Metacity as a compositing manager

[Christopher James Halse Rogers]

On Tue, 2009-02-10 at 01:25 +0100, Remco wrote:
> On Tue, Feb 10, 2009 at 12:03 AM, Christopher James Halse Rogers
> <chalserogers at gmail.com> wrote:
> > The characterisation of Compiz as just about shiny effects is wrong.
> > The default plugin set also provides a better _window manager_ than
> > Metacity in many ways.
> 
> I wouldn't know about that last claim. Metacity doesn't have all the
> useful features of Compiz, but it does work a lot better. While pure
> compositing actions such as Alt+Tab may be faster on Compiz (I don't
> notice any difference), the applications themselves are a lot slower.
> Have you ever tried resizing a window in Compiz? Metacity is much
> smoother.
If I remember correctly, this is an artefact of the slowness of
GL_EXT_tfp and making lots of new textures.  This is why the default
resize mode for Compiz is 'rectangle', which isn't slow at all.  Some of
this slowness will be going away as drivers get better.

>  Also, Compiz is different with regards to snapping windows.
> That's a very subtle difference, but combined with the slow resizing,
> it makes the desktop feel a lot harder to manipulate.
I, personally, don't find Compiz's snapping behaviour better or worse
than Metacity's.  If you can provide a use-case where Compiz's snapping
behaviour is bad (as opposed to simply different from Metacity's
behaviour), then this can be fixed in Compiz.

> 
> Switching between non-composited and composited Metacity is also a
> smoother transition. One, it doesn't take too long for the desktop to
> come up again (though it should really be as seamless as in Windows
> Vista). But what's more important: everything still works the same.
> It's just slightly more beautiful and useful.
> 
> Would you recommend switching from Compiz to Metacity when your laptop
> goes from AC to batery power? That's not a pretty sight. While
> Metacity doesn't do this perfectly seamlessly either, at least it's
> relatively fast, and it doesn't mess up your window positions.

No, I wouldn't.  But mainly because Compiz is no worse on battery life
than Metacity.  Compositing should be a battery-life _win_, generally.
There were some powertop benchmarks done, Compiz vs Metacity a year or
so ago, and the outcome was that they didn't make a consistent
difference.

I don't switch between Metacity and Compiz, and I don't suggest other
people do, either.

> 
> The ideal solution would be for Metacity (or the appropriate Gnome
> app) to implement some of the features that Compiz provides. Scale,
> Animations and the Desktop Wall come to mind. Animations may sound
> like a useless eye-candy thing, but when done subtly, it just provides
> more clues as to where objects are moving toward. Right now, for
> example, even compositing Metacity shows some kind of black rectangle
> effect when minimizing. That doesn't fit with the nicely shaded
> windows.

You appear to be describing something we already have.  Compiz.  It
behaves differently to Metacity, yes, but that's not necessarily a bad
thing in and of itself.  If Compiz does something badly, file a bug.  If
Metacity does something badly, file a bug.  But having Compiz behave
exactly the same as Metacity is an explicit non-goal.

> 
> Bottom line: the core of Metacity is just a lot better than that of
> Compiz. Compiz has the advantage of a huge amount of plugins. But I
> don't see why Metacity couldn't get plugins itself.

Because this is pretty much anathema to the goals of Metacity.  The
motto is "Metacity is Cheerios"!  Also, providing a plugin system would
almost certainly require serious changes to Metacity's core; you'd end
up with something like... Compiz.

> 
> Does anyone know if there is any development going on with Metacity's
> compositing mode (or the appropriate Gnome app)?
> 
There is gnome-shell, which uses a forked metacity with a completely
different compositor to provide a whole desktop, with panels and
task-switcher and such.

I would be amazed if any of these suggestions moved into Metacity's
trunk.

I'm not suggesting that Compiz is perfect; far from it.  I *am*
suggesting that the way to get a better desktop is to improve Compiz,
rather than reimplementing it in Metacity.
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