This seems to be a regression caused by compiz r3623 (reverting that revision makes the gap disappear) and is not Unity related (this can be reproduced by just loading core and decor plugins).
** Package changed: unity (Ubuntu) => compiz (Ubuntu) ** Also affects: compiz Importance: Undecided Status: New ** Changed in: compiz Status: New => Confirmed -- You received this bug notification because you are a member of compiz packagers, which is subscribed to compiz in Ubuntu. https://bugs.launchpad.net/bugs/1140505 Title: [regression-r3623] Wallpaper bleeds through on top right when a window is opened maximized To manage notifications about this bug go to: https://bugs.launchpad.net/compiz/+bug/1140505/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~compiz Post to : compiz@lists.launchpad.net Unsubscribe : https://launchpad.net/~compiz More help : https://help.launchpad.net/ListHelp