Support R2L rows. Continued lines still don't work correctly.

 xdisp.c (mouse_face_from_buffer_pos): Fix code using bug#1220 as
 test case.  Implement  highlight for R2L rows.

2 files changed, 112 insertions, 8 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 9b7c11d3bde..01dc3dfb305 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,7 +1,7 @@
 2010-08-28  Eli Zaretskii  <eliz@gnu.org>
 
         * xdisp.c (mouse_face_from_buffer_pos): Fix code using bug#1220 as
-        test case.
+        test case.  Implement  highlight for R2L rows.
 
 2010-08-21  Eli Zaretskii  <eliz@gnu.org>
 
diff --git a/src/xdisp.c b/src/xdisp.c
index c6d441fa6c1..296fe5d2c59 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -23916,9 +23916,10 @@ mouse_face_from_buffer_pos (Lisp_Object window,
                  ++glyph)
               x += glyph->pixel_width;
 
-      /* 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.  */
+          /* Scan the glyph row, looking for BEFORE_STRING,
+             AFTER_STRING, or DISPLAY_STRING, and the first glyph from
+             buffer whose position is between START_CHARPOS and
+             END_CHARPOS.  */
           for (; glyph < end
                  && !INTEGERP (glyph->object)
                  && !EQ (glyph->object, display_string)
@@ -23953,7 +23954,64 @@ mouse_face_from_buffer_pos (Lisp_Object window,
         }
       else
         {
-          /* FIXME! */
+          /* This row is in a right to left paragraph.  Scan it right
+             to left.  */
+          struct glyph *g;
+
+          end = row->glyphs[TEXT_AREA] - 1;
+          glyph = end + row->used[TEXT_AREA];
+
+          /* 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)
+              ;
+
+          /* Scan the glyph row, looking for BEFORE_STRING,
+             AFTER_STRING, or DISPLAY_STRING, and the first glyph from
+             buffer 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, or if they come from
+                 an overlay.  */
+              if (EQ (glyph->object, before_string))
+                {
+                  pos = string_buffer_position (w, before_string,
+                                                start_charpos);
+                  /* If pos == 0, it means before_string came from an
+                     overlay, not from a buffer position.  */
+                  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;
+                }
+            }
+
+          /* Mouse highlight uses the screen geometry, which is left
+             to right even in R2L paragraphs.  Therefore, for R2L
+             paragraphs, the "first" highlighted glyph actually
+             determines the _end_ column and x of the highlighted
+             area.  */
+          glyph++;      /* first glyph beyond the highlighted area */
+          for (g = row->glyphs[TEXT_AREA], x = row->x; g < glyph; g++)
+            x += g->pixel_width;
+          dpyinfo->mouse_face_end_x = x;
+          dpyinfo->mouse_face_end_col = glyph - row->glyphs[TEXT_AREA];
         }
     }
 
@@ -24023,14 +24081,60 @@ mouse_face_from_buffer_pos (Lisp_Object window,
       /* Find the X coordinate of the last glyph to be highlighted.  */
       for (; glyph <= end; ++glyph)
         x += glyph->pixel_width;
+
+      dpyinfo->mouse_face_end_x = x;
+      dpyinfo->mouse_face_end_col = glyph - row->glyphs[TEXT_AREA];
     }
   else
     {
-      /* FIXME! */
+      /* 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.  */
+      x = row->x;
+      end++;
+      while (end < glyph
+             && INTEGERP (end->object)
+             && end->charpos <= 0)
+        {
+          x += end->pixel_width;
+          ++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 < 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, or if they come from an overlay.  */
+          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;
+            }
+          x += end->pixel_width;
+        }
+      /* In the left-to-right screen geometry, END is actually the
+         _beginning_ of the highlighted area for R2L paragraphs.  */
+      dpyinfo->mouse_face_beg_x = x;
+      dpyinfo->mouse_face_beg_col = end - row->glyphs[TEXT_AREA];
     }
 
-  dpyinfo->mouse_face_end_x = x;
-  dpyinfo->mouse_face_end_col = glyph - row->glyphs[TEXT_AREA];
   dpyinfo->mouse_face_window = window;
   dpyinfo->mouse_face_face_id
     = face_at_buffer_position (w, mouse_charpos, 0, 0, &ignore,