http://bugs.winehq.org/show_bug.cgi?id=23745
--- Comment #28 from Lance lancerdot@gmail.com 2011-02-01 21:48:17 CST --- (In reply to comment #27)
Set the in-game resolution to your native/full-screen resolution and close WAR3. Then, use CompizConfig Window Rules to make the window full-screen. Warcraft III will work as it does windowed mode, so minimizing and maximizing should not be a problem, but Compiz will make it full screen without stretching.
Oh, and I should add WAR3 needs to be run with (-window) for this to work.