So, you want to map buttons to F1-F5?
Check this doc: http://openmsx.sourceforge.net/manual/commands.html#bind
It contains this example:
Map button 8 of joystick 1 to F2-key:
bind "joy1 button8 down" "keymatrixdown 6 0x40"
bind "joy1 button8 up" "keymatrixup 6 0x40"
That 6 and 0x40 refer to row 6 of the keyboard matrix and bit 6 (0100 0000 = 0x40). This matches with the position of F-2 in the tables shown on this web page: http://map.grauw.nl/articles/keymatrix.php
So, for F3 you need 6 0x80
, for F4 you need 7 0x01
, and for F5 you need 7 0x02
. You get what I mean now, I guess.
And button 8... I don't have a GCW Zero myself, so I don't know which buttons map to which button numbers in SDL... 8 is just an example here. If it works like the Dingoo A320, the buttons aren't mapped to joystick buttons at all, and the "joy1 button8"
stuff is not applicable... then you would have to use the key name instead, like this example:
bind TAB "keymatrixdown 6 0x40"
bind TAB,release "keymatrixup 6 0x40"
(On Dingoo A320, TAB is mapped to the left shoulder key. So the above code would remove the mapping to of the left shoulder key from 'decrease volume' (see mth's README) to press F2 on the MSX.)
Yes, it's a bit complicated, I warned you
But I hope this helps.
For crawling in MG2:SS I think you can just press button A and B at the same time, just like on a real MSX.