Re: Shift selection using interactive spec

[Stefan Monnier]

> --- 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