bug#21551: Fix Mac OS X key bindings bug

[Philipp Stephani <p.stephani2@gmail.com>]

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Anders Lindgren <andlind@gmail.com> schrieb am Sa., 2. Jan. 2016 um
09:08 Uhr:

> I found a case where the code in question is needed, which none of the
> suggested patches handle correctly.
>
> Steps to repeat:
>
>     (setq ns-alternate-modifier nil)
>
>     Press left CMD-ALT-9
>
>     An unmodified Emacs replies "s-]" is not bound. (This assumes a
> Swedish keyboard layout, other layouts would yield a different character,
> but the principle is the same).
>
>     With either of the two patches, Emacs respond with "s-9" is not bound,
> which isn't correct.
>

In the current master this is now interpreted as M-s-9, which is at least
somewhat reasonable.


>
> Unfortunately, I don't know how to distinguish between the cases where we
> need to strip away modifiers (C-s-a) and when we shouldn't, so I'm leaving
> this open for now.
>

It seems like in the macOS input model, we can't: either we strip away all
modifiers, or none.


>
>     -- Anders Lindgren
>
>
> On Wed, Dec 30, 2015 at 9:50 AM, Anders Lindgren <andlind@gmail.com>
> wrote:
>
>> Hi,
>>
>> I'm looking into a key binding bug on OS X reported multiple times
>> (19977, 21330, 21551). Two different patches have been submitted.
>>
>> The original code looks like:
>>
>>       if (is_left_key)
>>         {
>>           emacs_event->modifiers |= parse_solitary_modifier
>>             (ns_command_modifier);
>>
>>           /* if super (default), take input manager's word so things like
>>              dvorak / qwerty layout work */
>>           if (EQ (ns_command_modifier, Qsuper)
>>               && !fnKeysym
>>               && [[theEvent characters] length] != 0)
>>             {
>>               /* XXX: the code we get will be unshifted, so if we have
>>                  a shift modifier, must convert ourselves */
>>               if (!(flags & NSShiftKeyMask))
>>                 code = [[theEvent characters] characterAtIndex: 0];
>>
>> One of the patches simply removes the `if (EQ(...))' statement. The other
>> modifies the code to strip away modifiers.
>>
>> First question: What is the code in the `if (EQ(...))' supposed to do? In
>> other words, what will stop working if it is removed?
>>
>> Second question: if it is needed for the LEFT command key, should the
>> corresponding code be added for the RIGHT?
>>
>> I've tested removing the `if' and Emacs still seems to be working as
>> intended, both with a normal key layout and when Dvorak is used. If no one
>> comes up with a reason to keep the code, I will remove it.
>>
>> Third question: Does anybody know of a good way to automatically test
>> things like this? What I'm looking for is a way to send keystrokes like
>> Cmd-Alt-a to Emacs, that way it could be possible to write tests ensuring
>> that things like this don't break in the future.
>>
>>     -- Anders Lindgren
>>
>>
>

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