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.

9 files changed, 31 insertions, 26 deletions

diff --git a/lisp/composite.el b/lisp/composite.el
index 3d4805e8fa0..6d280c84d78 100644
--- a/lisp/composite.el
+++ b/lisp/composite.el
@@ -382,8 +382,8 @@ This function is the default value of `compose-chars-after-function'."
 			   (looking-at pattern))
 			 (<= (match-end 0) limit))
 		    (setq result
-			  (funcall func pos (match-end 0) font-obj object)))
-	      (setq result (funcall func pos limit font-obj  object)))
+			  (funcall func pos (match-end 0) font-obj object nil)))
+	      (setq result (funcall func pos limit font-obj  object nil)))
 	    (if result (setq tail nil))))))
     result))
 
@@ -524,8 +524,9 @@ after a sequence of character events."
       (setq from (1+ from)))
     gstring))
 
-(defun compose-gstring-for-graphic (gstring)
-  "Compose glyph-string GSTRING for graphic display.
+(defun compose-gstring-for-graphic (gstring direction)
+  "Compose glyph-string GSTRING under bidi DIRECTION for graphic display.
+DIRECTION is either L2R or R2L, or nil if unknown.
 Combining characters are composed with the preceding base
 character.  If the preceding character is not a base character,
 each combining character is composed as a spacing character by
@@ -559,7 +560,7 @@ All non-spacing characters have this function in
 
      ;; A base character and the following non-spacing characters.
      (t
-      (let ((gstr (font-shape-gstring gstring)))
+      (let ((gstr (font-shape-gstring gstring direction)))
 	(if (and gstr
 		 (> (lglyph-to (lgstring-glyph gstr 0)) 0))
 	    gstr
@@ -686,12 +687,12 @@ All non-spacing characters have this function in
 	      (setq i (1+ i))))
 	  gstring))))))
 
-(defun compose-gstring-for-dotted-circle (gstring)
+(defun compose-gstring-for-dotted-circle (gstring direction)
   (let* ((dc (lgstring-glyph gstring 0)) ; glyph of dotted-circle
 	 (dc-id (lglyph-code dc))
 	 (fc (lgstring-glyph gstring 1)) ; glyph of the following char
 	 (fc-id (lglyph-code fc))
-	 (gstr (and nil (font-shape-gstring gstring))))
+	 (gstr (and nil (font-shape-gstring gstring direction))))
     (if (and gstr
 	     (or (= (lgstring-glyph-len gstr) 1)
 		 (and (= (lgstring-glyph-len gstr) 2)
@@ -742,7 +743,7 @@ All non-spacing characters have this function in
   (aset composition-function-table #x25CC
 	`([,(purecopy ".\\c^") 0 compose-gstring-for-dotted-circle])))
 
-(defun compose-gstring-for-terminal (gstring)
+(defun compose-gstring-for-terminal (gstring _direction)
   "Compose glyph-string GSTRING for terminal display.
 Non-spacing characters are composed with the preceding base
 character.  If the preceding character is not a base character,
@@ -799,10 +800,11 @@ prepending a space before it."
     gstring))
 
 
-(defun auto-compose-chars (func from to font-object string)
+(defun auto-compose-chars (func from to font-object string direction)
   "Compose the characters at FROM by FUNC.
-FUNC is called with one argument GSTRING which is built for characters
-in the region FROM (inclusive) and TO (exclusive).
+FUNC is called with two arguments: GSTRING, which is built for
+characters in the region FROM (inclusive) and TO (exclusive);
+and DIRECTION, which is the bidi directionality of the characters.
 
 If the character are composed on a graphic display, FONT-OBJECT
 is a font to use.  Otherwise, FONT-OBJECT is nil, and the function
@@ -819,7 +821,7 @@ This function is the default value of `auto-composition-function' (which see)."
 	gstring
       (or (fontp font-object 'font-object)
 	  (setq func 'compose-gstring-for-terminal))
-      (funcall func gstring))))
+      (funcall func gstring direction))))
 
 (put 'auto-composition-mode 'permanent-local t)
 
diff --git a/lisp/language/ethio-util.el b/lisp/language/ethio-util.el
index 1ea01684eaa..0729a6d3a63 100644
--- a/lisp/language/ethio-util.el
+++ b/lisp/language/ethio-util.el
@@ -1014,7 +1014,7 @@ With ARG, insert that many delimiters."
 ;;
 
 ;;;###autoload
-(defun ethio-composition-function (pos to font-object string)
+(defun ethio-composition-function (pos to font-object string _direction)
   (setq pos (1- pos))
   (let ((pattern "\\ce\\(፟\\|����\\)"))
     (if string
diff --git a/lisp/language/hebrew.el b/lisp/language/hebrew.el
index c004337c2f8..52188f44725 100644
--- a/lisp/language/hebrew.el
+++ b/lisp/language/hebrew.el
@@ -152,7 +152,7 @@ Bidirectional editing is supported.")))
 ;; (3) If the font has precomposed glyphs, use them as far as
 ;; possible.  Adjust the remaining glyphs artificially.
 
-(defun hebrew-shape-gstring (gstring)
+(defun hebrew-shape-gstring (gstring direction)
   (let* ((font (lgstring-font gstring))
 	 (otf (font-get font :otf))
 	 (nchars (lgstring-char-len gstring))
@@ -172,7 +172,7 @@ Bidirectional editing is supported.")))
 
      ((or (assq 'hebr (car otf)) (assq 'hebr (cdr otf)))
       ;; FONT has OpenType features for Hebrew.
-      (font-shape-gstring gstring))
+      (font-shape-gstring gstring direction))
 
      (t
       ;; FONT doesn't have OpenType features for Hebrew.
@@ -217,7 +217,7 @@ Bidirectional editing is supported.")))
 	;; Now IDX is an index to the first non-precomposed glyph.
 	;; Adjust positions of the remaining glyphs artificially.
         (if (font-get font :combining-capability)
-            (font-shape-gstring gstring)
+            (font-shape-gstring gstring direction)
           (setq base-width (lglyph-width (lgstring-glyph gstring 0)))
           (while (< idx nglyphs)
             (setq glyph (lgstring-glyph gstring idx))
diff --git a/lisp/language/ind-util.el b/lisp/language/ind-util.el
index 85e99181b5c..e5eaf1cb4a4 100644
--- a/lisp/language/ind-util.el
+++ b/lisp/language/ind-util.el
@@ -829,6 +829,9 @@ Returns new end position."
       (let ((pos from) newpos func (max to))
 	(narrow-to-region from to)
 	(while (< pos max)
+          ;; FIXME: The below seems to assume
+          ;; composition-function-table holds functions?  That is no
+          ;; longer true, since long ago.
 	  (setq func (aref composition-function-table (char-after pos)))
 	  (if (fboundp func)
 	      (setq newpos (funcall func pos nil)
diff --git a/lisp/language/japanese.el b/lisp/language/japanese.el
index f6d9e1bf450..b1fb56980a4 100644
--- a/lisp/language/japanese.el
+++ b/lisp/language/japanese.el
@@ -248,7 +248,7 @@ eucJP-ms is defined in <http://www.opengroup.or.jp/jvc/cde/appendix.html>."
   (define-translation-table 'unicode-to-jisx0213
     (char-table-extra-slot table 0)))
 
-(defun compose-gstring-for-variation-glyph (gstring)
+(defun compose-gstring-for-variation-glyph (gstring _direction)
   "Compose glyph-string GSTRING for graphic display.
 GSTRING must have two glyphs; the first is a glyph for a han character,
 and the second is a glyph for a variation selector."
diff --git a/lisp/language/lao-util.el b/lisp/language/lao-util.el
index 554f7cfd83a..4d58be2fc57 100644
--- a/lisp/language/lao-util.el
+++ b/lisp/language/lao-util.el
@@ -489,10 +489,10 @@ syllable.  In that case, FROM and TO are indexes to STR."
       lao-str)))
 
 ;;;###autoload
-(defun lao-composition-function (gstring)
+(defun lao-composition-function (gstring direction)
   (if (= (lgstring-char-len gstring) 1)
-      (compose-gstring-for-graphic gstring)
-    (or (font-shape-gstring gstring)
+      (compose-gstring-for-graphic gstring direction)
+    (or (font-shape-gstring gstring direction)
 	(let ((glyph-len (lgstring-glyph-len gstring))
 	      (i 0)
 	      glyph)
diff --git a/lisp/language/misc-lang.el b/lisp/language/misc-lang.el
index c1aa79cae45..e25e63b4c5c 100644
--- a/lisp/language/misc-lang.el
+++ b/lisp/language/misc-lang.el
@@ -101,8 +101,8 @@ thin (i.e. 1-dot width) space."
 ;; Record error in arabic-change-gstring.
 (defvar arabic-shape-log nil)
 
-(defun arabic-shape-gstring (gstring)
-  (setq gstring (font-shape-gstring gstring))
+(defun arabic-shape-gstring (gstring direction)
+  (setq gstring (font-shape-gstring gstring direction))
   (condition-case err
       (when arabic-shaper-ZWNJ-handling
         (let ((font (lgstring-font gstring))
diff --git a/lisp/language/thai-util.el b/lisp/language/thai-util.el
index d6c9732a9e8..638d4832d93 100644
--- a/lisp/language/thai-util.el
+++ b/lisp/language/thai-util.el
@@ -225,10 +225,10 @@ positions (integers or markers) specifying the region."
   (thai-compose-region (point-min) (point-max)))
 
 ;;;###autoload
-(defun thai-composition-function (gstring)
+(defun thai-composition-function (gstring direction)
   (if (= (lgstring-char-len gstring) 1)
-      (compose-gstring-for-graphic gstring)
-    (or (font-shape-gstring gstring)
+      (compose-gstring-for-graphic gstring direction)
+    (or (font-shape-gstring gstring direction)
 	(let ((glyph-len (lgstring-glyph-len gstring))
 	      (last-char (lgstring-char gstring
 					(1- (lgstring-char-len gstring))))
diff --git a/lisp/language/tv-util.el b/lisp/language/tv-util.el
index a667956a060..7ce8ee1e500 100644
--- a/lisp/language/tv-util.el
+++ b/lisp/language/tv-util.el
@@ -128,7 +128,7 @@
 
 
 ;;;###autoload
-(defun tai-viet-composition-function (from to font-object string)
+(defun tai-viet-composition-function (from to font-object string _direction)
   (if string
       (if (string-match tai-viet-re string from)
 	  (tai-viet-compose-string from (match-end 0) string))