really annoying to have to assort to hacks in for something
that should be implemented in the graphics subsystem itself. Just give
be a buffer and I will tell you when to swap but please handle every‐
thing else on your own. That’s what dbe does, but more hacks interfere
with other hacks (Xinerama) which do hacking hacks in hacking the hack


Christoph Lohmann
Received on Sat Jan 19 2013 - 15:03:27 CET

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