🚀 go-pugleaf

Bug description:
  Mouse buttons act strange when the caps-lock is depressed.  
  This was detected in emacs 18.57 running X under OS 4.1.1, on
  a Sun Sparc II, but probably occurs on most X systems.

Bug cause:
  X events and emacs use different bit fields to represent the same
  keyboard state.  The emacs routine x-proc-mouse-event is responsible
  for doing this conversion.  Some of these bit fields are:

  X event:               Emacs Key Mask:
     0x01 shift key          0x10  shift key
     0x02 caps lock          0x20  meta key
     0x04 control key        0x40  control key
     0x08 meta key           0x80  zero

   In emacs, there appears as if there was never any need to detect
   wether caps lock was depressed in the event handler, so the X meta key
   was copied down to where the X shift lock bit goes.
   Unfortunately, this bit doesn't get cleared before the meta bit is 
   copied. Hence, when the caps lock key is depressed, many events
   (in particular mouse events which don't set the shift bit)
   act as if the meta key is depressed.

Bug Fixes:

   One way around this is to declare meta-mouse buttons in 
   your .emacs file like so.
   
(define-key mouse-map x-button-m-left   'x-mouse-set-point)
(define-key mouse-map x-button-m-middle 'x-mouse-paste-and-mark-at-point)
(define-key mouse-map x-button-m-right  'x-mouse-set-mark)

   A better way is to fix the offending code.  This is in the file 
   emacs/src/x11fns.c, in the function x-proc-mouse-event. 
   Add the indicated line.

        ...
	if (XXm_queue_num) {
		event = *XXm_queue[XXm_queue_out];
		free (XXm_queue[XXm_queue_out]);
		XXm_queue_out = (XXm_queue_out + 1) % XMOUSEBUFSIZE;
		XXm_queue_num--;
		com_letter = 3-(event.xbutton.button & 3);

		key_mask = (event.xbutton.state & 15) << 4;

				/**** Add next line to fix bug ****/
		key_mask &= ~0x20;		/* clear X shift-lock status */

		/* Report meta in 2 bit, not in 8 bit.  */
		if (key_mask & 0x80)
		  {
		    key_mask |= 0x20;
		    key_mask &= ~0x80;
		  }

		...

A more elegant, but extremely obscure fix would be to change the 
(... & 15) to (... & 0xB).  A much clearer fix would be to use
the X11 key mask #defines from X.h.



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