Why you would want to do that? Because it uses less resources and it may run better for old or incompatible video cards (including Intel). You don’t even need accelerated graphics to run Metacity with compositing and it even works well inside VirtualBox.

This will be enough for running applications that require a compositing manager, such as Avant Window Navigator (for which I posted installation instructions a while ago), Screenlets and probably the new Cairo Dock v2 too (although I only tested Metacity Compositing Manager with Avant Window Navigator). In addition, you get shadows, max/minimize animations, and shaded Alt-Tab effects.

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