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1 /*
2  * Copyright 2011 Google Inc. All Rights Reserved.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #include "subtly/font_assembler.h"
18 
19 #include <stdio.h>
20 
21 #include <set>
22 #include <map>
23 
24 #include "sfntly/tag.h"
25 #include "sfntly/font.h"
26 #include "sfntly/font_factory.h"
27 #include "sfntly/table/core/cmap_table.h"
28 #include "sfntly/table/truetype/loca_table.h"
29 #include "sfntly/table/truetype/glyph_table.h"
30 #include "sfntly/table/core/maximum_profile_table.h"
31 #include "sfntly/port/type.h"
32 #include "sfntly/port/refcount.h"
33 #include "subtly/font_info.h"
34 
35 namespace subtly {
36 using namespace sfntly;
37 
FontAssembler(FontInfo * font_info,IntegerSet * table_blacklist)38 FontAssembler::FontAssembler(FontInfo* font_info,
39                              IntegerSet* table_blacklist)
40     : table_blacklist_(table_blacklist) {
41   font_info_ = font_info;
42   Initialize();
43 }
44 
FontAssembler(FontInfo * font_info)45 FontAssembler::FontAssembler(FontInfo* font_info)
46     : table_blacklist_(NULL) {
47   font_info_ = font_info;
48   Initialize();
49 }
50 
Initialize()51 void FontAssembler::Initialize() {
52   font_factory_.Attach(sfntly::FontFactory::GetInstance());
53   font_builder_.Attach(font_factory_->NewFontBuilder());
54 }
55 
Assemble()56 CALLER_ATTACH Font* FontAssembler::Assemble() {
57   // Assemble tables we can subset.
58   if (!AssembleCMapTable() || !AssembleGlyphAndLocaTables()) {
59     return NULL;
60   }
61   // For all other tables, either include them unmodified or don't at all.
62   const TableMap* common_table_map =
63       font_info_->GetTableMap(font_info_->fonts()->begin()->first);
64   for (TableMap::const_iterator it = common_table_map->begin(),
65            e = common_table_map->end(); it != e; ++it) {
66     if (table_blacklist_
67         && table_blacklist_->find(it->first) != table_blacklist_->end()) {
68       continue;
69     }
70     font_builder_->NewTableBuilder(it->first, it->second->ReadFontData());
71   }
72   return font_builder_->Build();
73 }
74 
AssembleCMapTable()75 bool FontAssembler::AssembleCMapTable() {
76   // Creating the new CMapTable and the new format 4 CMap
77   Ptr<CMapTable::Builder> cmap_table_builder =
78       down_cast<CMapTable::Builder*>
79       (font_builder_->NewTableBuilder(Tag::cmap));
80   if (!cmap_table_builder)
81     return false;
82   Ptr<CMapTable::CMapFormat4::Builder> cmap_builder =
83       down_cast<CMapTable::CMapFormat4::Builder*>
84       (cmap_table_builder->NewCMapBuilder(CMapFormat::kFormat4,
85                                           CMapTable::WINDOWS_BMP));
86   if (!cmap_builder)
87     return false;
88   // Creating the segments and the glyph id array
89   CharacterMap* chars_to_glyph_ids = font_info_->chars_to_glyph_ids();
90   SegmentList* segment_list = new SegmentList;
91   IntegerList* glyph_id_array = new IntegerList;
92   int32_t last_chararacter = -2;
93   int32_t last_offset = 0;
94   Ptr<CMapTable::CMapFormat4::Builder::Segment> current_segment;
95 
96   // For simplicity, we will have one segment per contiguous range.
97   // To test the algorithm, we've replaced the original CMap with the CMap
98   // generated by this code without removing any character.
99   // Tuffy.ttf: CMap went from 3146 to 3972 bytes (1.7% to 2.17% of file)
100   // AnonymousPro.ttf: CMap went from 1524 to 1900 bytes (0.96% to 1.2%)
101   for (CharacterMap::iterator it = chars_to_glyph_ids->begin(),
102            e = chars_to_glyph_ids->end(); it != e; ++it) {
103     int32_t character = it->first;
104     int32_t glyph_id = it->second.glyph_id();
105     if (character != last_chararacter + 1) {  // new segment
106       if (current_segment != NULL) {
107         current_segment->set_end_count(last_chararacter);
108         segment_list->push_back(current_segment);
109       }
110       // start_code = character
111       // end_code = -1 (unknown for now)
112       // id_delta = 0 (we don't use id_delta for this representation)
113       // id_range_offset = last_offset (offset into the glyph_id_array)
114       current_segment =
115           new CMapTable::CMapFormat4::Builder::
116           Segment(character, -1, 0, last_offset);
117     }
118     glyph_id_array->push_back(glyph_id);
119     last_offset += DataSize::kSHORT;
120     last_chararacter = character;
121   }
122   // The last segment is still open.
123   current_segment->set_end_count(last_chararacter);
124   segment_list->push_back(current_segment);
125   // Updating the id_range_offset for every segment.
126   for (int32_t i = 0, num_segs = segment_list->size(); i < num_segs; ++i) {
127     Ptr<CMapTable::CMapFormat4::Builder::Segment> segment = segment_list->at(i);
128     segment->set_id_range_offset(segment->id_range_offset()
129                                  + (num_segs - i + 1) * DataSize::kSHORT);
130   }
131   // Adding the final, required segment.
132   current_segment =
133       new CMapTable::CMapFormat4::Builder::Segment(0xffff, 0xffff, 1, 0);
134   segment_list->push_back(current_segment);
135   // Writing the segments and glyph id array to the CMap
136   cmap_builder->set_segments(segment_list);
137   cmap_builder->set_glyph_id_array(glyph_id_array);
138   delete segment_list;
139   delete glyph_id_array;
140   return true;
141 }
142 
AssembleGlyphAndLocaTables()143 bool FontAssembler::AssembleGlyphAndLocaTables() {
144   Ptr<LocaTable::Builder> loca_table_builder =
145       down_cast<LocaTable::Builder*>
146       (font_builder_->NewTableBuilder(Tag::loca));
147   Ptr<GlyphTable::Builder> glyph_table_builder =
148       down_cast<GlyphTable::Builder*>
149       (font_builder_->NewTableBuilder(Tag::glyf));
150 
151   GlyphIdSet* resolved_glyph_ids = font_info_->resolved_glyph_ids();
152   IntegerList loca_list;
153   // Basic sanity check: all LOCA tables are of the same size
154   // This is necessary but not suficient!
155   int32_t previous_size = -1;
156   for (FontIdMap::iterator it = font_info_->fonts()->begin();
157        it != font_info_->fonts()->end(); ++it) {
158     Ptr<LocaTable> loca_table =
159         down_cast<LocaTable*>(font_info_->GetTable(it->first, Tag::loca));
160     int32_t current_size = loca_table->header_length();
161     if (previous_size != -1 && current_size != previous_size) {
162       return false;
163     }
164     previous_size = current_size;
165   }
166 
167   // Assuming all fonts referenced by the FontInfo are the subsets of the same
168   // font, their loca tables should all have the same sizes.
169   // We'll just get the size of the first font's LOCA table for simplicty.
170   Ptr<LocaTable> first_loca_table =
171     down_cast<LocaTable*>
172     (font_info_->GetTable(font_info_->fonts()->begin()->first, Tag::loca));
173   int32_t num_loca_glyphs = first_loca_table->num_glyphs();
174   loca_list.resize(num_loca_glyphs);
175   loca_list.push_back(0);
176   int32_t last_glyph_id = 0;
177   int32_t last_offset = 0;
178   GlyphTable::GlyphBuilderList* glyph_builders =
179       glyph_table_builder->GlyphBuilders();
180 
181   for (GlyphIdSet::iterator it = resolved_glyph_ids->begin(),
182            e = resolved_glyph_ids->end(); it != e; ++it) {
183     // Get the glyph for this resolved_glyph_id.
184     int32_t resolved_glyph_id = it->glyph_id();
185     int32_t font_id = it->font_id();
186     // Get the LOCA table for the current glyph id.
187     Ptr<LocaTable> loca_table =
188         down_cast<LocaTable*>
189         (font_info_->GetTable(font_id, Tag::loca));
190     int32_t length = loca_table->GlyphLength(resolved_glyph_id);
191     int32_t offset = loca_table->GlyphOffset(resolved_glyph_id);
192 
193     // Get the GLYF table for the current glyph id.
194     Ptr<GlyphTable> glyph_table =
195         down_cast<GlyphTable*>
196         (font_info_->GetTable(font_id, Tag::glyf));
197     GlyphPtr glyph;
198     glyph.Attach(glyph_table->GetGlyph(offset, length));
199 
200     // The data reference by the glyph is copied into a new glyph and
201     // added to the glyph_builders belonging to the glyph_table_builder.
202     // When Build gets called, all the glyphs will be built.
203     Ptr<ReadableFontData> data = glyph->ReadFontData();
204     Ptr<WritableFontData> copy_data;
205     copy_data.Attach(WritableFontData::CreateWritableFontData(data->Length()));
206     data->CopyTo(copy_data);
207     GlyphBuilderPtr glyph_builder;
208     glyph_builder.Attach(glyph_table_builder->GlyphBuilder(copy_data));
209     glyph_builders->push_back(glyph_builder);
210 
211     // If there are missing glyphs between the last glyph_id and the
212     // current resolved_glyph_id, since the LOCA table needs to have the same
213     // size, the offset is kept the same.
214     loca_list.resize(std::max(loca_list.size(),
215                      static_cast<size_t>(resolved_glyph_id + 2)));
216     for (int32_t i = last_glyph_id + 1; i <= resolved_glyph_id; ++i)
217       loca_list[i] = last_offset;
218     last_offset += length;
219     loca_list[resolved_glyph_id + 1] = last_offset;
220     last_glyph_id = resolved_glyph_id + 1;
221   }
222   // If there are missing glyph ids, their loca entries must all point
223   // to the same offset as the last valid glyph id making them all zero length.
224   for (int32_t i = last_glyph_id + 1; i <= num_loca_glyphs; ++i)
225     loca_list[i] = last_offset;
226   loca_table_builder->SetLocaList(&loca_list);
227   return true;
228 }
229 }
230