From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20021218

Description of problem:
If you choose Mod1-Shift_L (the default) as the keyboard layout switch hotkey,
it only switches the keyboard layout if you hold alt, press left shift, release
shift and then release alt.  If you release alt before shift, it seems to revert
to the original state.  Is this intentional, just to avoid accidental switching? 

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1.Press Alt and hold
2.Press shift
3.Release Alt


Actual Results:  Keyboard layout is unchanged.

Expected Results:  I'd expect it to change.

Additional info:

I can see that this may well be a feature, but it can be annoying if you release
both keys almost at the same time.  It could try to time the events to avoid
unintended changes, e.g., if the time between the pressing of the second key and
the releasing either key is larger than the interval between the pressing of
both keys, then it's an intended layout switch.  This helps avoid pressing the
shift right before releasing the alt when a layout switch is not intended.