Add method to FontHelper to get the size of the outline data for a set of glyphs.

Author: garretrieger

common/font_helper.cc

@@ -13,6 +13,7 @@
 #include "hb-ot.h"
 #include "hb-subset.h"
 #include "hb.h"
+#include "common/try.h"
 
 using absl::btree_set;
 using absl::flat_hash_map;
@@ -47,6 +48,7 @@ bool FontHelper::HasWideGvar(const hb_face_t* face) {
   return (((uint8_t)gvar.str()[gvar_flags_offset]) & 0x01);
 }
 
+
 absl::StatusOr<string_view> FontHelper::GlyfData(const hb_face_t* face,
                                                  uint32_t gid) {
   auto loca = Loca(face);
@@ -124,6 +126,33 @@ FontData FontHelper::Cff2Data(hb_face_t* face, uint32_t gid) {
   return data;
 }
 
+StatusOr<uint32_t> FontHelper::TotalGlyphData(hb_face_t* face, const GlyphSet& gids) {
+  auto tags = FontHelper::GetTags(face);
+
+  uint32_t total = 0;
+  for (uint32_t gid : gids) {
+    // TODO(grieger): write this using indexed data readers instead so we can
+    // avoid the per glyph setup overhead incurred by the *Data() methods.
+    if (tags.contains(FontHelper::kGlyf)) {
+      total += TRY(FontHelper::GlyfData(face, gid)).size();
+    }
+
+    if (tags.contains(FontHelper::kGvar)) {
+      total += TRY(FontHelper::GvarData(face, gid)).size();
+    }
+
+    if (tags.contains(FontHelper::kCFF)) {
+      total += FontHelper::CffData(face, gid).size();
+    }
+
+    if (tags.contains(FontHelper::kCFF2)) {
+      total += FontHelper::Cff2Data(face, gid).size();
+    }
+  }
+
+  return total;
+}
+
 Status FontHelper::Cff2GetCharstrings(hb_face_t* face,
                                       FontData& non_charstrings,
                                       FontData& charstrings) {

common/font_helper.h

@@ -145,6 +145,10 @@ class FontHelper {
 
   static FontData Cff2Data(hb_face_t* face, uint32_t gid);
 
+  // Counts up the total size of all glyph data (gvar, glyf, cff, cff2)
+  // for the provided set of gids.
+  static absl::StatusOr<uint32_t> TotalGlyphData(hb_face_t* face, const GlyphSet& gids);
+
   static absl::Status Cff2GetCharstrings(hb_face_t* face,
                                          FontData& non_charstrings,
                                          FontData& charstrings);

common/font_helper_test.cc

@@ -618,6 +618,48 @@ TEST_F(FontHelperTest, GlyfData_ShortOverflowSynthetic) {
   ASSERT_EQ(*data, expected);
 }
 
+TEST_F(FontHelperTest, TotalGlyphData_GlyfGvar) {
+  auto size = FontHelper::TotalGlyphData(roboto_vf.get(), GlyphSet {78, 83, 95});
+  ASSERT_TRUE(size.ok()) << size.status();
+
+  uint32_t expected =
+    FontHelper::GlyfData(roboto_vf.get(), 78)->size() +
+    FontHelper::GlyfData(roboto_vf.get(), 83)->size() +
+    FontHelper::GlyfData(roboto_vf.get(), 95)->size() +
+    FontHelper::GvarData(roboto_vf.get(), 78)->size() +
+    FontHelper::GvarData(roboto_vf.get(), 83)->size() +
+    FontHelper::GvarData(roboto_vf.get(), 95)->size();
+
+  ASSERT_GT(*size, 0);
+  ASSERT_EQ(*size, expected);
+}
+
+TEST_F(FontHelperTest, TotalGlyphData_Cff) {
+  auto size = FontHelper::TotalGlyphData(noto_sans_jp_otf.get(), GlyphSet {78, 83, 95});
+  ASSERT_TRUE(size.ok()) << size.status();
+
+  uint32_t expected =
+    FontHelper::CffData(noto_sans_jp_otf.get(), 78).size() +
+    FontHelper::CffData(noto_sans_jp_otf.get(), 83).size() +
+    FontHelper::CffData(noto_sans_jp_otf.get(), 95).size();
+
+  ASSERT_GT(*size, 0);
+  ASSERT_EQ(*size, expected);
+}
+
+TEST_F(FontHelperTest, TotalGlyphData_Cff2) {
+  auto size = FontHelper::TotalGlyphData(noto_sans_vf_jp_otf.get(), GlyphSet {34, 35, 46});
+  ASSERT_TRUE(size.ok()) << size.status();
+
+  uint32_t expected =
+    FontHelper::Cff2Data(noto_sans_vf_jp_otf.get(), 34).size() +
+    FontHelper::Cff2Data(noto_sans_vf_jp_otf.get(), 35).size() +
+    FontHelper::Cff2Data(noto_sans_vf_jp_otf.get(), 46).size();
+
+  ASSERT_GT(*size, 0);
+  ASSERT_EQ(*size, expected);
+}
+
 // TODO test BuildFont...
 
 }  // namespace common