Only grab the necessary Ctrl+DIGIT

These shortcuts are used for switching screens, and if we only have two
screens, we only need two shortcuts.

Signed-off-by: Morten Hustveit <mortehu@google.com>
Use _exit rather than exit after failed execve

exit after fork risks messing with the parent's file descriptors.

Signed-off-by: Morten Hustveit <mortehu@google.com>
Corrected rect::union_rect logic

Signed-off-by: Morten Hustveit <mortehu@google.com>
Fixed dual-monitor support

This was partly implemented from before, but never tested.

Signed-off-by: Morten Hustveit <mortehu@google.com>