Some applications make use of the alt (e.g firefox) and meta (e.g gnome)
keys in isolation. Thus it is necessary to interpose additional events
to prevent the likes of '<alt down> <alt up>' from being interpreted as
key presses.
E.G
[alt]
a = x
will currently cause 'alt+a' to produce:
<alt down>
<alt up>
<x down>
<x up>
In most cases this is identical to '<x>', however in some contexts the
additional alt keypress is meaningful.
To prevent this, we intelligently emit '<alt>+<control>' instead by sandwiching the
'<alt up>' event like so: '<control down> <alt up> <control up>'
The full sequence thus becomes:
<alt down>
<control down>
<alt up>
<control up>
<x down>
<x up>
Raheman Vaiya