[ttc] Implement table sharing in save()

Lib/fontTools/ttLib/sfnt.py

@@ -215,6 +215,12 @@ class SFNTWriter(object):
 		self.file.write(b'\0' * (self.nextTableOffset - self.file.tell()))
 		self.tables = OrderedDict()
 
+	def setEntry(self, tag, entry):
+		if tag in self.tables:
+			raise TTLibError("cannot rewrite '%s' table" % tag)
+
+		self.tables[tag] = entry
+
 	def __setitem__(self, tag, data):
 		"""Write raw table data to disk."""
 		if tag in self.tables:
@@ -243,7 +249,10 @@ class SFNTWriter(object):
 		self.file.write(b'\0' * (self.nextTableOffset - self.file.tell()))
 		assert self.nextTableOffset == self.file.tell()
 
-		self.tables[tag] = entry
+		self.setEntry(tag, entry)
+
+	def __getitem__(self, tag):
+		return self.tables[tag]
 
 	def close(self):
 		"""All tables must have been written to disk. Now write the

Lib/fontTools/ttLib/ttCollection.py

@@ -37,7 +37,7 @@ class TTCollection(object):
 			font = TTFont(file, fontNumber=i, _tableCache=tableCache, **kwargs)
 			fonts.append(font)
 
-	def save(self, file):
+	def save(self, file, shareTables=True):
 		"""Save the font to disk. Similarly to the constructor,
 		the 'file' argument can be either a pathname or a writable
 		file object.
@@ -51,12 +51,13 @@ class TTCollection(object):
 			final = file
 			file = BytesIO()
 
-		offsets_offset = writeTTCHeader(file, len(self.fonts))
+		tableCache = {} if shareTables else None
 
+		offsets_offset = writeTTCHeader(file, len(self.fonts))
 		offsets = []
 		for font in self.fonts:
 			offsets.append(file.tell())
-			font._save(file)
+			font._save(file, tableCache=tableCache)
 			file.seek(0,2)
 
 		file.seek(offsets_offset)

Lib/fontTools/ttLib/ttFont.py

@@ -134,7 +134,7 @@ class TTFont(object):
 			if closeStream:
 				file.close()
 			file = tmp
-		self.tableCache = _tableCache
+		self._tableCache = _tableCache
 		self.reader = SFNTReader(file, checkChecksums, fontNumber=fontNumber)
 		self.sfntVersion = self.reader.sfntVersion
 		self.flavor = self.reader.flavor
@@ -186,7 +186,7 @@ class TTFont(object):
 		if closeStream:
 			file.close()
 
-	def _save(self, file):
+	def _save(self, file, tableCache=None):
 		"""Internal function, to be shared by save() and TTCollection.save()"""
 
 		if self.recalcTimestamp and 'head' in self:
@@ -201,7 +201,7 @@ class TTFont(object):
 
 		done = []
 		for tag in tags:
-			self._writeTable(tag, writer, done)
+			self._writeTable(tag, writer, done, tableCache)
 
 		writer.close()
 
@@ -380,8 +380,8 @@ class TTFont(object):
 				import traceback
 				log.debug("Reading '%s' table from disk", tag)
 				data = self.reader[tag]
-				if self.tableCache is not None:
+				if self._tableCache is not None:
-					table = self.tableCache.get((Tag(tag), data))
+					table = self._tableCache.get((Tag(tag), data))
 					if table is not None:
 						return table
 				tableClass = getTableClass(tag)
@@ -403,8 +403,8 @@ class TTFont(object):
 					table.ERROR = file.getvalue()
 					self.tables[tag] = table
 					table.decompile(data, self)
-				if self.tableCache is not None:
+				if self._tableCache is not None:
-					self.tableCache[(Tag(tag), data)] = table
+					self._tableCache[(Tag(tag), data)] = table
 				return table
 			else:
 				raise KeyError("'%s' table not found" % tag)
@@ -612,7 +612,7 @@ class TTFont(object):
 		for glyphID in range(len(glyphOrder)):
 			d[glyphOrder[glyphID]] = glyphID
 
-	def _writeTable(self, tag, writer, done):
+	def _writeTable(self, tag, writer, done, tableCache=None):
 		"""Internal helper function for self.save(). Keeps track of
 		inter-table dependencies.
 		"""
@@ -622,13 +622,21 @@ class TTFont(object):
 		for masterTable in tableClass.dependencies:
 			if masterTable not in done:
 				if masterTable in self:
-					self._writeTable(masterTable, writer, done)
+					self._writeTable(masterTable, writer, done, tableCache)
 				else:
 					done.append(masterTable)
+		done.append(tag)
 		tabledata = self.getTableData(tag)
+		if tableCache is not None:
+			entry = tableCache.get((Tag(tag), tabledata))
+			if entry is not None:
+				log.debug("reusing '%s' table", tag)
+				writer.setEntry(tag, entry)
+				return
 		log.debug("writing '%s' table to disk", tag)
 		writer[tag] = tabledata
-		done.append(tag)
+		if tableCache is not None:
+			tableCache[(Tag(tag), tabledata)] = writer[tag]
 
 	def getTableData(self, tag):
 		"""Returns raw table data, whether compiled or directly read from disk.