How do I zoom in one window in Unity

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http://askubuntu.com – I'm trying to zoom in (or scale up) one window on the Macbook Pro with HiDPI/retina screen in Unity on 12.04. This is useful for some applications that doesn't allow the font size etc. to be changed. It would also be useful to e.g. scale up Virtualbox on hi-res screens. The compiz zoom plugin zooms the entire desktop, so that's not what I need. The shelf plugin does what I want, but only scales windows down. Thanks for any help! (HowTos)