bug#44533: 27.1; Mac special key modifiers not functioning as expected

[YH Tan <astyh83@gmail.com>]

> On Nov 10, 2020, at 19:11, Alan Third <alan@idiocy.org> wrote:
> 
> On Mon, Nov 09, 2020 at 11:23:13PM +0800, YH Tan wrote:
>> The functioning of certain special key modifiers doesn't seem to work as
>> expected in 27.1.
>> 
>> For example, when I do:
>> 
>> (setq mac-left-option-modifier 'nil)
>            ^^^^
>> 
>> nothing happens to the left option key, which retains its meta function. 
> 
> You should be using mac-option-modifier, not mac-left-option-modifier.

This would reset both option keys. I would like to retain meta on the right. 

> 
>> If I use: 
>> 
>> (setq mac-option-modifier 'nil)
>> (setq mac-right-option-modifier 'meta)
>> 
>> the left option key is revived, but the right option key fails to capture
>> some of the regular meta keybindings, such as org-do-promote/demote,
>> org-move-subtree-up/down etc. 
>> 
>> The error can be replicated with emacs -Q and evaluating the above
>> functions. 
> 
> I can't replicate this.
> 
>> option+up/down/left/right doesn’t do anything on its own in the system.
>> 
>> In org-mode ‘C-h k’ just ignores the meta key and returns the arrow or
>> RET key (in the case of org-insert-heading). Only things like ‘M-x’
>> works with the reset right option in this case.
> 
> This actually sounds suspiciously like you've remapped fn as option in
> the system preferences. The fn key has some strange behaviours when
> used with "control" keys like the arrows.
> 

Yes. I do have: 

(setq mac-function-modifier 'meta)

which maps function to meta. You mean this can actually interfere with the right-option meta key? 
I’ve been using the same setup for previous versions of emacs without problem. 

> Do you have any other remapping set up? Are you using a USB keyboard?
> 
> -- 
> Alan Third