Improve support for shaping Egyptian Hieroglyphs

* src/composite.c (composition_gstring_lookup_cache): Renamed from
gstring_lookup_cache and made external.  All callers changed.
* src/composite.h (composition_gstring_lookup_cache): Add
prototype.
* src/font.c (Ffont_shape_gstring): Call
composition_gstring_lookup_cache and return the cached composition
if it is already in the cache.

* lisp/language/misc-lang.el (egyptian-shape-grouping): New
function.
(composition-function-table): Use egyptian-shape-grouping in
setting up compositions for Egyptian Hieroglyphs.  Fix the
composition setup for horizontal and vertical joiners.

3 files changed, 8 insertions, 5 deletions

diff --git a/src/composite.c b/src/composite.c
index 984e0d9cda8..90f8536b2de 100644
--- a/src/composite.c
+++ b/src/composite.c
@@ -637,10 +637,8 @@ compose_text (ptrdiff_t start, ptrdiff_t end, Lisp_Object components,
 
 static Lisp_Object gstring_hash_table;
 
-static Lisp_Object gstring_lookup_cache (Lisp_Object);
-
-static Lisp_Object
-gstring_lookup_cache (Lisp_Object header)
+Lisp_Object
+composition_gstring_lookup_cache (Lisp_Object header)
 {
   struct Lisp_Hash_Table *h = XHASH_TABLE (gstring_hash_table);
   ptrdiff_t i = hash_lookup (h, header, NULL);
@@ -1781,7 +1779,7 @@ should be ignored.  */)
 
   header = fill_gstring_header (frompos, frombyte,
                                 topos, font_object, string);
-  gstring = gstring_lookup_cache (header);
+  gstring = composition_gstring_lookup_cache (header);
   if (! NILP (gstring))
     return gstring;
 
diff --git a/src/composite.h b/src/composite.h
index 239f1e531ef..d39fdbaae05 100644
--- a/src/composite.h
+++ b/src/composite.h
@@ -330,6 +330,7 @@ extern int composition_update_it (struct composition_it *,
                                   ptrdiff_t, ptrdiff_t, Lisp_Object);
 
 extern ptrdiff_t composition_adjust_point (ptrdiff_t, ptrdiff_t);
+extern Lisp_Object composition_gstring_lookup_cache (Lisp_Object);
 
 INLINE_HEADER_END
 
diff --git a/src/font.c b/src/font.c
index fe257f47dc3..f7c4c816b5d 100644
--- a/src/font.c
+++ b/src/font.c
@@ -4461,6 +4461,10 @@ GSTRING.  */)
     signal_error ("Invalid glyph-string: ", gstring);
   if (! NILP (LGSTRING_ID (gstring)))
     return gstring;
+  Lisp_Object cached_gstring =
+    composition_gstring_lookup_cache (LGSTRING_HEADER (gstring));
+  if (! NILP (cached_gstring))
+    return cached_gstring;
   font_object = LGSTRING_FONT (gstring);
   CHECK_FONT_OBJECT (font_object);
   font = XFONT_OBJECT (font_object);