(fast_find_position) [0]: Add a presumably more correct

version for after 21.1.

2 files changed, 83 insertions, 5 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index f4bdfbe7303..c54824eacbf 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,12 @@
 2001-09-25  Gerd Moellmann  <gerd@gnu.org>
 
+        * xterm.c (fast_find_position) [0]: Add a presumably more correct
+        version for after 21.1.
+
+        * xdisp.c (row_containing_pos): Make externally visible.
+
+        * dispextern.h (row_containing_pos): Add prototype.
+
         * process.c (send_process): Disable composition if from_byte < 0.
         From Kenichi Handa <handa@etl.go.jp>.
 
diff --git a/src/xterm.c b/src/xterm.c
index 2d56ae1c60f..2c3471509d7 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -7493,13 +7493,82 @@ note_tool_bar_highlight (f, x, y)
 
 
 
-/* Find the glyph matrix position of buffer position POS in window W.
-   *HPOS, *VPOS, *X, and *Y are set to the positions found.  W's
-   current glyphs must be up to date.  If POS is above window start
-   return (0, 0, 0, 0).  If POS is after end of W, return end of
-   last line in W.  In the row containing POS, stop before glyphs
+/* Find the glyph matrix position of buffer position CHARPOS in window
+   *W.  HPOS, *VPOS, *X, and *Y are set to the positions found.  W's
+   current glyphs must be up to date.  If CHARPOS is above window
+   start return (0, 0, 0, 0).  If CHARPOS is after end of W, return end
+   of last line in W.  In the row containing CHARPOS, stop before glyphs
    having STOP as object.  */
 
+#if 0 /* This is a version of fast_find_position that's more correct
+         in the presence of hscrolling, for example.  I didn't install
+         it right away because the problem fixed is minor, it failed
+         in 20.x as well, and I think it's too risky to install 
+         so near the release of 21.1.  2001-09-25 gerd.  */
+
+static int
+fast_find_position (w, charpos, hpos, vpos, x, y, stop)
+     struct window *w;
+     int charpos;
+     int *hpos, *vpos, *x, *y;
+     Lisp_Object stop;
+{
+  struct glyph_row *row, *first;
+  struct glyph *glyph, *end;
+  int i, past_end = 0;
+
+  first = MATRIX_FIRST_TEXT_ROW (w->current_matrix);
+  row = row_containing_pos (w, charpos, first, NULL);
+  if (row == NULL)
+    {
+      if (charpos < MATRIX_ROW_START_CHARPOS (first))
+        {
+          *x = *y = *hpos = *vpos = 0;
+          return 0;
+        }
+      else
+        {
+          row = MATRIX_ROW (w->current_matrix, XFASTINT (w->window_end_vpos));
+          past_end = 1;
+        }
+    }
+
+  *x = row->x;
+  *y = row->y;
+  *vpos = MATRIX_ROW_VPOS (row, w->current_matrix);
+  
+  glyph = row->glyphs[TEXT_AREA];
+  end = glyph + row->used[TEXT_AREA];
+  
+  /* Skip over glyphs not having an object at the start of the row.
+     These are special glyphs like truncation marks on terminal
+     frames.  */
+  if (row->displays_text_p)
+    while (glyph < end
+           && INTEGERP (glyph->object)
+           && !EQ (stop, glyph->object)
+           && glyph->charpos < 0)
+      {
+        *x += glyph->pixel_width;
+        ++glyph;
+      }
+
+  while (glyph < end
+         && !INTEGERP (glyph->object)
+         && !EQ (stop, glyph->object)
+         && (!BUFFERP (glyph->object)
+             || glyph->charpos < charpos))
+    {
+      *x += glyph->pixel_width;
+      ++glyph;
+    }
+
+  *hpos = glyph - row->glyphs[TEXT_AREA];
+  return past_end;
+}
+
+#else /* not 0 */
+
 static int
 fast_find_position (w, pos, hpos, vpos, x, y, stop)
      struct window *w;
@@ -7596,6 +7665,8 @@ fast_find_position (w, pos, hpos, vpos, x, y, stop)
   return 0;
 }
 
+#endif /* not 0 */
+
 
 /* Find the position of the the glyph for position POS in OBJECT in
    window W's current matrix, and return in *X/*Y the pixel