Fix Arabic shaping when column-number-mode is in effect

* src/indent.c (scan_for_column, compute_motion): Pass -1,
instead of NEUTRAL_DIR, to 'composition_reseat_it'.
* src/composite.c (composition_reseat_it): Interpret negative
value of BIDI_LEVEL to mean the caller doesn't know what is the
bidi direction of the text.  (Bug#41005)

2 files changed, 5 insertions, 3 deletions

diff --git a/src/composite.c b/src/composite.c
index 364d5c9316e..2fbe6796b59 100644
--- a/src/composite.c
+++ b/src/composite.c
@@ -1217,7 +1217,9 @@ composition_reseat_it (struct composition_it *cmp_it, ptrdiff_t charpos,
         continue;
       if (charpos < endpos)
         {
-          if ((bidi_level & 1) == 0)
+          if (bidi_level < 0)
+            direction = Qnil;
+          else if ((bidi_level & 1) == 0)
             direction = QL2R;
           else
             direction = QR2L;
diff --git a/src/indent.c b/src/indent.c
index f7db42783c1..939e5931db0 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -598,7 +598,7 @@ scan_for_column (ptrdiff_t *endpos, EMACS_INT *goalcol, ptrdiff_t *prevcol)
       if (cmp_it.id >= 0
           || (scan == cmp_it.stop_pos
               && composition_reseat_it (&cmp_it, scan, scan_byte, end,
-                                        w, NEUTRAL_DIR, NULL, Qnil)))
+                                        w, -1, NULL, Qnil)))
         composition_update_it (&cmp_it, scan, scan_byte, Qnil);
       if (cmp_it.id >= 0)
         {
@@ -1506,7 +1506,7 @@ compute_motion (ptrdiff_t from, ptrdiff_t frombyte, EMACS_INT fromvpos,
           if (cmp_it.id >= 0
               || (pos == cmp_it.stop_pos
                   && composition_reseat_it (&cmp_it, pos, pos_byte, to, win,
-                                            NEUTRAL_DIR, NULL, Qnil)))
+                                            -1, NULL, Qnil)))
             composition_update_it (&cmp_it, pos, pos_byte, Qnil);
           if (cmp_it.id >= 0)
             {