AIGLX, metacity, nvidia and Xgl

[David Reveman]

On Fri, 2006-02-24 at 04:41 +0100, Soeren Sandmann wrote: 
> David Reveman <davidr at novell.com> writes:
> 
> > Others might be able to do a better job than me on figuring out how
> > to extend metacity but I think it's to early to tell as the people
> > working on metacity that I talked to at xdevconf didn't seem to be
> > aware of issues I'm solving by not using an ordinary window manager
> > like metacity for compositing.
> 
> For people who are curious what this means:
> 
> "People working on metacity" means Søren, and "issues David is
> solving" means "argb window with an rgb child window results in an
> extra layer of redirection with the current Xorg code".

That's one important thing. There are also other things related to when
you have multiple screens that will require significant changes to
metacity. We don't want screens to be separated in then same way as
before with Composite and a window can with Composite possibly exist on
more than one screen and in different forms on different screens.

> 
> There are at least the following way to solve this, in order of
> increasing complexity:
> 
> - Fix up the X server so that the rgb child windows are allocated with
>   32 bits per pixel. Initialize the extra byte to 0xff and make sure
>   the drivers don't mess it up.
> 
> or
> 
> - Shape the reparent window such that it becomes invisible but retains
>   its input shape, then paint the decorations directly on the desktop.

Neither of those solutions solve the performance related problems.

> 
> or
> 
> - Change the window manager to not reparent when it is also working as
>   a compositing manager.
> 
> or
> 
> - Write a new window manager from scratch that doesn't reparent and
>   only works when it is also a compositing manager.
> 

To get the most out of Composite and for the richest possible desktop
experience I believe that writing a new window/composite manager from
scratch is the best way to go. Supporting both a composited desktop and
non-composited desktop in the same window manager will make it much
harder to provide all the functionality that is possible with Composite.

It's not harder than "metacity --replace" to switch to a non composited
desktop when you're running compiz and "compiz --replace" to switch
back. 

-David