From b2a1acccd9776beddb25fb4f9e24ca6e272958f4 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Thu, 18 Jun 2020 16:41:31 -0700
Subject: [PATCH] Simplify get_glyph_alternates() dispatcher

Trying to make it **very simple** to add a specialized dispatcher for
one API to be routed to just a few objects (one in this case).
---
 src/hb-ot-layout-gsub-table.hh |  9 +++++---
 src/hb-ot-layout-gsubgpos.hh   | 40 ----------------------------------
 src/hb-ot-layout.cc            | 32 +++++++++++++++++++++++++--
 3 files changed, 36 insertions(+), 45 deletions(-)

diff --git a/src/hb-ot-layout-gsub-table.hh b/src/hb-ot-layout-gsub-table.hh
index 11c9bf19e..4a9d38a5b 100644
--- a/src/hb-ot-layout-gsub-table.hh
+++ b/src/hb-ot-layout-gsub-table.hh
@@ -643,9 +643,12 @@ struct AlternateSubstFormat1
   { return c->len == 1 && (this+coverage).get_coverage (c->glyphs[0]) != NOT_COVERED; }
 
   unsigned
-  get_glyph_alternates (hb_get_glyph_alternates_context_t *c) const
-  { return (this+alternateSet[(this+coverage).get_coverage (c->gid)])
-	   .get_alternates (c->start_offset, c->alternate_count, c->alternate_glyphs); }
+  get_glyph_alternates (hb_codepoint_t  gid,
+			unsigned        start_offset,
+			unsigned       *alternate_count  /* IN/OUT.  May be NULL. */,
+			hb_codepoint_t *alternate_glyphs /* OUT.     May be NULL. */) const
+  { return (this+alternateSet[(this+coverage).get_coverage (gid)])
+	   .get_alternates (start_offset, alternate_count, alternate_glyphs); }
 
   bool apply (hb_ot_apply_context_t *c) const
   {
diff --git a/src/hb-ot-layout-gsubgpos.hh b/src/hb-ot-layout-gsubgpos.hh
index 75ef76a4b..991fef6bb 100644
--- a/src/hb-ot-layout-gsubgpos.hh
+++ b/src/hb-ot-layout-gsubgpos.hh
@@ -227,46 +227,6 @@ struct hb_would_apply_context_t :
 			      debug_depth (0) {}
 };
 
-struct hb_get_glyph_alternates_context_t :
-       hb_dispatch_context_t<hb_get_glyph_alternates_context_t, unsigned, 0>
-{
-  const char *get_name () { return "GET_GLYPH_ALTERNATES"; }
-  static return_t default_return_value () { return 0; }
-  bool stop_sublookup_iteration (return_t r) const { return r; }
-
-  hb_face_t *face;
-  hb_codepoint_t gid;
-  unsigned        start_offset;
-  unsigned       *alternate_count;
-  hb_codepoint_t *alternate_glyphs;
-  unsigned int debug_depth;
-
-  hb_get_glyph_alternates_context_t (hb_face_t *face_,
-				     hb_codepoint_t gid_,
-				     unsigned        start_offset_,
-				     unsigned       *alternate_count_,
-				     hb_codepoint_t *alternate_glyphs_) :
-				       face (face_),
-				       gid (gid_),
-				       start_offset (start_offset_),
-				       alternate_count (alternate_count_),
-				       alternate_glyphs (alternate_glyphs_),
-				       debug_depth (0) {}
-
-  private:
-  template <typename T> auto
-  _dispatch (const T &obj, hb_priority<1>) HB_AUTO_RETURN
-  ( obj.get_glyph_alternates (this) )
-  template <typename T> auto
-  _dispatch (const T &obj, hb_priority<0>) HB_AUTO_RETURN
-  ( default_return_value () )
-  public:
-  template <typename T> auto
-  dispatch (const T &obj) HB_AUTO_RETURN
-  ( _dispatch (obj, hb_prioritize) )
-};
-
-
 struct hb_collect_glyphs_context_t :
        hb_dispatch_context_t<hb_collect_glyphs_context_t, hb_empty_t, 0>
 {
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index c042ce9cc..542d059d4 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1969,6 +1969,34 @@ hb_ot_layout_get_baseline (hb_font_t                   *font,
 }
 #endif
 
+
+struct hb_get_glyph_alternates_context_t :
+       hb_dispatch_context_t<hb_get_glyph_alternates_context_t, unsigned, 0>
+{
+  const char *get_name () { return "GET_GLYPH_ALTERNATES"; }
+  static return_t default_return_value () { return 0; }
+  bool stop_sublookup_iteration (return_t r) const { return r; }
+
+  hb_face_t *face;
+  unsigned int debug_depth;
+
+  hb_get_glyph_alternates_context_t (hb_face_t *face) :
+				       face (face),
+				       debug_depth (0) {}
+
+  private:
+  template <typename T, typename ...Ts> auto
+  _dispatch (const T &obj, hb_priority<1>, Ts&&... ds) HB_AUTO_RETURN
+  ( obj.get_glyph_alternates (hb_forward<Ts> (ds)...) )
+  template <typename T, typename ...Ts> auto
+  _dispatch (const T &obj, hb_priority<0>, Ts&&... ds) HB_AUTO_RETURN
+  ( default_return_value () )
+  public:
+  template <typename T, typename ...Ts> auto
+  dispatch (const T &obj, Ts&&... ds) HB_AUTO_RETURN
+  ( _dispatch (obj, hb_prioritize, hb_forward<Ts> (ds)...) )
+};
+
 /**
  * hb_ot_layout_lookup_get_glyph_alternates:
  * @face: a face.
@@ -1994,9 +2022,9 @@ hb_ot_layout_lookup_get_glyph_alternates (hb_face_t      *face,
 					  unsigned       *alternate_count  /* IN/OUT.  May be NULL. */,
 					  hb_codepoint_t *alternate_glyphs /* OUT.     May be NULL. */)
 {
-  OT::hb_get_glyph_alternates_context_t c (face, glyph, start_offset, alternate_count, alternate_glyphs);
+  hb_get_glyph_alternates_context_t c (face);
   const OT::SubstLookup &lookup = face->table.GSUB->table->get_lookup (lookup_index);
-  auto ret = lookup.dispatch (&c);
+  auto ret = lookup.dispatch (&c, glyph, start_offset, alternate_count, alternate_glyphs);
   if (!ret && alternate_count) *alternate_count = 0;
   return ret;
 }