Re: Shift selection using interactive spec

[Stefan Monnier <monnier@iro.umontreal.ca>]

> --- 1758,1765 ----
>   	}
>         else
>   	{
> ! 	  if (NILP (current_kboard->Vprefix_arg)
> ! 	      && NILP (Vthis_command_keys_shift_translated))
>   	    {
>   	      /* In case we jump to directly_done.  */
>   	      Vcurrent_prefix_arg = current_kboard->Vprefix_arg;
> ***************
> *** 1801,1807 ****
>   		    direct_output_forward_char (1);
>   		  goto directly_done;
>   		}
> ! 	      else if (EQ (Vthis_command, Qbackward_char) && PT > BEGV)
>   		{
>                     struct Lisp_Char_Table *dp
>   		    = window_display_table (XWINDOW (selected_window));
> --- 1806,1813 ----
>   		    direct_output_forward_char (1);
>   		  goto directly_done;
>   		}
> ! 	      else if (EQ (Vthis_command, Qbackward_char) && PT > BEGV
> ! 		       && NILP (Vthis_command_keys_shift_translated))
>   		{
>                     struct Lisp_Char_Table *dp
>   		    = window_display_table (XWINDOW (selected_window));

Shouldn't we just get rid of those special cases "to speed up the cases
that are plenty fast anyway"?

> ***************
> *** 1964,1972 ****
>   	  /* Setting transient-mark-mode to `only' is a way of
>   	     turning it on for just one command.  */
  
> ! 	  if (EQ (Vtransient_mark_mode, Qidentity))
>   	    Vtransient_mark_mode = Qnil;
> ! 	  if (EQ (Vtransient_mark_mode, Qonly))
>   	    Vtransient_mark_mode = Qidentity;
  
>   	  if (!NILP (Vdeactivate_mark) && !NILP (Vtransient_mark_mode))
> --- 1970,1989 ----
>   	  /* Setting transient-mark-mode to `only' is a way of
>   	     turning it on for just one command.  */
  
> ! 	  if (CONSP (Vtransient_mark_mode))
> ! 	    {
> ! 	      if (EQ (XCAR (Vtransient_mark_mode), Qidentity))
> ! 		{
> ! 		  Vtransient_mark_mode = XCDR (Vtransient_mark_mode);
> ! 		  if (! NILP (Vtransient_mark_mode))
> ! 		    Vdeactivate_mark = Qt;
> ! 		}
> ! 	      else if (EQ (XCAR (Vtransient_mark_mode), Qonly))
> ! 		XSETCAR (Vtransient_mark_mode, Qidentity);
> ! 	    }
> ! 	  else if (EQ (Vtransient_mark_mode, Qidentity))
>   	    Vtransient_mark_mode = Qnil;
> ! 	  else if (EQ (Vtransient_mark_mode, Qonly))
>   	    Vtransient_mark_mode = Qidentity;

It is ugly right now and this makes it worse.  How 'bout just

   if (CONSP (Vtransient_mark_mode))
      Vtransient_mark_mode = XCDR (Vtransient_mark_mode);

and then replace `identity' with (t . nil) and `only' with (t . (t . nil)).
Or something like that?
  
> + (defun handle-shift-selection ()
> +   (when this-command-keys-shift-translated
> +     (temporary-region-highlight)))
> + 
> + (defun temporary-region-highlight ()
> +   (if (consp transient-mark-mode)
> +       (progn (unless (eq (car transient-mark-mode) 'identity)
> + 	       (push-mark nil nil t))
> + 	     (setcar transient-mark-mode 'only))
> +     (unless (eq transient-mark-mode 'identity)
> +       (push-mark nil nil t))
> +     (setq transient-mark-mode (cons 'only transient-mark-mode))))

Any reason to use `only' rather than to explicitly deactivate the mark
in handle-shift-selection when this-command-keys-shift-translated is
(and the region was selected with this-command-keys-shift-translated)?
Apparently that is the approach that is used in pc-selection-mode and in
cua-selection-mode, so it seems to work well enough.  The `only' form of
transient-mark-mode is a bit brittle for my taste (gets broken by
switch-frame events and things like that), so I'd rather only use it if
really necessary.


        Stefan