Continue debugging continuation lines.

 .gdbinit (prowlims, pmtxrows): New commands.
 xdisp.c (display_line): Special-case the calculation of row->end
 in rows that end at ZV, to avoid abort in CHAR_TO_BYTE.  Handle
 empty lines correctly when calculating row's max and min pos.
 Display cursor at the first glyph row that has its ends_at_zv_p
 flag set.

3 files changed, 100 insertions, 32 deletions

diff --git a/src/.gdbinit b/src/.gdbinit
index 8949e66134c..659bc870710 100644
--- a/src/.gdbinit
+++ b/src/.gdbinit
@@ -613,6 +613,28 @@ document pgrowit
 Pretty print all glyphs in it->glyph_row.
 end
 
+define prowlims
+  printf "start=%d,end=%d,reversed=%d,cont=%d\n", $arg0->start.pos.charpos, $arg0->end.pos.charpos, $arg0->reversed_p, $arg0->continued_p
+end
+document prowlims
+Print important attributes of a glyph_row structure.
+Takes one argument, a pointer to a glyph_row structure.
+end
+
+define pmtxrows
+  set $mtx = $arg0
+  set $gl = $mtx->rows
+  set $glend = $mtx->rows + $mtx->nrows
+  while ($gl < $glend)
+    prowlims $gl
+    set $gl = $gl + 1
+  end
+end
+document pmtxrows
+Print data about glyph rows in a glyph matrix.
+Takes one argument, a pointer to a glyph_matrix structure.
+end
+
 define xtype
   xgettype $
   output $type
diff --git a/src/ChangeLog.bidi b/src/ChangeLog.bidi
index 234723bf6f7..7f7eb0808d2 100644
--- a/src/ChangeLog.bidi
+++ b/src/ChangeLog.bidi
@@ -1,3 +1,13 @@
+2010-03-06  Eli Zaretskii  <eliz@gnu.org>
+
+        * .gdbinit (prowlims, pmtxrows): New commands.
+
+        * xdisp.c (display_line): Special-case the calculation of row->end
+        in rows that end at ZV, to avoid abort in CHAR_TO_BYTE.  Handle
+        empty lines correctly when calculating row's max and min pos.
+        Display cursor at the first glyph row that has its ends_at_zv_p
+        flag set.
+
 2010-02-20  Eli Zaretskii  <eliz@gnu.org>
 
         * xdisp.c (set_cursor_from_row): Compare candidate cursor
diff --git a/src/xdisp.c b/src/xdisp.c
index 056a009a7d9..e481809164d 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -17604,19 +17604,18 @@ display_line (it)
   compute_line_metrics (it);
 
   /* Remember the position at which this line ends.  */
-  if (!it->bidi_p)
-    row->end = row_end = it->current;
-  else
+  row->end = row_end = it->current;
+  if (it->bidi_p)
     {
-      EMACS_INT min_pos = row->start.pos.charpos, max_pos = 0;
-      struct glyph *g;
-      struct it save_it;
-      struct text_pos tpos;
-
       /* ROW->start and ROW->end must be the smallest and largest
          buffer positions in ROW.  But if ROW was bidi-reordered,
          these two positions can be anywhere in the row, so we must
          rescan all of the ROW's glyphs to find them.  */
+      EMACS_INT min_pos = ZV + 1, max_pos = 0;
+      struct glyph *g;
+      struct it save_it;
+      struct text_pos tpos;
+
       for (g = row->glyphs[TEXT_AREA];
            g < row->glyphs[TEXT_AREA] + row->used[TEXT_AREA];
            g++)
@@ -17629,34 +17628,68 @@ display_line (it)
                 max_pos = g->charpos;
             }
         }
-      if (min_pos < row->start.pos.charpos)
+      /* Empty lines have a valid buffer position at their first
+         glyph, but that glyph's OBJECT is zero, as if it didn't come
+         from a buffer.  If we didn't find any valid buffer positions
+         in this row, maybe we have such an empty line.  */
+      if (min_pos == ZV + 1 && row->used[TEXT_AREA])
         {
-          row->start.pos.charpos = min_pos;
-          row->start.pos.bytepos = CHAR_TO_BYTE (min_pos);
+          for (g = row->glyphs[TEXT_AREA];
+               g < row->glyphs[TEXT_AREA] + row->used[TEXT_AREA];
+               g++)
+            {
+              if (INTEGERP (g->object))
+                {
+                  if (g->charpos && g->charpos < min_pos)
+                    min_pos = g->charpos;
+                  if (g->charpos > max_pos)
+                    max_pos = g->charpos;
+                }
+            }
+        }
+      if (min_pos <= ZV)
+        {
+          if (min_pos != row->start.pos.charpos)
+            {
+              row->start.pos.charpos = min_pos;
+              row->start.pos.bytepos = CHAR_TO_BYTE (min_pos);
+            }
+          if (max_pos == 0)
+            max_pos = min_pos;
         }
-      if (max_pos == 0)
-        max_pos = min_pos;
       /* For ROW->end, we need the position that is _after_ max_pos,
-         in the logical order.  */
-      SET_TEXT_POS (tpos, max_pos + 1, CHAR_TO_BYTE (max_pos + 1));
-      /* If the character at max_pos+1 is a newline, skip that as
-         well.  Note that this may skip some invisible text.  */
-      if (FETCH_CHAR (tpos.bytepos) == '\n'
-          || (FETCH_CHAR (tpos.bytepos) == '\r' && it->selective))
-        {
-          save_it = *it;
-          it->bidi_p = 0;
-          reseat_1 (it, tpos, 0);
-          set_iterator_to_next (it, 1);
-          row_end = it->current;
-          *it = save_it;
+         in the logical order, unless we are at ZV.  */
+      if (row->ends_at_zv_p)
+        {
+          row_end = row->end = it->current;
+          if (!row->used[TEXT_AREA])
+            {
+              row->start.pos.charpos = row_end.pos.charpos;
+              row->start.pos.bytepos = row_end.pos.bytepos;
+            }
         }
-      else
+      else if (row->used[TEXT_AREA] && max_pos)
         {
-          row_end = it->current;
-          row_end.pos = tpos;
+          SET_TEXT_POS (tpos, max_pos + 1, CHAR_TO_BYTE (max_pos + 1));
+          /* If the character at max_pos+1 is a newline, skip that as
+             well.  Note that this may skip some invisible text.  */
+          if (FETCH_CHAR (tpos.bytepos) == '\n'
+              || (FETCH_CHAR (tpos.bytepos) == '\r' && it->selective))
+            {
+              save_it = *it;
+              it->bidi_p = 0;
+              reseat_1 (it, tpos, 0);
+              set_iterator_to_next (it, 1);
+              row_end = it->current;
+              *it = save_it;
+            }
+          else
+            {
+              row_end = it->current;
+              row_end.pos = tpos;
+            }
+          row->end = row_end;
         }
-      row->end = row_end;
     }
 
   /* Record whether this row ends inside an ellipsis.  */
@@ -17680,8 +17713,11 @@ display_line (it)
        /* In bidi-reordered rows, keep checking for proper cursor
           position even if one has been found already, because buffer
           positions in such rows change non-linearly with ROW->VPOS,
-          when a line is continued.  */
-       || it->bidi_p)
+          when a line is continued.  One exception: when we are at ZV,
+          display cursor on the first suitable glyph row, since all
+          the empty rows after that also have their ends_at_zv_p flag
+          set.  */
+       || (it->bidi_p && !row->ends_at_zv_p))
       && PT >= MATRIX_ROW_START_CHARPOS (row)
       && PT <= MATRIX_ROW_END_CHARPOS (row)
       && cursor_row_p (it->w, row))