In short: there was an option to deactivate keyboards/mouse grabs (therefore, allowing to Alt+Tab to other applications) or to kill the application with grabs by pressing special hotkeys. However, this option was removed in 2008 and, at least to my knowledge, there are no signs of its return in any form.
Gabriel, this bug is relevant to your question: https:/ /bugs.launchpad .net/ubuntu/ +source/ xorg-server/ +bug/338489 (and upstream bug http:// bugs.freedeskto p.org/show_ bug.cgi? id=21652 and mailing list discussion http:// bugs.freedeskto p.org/show_ bug.cgi? id=21652)
In short: there was an option to deactivate keyboards/mouse grabs (therefore, allowing to Alt+Tab to other applications) or to kill the application with grabs by pressing special hotkeys. However, this option was removed in 2008 and, at least to my knowledge, there are no signs of its return in any form.
Just my 2 roubles.