Retrospective commit from 2009-10-17.

Continue working on display of R2L glyph rows.  Reverse glyphs in
term.c:append_glyph rather than in extend_face_to_end_of_line.
Fix bidi iteration near BEGV and ZV.

 dispextern.h (struct glyph): New members resolved_level and
 bidi_type.

 xdisp.c (append_glyph, append_composite_glyph)
 (produce_image_glyph, append_stretch_glyph): Set them.

 term.c (append_glyph): Ditto.

 xdisp.c (display_line, next_element_from_buffer): Set the glyph
 row's reversed_p flag if the paragraph base direction is odd.
 (extend_face_to_end_of_line): Don't reverse the glyphs here.

 term.c (append_glyph): Reverse glyphs here.

 bidi.c (bidi_get_next_char_visually): Don't exit early when at ZV.
 (bidi_paragraph_init): Don't step over a newline if at BEGV.
 (bidi_paragraph_init): Handle empty buffers.

5 files changed, 96 insertions, 26 deletions

diff --git a/src/ChangeLog.bidi b/src/ChangeLog.bidi
index ae5807ce13a..9824981c086 100644
--- a/src/ChangeLog.bidi
+++ b/src/ChangeLog.bidi
@@ -1,3 +1,27 @@
+2009-10-17  Eli Zaretskii  <eliz@gnu.org>
+
+        * dispextern.h (struct glyph): New members resolved_level and
+        bidi_type.
+
+        * xdisp.c (append_glyph, append_composite_glyph)
+        (produce_image_glyph, append_stretch_glyph): Set them.
+
+        * term.c (append_glyph): Ditto.
+
+        * xdisp.c (display_line, next_element_from_buffer): Set the glyph
+        row's reversed_p flag if the paragraph base direction is odd.
+        (extend_face_to_end_of_line): Don't reverse the glyphs here.
+
+        * term.c (append_glyph): Reverse glyphs here.
+
+        * bidi.c (bidi_get_next_char_visually): Don't exit early when at
+        ZV.
+        (bidi_paragraph_init): Don't step over a newline if at BEGV.
+
+2009-10-16  Eli Zaretskii  <eliz@gnu.org>
+
+        * bidi.c (bidi_paragraph_init): Handle empty buffers.
+
 2009-10-10  Eli Zaretskii  <eliz@gnu.org>
 
         * xdisp.c (set_cursor_from_row): Skip over glyphs near end of row
diff --git a/src/bidi.c b/src/bidi.c
index f6ca8cd20e9..3a2d45cdb4d 100644
--- a/src/bidi.c
+++ b/src/bidi.c
@@ -853,8 +853,11 @@ bidi_paragraph_init (bidi_dir_t dir, struct bidi_it *bidi_it)
 {
   EMACS_INT bytepos = bidi_it->bytepos;
 
+  /* Special case for an empty buffer. */
+  if (bytepos == BEGV_BYTE && bytepos == ZV_BYTE)
+    dir = L2R;
   /* We should never be called at EOB or before BEGV.  */
-  if (bytepos >= ZV_BYTE || bytepos < BEGV_BYTE)
+  else if (bytepos >= ZV_BYTE || bytepos < BEGV_BYTE)
     abort ();
 
   if (dir == L2R)
@@ -883,9 +886,11 @@ bidi_paragraph_init (bidi_dir_t dir, struct bidi_it *bidi_it)
         return;
 
       /* If we are on a newline, get past it to where the next
-         paragraph might start.  */
+         paragraph might start.  But don't do that at BEGV since then
+         we are potentially in a new paragraph that doesn't yet
+         exist.  */
       pos = bidi_it->charpos;
-      if (FETCH_CHAR (bytepos) == '\n')
+      if (bytepos > BEGV_BYTE && FETCH_CHAR (bytepos) == '\n')
         {
           bytepos++;
           pos++;
@@ -1900,8 +1905,6 @@ bidi_get_next_char_visually (struct bidi_it *bidi_it)
 
   old_level = bidi_it->resolved_level;
   new_level = bidi_level_of_next_char (bidi_it);
-  if (bidi_it->ch == BIDI_EOB)
-    return;
 
   /* Reordering of resolved levels (clause L2) is implemented by
      jumping to the other edge of the level and flipping direction of
diff --git a/src/dispextern.h b/src/dispextern.h
index ae6ecbb0d5c..5f18b7f3a4a 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -370,6 +370,13 @@ struct glyph
   /* Non-zero means don't display cursor here.  */
   unsigned avoid_cursor_p : 1;
 
+  /* Resolved bidirection level of the characters [0..63].  */
+  unsigned resolved_level : 6;
+
+  /* Resolved bidirectional type of this character, see enum
+     bidi_type_t below.  */
+  unsigned bidi_type : 5;
+
 #define FACE_ID_BITS    20
 
   /* Face of the glyph.  This is a realized face ID,
diff --git a/src/term.c b/src/term.c
index fda06d6b2ed..7c9e05f36b2 100644
--- a/src/term.c
+++ b/src/term.c
@@ -1545,6 +1545,26 @@ append_glyph (it)
            + it->glyph_row->used[it->area]);
   end = it->glyph_row->glyphs[1 + it->area];
 
+  /* If the glyph row is reversed, we need to prepend the glyph rather
+     than append it.  */
+  if (it->glyph_row->reversed_p && it->area == TEXT_AREA)
+    {
+      struct glyph *g;
+      int move_by = it->pixel_width;
+
+      /* Make room for the new glyphs.  */
+      if (move_by > end - glyph) /* don't overstep end of this area */
+        move_by = end - glyph;
+      for (g = glyph - 1; g >= it->glyph_row->glyphs[it->area]; g--)
+        g[move_by] = *g;
+      glyph = it->glyph_row->glyphs[it->area];
+      end = glyph + move_by;
+    }
+
+  /* BIDI Note: we put the glyphs of a "multi-pixel" character left to
+     right, even in the REVERSED_P case, since (a) all of its u.ch are
+     identical, and (b) the PADDING_P flag needs to be set for the
+     leftmost one, because we write to the terminal left-to-right.  */
   for (i = 0;
        i < it->pixel_width && glyph < end;
        ++i)
@@ -1556,6 +1576,11 @@ append_glyph (it)
       glyph->padding_p = i > 0;
       glyph->charpos = CHARPOS (it->position);
       glyph->object = it->object;
+      if (it->bidi_p)
+        {
+          glyph->resolved_level = it->bidi_it.resolved_level;
+          glyph->bidi_type = it->bidi_it.type;
+        }
 
       ++it->glyph_row->used[it->area];
       ++glyph;
diff --git a/src/xdisp.c b/src/xdisp.c
index 581a7a0faa2..90f16b938c0 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -6571,6 +6571,12 @@ next_element_from_buffer (it)
           || FETCH_CHAR (it->bidi_it.bytepos) == '\n')
         {
           bidi_paragraph_init (it->paragraph_embedding, &it->bidi_it);
+          /* If the paragraph base direction is R2L, its glyphs should
+             be reversed.  */
+          if (it->glyph_row && (it->bidi_it.level_stack[0].level & 1) != 0)
+            it->glyph_row->reversed_p = 1;
+          if (it->glyph_row && (it->bidi_it.level_stack[0].level & 1) != 0)
+            it->glyph_row->reversed_p = 1;
           bidi_get_next_char_visually (&it->bidi_it);
         }
       else
@@ -6585,6 +6591,8 @@ next_element_from_buffer (it)
           it->bidi_it.charpos = IT_CHARPOS (*it);
           it->bidi_it.bytepos = IT_BYTEPOS (*it);
           bidi_paragraph_init (it->paragraph_embedding, &it->bidi_it);
+          if (it->glyph_row && (it->bidi_it.level_stack[0].level & 1) != 0)
+            it->glyph_row->reversed_p = 1;
           do {
             /* Now return to buffer position where we were asked to
                get the next display element, and produce that.  */
@@ -16538,27 +16546,6 @@ extend_face_to_end_of_line (it)
       while (it->current_x <= it->last_visible_x)
         PRODUCE_GLYPHS (it);
 
-      /* If the paragraph base direction is right to left, reverse the
-         glyphs of a non-empty glyph row.  */
-      if (it->bidi_p && it->bidi_it.level_stack[0].level == 1)
-        {
-          if (text_len > 0)
-            {
-              struct glyph *gleft = it->glyph_row->glyphs[TEXT_AREA];
-              struct glyph *gright =
-                gleft + it->glyph_row->used[TEXT_AREA] - 1;
-              struct glyph tem;
-
-              for ( ; gleft < gright; gleft++, gright--)
-                {
-                  tem = *gleft;
-                  *gleft = *gright;
-                  *gright = tem;
-                }
-            }
-          it->glyph_row->reversed_p = 1;
-        }
-
       /* Don't count these blanks really.  It would let us insert a left
          truncation glyph below and make us set the cursor on them, maybe.  */
       it->current_x = saved_x;
@@ -16850,6 +16837,10 @@ display_line (it)
   row->displays_text_p = 1;
   row->starts_in_middle_of_char_p = it->starts_in_middle_of_char_p;
   it->starts_in_middle_of_char_p = 0;
+  /* If the paragraph base direction is R2L, its glyphs should be
+     reversed.  */
+  if (it->bidi_p && (it->bidi_it.level_stack[0].level & 1) != 0)
+    row->reversed_p = 1;
 
   /* Arrange the overlays nicely for our purposes.  Usually, we call
      display_line on only one line at a time, in which case this
@@ -20932,6 +20923,11 @@ append_glyph (it)
       glyph->u.ch = it->char_to_display;
       glyph->slice = null_glyph_slice;
       glyph->font_type = FONT_TYPE_UNKNOWN;
+      if (it->bidi_p)
+        {
+          glyph->resolved_level = it->bidi_it.resolved_level;
+          glyph->bidi_type = it->bidi_it.type;
+        }
       ++it->glyph_row->used[area];
     }
   else
@@ -20984,6 +20980,11 @@ append_composite_glyph (it)
       glyph->face_id = it->face_id;
       glyph->slice = null_glyph_slice;
       glyph->font_type = FONT_TYPE_UNKNOWN;
+      if (it->bidi_p)
+        {
+          glyph->resolved_level = it->bidi_it.resolved_level;
+          glyph->bidi_type = it->bidi_it.type;
+        }
       ++it->glyph_row->used[area];
     }
   else
@@ -21158,6 +21159,11 @@ produce_image_glyph (it)
           glyph->u.img_id = img->id;
           glyph->slice = slice;
           glyph->font_type = FONT_TYPE_UNKNOWN;
+          if (it->bidi_p)
+            {
+              glyph->resolved_level = it->bidi_it.resolved_level;
+              glyph->bidi_type = it->bidi_it.type;
+            }
           ++it->glyph_row->used[area];
         }
       else
@@ -21204,6 +21210,11 @@ append_stretch_glyph (it, object, width, height, ascent)
       glyph->u.stretch.height = height;
       glyph->slice = null_glyph_slice;
       glyph->font_type = FONT_TYPE_UNKNOWN;
+      if (it->bidi_p)
+        {
+          glyph->resolved_level = it->bidi_it.resolved_level;
+          glyph->bidi_type = it->bidi_it.type;
+        }
       ++it->glyph_row->used[area];
     }
   else