Fix text direction of the HarfBuzz shaping buffer

* src/indent.c (scan_for_column, compute_motion):
* src/xdisp.c (CHAR_COMPOSED_P): Pass PDIR argument to
composition_reseat_it.
* src/composite.c (composition_reseat_it): Accept an
additional argument PDIR that provides the current paragraph's
base direction; all callers changed.  Use PDIR to fix
calculation of the DIRECTION argument to autocmp_chars.
(Bug#33944)
* src/composite.h: Include dispextern.h.
(composition_reseat_it): Update prototype.

4 files changed, 20 insertions, 8 deletions

diff --git a/src/composite.c b/src/composite.c
index 48824946e64..7cb97934a20 100644
--- a/src/composite.c
+++ b/src/composite.c
@@ -1167,7 +1167,9 @@ composition_compute_stop_pos (struct composition_it *cmp_it, ptrdiff_t charpos,
    characters to be composed.  FACE, if non-NULL, is a base face of
    the character.  If STRING is not nil, it is a string containing the
    character to check, and CHARPOS and BYTEPOS are indices in the
-   string.  In that case, FACE must not be NULL.
+   string.  In that case, FACE must not be NULL.  PDIR is the base
+   direction of the current paragraph, and is used to calculate the
+   direction argument to pass to the font shaper.
 
    If the character is composed, setup members of CMP_IT (id, nglyphs,
    from, to, reversed_p), and return true.  Otherwise, update
@@ -1176,7 +1178,7 @@ composition_compute_stop_pos (struct composition_it *cmp_it, ptrdiff_t charpos,
 bool
 composition_reseat_it (struct composition_it *cmp_it, ptrdiff_t charpos,
                        ptrdiff_t bytepos, ptrdiff_t endpos, struct window *w,
-                       struct face *face, Lisp_Object string)
+                       bidi_dir_t pdir, struct face *face, Lisp_Object string)
 {
   if (cmp_it->ch == -2)
     {
@@ -1206,7 +1208,7 @@ composition_reseat_it (struct composition_it *cmp_it, ptrdiff_t charpos,
   else if (w)
     {
       Lisp_Object lgstring = Qnil;
-      Lisp_Object val, elt;
+      Lisp_Object val, elt, direction = Qnil;
 
       val = CHAR_TABLE_REF (Vcomposition_function_table, cmp_it->ch);
       for (EMACS_INT i = 0; i < cmp_it->rule_idx; i++, val = XCDR (val))
@@ -1221,8 +1223,12 @@ composition_reseat_it (struct composition_it *cmp_it, ptrdiff_t charpos,
                 continue;
               if (XFIXNAT (AREF (elt, 1)) != cmp_it->lookback)
                 goto no_composition;
+              if (pdir == L2R)
+                direction = QL2R;
+              else if (pdir == R2L)
+                direction = QR2L;
               lgstring = autocmp_chars (elt, charpos, bytepos, endpos,
-                                        w, face, string, QL2R);
+                                        w, face, string, direction);
               if (composition_gstring_p (lgstring))
                 break;
               lgstring = Qnil;
@@ -1246,8 +1252,12 @@ composition_reseat_it (struct composition_it *cmp_it, ptrdiff_t charpos,
               else
                 bpos = CHAR_TO_BYTE (cpos);
             }
+          if (pdir == L2R)
+            direction = QR2L;
+          else if (pdir == R2L)
+            direction = QL2R;
           lgstring = autocmp_chars (elt, cpos, bpos, charpos + 1, w, face,
-                                    string, QR2L);
+                                    string, direction);
           if (! composition_gstring_p (lgstring)
               || cpos + LGSTRING_CHAR_LEN (lgstring) - 1 != charpos)
             /* Composition failed or didn't cover the current
diff --git a/src/composite.h b/src/composite.h
index ad39a08dca3..44f7ab7f616 100644
--- a/src/composite.h
+++ b/src/composite.h
@@ -26,6 +26,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #define EMACS_COMPOSITE_H
 
 #include "font.h"
+#include "dispextern.h"
 
 INLINE_HEADER_BEGIN
 
@@ -321,7 +322,7 @@ extern void composition_compute_stop_pos (struct composition_it *,
                                           Lisp_Object);
 extern bool composition_reseat_it (struct composition_it *, ptrdiff_t,
                                    ptrdiff_t, ptrdiff_t, struct window *,
-                                   struct face *, Lisp_Object);
+                                   bidi_dir_t, struct face *, Lisp_Object);
 extern int composition_update_it (struct composition_it *,
                                   ptrdiff_t, ptrdiff_t, Lisp_Object);
 
diff --git a/src/indent.c b/src/indent.c
index 18855768d37..e0d35f87652 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -599,7 +599,7 @@ 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, NULL, Qnil)))
+                                        w, NEUTRAL_DIR, 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,
-                                            NULL, Qnil)))
+                                            NEUTRAL_DIR, NULL, Qnil)))
             composition_update_it (&cmp_it, pos, pos_byte, Qnil);
           if (cmp_it.id >= 0)
             {
diff --git a/src/xdisp.c b/src/xdisp.c
index 4d9990cf46c..413d64f80c7 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -6906,6 +6906,7 @@ static next_element_function const get_next_element[NUM_IT_METHODS] =
    || ((IT)->cmp_it.stop_pos == (CHARPOS)                               \
        && composition_reseat_it (&(IT)->cmp_it, CHARPOS, BYTEPOS,       \
                                  END_CHARPOS, (IT)->w,                  \
+                                 (IT)->bidi_it.paragraph_dir,           \
                                  FACE_FROM_ID_OR_NULL ((IT)->f,         \
                                                        (IT)->face_id),  \
                                  (IT)->string)))