(UPDATED) Compositing window manager in Linux under VMWare?

Prima facie it seems not to be possible to enable compositing (*) in Linux running as a virtual machine, Trying to "enable desktop effects" in Ubuntu does not work. But xorg-vmware driver supports compositing out of the box, without any configuration needed on xorg.conf. So what?

The trick is to activate it directly on Metacity window manager GConf, without configuring any desktop effects. Opening gconf-editor, going to apps -> metacity -> general and enabling compositing_manager solves the issue.

Once you do this, window shadows show up immediately. Gnome-terminal can display a truly transparent background (once reloaded). I had some Qt examples that did translucent windows and OSX widget-like screen elements, and they all worked after Metacity configuration.

This was tested with Ubuntu Intrepid running as a virtual machine in VMWare Fusion 2.04. I am not sure whether "enabling desktop effects" fails because of some bug or because it needs OpenGL. By the way, OpenGL applications also work in that Linux, albeit slowly (tested with Billard-GL). If OpenGL were the problem, desktop effects would be just slow.

(*) Composition: X11 extension that allows windows to be rendered in offscreen buffers, and then composed together on-screen by the window manager. This feature allows truly translucent windows like Mac OS X, and also allows transformations and manipulations on window images. Composition is obviously faster when hardware OpenGL can be used for that.