Comment 35 for bug 36812

(In reply to comment #24)
> Action taken - a four step MKPR sequence:
> 1) press (and hold) Alt 2) press Shift 3) release Shift 4) release Alt
.
.
.
> It would be IMHO practical, if the switching among layouts with Alt+Shift could
> work similarly as Alt+Tab switching between windows in XFCE/GNOME/KDE etc.,
> i.e. there would be some internal recency list, enabling to quickly switch
> between two most recently used layouts. I.e. press and hold Alt and then

To make this happen, the event should be triggered following step 3.
So, basically what needed to be done is whenever a key is pressed, key combination should be matched against the current pressed keys, and if a combination is met exactly, we should only set a flag for this combination - and not actually fire the event.
Whenever a key is released, this flag is checked - if the flag was set, the event shoud be fired and the flag should be cleared.
Whenever a key is pressed, the flag should also be cleared, so:
Example A:
Step Action Flag
---- ----------------------------- ----
                                      0
1 Alt pressed 0
2 Shift Pressed - match! 1
3 Shift released - EVENT FIRED 0
4 Alt released 0

Example B:
Step Action Flag
---- ----------------------------- ----
                                      0
1 Alt pressed 0
2 Shift Pressed - match! 1
3 Tab Pressed 0
4 Tab released 0
5 Shift released 0
6 Alt released 0

Example C:
Step Action Flag
---- ----------------------------- ----
                                      0
1 Alt pressed 0
2 Shift Pressed - match! 1
3 Shift released - EVENT FIRED 0
4 Shift Pressed - match! 1
5 Shift released - EVENT FIRED 0
6 Alt released 0

Example D: (very strange case, unexpected, just for "fun")
Step Action Flag
---- ----------------------------- ----
                                      0
1 Alt pressed 0
2 Shift Pressed - match! 1
3 Tab Pressed 0
4 Tab released 0
5 Shift released 0
4 Shift Pressed - match! 1
5 Shift released - EVENT FIRED 0
6 Alt released 0

I think this is good enough for 99% of the cases.
I did not dive into the protocol, but I have a feeling that adding such a flag is not a big deal, and does not require a rewrite, but please, correct me if I am wrong.

Udi