(update_text_area): Don't skip over equal glyphs

when the last current glyph overlaps the glyph to its right.

2 files changed, 34 insertions, 8 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 3677236528a..f7fef12be29 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2000-11-18  Gerd Moellmann  <gerd@gnu.org>
+
+        * dispnew.c (update_text_area): Don't skip over equal glyphs
+        when the last current glyph overlaps the glyph to its right.
+
 2000-11-18  Miles Bader  <miles@gnu.org>
 
         * xdisp.c (message_log_check_duplicate): Let "..."-detection match
diff --git a/src/dispnew.c b/src/dispnew.c
index eff7bb2bf15..8e8f6c5b437 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -1,5 +1,5 @@
 /* Updating of data structures for redisplay.
-   Copyright (C) 1985, 86, 87, 88, 93, 94, 95, 97, 98, 1999
+   Copyright (C) 1985, 86, 87, 88, 93, 94, 95, 97, 98, 1999, 2000
        Free Software Foundation, Inc.
 
 This file is part of GNU Emacs.
@@ -3981,6 +3981,7 @@ update_text_area (w, vpos)
       int stop, i, x;
       struct glyph *current_glyph = current_row->glyphs[TEXT_AREA];
       struct glyph *desired_glyph = desired_row->glyphs[TEXT_AREA];
+      int overlapping_glyphs_p = current_row->contains_overlapping_glyphs_p;
 
       /* If the desired row extends its face to the text area end,
          make sure we write at least one glyph, so that the face
@@ -3995,15 +3996,34 @@ update_text_area (w, vpos)
       
       while (i < stop)
         {
+          int skip_equal_glyphs_p = 1;
+          
           /* Skip over glyphs that both rows have in common.  These
-             don't have to be written.  */
-          while (i < stop
-                 && GLYPH_EQUAL_P (desired_glyph, current_glyph))
+             don't have to be written.  We can't skip if the last
+             current glyph overlaps the glyph to its right.  For
+             example, consider a current row of `if ' with the `f' in
+             Courier bold so that it overlaps the ` ' to its right.
+             If the desired row is ` ', we would skip over the space
+             after the `if' and there would remain a pixel from the
+             `f' on the screen.  */
+          if (overlapping_glyphs_p && i > 0)
             {
-              x += desired_glyph->pixel_width;
-              ++desired_glyph, ++current_glyph, ++i;
+              struct glyph *glyph = &current_row->glyphs[TEXT_AREA][i - 1];
+              int left, right;
+              
+              rif->get_glyph_overhangs (glyph, XFRAME (w->frame),
+                                        &left, &right);
+              skip_equal_glyphs_p = right == 0;
             }
 
+          if (skip_equal_glyphs_p)
+            while (i < stop
+                   && GLYPH_EQUAL_P (desired_glyph, current_glyph))
+              {
+                x += desired_glyph->pixel_width;
+                ++desired_glyph, ++current_glyph, ++i;
+              }
+
           /* Consider the case that the current row contains "xxx ppp
              ggg" in italic Courier font, and the desired row is "xxx
              ggg".  The character `p' has lbearing, `g' has not.  The
@@ -4011,12 +4031,13 @@ update_text_area (w, vpos)
              current row.  If we would start writing glyphs there, we
              wouldn't erase the lbearing of the `p'.  The rest of the
              lbearing problem is then taken care of by x_draw_glyphs.  */
-          if (current_row->contains_overlapping_glyphs_p
+          if (overlapping_glyphs_p
               && i > 0
               && i < current_row->used[TEXT_AREA]
               && current_row->used[TEXT_AREA] != desired_row->used[TEXT_AREA])
             {
               int left, right;
+              
               rif->get_glyph_overhangs (current_glyph, XFRAME (w->frame),
                                         &left, &right);
               while (left > 0 && i > 0)
@@ -4054,7 +4075,7 @@ update_text_area (w, vpos)
                   desired_glyph = start;
                   break;
                 }
-              
+
               rif->cursor_to (vpos, start_hpos, desired_row->y, start_x);
               rif->write_glyphs (start, i - start_hpos);
               changed_p = 1;