Initial partial support for mouse highlight in bidi-reordered text.

 xdisp.c (mouse_face_from_buffer_pos): Support mouse highlight in
 bidi-reordered L2R lines.  Continued lines are not yet supported.

2 files changed, 113 insertions, 71 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 403a588df4c..242018c4061 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,8 @@
 2010-08-21  Eli Zaretskii  <eliz@gnu.org>
 
+        * xdisp.c (mouse_face_from_buffer_pos): Support mouse highlight in
+        bidi-reordered L2R lines.  Continued lines are not yet supported.
+
         * dispnew.c (buffer_posn_from_coords): Fix off-by-one error in
         mirroring pixel positions.
 
diff --git a/src/xdisp.c b/src/xdisp.c
index c80e1f35df3..7fcbab718b1 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -23839,7 +23839,7 @@ mouse_face_from_buffer_pos (Lisp_Object window,
   struct glyph_row *first = MATRIX_FIRST_TEXT_ROW (w->current_matrix);
   struct glyph_row *row;
   struct glyph *glyph, *end;
-  EMACS_INT ignore;
+  EMACS_INT ignore, pos;
   int x;
 
   xassert (NILP (display_string) || STRINGP (display_string));
@@ -23847,7 +23847,9 @@ mouse_face_from_buffer_pos (Lisp_Object window,
   xassert (NILP (after_string) || STRINGP (after_string));
 
   /* Find the first highlighted glyph.  */
-  if (start_charpos < MATRIX_ROW_START_CHARPOS (first))
+  if (start_charpos < MATRIX_ROW_START_CHARPOS (first)
+      && (NILP (XBUFFER (w->buffer)->bidi_display_reordering)
+          || row_containing_pos (w, start_charpos, first, NULL, 0) == NULL))
     {
       dpyinfo->mouse_face_beg_col = 0;
       dpyinfo->mouse_face_beg_row = MATRIX_ROW_VPOS (first, w->current_matrix);
@@ -23856,6 +23858,10 @@ mouse_face_from_buffer_pos (Lisp_Object window,
     }
   else
     {
+      /* FIXME: this assumes that START_CHARPOS is in beg_row.  This
+         is false for reordered lines that are continued.  Need to
+         compute beg_row and end_row separately from beg_col and
+         end_col.  */
       row = row_containing_pos (w, start_charpos, first, NULL, 0);
       if (row == NULL)
         row = MATRIX_ROW (w->current_matrix, XFASTINT (w->window_end_vpos));
@@ -23880,33 +23886,72 @@ mouse_face_from_buffer_pos (Lisp_Object window,
             }
         }
 
-      glyph = row->glyphs[TEXT_AREA];
-      end = glyph + row->used[TEXT_AREA];
-      x = row->x;
       dpyinfo->mouse_face_beg_y = row->y;
       dpyinfo->mouse_face_beg_row = MATRIX_ROW_VPOS (row, w->current_matrix);
 
-      /* Skip truncation glyphs at the start of the glyph row.  */
-      if (row->displays_text_p)
-        for (; glyph < end
-               && INTEGERP (glyph->object)
-               && glyph->charpos < 0;
-             ++glyph)
-          x += glyph->pixel_width;
-
-      /* Scan the glyph row, stopping before BEFORE_STRING or
-         DISPLAY_STRING or START_CHARPOS.  */
-      for (; glyph < end
-             && !INTEGERP (glyph->object)
-             && !EQ (glyph->object, before_string)
-             && !EQ (glyph->object, display_string)
-             && !(BUFFERP (glyph->object)
-                  && glyph->charpos >= start_charpos);
-           ++glyph)
-        x += glyph->pixel_width;
+      /* For a bidi-reordered row, the positions of BEFORE_STRING,
+         AFTER_STRING, DISPLAY_STRING, START_CHARPOS, and END_CHARPOS
+         could be anywhere in the row and in any order.  The strategy
+         below is to find the leftmost and the rightmost glyph that
+         belongs to either of these 3 strings, or whose position is
+         between START_CHARPOS and END_CHARPOS, and highlight all the
+         glyphs between those two.  This may cover more than just the
+         text between START_CHARPOS and END_CHARPOS if the range of
+         characters strides the the bidi level boundary, e.g. if the
+         beginning is in R2L text while the end is in L2R text or vice
+         versa.  */
+      if (!row->reversed_p)
+        {
+          /* This row is in a left to right paragraph.  Scan it left
+             to right.  */
+          glyph = row->glyphs[TEXT_AREA];
+          end = glyph + row->used[TEXT_AREA];
+          x = row->x;
+
+          /* Skip truncation glyphs at the start of the glyph row.  */
+          if (row->displays_text_p)
+            for (; glyph < end
+                   && INTEGERP (glyph->object)
+                   && glyph->charpos < 0;
+                 ++glyph)
+              x += glyph->pixel_width;
 
-      dpyinfo->mouse_face_beg_x = x;
-      dpyinfo->mouse_face_beg_col = glyph - row->glyphs[TEXT_AREA];
+      /* Scan the glyph row, looking for BEFORE_STRING, AFTER_STRING,
+         or DISPLAY_STRING, and the first glyph whose position is
+         between START_CHARPOS and END_CHARPOS.  */
+          for (; glyph < end
+                 && !INTEGERP (glyph->object)
+                 && !EQ (glyph->object, display_string)
+                 && !(BUFFERP (glyph->object)
+                      && (glyph->charpos >= start_charpos
+                          && glyph->charpos < end_charpos));
+               ++glyph)
+            {
+              /* BEFORE_STRING or AFTER_STRING are only relevant if
+                 they are present at buffer positions between
+                 START_CHARPOS and END_CHARPOS.  */
+              if (EQ (glyph->object, before_string))
+                {
+                  pos = string_buffer_position (w, before_string,
+                                                start_charpos);
+                  if (pos && pos >= start_charpos && pos < end_charpos)
+                    break;
+                }
+              else if (EQ (glyph->object, after_string))
+                {
+                  pos = string_buffer_position (w, after_string, end_charpos);
+                  if (pos && pos >= start_charpos && pos < end_charpos)
+                    break;
+                }
+              x += glyph->pixel_width;
+            }
+          dpyinfo->mouse_face_beg_x = x;
+          dpyinfo->mouse_face_beg_col = glyph - row->glyphs[TEXT_AREA];
+        }
+      else
+        {
+          /* FIXME! */
+        }
     }
 
   /* Find the last highlighted glyph.  */
@@ -23931,60 +23976,54 @@ mouse_face_from_buffer_pos (Lisp_Object window,
         row = next;
     }
 
-  glyph = row->glyphs[TEXT_AREA];
-  end = glyph + row->used[TEXT_AREA];
-  x = row->x;
   dpyinfo->mouse_face_end_y = row->y;
   dpyinfo->mouse_face_end_row = MATRIX_ROW_VPOS (row, w->current_matrix);
 
-  /* Skip truncation glyphs at the start of the row.  */
-  if (row->displays_text_p)
-    for (; glyph < end
-           && INTEGERP (glyph->object)
-           && glyph->charpos < 0;
-         ++glyph)
-      x += glyph->pixel_width;
-
-  /* Scan the glyph row, stopping at END_CHARPOS or when we encounter
-     AFTER_STRING.  */
-  for (; glyph < end
-         && !INTEGERP (glyph->object)
-         && !EQ (glyph->object, after_string)
-         && !(BUFFERP (glyph->object) && glyph->charpos >= end_charpos);
-       ++glyph)
-    x += glyph->pixel_width;
-
-  /* If we found AFTER_STRING, consume it and stop.  */
-  if (EQ (glyph->object, after_string))
+  if (!row->reversed_p)
     {
-      for (; EQ (glyph->object, after_string) && glyph < end; ++glyph)
+      /* Skip truncation and continuation glyphs near the end of the
+         row, and also blanks and stretch glyphs inserted by
+         extend_face_to_end_of_line.  */
+      while (end > glyph
+             && INTEGERP ((end - 1)->object)
+             && (end - 1)->charpos <= 0)
+        --end;
+      /* Scan the rest of the glyph row from the end, looking for the
+         first glyph that comes from BEFORE_STRING, AFTER_STRING, or
+         DISPLAY_STRING, or whose position is between START_CHARPOS
+         and END_CHARPOS */
+      for (--end;
+             end > glyph
+             && !INTEGERP (end->object)
+             && !EQ (end->object, display_string)
+             && !(BUFFERP (end->object)
+                  && (end->charpos >= start_charpos
+                      && end->charpos < end_charpos));
+           --end)
+        {
+          /* BEFORE_STRING or AFTER_STRING are only relevant if
+             they are present at buffer positions between
+             START_CHARPOS and END_CHARPOS.  */
+          if (EQ (end->object, before_string))
+            {
+              pos = string_buffer_position (w, before_string, start_charpos);
+              if (pos && pos >= start_charpos && pos < end_charpos)
+                break;
+            }
+          else if (EQ (end->object, after_string))
+            {
+              pos = string_buffer_position (w, after_string, end_charpos);
+              if (pos && pos >= start_charpos && pos < end_charpos)
+                break;
+            }
+        }
+      /* Find the X coordinate of the last glyph to be highlighted.  */
+      for (; glyph <= end; ++glyph)
         x += glyph->pixel_width;
     }
   else
     {
-      /* If there's no after-string, we must check if we overshot,
-         which might be the case if we stopped after a string glyph.
-         That glyph may belong to a before-string or display-string
-         associated with the end position, which must not be
-         highlighted.  */
-      Lisp_Object prev_object;
-      EMACS_INT pos;
-
-      while (glyph > row->glyphs[TEXT_AREA])
-        {
-          prev_object = (glyph - 1)->object;
-          if (!STRINGP (prev_object) || EQ (prev_object, display_string))
-            break;
-
-          pos = string_buffer_position (w, prev_object, end_charpos);
-          if (pos && pos < end_charpos)
-            break;
-
-          for (; glyph > row->glyphs[TEXT_AREA]
-                 && EQ ((glyph - 1)->object, prev_object);
-               --glyph)
-            x -= (glyph - 1)->pixel_width;
-        }
+      /* FIXME! */
     }
 
   dpyinfo->mouse_face_end_x = x;