master 3553904a90: Fix some issues with vertical-motion in bidi-reordered text

[Eli Zaretskii]

branch: master
commit 3553904a90a242b7ee7b48607ac02cf57e2ab753
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Fix some issues with vertical-motion in bidi-reordered text
    
    This fixes some uses of vertical-motion when a screen line
    starts withcharacters of directionality that is opposite to
    the current paragraph's base direction.
    * src/xdisp.c (move_it_vertically_backward): Adjust NLINES to
    compensate for its increasing when DY == 0.
---
 src/xdisp.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index 1f6f35e6c0..55e74a3603 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -10709,6 +10709,11 @@ move_it_vertically_backward (struct it *it, int dy)
 
   /* Estimate how many newlines we must move back.  */
   nlines = max (1, dy / default_line_pixel_height (it->w));
+  /* 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)
+    nlines++;
   if (it->line_wrap == TRUNCATE || nchars_per_row == 0)
     pos_limit = BEGV;
   else
@@ -10720,11 +10725,6 @@ 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,
@@ -10775,6 +10775,8 @@ move_it_vertically_backward (struct it *it, int dy)
 
   if (dy == 0)
     {
+      /* Adjust nlines for increasing it at the beginning.  */
+      nlines -= !!it->bidi_p;
       /* DY == 0 means move to the start of the screen line.  The
         value of nlines is > 0 if continuation lines were involved,
         or if the original IT position was at start of a line.  */