XOrg 1.4.0.90 hangs up when pressing Alt+Tab with IceWM due to XOrg bug #13511. The first comment in that bug provides a patch that worked for me: https://bugs.freedesktop.org/show_bug.cgi?id=13511#c1 References: IceWM bug #1834961: https://sourceforge.net/tracker/?func=detail&atid=100031&aid=1834961&group_id=31 XOrg bug #13511: https://bugs.freedesktop.org/show_bug.cgi?id=13511
The following patch (reverting changes quoted here https://bugs.freedesktop.org/show_bug.cgi?id=13511#c11 and some other using the new macro) fixed the freeze for me.
Created attachment 146028 [details, diff] 1.4-fix-xkb-freeze.patch
The first patch didn't solve the problem when I did emerge --update and had to use the second one posted by Vincent which worked.
This should be fixed by a patch updating 1.4 to the current 1.4-branch in git.
Fixed in xorg-server-1.4.0.90-r4, which I expect to rekeyword as soon as a few last patches find their way in.