What is the most basic window manager for ubuntu that can be used to display a single application

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http://askubuntu.com – I've tried starting a full screen application without a window manager, using xinit, which works but instead of starting at the top left of the screen the application starts somewhere in the middle of my screen. I've tried the same using a custom entry in /usr/share/xsessions and starting that from lightdm instead of the default ubuntu window manager, but that gives me the same result. I've then added my application to the startup applications of the ubuntu window manager and that works properly... but I don't want to start the entire desktop So I'm thinking perhaps a simple window manager (HowTos)