GNOME 2.22 released

I tried the compositing in Metacity and it was quite slow, this is because it's using no hardware acceleration. You notice the most the slowness when you drag a window as all pixels have to be moved through software. I wish that there was a way to keep some of the nice features like the windows previews in ALT-TAB but to disable the slow and expensive operations like window moving and resizing.

Finally I had to turn it off since it was too slow for my old laptop (a 3 years old laptop).

By the way this is not Metacity's only problem I had a similar problem with XFCE's compositing since it's also made in software.

The release notes say you can enable hardware acceleration by setting the appropriate key in the gconf-configurator (or via command line):

gconftool-2 -s --type bool /apps/metacity/general/compositing_manager true

but that hardware compositing is (depending on hardware/driver) not considered sufficiently stable to be included as an option in the preferences dialogue. I didn't try, though, still happily running 2.20.

Saddly the laptop I have at work, the one on which I compiled Metacity, has an ATI video card and the hardware acceleration doesn't work for me since my last upgrade.

I will give it a try with my EEE PC which uses an intel video card and see if it works better. I will post my results here.

I tried it on the EEE PC and it works smother, the reason is probably because there are less pixels to move. But I'm still convinced that there's no hardware acceleration in metacity for the composite effects.

The release notes simply says that: "Not all graphics hardware reliably supports compositing", this means that first the Xorg graphics card drivers must support the extension "composite". Still even if the graphics card has support for the "composite" extension this doesn't imply that the composite operations will be performed through hardware acceleration (OpenGL). That's exactly the case with Metacity, all the pixels manipulations are still performed in software. So if big windows are moved it's slow and jerky, plus it eats a lot of CPU. That's exactly what I experience.

Hopefully things will improve in Metacity and we can have some more eye candy. The future looks promising.

Huh, that's a little strange. My understanding of compositing window managers is that the window manager doesn't have to know anything about the xserver. It just uses OpenGL operations, and if it can be accelerated it will be.

Maybe you have to do something to configure Xgl or AIGLX yourself? It's been a while since I've tried to set this up (with Beryl) so I don't remember. I know Ubuntu has a tool that sets everything up for you, and it involves getting some extra packages for the xserver, as well as making sure you have the right drivers for your video card.

From my understanding compositing is a technology that lets the Xserver draw windows into pixmaps (buffers) instead of directly into the screen. With this technology an application can ask to have a live preview of a window without having the window been rendered into the screen. That's all that there's in the composite extension of the XServer.

In order to have the composite extension working, graphic drivers have to provide support for this. This doesn't imply that the composite is performed through software acceleration, beside composite only gives you the actual 'screenshot' of a window, no more. But this is the minimum that's needed in order to have nice drop shadows, real transparencies and live previews. Keep in mind that all of this can be done without any hardware acceleration (OpenGL). In fact xcompmgr was able to do drop shadows and to have some transparency without OpenGL along time ago.

What happens now is that thanks to the composite extension we can make a lot of fancy stuff because we are able to see live renderings of the windows and to manipulate them. This is exactly what window managers or composite managers like compiz, xfce's window manager, KDE 4 window manager an Metacity are doing.

Manipulate window previews can be done through dedicated libraries like OpenGL. This makes a lot of sense since window previews can be seen as texture and can be manipulated very easily. This is even more interesting because OpenGL can be accelerated through hardware acceleration, thus relieving the CPU of this hard burden.