Roll sfntly 111

third_party/sfntly/src/subsetter/subsetter_impl.cc

Index: third_party/sfntly/src/subsetter/subsetter_impl.cc
diff --git a/third_party/sfntly/src/subsetter/subsetter_impl.cc b/third_party/sfntly/src/subsetter/subsetter_impl.cc
index bed1fc1d2cf5215d73cc2fc12a671c105cd3978b..f317f981b039cf645b53290b4c4e02f7837e96b4 100644
--- a/third_party/sfntly/src/subsetter/subsetter_impl.cc
+++ b/third_party/sfntly/src/subsetter/subsetter_impl.cc
@@ -18,21 +18,38 @@
 
 #include <string.h>
 
+#include <algorithm>
+#include <iterator>
 #include <map>
 #include <set>
 
+#include "third_party/sfntly/src/sfntly/table/bitmap/eblc_table.h"
+#include "third_party/sfntly/src/sfntly/table/bitmap/ebdt_table.h"
+#include "third_party/sfntly/src/sfntly/table/bitmap/index_sub_table.h"
+#include "third_party/sfntly/src/sfntly/table/bitmap/index_sub_table_format1.h"
+#include "third_party/sfntly/src/sfntly/table/bitmap/index_sub_table_format2.h"
+#include "third_party/sfntly/src/sfntly/table/bitmap/index_sub_table_format3.h"
+#include "third_party/sfntly/src/sfntly/table/bitmap/index_sub_table_format4.h"
+#include "third_party/sfntly/src/sfntly/table/bitmap/index_sub_table_format5.h"
 #include "third_party/sfntly/src/sfntly/table/core/name_table.h"
-#include "third_party/sfntly/src/sfntly/table/truetype/glyph_table.h"
-#include "third_party/sfntly/src/sfntly/table/truetype/loca_table.h"
 #include "third_party/sfntly/src/sfntly/tag.h"
 #include "third_party/sfntly/src/sfntly/data/memory_byte_array.h"
 #include "third_party/sfntly/src/sfntly/port/memory_input_stream.h"
 #include "third_party/sfntly/src/sfntly/port/memory_output_stream.h"
 
-namespace sfntly {
+#if defined U_USING_ICU_NAMESPACE
+  U_NAMESPACE_USE
+#endif
+
+namespace {
+
+using namespace sfntly;
+
+// The bitmap tables must be greater than 16KB to trigger bitmap subsetter.
+static const int BITMAP_SIZE_THRESHOLD = 16384;
 
 void ConstructName(UChar* name_part, UnicodeString* name, int32_t name_id) {
-  switch(name_id) {
+  switch (name_id) {
     case NameId::kFullFontName:
       *name = name_part;
       break;
@@ -71,80 +88,7 @@ int32_t HashCode(int32_t platform_id, int32_t encoding_id, int32_t language_id,
   return result;
 }
 
-SubsetterImpl::SubsetterImpl() {
-}
-
-SubsetterImpl::~SubsetterImpl() {
-}
-
-bool SubsetterImpl::LoadFont(const char* font_name,
-                             const unsigned char* original_font,
-                             size_t font_size) {
-  MemoryInputStream mis;
-  mis.Attach(original_font, font_size);
-  if (factory_ == NULL) {
-    factory_.Attach(FontFactory::GetInstance());
-  }
-
-  FontArray font_array;
-  factory_->LoadFonts(&mis, &font_array);
-  font_ = FindFont(font_name, font_array);
-  if (font_ == NULL) {
-    return false;
-  }
-
-  return true;
-}
-
-int SubsetterImpl::SubsetFont(const unsigned int* glyph_ids,
-                              size_t glyph_count,
-                              unsigned char** output_buffer) {
-  if (factory_ == NULL || font_ == NULL) {
-    return -1;
-  }
-
-  IntegerSet glyph_id_processed;
-  if (!ResolveCompositeGlyphs(glyph_ids, glyph_count, &glyph_id_processed) ||
-      glyph_id_processed.empty()) {
-    return 0;
-  }
-
-  FontPtr new_font;
-  new_font.Attach(Subset(glyph_id_processed));
-  if (new_font == NULL) {
-    return 0;
-  }
-
-  MemoryOutputStream output_stream;
-  factory_->SerializeFont(new_font, &output_stream);
-  int length = static_cast<int>(output_stream.Size());
-  if (length > 0) {
-    *output_buffer = new unsigned char[length];
-    memcpy(*output_buffer, output_stream.Get(), length);
-  }
-
-  return length;
-}
-
-Font* SubsetterImpl::FindFont(const char* font_name,
-                              const FontArray& font_array) {
-  if (font_array.empty() || font_array[0] == NULL) {
-    return NULL;
-  }
-
-  if (font_name && strlen(font_name)) {
-    for (FontArray::const_iterator b = font_array.begin(), e = font_array.end();
-         b != e; ++b) {
-      if (HasName(font_name, (*b).p_)) {
-        return (*b).p_;
-      }
-    }
-  }
-
-  return font_array[0].p_;
-}
-
-bool SubsetterImpl::HasName(const char* font_name, Font* font) {
+bool HasName(const char* font_name, Font* font) {
   UnicodeString font_string = UnicodeString::fromUTF8(font_name);
   if (font_string.isEmpty())
     return false;
@@ -160,7 +104,7 @@ bool SubsetterImpl::HasName(const char* font_name, Font* font) {
   }
 
   for (int32_t i = 0; i < name_table->NameCount(); ++i) {
-    switch(name_table->NameId(i)) {
+    switch (name_table->NameId(i)) {
       case NameId::kFontFamilyName:
       case NameId::kFontSubfamilyName:
       case NameId::kFullFontName:
@@ -183,9 +127,9 @@ bool SubsetterImpl::HasName(const char* font_name, Font* font) {
   }
 
   if (!names.empty()) {
-    for (NameMap::iterator b = names.begin(), e = names.end(); b != e; ++b) {
-      if (b->second.caseCompare(font_string, 0) == 0 ||
-          b->second.caseCompare(alt_font_string, 0) == 0) {
+    for (NameMap::iterator i = names.begin(), e = names.end(); i != e; ++i) {
+      if (i->second.caseCompare(font_string, 0) == 0 ||
+          i->second.caseCompare(alt_font_string, 0) == 0) {
         return true;
       }
     }
@@ -193,19 +137,30 @@ bool SubsetterImpl::HasName(const char* font_name, Font* font) {
   return false;
 }
 
-bool SubsetterImpl::ResolveCompositeGlyphs(const unsigned int* glyph_ids,
-                                           size_t glyph_count,
-                                           IntegerSet* glyph_id_processed) {
-  if (glyph_ids == NULL || glyph_count == 0 || glyph_id_processed == NULL) {
-    return false;
+Font* FindFont(const char* font_name, const FontArray& font_array) {
+  if (font_array.empty() || font_array[0] == NULL) {
+    return NULL;
   }
 
-  // Find glyf and loca table.
-  GlyphTablePtr glyph_table =
-      down_cast<GlyphTable*>(font_->GetTable(Tag::glyf));
-  LocaTablePtr loca_table = down_cast<LocaTable*>(font_->GetTable(Tag::loca));
-  if (glyph_table == NULL || loca_table == NULL) {
-    // The font is invalid.
+  if (font_name && strlen(font_name)) {
+    for (FontArray::const_iterator i = font_array.begin(), e = font_array.end();
+         i != e; ++i) {
+      if (HasName(font_name, i->p_)) {
+        return i->p_;
+      }
+    }
+  }
+
+  return font_array[0].p_;
+}
+
+bool ResolveCompositeGlyphs(GlyphTable* glyph_table,
+                            LocaTable* loca_table,
+                            const unsigned int* glyph_ids,
+                            size_t glyph_count,
+                            IntegerSet* glyph_id_processed) {
+  if (glyph_table == NULL || loca_table == NULL ||
+      glyph_ids == NULL || glyph_count == 0 || glyph_id_processed == NULL) {
     return false;
   }
 
@@ -263,15 +218,13 @@ bool SubsetterImpl::ResolveCompositeGlyphs(const unsigned int* glyph_ids,
   return true;
 }
 
-CALLER_ATTACH Font* SubsetterImpl::Subset(const IntegerSet& glyph_ids) {
-  // The tables are already checked in ResolveCompositeGlyphs().
-  GlyphTablePtr glyph_table =
-      down_cast<GlyphTable*>(font_->GetTable(Tag::glyf));
-  LocaTablePtr loca_table = down_cast<LocaTable*>(font_->GetTable(Tag::loca));
-
-  // Setup font builders we need.
-  FontBuilderPtr font_builder;
-  font_builder.Attach(factory_->NewFontBuilder());
+bool SetupGlyfBuilders(Font::Builder* font_builder,
+                       GlyphTable* glyph_table,
+                       LocaTable* loca_table,
+                       const IntegerSet& glyph_ids) {
+  if (!font_builder || !glyph_table || !loca_table) {
+    return false;
+  }
 
   GlyphTableBuilderPtr glyph_table_builder =
       down_cast<GlyphTable::Builder*>(font_builder->NewTableBuilder(Tag::glyf));
@@ -279,7 +232,7 @@ CALLER_ATTACH Font* SubsetterImpl::Subset(const IntegerSet& glyph_ids) {
       down_cast<LocaTable::Builder*>(font_builder->NewTableBuilder(Tag::loca));
   if (glyph_table_builder == NULL || loca_table_builder == NULL) {
     // Out of memory.
-    return NULL;
+    return false;
   }
 
   // Extract glyphs and setup loca list.
@@ -320,12 +273,496 @@ CALLER_ATTACH Font* SubsetterImpl::Subset(const IntegerSet& glyph_ids) {
   }
   loca_table_builder->SetLocaList(&loca_list);
 
+  return true;
+}
+
+bool HasOverlap(int32_t range_begin, int32_t range_end,
+                const IntegerSet& glyph_ids) {
+  if (range_begin == range_end) {
+    return glyph_ids.find(range_begin) != glyph_ids.end();
+  } else if (range_end > range_begin) {
+    IntegerSet::const_iterator left = glyph_ids.lower_bound(range_begin);
+    IntegerSet::const_iterator right = glyph_ids.lower_bound(range_end);
+    return right != left;
+  }
+  return false;
+}
+
+// Initialize builder, returns false if glyph_id subset is not covered.
+// Not thread-safe, caller to ensure object life-time.
+bool InitializeBitmapBuilder(EbdtTable::Builder* ebdt, EblcTable::Builder* eblc,
+                             const IntegerSet& glyph_ids) {
+  BitmapLocaList loca_list;
+  BitmapSizeTableBuilderList* strikes = eblc->BitmapSizeBuilders();
+
+  // Note: Do not call eblc_builder->GenerateLocaList(&loca_list) and then
+  //       ebdt_builder->SetLoca(loca_list).  For fonts like SimSun, there are
+  //       >28K glyphs inside, where a typical usage will be <1K glyphs.  Doing
+  //       the calls improperly will result in creation of >100K objects that
+  //       will be destroyed immediately, inducing significant slowness.
+  IntegerList removed_strikes;
+  for (size_t i = 0; i < strikes->size(); i++) {
+    if (!HasOverlap((*strikes)[i]->StartGlyphIndex(),
+                    (*strikes)[i]->EndGlyphIndex(), glyph_ids)) {
+      removed_strikes.push_back(i);
+      continue;
+    }
+
+    IndexSubTableBuilderList* index_builders =
+        (*strikes)[i]->IndexSubTableBuilders();
+    IntegerList removed_indexes;
+    BitmapGlyphInfoMap info_map;
+    for (size_t j = 0; j < index_builders->size(); ++j) {
+      int32_t first_glyph_id = (*index_builders)[j]->first_glyph_index();
+      int32_t last_glyph_id = (*index_builders)[j]->last_glyph_index();
+      if (!HasOverlap(first_glyph_id, last_glyph_id, glyph_ids)) {
+        removed_indexes.push_back(j);
+        continue;
+      }
+      for (IntegerSet::const_iterator gid = glyph_ids.begin(),
+                                      gid_end = glyph_ids.end();
+                                      gid != gid_end; gid++) {
+        if (*gid < first_glyph_id) {
+          continue;
+        }
+        if (*gid > last_glyph_id) {
+          break;
+        }
+        BitmapGlyphInfoPtr info;
+        info.Attach((*index_builders)[j]->GlyphInfo(*gid));
+        if (info && info->length()) {  // Do not include gid without bitmap
+          info_map[*gid] = info;
+        }
+      }
+    }
+    if (!info_map.empty()) {
+      loca_list.push_back(info_map);
+    } else {
+      removed_strikes.push_back(i);  // Detected null entries.
+    }
+
+    // Remove unused index sub tables
+    for (IntegerList::reverse_iterator j = removed_indexes.rbegin(),
+                                       e = removed_indexes.rend();
+                                       j != e; j++) {
+      index_builders->erase(index_builders->begin() + *j);
+    }
+  }
+  if (removed_strikes.size() == strikes->size() || loca_list.empty()) {
+    return false;
+  }
+
+  for (IntegerList::reverse_iterator i = removed_strikes.rbegin(),
+                                     e = removed_strikes.rend(); i != e; i++) {
+    strikes->erase(strikes->begin() + *i);
+  }
+
+  if (strikes->empty()) {  // no glyph covered, can safely drop the builders.
+    return false;
+  }
+
+  ebdt->SetLoca(&loca_list);
+  ebdt->GlyphBuilders();  // Initialize the builder.
+  return true;
+}
+
+void CopyBigGlyphMetrics(BigGlyphMetrics::Builder* source,
+                         BigGlyphMetrics::Builder* target) {
+  target->SetHeight(static_cast<byte_t>(source->Height()));
+  target->SetWidth(static_cast<byte_t>(source->Width()));
+  target->SetHoriBearingX(static_cast<byte_t>(source->HoriBearingX()));
+  target->SetHoriBearingY(static_cast<byte_t>(source->HoriBearingY()));
+  target->SetHoriAdvance(static_cast<byte_t>(source->HoriAdvance()));
+  target->SetVertBearingX(static_cast<byte_t>(source->VertBearingX()));
+  target->SetVertBearingY(static_cast<byte_t>(source->VertBearingY()));
+  target->SetVertAdvance(static_cast<byte_t>(source->VertAdvance()));
+}
+
+CALLER_ATTACH IndexSubTable::Builder*
+ConstructIndexFormat4(IndexSubTable::Builder* b, const BitmapGlyphInfoMap& loca,
+                      int32_t* image_data_offset) {
+  IndexSubTableFormat4BuilderPtr builder4;
+  builder4.Attach(IndexSubTableFormat4::Builder::CreateBuilder());
+  CodeOffsetPairBuilderList offset_pairs;
+
+  size_t offset = 0;
+  int32_t lower_bound = b->first_glyph_index();
+  int32_t upper_bound = b->last_glyph_index();
+  int32_t last_gid = -1;
+  BitmapGlyphInfoMap::const_iterator i = loca.lower_bound(lower_bound);
+  BitmapGlyphInfoMap::const_iterator end = loca.end();
+  if (i != end) {
+    last_gid = i->first;
+    builder4->set_first_glyph_index(last_gid);
+    builder4->set_image_format(b->image_format());
+    builder4->set_image_data_offset(*image_data_offset);
+  }
+  for (; i != end; i++) {
+    int32_t gid = i->first;
+    if (gid > upper_bound) {
+      break;
+    }
+    offset_pairs.push_back(
+        IndexSubTableFormat4::CodeOffsetPairBuilder(gid, offset));
+    offset += i->second->length();
+    last_gid = gid;
+  }
+  offset_pairs.push_back(
+      IndexSubTableFormat4::CodeOffsetPairBuilder(-1, offset));
+  builder4->set_last_glyph_index(last_gid);
+  *image_data_offset += offset;
+  builder4->SetOffsetArray(offset_pairs);
+
+  return builder4.Detach();
+}
+
+CALLER_ATTACH IndexSubTable::Builder*
+ConstructIndexFormat5(IndexSubTable::Builder* b, const BitmapGlyphInfoMap& loca,
+                      int32_t* image_data_offset) {
+  IndexSubTableFormat5BuilderPtr new_builder;
+  new_builder.Attach(IndexSubTableFormat5::Builder::CreateBuilder());
+
+  // Copy BigMetrics
+  int32_t image_size = 0;
+  if (b->index_format() == IndexSubTable::Format::FORMAT_2) {
+    IndexSubTableFormat2BuilderPtr builder2 =
+      down_cast<IndexSubTableFormat2::Builder*>(b);
+    CopyBigGlyphMetrics(builder2->BigMetrics(), new_builder->BigMetrics());
+    image_size = builder2->ImageSize();
+  } else {
+    IndexSubTableFormat5BuilderPtr builder5 =
+      down_cast<IndexSubTableFormat5::Builder*>(b);
+    BigGlyphMetricsBuilderPtr metrics_builder;
+    CopyBigGlyphMetrics(builder5->BigMetrics(), new_builder->BigMetrics());
+    image_size = builder5->ImageSize();
+  }
+
+  IntegerList* glyph_array = new_builder->GlyphArray();
+  size_t offset = 0;
+  int32_t lower_bound = b->first_glyph_index();
+  int32_t upper_bound = b->last_glyph_index();
+  int32_t last_gid = -1;
+  BitmapGlyphInfoMap::const_iterator i = loca.lower_bound(lower_bound);
+  BitmapGlyphInfoMap::const_iterator end = loca.end();
+  if (i != end) {
+    last_gid = i->first;
+    new_builder->set_first_glyph_index(last_gid);
+    new_builder->set_image_format(b->image_format());
+    new_builder->set_image_data_offset(*image_data_offset);
+    new_builder->SetImageSize(image_size);
+  }
+  for (; i != end; i++) {
+    int32_t gid = i->first;
+    if (gid > upper_bound) {
+      break;
+    }
+    glyph_array->push_back(gid);
+    offset += i->second->length();
+    last_gid = gid;
+  }
+  new_builder->set_last_glyph_index(last_gid);
+  *image_data_offset += offset;
+  return new_builder.Detach();
+}
+
+CALLER_ATTACH IndexSubTable::Builder*
+SubsetIndexSubTable(IndexSubTable::Builder* builder,
+                    const BitmapGlyphInfoMap& loca,
+                    int32_t* image_data_offset) {
+  switch (builder->index_format()) {
+    case IndexSubTable::Format::FORMAT_1:
+    case IndexSubTable::Format::FORMAT_3:
+    case IndexSubTable::Format::FORMAT_4:
+      return ConstructIndexFormat4(builder, loca, image_data_offset);
+    case IndexSubTable::Format::FORMAT_2:
+    case IndexSubTable::Format::FORMAT_5:
+      return ConstructIndexFormat5(builder, loca, image_data_offset);
+    default:
+      assert(false);
+      break;
+  }
+  return NULL;
+}
+
+}
+
+namespace sfntly {
+
+// Not thread-safe, caller to ensure object life-time.
+void SubsetEBLC(EblcTable::Builder* eblc, const BitmapLocaList& new_loca) {
+  BitmapSizeTableBuilderList* size_builders = eblc->BitmapSizeBuilders();
+  if (size_builders == NULL) {
+    return;
+  }
+
+  int32_t image_data_offset = EbdtTable::Offset::kHeaderLength;
+  for (size_t strike = 0; strike < size_builders->size(); ++strike) {
+    IndexSubTableBuilderList* index_builders =
+        (*size_builders)[strike]->IndexSubTableBuilders();
+    for (size_t index = 0; index < index_builders->size(); ++index) {
+      IndexSubTable::Builder* new_builder_raw =
+          SubsetIndexSubTable((*index_builders)[index], new_loca[strike],
+                              &image_data_offset);
+      if (NULL != new_builder_raw) {
+        (*index_builders)[index].Attach(new_builder_raw);
+      }
+    }
+  }
+}
+
+// EBLC structure (from stuartg)
+//  header
+//  bitmapSizeTable[]
+//    one per strike
+//    holds strike metrics - sbitLineMetrics
+//    holds info about indexSubTableArray
+//  indexSubTableArray[][]
+//    one per strike and then one per indexSubTable for that strike
+//    holds info about the indexSubTable
+//    the indexSubTable entries pointed to can be of different formats
+//  indexSubTable
+//    one per indexSubTableArray entry
+//    tells how to get the glyphs
+//    may hold the glyph metrics if they are uniform for all the glyphs in range
+//
+// There is nothing that says that the indexSubTableArray entries and/or the
+// indexSubTable items need to be unique. They may be shared between strikes.
+//
+// EBDT structure:
+//  header
+//  glyphs
+//    amorphous blob of data
+//    different glyphs that are only able to be figured out from the EBLC table
+//    may hold metrics - depends on the EBLC entry that pointed to them
+
+// Subsetting EBLC table (from arthurhsu)
+//  Most pages use only a fraction (hundreds or less) glyphs out of a given font
+//  (which can have >20K glyphs for CJK).  It's safe to assume that the subset
+//  font will have sparse bitmap glyphs.  So we reconstruct the EBLC table as
+//  format 4 or 5 here.
+
+enum BuildersToRemove {
+  kRemoveNone,
+  kRemoveBDAT,
+  kRemoveBDATAndEBDT
+};
+
+int SetupBitmapBuilders(Font* font, Font::Builder* font_builder,
+                        const IntegerSet& glyph_ids) {
+  if (!font || !font_builder) {
+    return false;
+  }
+
+  // Check if bitmap table exists.
+  EbdtTablePtr ebdt_table = down_cast<EbdtTable*>(font->GetTable(Tag::EBDT));
+  EblcTablePtr eblc_table = down_cast<EblcTable*>(font->GetTable(Tag::EBLC));
+  bool use_ebdt = (ebdt_table != NULL && eblc_table != NULL);
+  if (!use_ebdt) {
+    ebdt_table = down_cast<EbdtTable*>(font->GetTable(Tag::bdat));
+    eblc_table = down_cast<EblcTable*>(font->GetTable(Tag::bloc));
+    if (ebdt_table == NULL || eblc_table == NULL) {
+      return kRemoveNone;
+    }
+  }
+
+  // If the bitmap table's size is too small, skip subsetting.
+  if (ebdt_table->DataLength() + eblc_table->DataLength() <
+      BITMAP_SIZE_THRESHOLD) {
+    return use_ebdt ? kRemoveBDAT : kRemoveNone;
+  }
+
+  // Get the builders.
+  EbdtTableBuilderPtr ebdt_table_builder = down_cast<EbdtTable::Builder*>(
+      font_builder->NewTableBuilder(use_ebdt ? Tag::EBDT : Tag::bdat,
+                                    ebdt_table->ReadFontData()));
+  EblcTableBuilderPtr eblc_table_builder = down_cast<EblcTable::Builder*>(
+      font_builder->NewTableBuilder(use_ebdt ? Tag::EBLC : Tag::bloc,
+                                    eblc_table->ReadFontData()));
+  if (ebdt_table_builder == NULL || eblc_table_builder == NULL) {
+    // Out of memory.
+    return use_ebdt ? kRemoveBDAT : kRemoveNone;
+  }
+
+  if (!InitializeBitmapBuilder(ebdt_table_builder, eblc_table_builder,
+                               glyph_ids)) {
+    // Bitmap tables do not cover the glyphs in our subset.
+    font_builder->RemoveTableBuilder(use_ebdt ? Tag::EBLC : Tag::bloc);
+    font_builder->RemoveTableBuilder(use_ebdt ? Tag::EBDT : Tag::bdat);
+    return kRemoveBDATAndEBDT;
+  }
+
+  BitmapLocaList new_loca;
+  ebdt_table_builder->GenerateLocaList(&new_loca);
+  SubsetEBLC(eblc_table_builder, new_loca);
+
+  return use_ebdt ? kRemoveBDAT : kRemoveNone;
+}
+
+SubsetterImpl::SubsetterImpl() {
+}
+
+SubsetterImpl::~SubsetterImpl() {
+}
+
+bool SubsetterImpl::LoadFont(const char* font_name,
+                             const unsigned char* original_font,
+                             size_t font_size) {
+  MemoryInputStream mis;
+  mis.Attach(original_font, font_size);
+  if (factory_ == NULL) {
+    factory_.Attach(FontFactory::GetInstance());
+  }
+
+  FontArray font_array;
+  factory_->LoadFonts(&mis, &font_array);
+  font_ = FindFont(font_name, font_array);
+  if (font_ == NULL) {
+    return false;
+  }
+
+  return true;
+}
+
+int SubsetterImpl::SubsetFont(const unsigned int* glyph_ids,
+                              size_t glyph_count,
+                              unsigned char** output_buffer) {
+  if (factory_ == NULL || font_ == NULL) {
+    return -1;
+  }
+
+  // Find glyf and loca table.
+  GlyphTablePtr glyph_table =
+      down_cast<GlyphTable*>(font_->GetTable(Tag::glyf));
+  LocaTablePtr loca_table = down_cast<LocaTable*>(font_->GetTable(Tag::loca));
+  if (glyph_table == NULL || loca_table == NULL) {
+    // We are not able to subset the font.
+    return 0;
+  }
+
+  IntegerSet glyph_id_processed;
+  if (!ResolveCompositeGlyphs(glyph_table, loca_table,
+                              glyph_ids, glyph_count, &glyph_id_processed) ||
+      glyph_id_processed.empty()) {
+    return 0;
+  }
+
+  FontPtr new_font;
+  new_font.Attach(Subset(glyph_id_processed, glyph_table, loca_table));
+  if (new_font == NULL) {
+    return 0;
+  }
+
+  MemoryOutputStream output_stream;
+  factory_->SerializeFont(new_font, &output_stream);
+  int length = static_cast<int>(output_stream.Size());
+  if (length > 0) {
+    *output_buffer = new unsigned char[length];
+    memcpy(*output_buffer, output_stream.Get(), length);
+  }
+
+  return length;
+}
+
+// Long comments regarding TTF tables and PDF (from stuartg)
+//
+// According to PDF spec 1.4 (section 5.8), the following tables must be
+// present:
+//  head, hhea, loca, maxp, cvt, prep, glyf, hmtx, fpgm
+//  cmap if font is used with a simple font dict and not a CIDFont dict
+//
+// Other tables we need to keep for PDF rendering to support zoom in/out:
+//  bdat, bloc, ebdt, eblc, ebsc, gasp
+//
+// Special table:
+//  CFF - if you have this table then you shouldn't have a glyf table and this
+//        is the table with all the glyphs.  Shall skip subsetting completely
+//        since sfntly is not capable of subsetting it for now.
+//  post - extra info here for printing on PostScript printers but maybe not
+//         enough to outweigh the space taken by the names
+//
+// Tables to break apart:
+//  name - could throw away all but one language and one platform strings/ might
+//         throw away some of the name entries
+//  cmap - could strip out non-needed cmap subtables
+//       - format 4 subtable can be subsetted as well using sfntly
+//
+// Graphite tables:
+//  silf, glat, gloc, feat - should be okay to strip out
+//
+// Tables that can be discarded:
+//  OS/2 - everything here is for layout and description of the font that is
+//         elsewhere (some in the PDF objects)
+//  BASE, GDEF, GSUB, GPOS, JSTF - all used for layout
+//  kern - old style layout
+//  DSIG - this will be invalid after subsetting
+//  hdmx - layout
+//  PCLT - metadata that's not needed
+//  vmtx - layout
+//  vhea - layout
+//  VDMX
+//  VORG - not used by TT/OT - used by CFF
+//  hsty - would be surprised to see one of these - used on the Newton
+//  AAT tables - mort, morx, feat, acnt, bsin, just, lcar, fdsc, fmtx, prop,
+//               Zapf, opbd, trak, fvar, gvar, avar, cvar
+//             - these are all layout tables and once layout happens are not
+//               needed anymore
+//  LTSH - layout
+
+CALLER_ATTACH
+Font* SubsetterImpl::Subset(const IntegerSet& glyph_ids, GlyphTable* glyf,
+                            LocaTable* loca) {
+  // The const is initialized here to workaround VC bug of rendering all Tag::*
+  // as 0.  These tags represents the TTF tables that we will embed in subset
+  // font.
+  const int32_t TABLES_IN_SUBSET[] = {
+    Tag::head, Tag::hhea, Tag::loca, Tag::maxp, Tag::cvt,
+    Tag::prep, Tag::glyf, Tag::hmtx, Tag::fpgm, Tag::EBDT,
+    Tag::EBLC, Tag::EBSC, Tag::bdat, Tag::bloc, Tag::bhed,
+    Tag::cmap,  // Keep here for future tagged PDF development.
+    Tag::name,  // Keep here due to legal concerns: copyright info inside.
+  };
+
+  // Setup font builders we need.
+  FontBuilderPtr font_builder;
+  font_builder.Attach(factory_->NewFontBuilder());
+  IntegerSet remove_tags;
+
+  if (SetupGlyfBuilders(font_builder, glyf, loca, glyph_ids)) {
+    remove_tags.insert(Tag::glyf);
+    remove_tags.insert(Tag::loca);
+  }
+
+  switch (SetupBitmapBuilders(font_, font_builder, glyph_ids)) {
+    case kRemoveBDATAndEBDT:
+      remove_tags.insert(Tag::EBDT);
+      remove_tags.insert(Tag::EBLC);
+      remove_tags.insert(Tag::EBSC);
+    case kRemoveBDAT:
+      remove_tags.insert(Tag::bdat);
+      remove_tags.insert(Tag::bloc);
+      remove_tags.insert(Tag::bhed);
+      break;
+    default:  // kRemoveNone
+      break;
+  }
+
+  IntegerSet allowed_tags;
+  for (size_t i = 0; i < sizeof(TABLES_IN_SUBSET) / sizeof(int32_t); ++i) {
+    allowed_tags.insert(TABLES_IN_SUBSET[i]);
+  }
+
+  IntegerSet result;
+  std::set_difference(allowed_tags.begin(), allowed_tags.end(),
+                      remove_tags.begin(), remove_tags.end(),
+                      std::inserter(result, result.end()));
+  allowed_tags = result;
+
   // Setup remaining builders.
-  for (TableMap::const_iterator i = font_->GetTableMap()->begin(),
-                                e = font_->GetTableMap()->end(); i != e; ++i) {
-    // We already build the builder for glyph and loca.
-    if (i->first != Tag::glyf && i->first != Tag::loca) {
-      font_builder->NewTableBuilder(i->first, i->second->ReadFontData());
+  for (IntegerSet::iterator i = allowed_tags.begin(), e = allowed_tags.end();
+                            i != e; ++i) {
+    Table* table = font_->GetTable(*i);
+    if (table) {
+      font_builder->NewTableBuilder(*i, table->ReadFontData());
     }
   }