[compiz] window decorations explained and how to move forward

[David Reveman]

On Sun, 2006-04-02 at 00:02 +0100, Mike Hearn wrote:
> Here are some unqualified opinions :) Don't worry, after today I will 
> run out of time and only be an observer ...
> 
> David Reveman wrote:
> > The window decoration system in compiz is implemented using a decoration
> > plugin and a separate window decoration drawing application (a
> > decorator).
> 
> Out of curiosity why is the decorator out of process rather than being 
> an integral part of the decorator plugin itself?

Window decorations and the things related to that is a large thing. The
window decorator can do more than just decorations, e.g. taskbar, root
window menu. Being able to move all this out of the compositing manager
is really nice.

Having main loops of toolkits running in compiz is not that easy, I
guess it's at least possible as long as we're just using one toolkit but
I'd like to avoid it.

Modularization is good. It will likely speed up and make development
easier.

> 
> > I'd like to move the drawing code out of gnome-window-decorator.c and
> > make it possible to plug in different drawing implementations. 
> 
> As there is nothing gnome specific about metacity themes, does it really 
> make sense for this to be "gnome-window-decorator"?

gnome-window-decorator should probably be renamed to
gtk-window-decorator, nothing gnome specific in it. I think most
metacity themes use gtk colors, or am I wrong?

> 
> > One drawing implementation that I'd like plug in here is metacity's current
> > drawing code so that compiz can be used with all existing metacity
> > themes. However, metacity's theme system is very limited and not design
> > for what we can do today with compiz. I believe that a new theme system
> > is necessary. How this theme system should be is currently beyond me,
> > SVG-based and shared between gtk/qt seems appropriate, though.
> 
> Well, it's easy to say we can do better, but I think it'd be better to 
> leave this until people have come up with alternatives to the boring 
> strip along the top. Otherwise we just end up with a slower way to draw 
> title bars.

Well, I think that gnome-window-decorator is currently doing better.
There's no rush with having a new theme system as long as we allow
programmatic themes like what we have in gnome-window-decorator today.

> 
> > I'm also a long time fan of blackbox WM 
> 
> What, not Waimae? Yeah some of us remember that ;) I even remember 
> people wondering where you had gone and what was going to happen with 
> it. "Where is David? Was he hit by a bus?" :p

:-)

> 
> > I'll probably put some, if not all, of this on the compiz page I just
> > created on freedektop wiki (http://www.freedesktop.org/Software/Compiz).
> 
> You may wish to check the writing plugin HTML page into CVS, so other 
> people can find it more easily.

Yes, maybe I should do that. I'll probably write some tutorials soon as
well, I'll make sure to look through existing once first though.

> 
> And finally, on a mildly related note, Xgl is currently eating a quarter 
> of my system RAM. I know it's time to upgrade - can't run 2006 
> technology on a box from '99 for sure - but is Xgl compressing the 
> pixmaps like MacOS X does?

No compression is currently used.

-David