From 5336ba70f6fc995858881c2e4339e035b16c70a0 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 20 May 2022 17:03:18 -0600
Subject: [PATCH] [HVAR] Cache VarStore region scalars

---
 src/hb-ot-font.cc           |  8 +++++++-
 src/hb-ot-hmtx-table.hh     |  9 +++++----
 src/hb-ot-var-hvar-table.hh | 11 ++++++++---
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/src/hb-ot-font.cc b/src/hb-ot-font.cc
index 0f44ee4d5..ef4115a8d 100644
--- a/src/hb-ot-font.cc
+++ b/src/hb-ot-font.cc
@@ -110,12 +110,18 @@ hb_ot_get_glyph_h_advances (hb_font_t* font, void* font_data,
   const hb_ot_face_t *ot_face = (const hb_ot_face_t *) font_data;
   const OT::hmtx_accelerator_t &hmtx = *ot_face->hmtx;
 
+  const OT::HVARVVAR &HVAR = *hmtx.var_table;
+  const OT::VariationStore &varStore = &HVAR + HVAR.varStore;
+  OT::VariationStore::cache_t *cache = font->num_coords ? varStore.create_cache () : nullptr;
+
   for (unsigned int i = 0; i < count; i++)
   {
-    *first_advance = font->em_scale_x (hmtx.get_advance (*first_glyph, font));
+    *first_advance = font->em_scale_x (hmtx.get_advance (*first_glyph, font, cache));
     first_glyph = &StructAtOffsetUnaligned<hb_codepoint_t> (first_glyph, glyph_stride);
     first_advance = &StructAtOffsetUnaligned<hb_position_t> (first_advance, advance_stride);
   }
+
+  OT::VariationStore::destroy_cache (cache);
 }
 
 #ifndef HB_NO_VERTICAL
diff --git a/src/hb-ot-hmtx-table.hh b/src/hb-ot-hmtx-table.hh
index d5e1fc91d..d0e46e0b0 100644
--- a/src/hb-ot-hmtx-table.hh
+++ b/src/hb-ot-hmtx-table.hh
@@ -242,7 +242,7 @@ struct hmtxvmtx
 	return side_bearing;
 
       if (var_table.get_length ())
-	return side_bearing + var_table->get_side_bearing_var (glyph, font->coords, font->num_coords); // TODO Optimize?!
+	return side_bearing + var_table->get_side_bearing_var (glyph, font->coords, font->num_coords);
 
       return _glyf_get_side_bearing_var (font, glyph, T::tableTag == HB_OT_TAG_vmtx);
 #else
@@ -284,7 +284,8 @@ struct hmtxvmtx
     }
 
     unsigned int get_advance (hb_codepoint_t  glyph,
-			      hb_font_t      *font) const
+			      hb_font_t      *font,
+			      VariationStore::cache_t *store_cache = nullptr) const
     {
       unsigned int advance = get_advance (glyph);
 
@@ -293,7 +294,7 @@ struct hmtxvmtx
 	return advance;
 
       if (var_table.get_length ())
-	return advance + roundf (var_table->get_advance_var (glyph, font)); // TODO Optimize?!
+	return advance + roundf (var_table->get_advance_var (glyph, font, store_cache)); // TODO Optimize?!
 
       return _glyf_get_advance_var (font, glyph, T::tableTag == HB_OT_TAG_vmtx);
 #else
@@ -310,7 +311,7 @@ struct hmtxvmtx
 
     unsigned int default_advance;
 
-    private:
+    public:
     hb_blob_ptr_t<hmtxvmtx> table;
     hb_blob_ptr_t<HVARVVAR> var_table;
   };
diff --git a/src/hb-ot-var-hvar-table.hh b/src/hb-ot-var-hvar-table.hh
index e9d90352f..56efcdbee 100644
--- a/src/hb-ot-var-hvar-table.hh
+++ b/src/hb-ot-var-hvar-table.hh
@@ -319,10 +319,15 @@ struct HVARVVAR
 						hvar_plan.index_map_plans.as_array ()));
   }
 
-  float get_advance_var (hb_codepoint_t glyph, hb_font_t *font) const
+  float get_advance_var (hb_codepoint_t  glyph,
+			 hb_font_t      *font,
+			 VariationStore::cache_t *store_cache = nullptr) const
   {
     uint32_t varidx = (this+advMap).map (glyph);
-    return (this+varStore).get_delta (varidx, font->coords, font->num_coords);
+    return (this+varStore).get_delta (varidx,
+				      font->coords,
+				      font->num_coords,
+				      store_cache);
   }
 
   float get_side_bearing_var (hb_codepoint_t glyph,
@@ -335,7 +340,7 @@ struct HVARVVAR
 
   bool has_side_bearing_deltas () const { return lsbMap && rsbMap; }
 
-  protected:
+  public:
   FixedVersion<>version;	/* Version of the metrics variation table
 				 * initially set to 0x00010000u */
   Offset32To<VariationStore>