[RFC] Enforcing Compositing

Martin Gräßlin mgraesslin at kde.org
Sun Feb 20 15:12:50 CET 2011

On Sunday 20 February 2011 14:47:17 Markus Slopianka wrote:
> > Since 4.2 we have enabled OpenGL based compositing by default and I was
> > wondering if in 4.7 we should go the next step: disabling the possibility
> > to turn compositing off if supported.
> > 
> > With Mesa 7.10 it seems that the driver problems (Mesa 7.8) which hit us
> > in 4.5 are finally gone
> > (...)
> > What do you think about this idea?
> Well, it's hard to predict the future. Drivers could get regressions again.
True, but I hope that the drivers developers and distributions are more aware 
of the situation now. And if compositing is enforced it will be detected more 
early as the affected KDE devs will come into #kwin and yell at us :-)

In general I think that the driver devs must be aware they their drivers may 
never regress again if they want that the DEs transit from X11 to Wayland - 
and we all want that.
> I think the problem is less the ability to turn off compositing, it's the
> wording. IMO the "Enable desktop effects" checkbox should only apply to
> the actual effects but not the compositing support. I've seen people in
> forums who are not interested in shadows, transparent windows etc. They
> dislike "eye candy". What they don't get in some cases is that enabled
> compositing and all effects turned off should be better in most situations
> (unless the driver is broken).
The problem is that the users are miss informed. Compositing is not about eye-
candy but about providing a better user interface. Why should it be possible 
to disable Present Windows or Desktop Grid? I don't see a reason why we should 
make it possible to disable such effects.

And concerning transparent windows and shadows: that's not done in effects. 
It's part of the base compositor.
> For disabling compositing, people could use the "Advanced" tab with the new
> option "None" added to the "Compositing type" drop down menu.
That might be a good idea
> > I would keep
> > * the shortcut to suspend compositing
> > * the dbus call to toggle compositing (might be useful for games and so
> > on)
> Could the shortcut call dbus? What I experienced when occasionally turning
> off composite support manually is that the shortcut does not flip the
> "composite switch" plasmoid and the shortcut always overrules the plasmoid
> which means that I can't turn it on again using the plasmoid.
The plasmoid is completely outdated and useless and not adjusted to KWin's 
current API. It should not be used and best deleted from the SVN.

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