Alt+Tab and other WM shortcuts not working while pointer is grabbed

[Wolfgang Draxinger]

Am Wed, 19 May 2010 15:07:09 -0700
schrieb "Octavio Alvarez" <alvarezp at alvarezp.ods.org>:

> Yes, but this should be a service of the Window Manager and/or the
> X server. Otherwise, it is also a security risk.

Agreed. Jamie Zawinsky already pointed out, that this is a serious lack
of the X11 system. The WM is not the right place to implement or to
control security grabs: The WM might implement it wrong or have other
bugs.

Please take a careful read of
<http://www.jwz.org/xscreensaver/toolkits.html>
Also note the date, Jamie wrote that in 2004, and as it happens a few
months ago gnome-screensaver happened to suffer from exactly the
problems outlined there (you could kill the screensaver/lock simply by
keeping the Return key pressed, causing some bug in GTK to tigger,
crashing the screensaver daemon, thus taking down the lock).

The clean solution would be some X extension for exclusive screen
access (and a own magic cookie maybe) i.e not just a grab, but the
ability to place a fullscreen window on top of everything else, with
it's own subwindow manager and stuff.

The screensaver daemon would then be responsible for managing that
exclusive overlay window, running graphic hacks and a separate,
crashable password entry program therein. But with the current X system
this is not possible, so the screensaver daemon must grab all input and
provide a properly audited, bugfree unlock dialog.


Wolfgang