Implement GUI display of R2L lines, fix TTY display of R2L lines.

 xdisp.c [HAVE_WINDOW_SYSTEM]: Add prototype for
 append_stretch_glyph.
 (set_cursor_from_row) <cursor_x>: Remove unused variable.  Fix
 off-by-one error in computing x at end of text in the row.
 (append_stretch_glyph): In reversed row, prepend the glyph rather
 than append it.  Set resolved_level and bidi_type of the glyph.
 (extend_face_to_end_of_line): If the row is reversed, prepend a
 stretch glyph whose width is such that the rightmost glyph will be
 drawn at the right margin of the window.  Fix off-by-one error on
 TTY frames in testing whether a line needs face extension.  Fix
 face extension at ZV.  If this is the last glyph row, use
 DEFAULT_FACE_ID, to avoid painting the rest of the window with the
 region face.
 (set_cursor_from_row, display_line): Use
 MATRIX_ROW_CONTINUATION_LINE_P instead of testing value of
 row->continuation_lines_width.
 (next_element_from_buffer): Don't call bidi_paragraph_init if we
 are at ZV.  Fixes a crash when reseated to ZV by
 try_window_reusing_current_matrix.
 (display_and_set_cursor, erase_phys_cursor): Handle negative HPOS,
 which happens with R2L glyph rows.  Fixes a crash when inserting a
 character at end of an R2L line.
 (set_cursor_from_row): Don't be fooled by truncated rows: don't
 treat them as having zero-width characters.  Improve comments.
 Don't reverse pos_before and pos_after for reversed glyph rows.
 Set cursor.x to negative value when the cursor might be on the
 left fringe.
 (IT_OVERFLOW_NEWLINE_INTO_FRINGE): For R2L lines, consider the
 left fringe, not the right one.
 (notice_overwritten_cursor, draw_phys_cursor_glyph)
 (erase_phys_cursor): For reversed cursor_row, support cursor on
 the left fringe.
 fringe.c (update_window_fringes): For R2L rows, swap the bitmaps
 of continuation indicators on the fringes.
 (draw_fringe_bitmap): For reversed glyph rows, allow cursor on the
 left fringe.
 w32term.c (w32_draw_window_cursor): For reversed glyph rows,
 draw cursor on the left fringe.
 xterm.c (x_draw_window_cursor): For reversed glyph rows, draw
 cursor on the left fringe.
 dispnew.c (update_text_area): Handle reversed desired rows when
 the cursor is on the left fringe.
 (set_window_cursor_after_update): Limit cursor's hpos by -1 from
 below, not by 0, for when the cursor is on the left fringe.

 xdisp.c (unproduce_glyphs): New function.
 (display_line): Use it when produced glyphs are discarded from R2L
 glyph rows.
 (append_composite_glyph): In R2L rows, prepend the glyph rather
 than appending it.
  term.c (append_composite_glyph): In R2L rows, prepend the glyph
 rather than append it.  Set up the resolved_level and bidi_type
 attributes of the appended glyph.
 (produce_special_glyphs): Mirror the backslash continuation
 character in R2L lines.

1 files changed, 30 insertions, 3 deletions

diff --git a/src/term.c b/src/term.c
index 20f746decdb..bb143207758 100644
--- a/src/term.c
+++ b/src/term.c
@@ -1589,7 +1589,6 @@ append_glyph (it)
     }
 }
 
-
 /* Produce glyphs for the display element described by IT.  *IT
    specifies what we want to produce a glyph for (character, image, ...),
    and where in the glyph matrix we currently are (glyph row and hpos).
@@ -1808,6 +1807,17 @@ append_composite_glyph (it)
   glyph = it->glyph_row->glyphs[it->area] + it->glyph_row->used[it->area];
   if (glyph < 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;
+
+          /* Make room for the new glyph.  */
+          for (g = glyph - 1; g >= it->glyph_row->glyphs[it->area]; g--)
+            g[1] = *g;
+          glyph = it->glyph_row->glyphs[it->area];
+        }
       glyph->type = COMPOSITE_GLYPH;
       glyph->pixel_width = it->pixel_width;
       glyph->u.cmp.id = it->cmp_it.id;
@@ -1828,6 +1838,18 @@ append_composite_glyph (it)
       glyph->padding_p = 0;
       glyph->charpos = CHARPOS (it->position);
       glyph->object = it->object;
+      if (it->bidi_p)
+        {
+          glyph->resolved_level = it->bidi_it.resolved_level;
+          if ((it->bidi_it.type & 7) != it->bidi_it.type)
+            abort ();
+          glyph->bidi_type = it->bidi_it.type;
+        }
+      else
+        {
+          glyph->resolved_level = 0;
+          glyph->bidi_type = UNKNOWN_BT;
+        }
 
       ++it->glyph_row->used[it->area];
       ++glyph;
@@ -1889,12 +1911,16 @@ produce_special_glyphs (it, what)
 
   if (what == IT_CONTINUATION)
     {
-      /* Continuation glyph.  */
-      SET_GLYPH_FROM_CHAR (glyph, '\\');
+      /* Continuation glyph.  For R2L lines, we mirror it by hand.  */
+      if (it->bidi_it.paragraph_dir == R2L)
+        SET_GLYPH_FROM_CHAR (glyph, '/');
+      else
+        SET_GLYPH_FROM_CHAR (glyph, '\\');
       if (it->dp
           && (gc = DISP_CONTINUE_GLYPH (it->dp), GLYPH_CODE_P (gc))
           && GLYPH_CODE_CHAR_VALID_P (gc))
         {
+          /* FIXME: Should we mirror GC for R2L lines?  */
           SET_GLYPH_FROM_GLYPH_CODE (glyph, gc);
           spec_glyph_lookup_face (XWINDOW (it->window), &glyph);
         }
@@ -1907,6 +1933,7 @@ produce_special_glyphs (it, what)
           && (gc = DISP_TRUNC_GLYPH (it->dp), GLYPH_CODE_P (gc))
           && GLYPH_CODE_CHAR_VALID_P (gc))
         {
+          /* FIXME: Should we mirror GC for R2L lines?  */
           SET_GLYPH_FROM_GLYPH_CODE (glyph, gc);
           spec_glyph_lookup_face (XWINDOW (it->window), &glyph);
         }