master 7592953553: Fix 'vertical-motion' in bidi-reordered text

[Eli Zaretskii]

branch: master
commit 75929535530d7c5ab48565a33b33b4e84026b368
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix 'vertical-motion' in bidi-reordered text
    
    * src/xdisp.c (move_it_vertically_backward): Fix the case of long
    bidi-reordered lines when starting from its last (top-most) screen
    line.
    (move_it_by_lines): Fix logic of detection when going by lines
    overshoots.
---
 src/xdisp.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index c756e7f04f..855f48f2bd 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -10711,6 +10711,11 @@ move_it_vertically_backward (struct it *it, int dy)
   while (nlines-- && IT_CHARPOS (*it) > pos_limit)
     back_to_previous_visible_line_start (it);
 
+  /* Move one line more back, for the (rare) situation where we have
+     bidi-reordered continued lines, and we start from the top-most
+     screen line, which is the last in logical order.  */
+  if (it->bidi_p && dy == 0)
+    back_to_previous_visible_line_start (it);
   /* Reseat the iterator here.  When moving backward, we don't want
      reseat to skip forward over invisible text, set up the iterator
      to deliver from overlay strings at the new position etc.  So,
@@ -10956,7 +10961,6 @@ move_it_by_lines (struct it *it, ptrdiff_t dvpos)
       int nchars_per_row
        = (it->last_visible_x - it->first_visible_x) / FRAME_COLUMN_WIDTH 
(it->f);
       bool hit_pos_limit = false;
-      bool reverse_rows = false;
       ptrdiff_t pos_limit;
 
       /* Start at the beginning of the screen line containing IT's
@@ -10967,10 +10971,6 @@ move_it_by_lines (struct it *it, ptrdiff_t dvpos)
       move_it_vertically_backward (it, 0);
       dvpos -= it->vpos;
 
-      /* Do we have glyph rows whose positions _increase_ as we go up?  */
-      if (IT_CHARPOS (*it) > start_charpos)
-       reverse_rows = true;
-
       /* Go back -DVPOS buffer lines, but no farther than -DVPOS full
         screen lines, and reseat the iterator there.  */
       start_charpos = IT_CHARPOS (*it);
@@ -11021,8 +11021,7 @@ move_it_by_lines (struct it *it, ptrdiff_t dvpos)
          SAVE_IT (it2, *it, it2data);
          move_it_to (it, -1, -1, -1, it->vpos + delta, MOVE_TO_VPOS);
          /* Move back again if we got too far ahead.  */
-         if ((IT_CHARPOS (*it) >= start_charpos && !reverse_rows)
-             || (IT_CHARPOS (*it) <= start_charpos && reverse_rows))
+         if (it->vpos - it2.vpos > delta)
            RESTORE_IT (it, &it2, it2data);
          else
            bidi_unshelve_cache (it2data, true);