Kristian Lyngstol kristian@bohemians.org
	
12/19/11
		
to Compiz
Greetings,

On Mon, Dec 19, 2011 at 12:41:31PM +0530, Ajay Garg wrote:
> Is there a way, that compiz-fusion ("Zoom Desktop" feature in
> particular), can be made to work in metacity, in a NON-gnome
> environment?

Compiz is not bound to Gnome, so yes, it's possible to use Compiz
without Gnome.

Metacity, however, is an other window manager entirely. Since both
Compiz and Metacity are window manager, you can not run both at the same
time.

> My major concerns are :
>
> a. Is the "compiz-fusion" code, inherently specific to the "compiz"
> window-manager, that "compiz-fusion" ships with?

Compiz Fusion was just a name for various plugins specific to Compiz.
The name is now defunct.

The code is pretty glued in with the logic of Compiz.

> b. Is the "compiz-fusion" code, inherently linked to "gnome"?

No.

Compiz was specifically made to be DE-agnostic. Hench the separation of
window decorations and window management (there are GTK and KDE-based
window decorators for Compiz, and others can be written).

There are some plugins that will be affected by DE, but mostly for
obvious reasons (like "GNOME Support"-plugins).

> I will be grateful to a reply, as it will get me started. More
> importantly, if it indeed is possible to kind-of "port"
> "compiz-fusion" to metacity-without-gnome, there will an overshoot of
> confidence in me. As I have said, coding (in any language) is not a
> problem for me.

If what you are most interested in is the enhanced zoom, I do believe
large parts of that plugin can be reused, assuming you use the original
C-version, not the C++ one.

It will not, however, be a matter of just tweaking it. The Compiz of
today is C++ and metacity is not. I am not familiar with the inner
workings of Metacity myself, so I am not able to answer whether or not
it's practical or even sensible to re-use the code.

Nor do I know just how much of Metacity is composite-aware or
OpenGL-aware.

Frankly, I don't really see the point in building on metacity for this
purpose. Compiz is quite modular and removing bits you don't like is
usually a matter of disabling plugins. It's often easier to think of
Compiz as a plugin framework to build a WM instead of as a WM in itself.

- Kristian

On Mon, Dec 19, 2011 at 3:11 PM, Ajay Garg <ajaygargnsit@gmail.com> wrote:
>
> I will be grateful to a reply, as it will get me started. More
> importantly, if it indeed is possible to kind-of "port"
> "compiz-fusion" to metacity-without-gnome, there will an overshoot of
> confidence in me. As I have said, coding (in any language) is not a
> problem for me.

Since the compositor and WM roles aren't strictly dependent on each
other, code-wise, it should be possible to run the compositor
separately to the WM, with some hacks.

Have a look at

http://git.compiz.org/~tuxmarkv/zcomp/

(That is very out of date, but the recent commits should show the idea).

Basically what is happening is that the compositor doesn't register
for SubstructureRedirectMask, so compiz is not permitted to intercept
configuration and mapping of windows. I believe that it also prevents
compiz from reparenting windows and as such, it also prevents compiz
from making and passive key or button grabs, since the ICCCM says that
only clients that own windows are allowed to make such grabs.

Keep in mind though, that a lot of the effects require window-manager
functionality in order to work correctly. Namely, the workspaces
switchers. Since those plugins will attempt to move windows around as
a result of their effects (eg, because of the way viewports are
implemented), it depends on the presiding window manager as to whether
or not that kind of interaction will be allowed, since it will
intercept all ConfigureWindow requests on the client windows.

You'll likely require some kind of abstraction service between the two
in order to handle the lack of privileges the compositor has.

All the best,

Sam