OS X: Modifier keys / option combinations / meta

[David Reitter]

Steven, Yamamoto-san, list,

I updated the mac modifier key patch to allow people to input all  
sorts of characters with the Option key that they can input by  
default, such as the Euro sign, the backslash or @ (on German  
keyboards with A-S-7 or A-L respectively), or the pound sign £ on US  
keyboards with A-3.

One can use the variable mac-pass-option-to-system to control this  
behavior: If non-nil, Emacs allows the system to define the  
characters and Option is not interpreted as modifier, unless another  
modifier key (Ctrl or Command) is pressed along with it. This allows  
me to use

(setq mac-option-modifier 'meta)

to still map Option to Meta and input keys like C-M-\ (on my US  
keyboard).

As discussed earlier, we allow people to use mac-command-modifier and  
mac-ctrl-modifier to assign Emacs keys to the other real keys. The  
only known drawback is that you can't enter C-M-\ on a, e.g., German  
keyboard, but I'm not sure if anybody would want to enter ESC S-C-A-7  
instead of redefining the command. One could make the default mapping  
of 'Option' to be empty for cases like these, saying that it is  
always handled by the system and never assumed to be Alt, even if  
other modifiers are pressed. Feedback on whether that would make  
sense would be appreciated.

As in the earlier version of the patch, mac-command-key-is-meta and  
mac-reverse-ctrl-meta  are declared deprecated, but work provided no  
mac-*-modifier is set to non-nil. This is the default - I don't know  
if this should actually be changed and if these variables can be  
kicked out before the release.

Patch for download here:

http://sourceforge.net/project/showfiles.php?group_id=138078