bug#65068: 29.1; xkb-interception interaction causes problems with key combinations

["Alexander Prähauser" <alexander.praehauser@gmx.at>]

Now when I press for instance Space, it doesn't seem to evaluate 
immediately, but it does evaluate when I
press another dual-function-modified key. So if I press the same 
sequence as below the first message doesn't appear but
the second one does.

Po Lu [2023-08-24 Thu 20:41] wrote:

> Alexander Prähauser <alexander.praehauser@gmx.at> writes:
>
>> It does seem to register the correct level shifts now, but it 
>> seems to
>> evaluate each key immediately after having been
>> pressed. For instance, when I press Space-CapsLock-U, this 
>> should
>> evaluate to C-; and it does, but this is the output
>> I'm receiving in-between:
>>
>> <Control_R> is undefined
>> C-' is undefined
>> C-; is undefined
>>
>> Po Lu [2023-08-24 Thu 17:56] wrote:
>>
>>> Alexander Prähauser <alexander.praehauser@gmx.at> writes:
>>>
>>>> The significance of the U-key is that when I press 
>>>> Space-CapsLock-U
>>>> (or any other key, I think), it doesn't send the signal
>>>> that is configured by xkb but the corresponding key of the 
>>>> default
>>>> English keymap (u for the U-key), which really
>>>> shouldn't happen. Anyway, here the output after pressing the
>>>> sequence
>>>> you wanted:
>>>>
>>>> keycode: 48, keysym: 65027, 0
>>>> keycode: 192, keysym: 269025093, 0
>>>> keycode: 37, keysym: 65507, 0
>>>> keycode: 37, keysym: 65507, 0 <- Control_R
>>>> keycode: 48, keysym: 65027, 0 <- AC11, ISO_Level3_Shift
>>>> keycode: 192, keysym: 269025093, <- XF86Launch5
>>>
>>> This attests to Emacs registering the keysyms you meant it 
>>> to. If
>>> ISO_Level3_Shift is registered as a modifier key, it should 
>>> not be
>>> translated into keyboard input afterwards, let alone the 
>>> original
>>> apostrophe symbol.
>>>
>>> Does this patch resolve your problems with typing level 3 
>>> characters
>>> coupled with Control?
>>>
>>> diff --git a/src/xterm.c b/src/xterm.c
>>> index 6a1642ff56e..7391041ea0c 100644
>>> --- a/src/xterm.c
>>> +++ b/src/xterm.c
>>> @@ -23734,6 +23734,7 @@ handle_one_xevent (struct 
>>> x_display_info
>>> *dpyinfo,
>>>  	      ptrdiff_t i;
>>>  	      unsigned int old_state;
>>>  	      struct xi_device_t *device, *source;
>>> +	      bool is_modifier_key;
>>>   	      coding = Qlatin_1;
>>>  @@ -24175,17 +24176,7 @@ handle_one_xevent (struct 
>>>  x_display_info
>>> *dpyinfo,
>>>  		       /* Any "vendor-specific" key is ok.  */
>>>  		       || (keysym & (1 << 28))
>>>  		       || (keysym != NoSymbol && nbytes == 0))
>>> -		      && ! (IsModifierKey (keysym)
>>> -			    /* The symbols from XK_ISO_Lock
>>> -			       to XK_ISO_Last_Group_Lock
>>> -			       don't have real modifiers but
>>> -			       should be treated similarly to
>>> -			       Mode_switch by Emacs. */
>>> -#if defined XK_ISO_Lock && defined XK_ISO_Last_Group_Lock
>>> -			    || (XK_ISO_Lock <= keysym
>>> -				&& keysym <= 
>>> XK_ISO_Last_Group_Lock)
>>> -#endif
>>> -			    ))
>>> +		      && !is_modifier_key)
>>>  		    {
>>>  		      STORE_KEYSYM_FOR_DEBUG (keysym);
>>>  		      /* make_lispy_event will convert this to a
>>> symbolic
>>> @@ -24204,7 +24195,11 @@ handle_one_xevent (struct 
>>> x_display_info
>>> *dpyinfo,
>>>  		      STORE_KEYSYM_FOR_DEBUG (copy_bufptr[i]);
>>>  		    }
>>>  -		  if (nbytes)
>>> +		  /* Mind that NBYTES can be set even if KEYSYM
>>> +		     represents a modifier key, but that no 
>>> character
>>> +		     events should be sent in that case.  */
>>> +
>>> +		  if (nbytes && !is_modifier_key)
>>>  		    {
>>>  		      inev.ie.kind = 
>>>  MULTIBYTE_CHAR_KEYSTROKE_EVENT;
>>>  		      inev.ie.arg = make_unibyte_string 
>>>  (copy_bufptr,
>>> nbytes);
>
> Please excuse my carelessness, I appear to have ommitted a chunk 
> of the
> diff:
>
> diff --git a/src/xterm.c b/src/xterm.c
> index 6a1642ff56e..4b2da066694 100644
> --- a/src/xterm.c
> +++ b/src/xterm.c
> @@ -23734,6 +23734,7 @@ handle_one_xevent (struct x_display_info 
> *dpyinfo,
>  	      ptrdiff_t i;
>  	      unsigned int old_state;
>  	      struct xi_device_t *device, *source;
> +	      bool is_modifier_key;
>  
>  	      coding = Qlatin_1;
>  
> @@ -24091,6 +24092,18 @@ handle_one_xevent (struct 
> x_display_info *dpyinfo,
>  		      goto xi_done_keysym;
>  		    }
>  
> +		  is_modifier_key = (IsModifierKey (keysym)
> +				     /* The symbols from 
> XK_ISO_Lock
> +					to XK_ISO_Last_Group_Lock
> +					don't have real modifiers 
> but
> +					should be treated 
> similarly to
> +					Mode_switch by Emacs. */
> +#if defined XK_ISO_Lock && defined XK_ISO_Last_Group_Lock
> +				     || (XK_ISO_Lock <= keysym
> +					 && keysym <= 
> XK_ISO_Last_Group_Lock)
> +#endif
> +				     );
> +
>  		  /* Random non-modifier sorts of keysyms.  */
>  		  if (((keysym >= XK_BackSpace && keysym <= 
>  XK_Escape)
>  		       || keysym == XK_Delete
> @@ -24175,17 +24188,7 @@ handle_one_xevent (struct 
> x_display_info *dpyinfo,
>  		       /* Any "vendor-specific" key is ok.  */
>  		       || (keysym & (1 << 28))
>  		       || (keysym != NoSymbol && nbytes == 0))
> -		      && ! (IsModifierKey (keysym)
> -			    /* The symbols from XK_ISO_Lock
> -			       to XK_ISO_Last_Group_Lock
> -			       don't have real modifiers but
> -			       should be treated similarly to
> -			       Mode_switch by Emacs. */
> -#if defined XK_ISO_Lock && defined XK_ISO_Last_Group_Lock
> -			    || (XK_ISO_Lock <= keysym
> -				&& keysym <= 
> XK_ISO_Last_Group_Lock)
> -#endif
> -			    ))
> +		      && !is_modifier_key)
>  		    {
>  		      STORE_KEYSYM_FOR_DEBUG (keysym);
>  		      /* make_lispy_event will convert this to a 
>  symbolic
> @@ -24204,7 +24207,11 @@ handle_one_xevent (struct 
> x_display_info *dpyinfo,
>  		      STORE_KEYSYM_FOR_DEBUG (copy_bufptr[i]);
>  		    }
>  
> -		  if (nbytes)
> +		  /* Mind that NBYTES can be set even if KEYSYM
> +		     represents a modifier key, but that no 
> character
> +		     events should be sent in that case.  */
> +
> +		  if (nbytes && !is_modifier_key)
>  		    {
>  		      inev.ie.kind = 
>  MULTIBYTE_CHAR_KEYSTROKE_EVENT;
>  		      inev.ie.arg = make_unibyte_string 
>  (copy_bufptr, nbytes);