Provide text directionality and language to HarfBuzz shaper

* lisp/language/tv-util.el (tai-viet-composition-function):
* lisp/language/ethio-util.el (ethio-composition-function):
* lisp/language/japanese.el (compose-gstring-for-variation-glyph):
* lisp/language/thai-util.el (thai-composition-function):
* lisp/language/misc-lang.el (arabic-shape-gstring):
* lisp/language/lao-util.el (lao-composition-function):
* lisp/language/hebrew.el (hebrew-shape-gstring):
* lisp/composite.el (compose-gstring-for-graphic)
(compose-gstring-for-dotted-circle, auto-compose-chars)
(compose-gstring-for-terminal): Accept 2nd argument DIRECTION; all
callers changed.

* src/composite.c (composition_reseat_it): Call
auto-composition-function with one more argument DIRECTION.
(syms_of_composite) <auto-composition-function>: Update the doc
string.
* src/ftfont.c (ftfont_shape_by_hb): Compute language and
direction, and set buffer properties accordingly.
* src/composite.c (autocmp_chars):
* src/w32uniscribe.c (uniscribe_shape):
* src/xftfont.c (xftfont_shape):
* src/ftfont.c (ftfont_shape, ftfont_shape_by_hb):
* src/font.c (Ffont_shape_gstring): Accept an additional argument
DIRECTION.
* src/macfont.m (lgstring_direction): New enum.
(mac_font_shape_1, mac_screen_font_shape, mac_font_shape):
Accept an additional argument specifying text direction.  All
callers changed.
* src/font.c (syms_of_font): New symbols QL2R and QR2L.
* src/font.h (shape): Accept new argument DIRECTION.  All
implementations changed.  (Bug#33729)
(ftfont_shape): Update prototype.

1 files changed, 12 insertions, 4 deletions

diff --git a/src/font.c b/src/font.c
index e81c267de41..fc8efa7f235 100644
--- a/src/font.c
+++ b/src/font.c
@@ -4397,18 +4397,22 @@ font_fill_lglyph_metrics (Lisp_Object glyph, Lisp_Object font_object)
 }
 
 
-DEFUN ("font-shape-gstring", Ffont_shape_gstring, Sfont_shape_gstring, 1, 1, 0,
-       doc: /* Shape the glyph-string GSTRING.
+DEFUN ("font-shape-gstring", Ffont_shape_gstring, Sfont_shape_gstring, 2, 2, 0,
+       doc: /* Shape the glyph-string GSTRING subject to bidi DIRECTION.
 Shaping means substituting glyphs and/or adjusting positions of glyphs
 to get the correct visual image of character sequences set in the
 header of the glyph-string.
 
+DIRECTION should be produced by the UBA, the Unicode Bidirectional
+Algorithm, and should be a symbol, either L2R or R2L.  It can also
+be nil if the bidi context is unknown.
+
 If the shaping was successful, the value is GSTRING itself or a newly
 created glyph-string.  Otherwise, the value is nil.
 
 See the documentation of `composition-get-gstring' for the format of
 GSTRING.  */)
-  (Lisp_Object gstring)
+  (Lisp_Object gstring, Lisp_Object direction)
 {
   struct font *font;
   Lisp_Object font_object, n, glyph;
@@ -4427,7 +4431,7 @@ GSTRING.  */)
   /* Try at most three times with larger gstring each time.  */
   for (i = 0; i < 3; i++)
     {
-      n = font->driver->shape (gstring);
+      n = font->driver->shape (gstring, direction);
       if (FIXNUMP (n))
 	break;
       gstring = larger_vector (gstring,
@@ -5350,6 +5354,10 @@ syms_of_font (void)
 
   DEFSYM (QCuser_spec, ":user-spec");
 
+  /* For shapers that need to know text directionality.  */
+  DEFSYM (QL2R, "L2R");
+  DEFSYM (QR2L, "R2L");
+
   staticpro (&scratch_font_spec);
   scratch_font_spec = Ffont_spec (0, NULL);
   staticpro (&scratch_font_prefer);