[font] Add get_nominal_glyphs() callback (note the plural)

Unused as of now.  To be wired up to normalizer, which would remove
overhead and allow hb-ot-font initialization to become a no-op, so
we can enable it by default.

docs/harfbuzz-sections.txt

@@ -237,6 +237,7 @@ hb_font_funcs_set_glyph_v_advance_func
 hb_font_funcs_set_glyph_v_advances_func
 hb_font_funcs_set_glyph_v_origin_func
 hb_font_funcs_set_nominal_glyph_func
+hb_font_funcs_set_nominal_glyphs_func
 hb_font_funcs_set_user_data
 hb_font_funcs_set_variation_glyph_func
 hb_font_funcs_t
@@ -273,6 +274,8 @@ hb_font_get_glyph_v_origin
 hb_font_get_glyph_v_origin_func_t
 hb_font_get_nominal_glyph
 hb_font_get_nominal_glyph_func_t
+hb_font_get_nominal_glyphs
+hb_font_get_nominal_glyphs_func_t
 hb_font_get_parent
 hb_font_get_ppem
 hb_font_get_ptem

src/hb-font.cc

@@ -101,9 +101,42 @@ hb_font_get_nominal_glyph_default (hb_font_t *font,
 				   hb_codepoint_t *glyph,
 				   void *user_data HB_UNUSED)
 {
+  if (font->has_nominal_glyphs_func ())
+  {
+    return font->get_nominal_glyphs (1, &unicode, 0, glyph, 0);
+  }
   return font->parent->get_nominal_glyph (unicode, glyph);
 }
 
+#define hb_font_get_nominal_glyphs_nil hb_font_get_nominal_glyphs_default
+static unsigned int
+hb_font_get_nominal_glyphs_default (hb_font_t *font,
+				    void *font_data HB_UNUSED,
+				    unsigned int count,
+				    const hb_codepoint_t *first_unicode,
+				    unsigned int unicode_stride,
+				    hb_codepoint_t *first_glyph,
+				    unsigned int glyph_stride,
+				    void *user_data HB_UNUSED)
+{
+  if (font->has_nominal_glyph_func ())
+  {
+    for (unsigned int i = 0; i < count; i++)
+    {
+      if (!font->get_nominal_glyph (*first_unicode, first_glyph))
+        return i;
+
+      first_unicode = &StructAtOffset<hb_codepoint_t> (first_unicode, unicode_stride);
+      first_glyph = &StructAtOffset<hb_codepoint_t> (first_glyph, glyph_stride);
+    }
+    return count;
+  }
+
+  return font->parent->get_nominal_glyphs (count,
+					   first_unicode, unicode_stride,
+					   first_glyph, glyph_stride);
+}
+
 static hb_bool_t
 hb_font_get_variation_glyph_nil (hb_font_t *font HB_UNUSED,
 				 void *font_data HB_UNUSED,

src/hb-font.h

@@ -125,6 +125,14 @@ typedef hb_bool_t (*hb_font_get_variation_glyph_func_t) (hb_font_t *font, void *
 							 hb_codepoint_t *glyph,
 							 void *user_data);
 
+typedef unsigned int (*hb_font_get_nominal_glyphs_func_t) (hb_font_t *font, void *font_data,
+							   unsigned int count,
+							   const hb_codepoint_t *first_unicode,
+							   unsigned int unicode_stride,
+							   hb_codepoint_t *first_glyph,
+							   unsigned int glyph_stride,
+							   void *user_data);
+
 
 typedef hb_position_t (*hb_font_get_glyph_advance_func_t) (hb_font_t *font, void *font_data,
 							   hb_codepoint_t glyph,
@@ -220,6 +228,22 @@ hb_font_funcs_set_nominal_glyph_func (hb_font_funcs_t *ffuncs,
 				      hb_font_get_nominal_glyph_func_t func,
 				      void *user_data, hb_destroy_func_t destroy);
 
+/**
+ * hb_font_funcs_set_nominal_glyphs_func:
+ * @ffuncs: font functions.
+ * @func: (closure user_data) (destroy destroy) (scope notified):
+ * @user_data:
+ * @destroy:
+ *
+ *
+ *
+ * Since: REPLACEME
+ **/
+HB_EXTERN void
+hb_font_funcs_set_nominal_glyphs_func (hb_font_funcs_t *ffuncs,
+				       hb_font_get_nominal_glyphs_func_t func,
+				       void *user_data, hb_destroy_func_t destroy);
+
 /**
  * hb_font_funcs_set_variation_glyph_func:
  * @ffuncs: font functions.

src/hb-font.hh

@@ -43,6 +43,7 @@
   HB_FONT_FUNC_IMPLEMENT (font_h_extents) \
   HB_FONT_FUNC_IMPLEMENT (font_v_extents) \
   HB_FONT_FUNC_IMPLEMENT (nominal_glyph) \
+  HB_FONT_FUNC_IMPLEMENT (nominal_glyphs) \
   HB_FONT_FUNC_IMPLEMENT (variation_glyph) \
   HB_FONT_FUNC_IMPLEMENT (glyph_h_advance) \
   HB_FONT_FUNC_IMPLEMENT (glyph_v_advance) \
@@ -212,6 +213,18 @@ struct hb_font_t
 				       unicode, glyph,
 				       klass->user_data.nominal_glyph);
   }
+  inline unsigned int get_nominal_glyphs ( unsigned int count,
+					  const hb_codepoint_t *first_unicode,
+					  unsigned int unicode_stride,
+					  hb_codepoint_t *first_glyph,
+					  unsigned int glyph_stride)
+  {
+    return klass->get.f.nominal_glyphs (this, user_data,
+					count,
+					first_unicode, unicode_stride,
+					first_glyph, glyph_stride,
+					klass->user_data.nominal_glyphs);
+  }
 
   inline hb_bool_t get_variation_glyph (hb_codepoint_t unicode, hb_codepoint_t variation_selector,
 					hb_codepoint_t *glyph)