recenter-redisplay

[Miles Bader]

I find the "dual functionality" of recenter, and particularly
recenter-top-bottom pretty annoying -- 99% of the time I just want to
shift the window contents around, and the frame-redrawing side-effect is
just irritating flicker.

[This is especially true these days, when lossy communication channels
are very rare, and in most cases, what redisplay is necessary happens
automatically.]

So I made the following patch, which adds a variable
`recenter-redisplay' to control whether recenter (and thus
recenter-top-bottom) also do redisplay or not.  For backward
compatibility it defaults to t.

I'm perfectly happen to use M-x redraw-display if I actually need to
redraw a display...

Opinions?

diff --git a/doc/emacs/display.texi b/doc/emacs/display.texi
index 905b47b..6144f94 100644
*** a/doc/emacs/display.texi
--- b/doc/emacs/display.texi
***************
*** 54,60 ****
  @table @kbd
  @item C-l
  Scroll the selected window to center point vertically within it and
! redisplay the screen (@code{recenter-top-bottom}).
  @item C-v
  @itemx @key{NEXT}
  @itemx @key{PAGEDOWN}
--- 54,60 ----
  @table @kbd
  @item C-l
  Scroll the selected window to center point vertically within it and
! maybe redisplay the screen (@code{recenter-top-bottom}).
  @item C-v
  @itemx @key{NEXT}
  @itemx @key{PAGEDOWN}
***************
*** 73,81 ****
    The most basic scrolling command is @kbd{C-l}
  (@code{recenter-top-bottom}).  This @dfn{recenters} the selected
  window, scrolling it so that the current screen line is exactly in the
! center of the window, or as close to the center as possible.  It also
! clears the screen and redisplays all windows; this is useful in case
! the screen becomes garbled for any reason (@pxref{Screen Garbled}).
  
    Typing @kbd{C-l} twice in a row (@kbd{C-l C-l}) scrolls the window
  so that point is on the topmost screen line.  Typing a third @kbd{C-l}
--- 73,82 ----
    The most basic scrolling command is @kbd{C-l}
  (@code{recenter-top-bottom}).  This @dfn{recenters} the selected
  window, scrolling it so that the current screen line is exactly in the
! center of the window, or as close to the center as possible.  If the
! variable @var{recenter-redisplay} is non-nil, it also clears the
! screen and redisplays all windows; this is useful in case the screen
! becomes garbled for any reason (@pxref{Screen Garbled}).
  
    Typing @kbd{C-l} twice in a row (@kbd{C-l C-l}) scrolls the window
  so that point is on the topmost screen line.  Typing a third @kbd{C-l}
***************
*** 95,100 ****
--- 96,106 ----
  lines from the bottom.  When given an argument, @kbd{C-l} does not
  clear the screen or cycle through different screen positions.
  
+ @vindex recenter-redisplay
+   When the variable @code{recenter-redisplay} is non-nil, the
+ @code{recenter} and @code{recenter-top-bottom} commands redisplay the
+ selected frame when they are invoked without a prefix argument.
+ 
  @kindex C-v
  @kindex M-v
  @kindex NEXT
diff --git a/lisp/cus-start.el b/lisp/cus-start.el
index d8d3cc5..4545f5a 100644
*** a/lisp/cus-start.el
--- b/lisp/cus-start.el
***************
*** 307,312 ****
--- 307,313 ----
                       (const :tag "Off (nil)" :value nil)
                       (const :tag "Full screen (t)" :value t)
                       (other :tag "Always" 1)) "22.1")
+            (recenter-redisplay windows boolean "23.1")
             ;; xdisp.c
             (scroll-step windows integer)
             (scroll-conservatively windows integer)
diff --git a/src/window.c b/src/window.c
index 4c68de2..126e8a3 100644
*** a/src/window.c
--- b/src/window.c
***************
*** 193,198 ****
--- 193,204 ----
  extern EMACS_INT scroll_margin;
  
  extern Lisp_Object Qwindow_scroll_functions, Vwindow_scroll_functions;
+ 
+ /* If non-zero, then the `recenter' command with a nil argument
+    also causes the entire frame to be redrawn.  */
+ 
+ static int recenter_redisplay;
+ 
  
  DEFUN ("windowp", Fwindowp, Swindowp, 1, 1, 0,
         doc: /* Return t if OBJECT is a window.  */)
***************
*** 5602,5615 ****
  
  
  DEFUN ("recenter", Frecenter, Srecenter, 0, 1, "P",
!        doc: /* Center point in selected window and redisplay frame.
  With prefix argument ARG, recenter putting point on screen line ARG
  relative to the selected window.  If ARG is negative, it counts up from the
  bottom of the window.  (ARG should be less than the height of the window.)
  
! If ARG is omitted or nil, erase the entire frame and then redraw with point
! in the center of the selected window.  If `auto-resize-tool-bars' is set to
! `grow-only', this resets the tool-bar's height to the minimum height needed.
  
  Just C-u as prefix means put point in the center of the window
  and redisplay normally--don't erase and redraw the frame.  */)
--- 5608,5623 ----
  
  
  DEFUN ("recenter", Frecenter, Srecenter, 0, 1, "P",
!        doc: /* Center point in selected window and maybe redisplay frame.
  With prefix argument ARG, recenter putting point on screen line ARG
  relative to the selected window.  If ARG is negative, it counts up from the
  bottom of the window.  (ARG should be less than the height of the window.)
  
! If ARG is omitted or nil, then recenter with point on the middle line
! of the selected window; if the variable `recenter-redisplay' is
! non-nil, also erase the entire frame and redraw it (if
! `auto-resize-tool-bars' is set to `grow-only', this resets the
! tool-bar's height to the minimum height needed).
  
  Just C-u as prefix means put point in the center of the window
  and redisplay normally--don't erase and redraw the frame.  */)
***************
*** 5629,5644 ****
  
    if (NILP (arg))
      {
!       int i;
  
!       /* Invalidate pixel data calculated for all compositions.  */
!       for (i = 0; i < n_compositions; i++)
!       composition_table[i]->font = NULL;
  
!       WINDOW_XFRAME (w)->minimize_tool_bar_window_p = 1;
  
-       Fredraw_frame (WINDOW_FRAME (w));
-       SET_FRAME_GARBAGED (WINDOW_XFRAME (w));
        center_p = 1;
      }
    else if (CONSP (arg)) /* Just C-u. */
--- 5637,5656 ----
  
    if (NILP (arg))
      {
!       if (recenter_redisplay)
!       {
!         int i;
  
!         /* Invalidate pixel data calculated for all compositions.  */
!         for (i = 0; i < n_compositions; i++)
!           composition_table[i]->font = NULL;
  
!         WINDOW_XFRAME (w)->minimize_tool_bar_window_p = 1;
! 
!         Fredraw_frame (WINDOW_FRAME (w));
!         SET_FRAME_GARBAGED (WINDOW_XFRAME (w));
!       }
  
        center_p = 1;
      }
    else if (CONSP (arg)) /* Just C-u. */
***************
*** 7246,7251 ****
--- 7258,7269 ----
  with the relevant frame selected.  */);
    Vwindow_configuration_change_hook = Qnil;
  
+   DEFVAR_BOOL ("recenter-redisplay", &recenter_redisplay,
+              doc: /* If non-nil, then the `recenter' command with a nil 
argument
+ also causes the entire frame to be redrawn.  */);
+   recenter_redisplay = 1;
+ 
+ 
    defsubr (&Sselected_window);
    defsubr (&Sminibuffer_window);
    defsubr (&Swindow_minibuffer_p);


-- 
"1971 pickup truck; will trade for guns"