Analogue-sequencer

I've asked this before, iirc, but I want to give it another 
shot.

1. The P3 has a number of key combinations (press key X+Y to 
do Z) built into the user interface that I optionally liked 
to be replaced with a dedicated key. 

2. Afaik, the P3 has room for additional keys in the key 
scanner hardware.

3. Since I still haven't designed my front plate, I have 
space for, say, a block of 9 addtional keys.

4. As keycombos are added, to my taste for direct keys 
changes, I'd like to be able to change the function of the 
direct keys, by modding the executable myself.




So here's my suggestion:

- Add support for a number of additional keys in the OS, say 
16. I call theys OptKeys (for Optional Keys).

- Add a OptKey table in the OS. This is a vector of bytes, 
one byte for each OptKey (so 16 bytes in our example). 
Default value is all zeroes.

- Define an enum with no more than 255 function codes that 
represent the functions that are called by pressing key 
combos. Codes for other functions can be added too.

- Add code in the OS that scans the OptKeys. When one of 
them is detected as pused down, use its key index (say #5) 
to lookup the function code in the OptKey table. Based on 
the function code, perform the corresponding function. A 
(default) function code of value 0 indicates no action.

- When an OS is released, supply the offset in the binary 
for the OptKey table, so that we users can hack our own 
OptKey functions into the OS, without bothering Colin for 
that. Every one can now have its own optional keys, with 
whatever layout. :)