[RFC] using "optimizaiton 1"

[RFC] using "optimizaiton 1"

[Dmitry Antipov]

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Surprisingly, "optimizaiton 1" from redisplay_internal can
handle the case if the region is highlighted, too. Comments?

Dmitry

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=== modified file 'src/xdisp.c'
--- src/xdisp.c	2012-12-13 16:55:28 +0000
+++ src/xdisp.c	2012-12-14 13:43:30 +0000
@@ -2559,8 +2559,8 @@
 
 #endif /* GLYPH_DEBUG and ENABLE_CHECKING */
 
-/* Return mark position if current buffer has the region of non-zero length,
-   or -1 otherwise.  */
+/* Return mark position if current buffer has the region of non-zero
+   length, zero if mark and point are the same, or -1 otherwise.  */
 
 static ptrdiff_t
 markpos_of_region (void)
@@ -2571,8 +2571,7 @@
     {
       ptrdiff_t markpos = XMARKER (BVAR (current_buffer, mark))->charpos;
 
-      if (markpos != PT)
-	return markpos;
+      return markpos == PT ? 0 : markpos;
     }
   return -1;
 }
@@ -2712,7 +2711,7 @@
      and IT->region_end_charpos to the start and end of a visible region
      in window IT->w.  Set both to -1 to indicate no region.  */
   markpos = markpos_of_region ();
-  if (0 <= markpos
+  if (0 < markpos
       /* Maybe highlight only in selected window.  */
       && (/* Either show region everywhere.  */
 	  highlight_nonselected_windows
@@ -13244,18 +13243,6 @@
       clear_garbaged_frames ();
     }
 
-
-  /* If showing the region, and mark has changed, we must redisplay
-     the whole window.  The assignment to this_line_start_pos prevents
-     the optimization directly below this if-statement.  */
-  if (((!NILP (Vtransient_mark_mode)
-	&& !NILP (BVAR (XBUFFER (w->buffer), mark_active)))
-       != !NILP (w->region_showing))
-      || (!NILP (w->region_showing)
-	  && !EQ (w->region_showing,
-		  Fmarker_position (BVAR (XBUFFER (w->buffer), mark)))))
-    CHARPOS (this_line_start_pos) = 0;
-
   /* Optimize the case that only the line containing the cursor in the
      selected window has changed.  Variables starting with this_ are
      set in display_line and record information about the line
@@ -13288,7 +13275,8 @@
 	      || FETCH_BYTE (BYTEPOS (tlbufpos)) == '\n'))
 	/* Former continuation line has disappeared by becoming empty.  */
 	goto cancel;
-      else if (window_outdated (w) || MINI_WINDOW_P (w))
+      else if (window_outdated (w) || MINI_WINDOW_P (w)
+	       || 0 <= markpos_of_region ())
 	{
 	  /* We have to handle the case of continuation around a
 	     wide-column character (see the comment in indent.c around
@@ -13410,6 +13398,10 @@
 	      if (w->cursor_off_p == w->last_cursor_off_p)
 		goto end_of_redisplay;
 	    }
+#ifdef GLYPH_DEBUG
+	      *w->desired_matrix->method = 0;
+	      debug_method_add (w, "optimization 2");
+#endif
 	  goto update;
 	}
       /* If highlighting the region, or if the cursor is in the echo area,
@@ -15083,7 +15075,7 @@
       /* Can't use this case if highlighting a region.  When a
          region exists, cursor movement has to do more than just
          set the cursor.  */
-      && markpos_of_region () < 0
+      && markpos_of_region () <= 0
       && NILP (w->region_showing)
       && NILP (Vshow_trailing_whitespace)
       /* This code is not used for mini-buffer for the sake of the case
@@ -15752,7 +15744,7 @@
 
 	  /* If we are highlighting the region, then we just changed
 	     the region, so redisplay to show it.  */
-	  if (0 <= markpos_of_region ())
+	  if (0 < markpos_of_region ())
 	    {
 	      clear_glyph_matrix (w->desired_matrix);
 	      if (!try_window (window, startp, 0))
@@ -16457,7 +16449,7 @@
     return 0;
 
   /* Can't do this if region may have changed.  */
-  if (0 <= markpos_of_region ()
+  if (0 < markpos_of_region ()
       || !NILP (w->region_showing)
       || !NILP (Vshow_trailing_whitespace))
     return 0;
@@ -17289,7 +17281,7 @@
 
   /* Can't use this if highlighting a region because a cursor movement
      will do more than just set the cursor.  */
-  if (0 <= markpos_of_region ())
+  if (0 < markpos_of_region ())
     GIVE_UP (9);
 
   /* Likewise if highlighting trailing whitespace.  */

Re: [RFC] using "optimizaiton 1"

[Eli Zaretskii]

> Date: Fri, 14 Dec 2012 18:10:10 +0400
> From: Dmitry Antipov <dmantipov@yandex.ru>
> CC: Eli Zaretskii <eliz@gnu.org>
> 
> Surprisingly, "optimizaiton 1" from redisplay_internal can
> handle the case if the region is highlighted, too. Comments?

Sorry, I don't understand: handle which case?

Re: [RFC] using "optimizaiton 1"

[Dmitry Antipov]

On 12/14/2012 06:15 PM, Eli Zaretskii wrote:

>> Date: Fri, 14 Dec 2012 18:10:10 +0400
>> From: Dmitry Antipov <dmantipov@yandex.ru>
>> CC: Eli Zaretskii <eliz@gnu.org>
>>
>> Surprisingly, "optimizaiton 1" from redisplay_internal can
>> handle the case if the region is highlighted, too. Comments?
>
> Sorry, I don't understand: handle which case?

IOW, I suspect that this code:

  13248    /* If showing the region, and mark has changed, we must redisplay
  13249       the whole window.  The assignment to this_line_start_pos prevents
  13250       the optimization directly below this if-statement.  */
  13251    if (((!NILP (Vtransient_mark_mode)
  13252          && !NILP (BVAR (XBUFFER (w->buffer), mark_active)))
  13253         != !NILP (w->region_showing))
  13254        || (!NILP (w->region_showing)
  13255            && !EQ (w->region_showing,
  13256                    Fmarker_position (BVAR (XBUFFER (w->buffer), mark)))))
  13257      CHARPOS (this_line_start_pos) = 0;

is obsolete (heh, it's there since 1993). If showing the region, and both PT and
mark are on the same line, we should go through the monster if-statement below to:

  13293            /* We have to handle the case of continuation around a
  13294               wide-column character (see the comment in indent.c around
  13295               line 1340).

Dmitry

Re: [RFC] using "optimizaiton 1"

[Eli Zaretskii]

> Date: Fri, 14 Dec 2012 20:47:28 +0400
> From: Dmitry Antipov <dmantipov@yandex.ru>
> CC: emacs-devel@gnu.org
> 
> On 12/14/2012 06:15 PM, Eli Zaretskii wrote:
> 
> IOW, I suspect that this code:
> 
>   13248    /* If showing the region, and mark has changed, we must redisplay
>   13249       the whole window.  The assignment to this_line_start_pos prevents
>   13250       the optimization directly below this if-statement.  */
>   13251    if (((!NILP (Vtransient_mark_mode)
>   13252          && !NILP (BVAR (XBUFFER (w->buffer), mark_active)))
>   13253         != !NILP (w->region_showing))
>   13254        || (!NILP (w->region_showing)
>   13255            && !EQ (w->region_showing,
>   13256                    Fmarker_position (BVAR (XBUFFER (w->buffer), mark)))))
>   13257      CHARPOS (this_line_start_pos) = 0;
> 
> is obsolete (heh, it's there since 1993). If showing the region, and
> both PT and mark are on the same line

How do you conclude that both point and mark are on the same line?
The above just tests whether mark has changed, it doesn't say anything
about point, AFAICT.

In any case, is this situation frequent enough to be worth optimizing?