1 files changed, 76 insertions, 0 deletions
diff --git a/Lib/fontTools/merge/base.py b/Lib/fontTools/merge/base.py
new file mode 100644
index 00000000..868b51a4
--- /dev/null
+++ b/Lib/fontTools/merge/base.py
@@ -0,0 +1,76 @@
+# Copyright 2013 Google, Inc. All Rights Reserved.
+#
+# Google Author(s): Behdad Esfahbod, Roozbeh Pournader
+
+from fontTools.ttLib.tables.DefaultTable import DefaultTable
+import logging
+
+
+log = logging.getLogger("fontTools.merge")
+
+
+def add_method(*clazzes, **kwargs):
+	"""Returns a decorator function that adds a new method to one or
+	more classes."""
+	allowDefault = kwargs.get('allowDefaultTable', False)
+	def wrapper(method):
+		done = []
+		for clazz in clazzes:
+			if clazz in done: continue # Support multiple names of a clazz
+			done.append(clazz)
+			assert allowDefault or clazz != DefaultTable, 'Oops, table class not found.'
+			assert method.__name__ not in clazz.__dict__, \
+				"Oops, class '%s' has method '%s'." % (clazz.__name__, method.__name__)
+			setattr(clazz, method.__name__, method)
+		return None
+	return wrapper
+
+def mergeObjects(lst):
+	lst = [item for item in lst if item is not NotImplemented]
+	if not lst:
+		return NotImplemented
+	lst = [item for item in lst if item is not None]
+	if not lst:
+		return None
+
+	clazz = lst[0].__class__
+	assert all(type(item) == clazz for item in lst), lst
+
+	logic = clazz.mergeMap
+	returnTable = clazz()
+	returnDict = {}
+
+	allKeys = set.union(set(), *(vars(table).keys() for table in lst))
+	for key in allKeys:
+		try:
+			mergeLogic = logic[key]
+		except KeyError:
+			try:
+				mergeLogic = logic['*']
+			except KeyError:
+				raise Exception("Don't know how to merge key %s of class %s" %
+						(key, clazz.__name__))
+		if mergeLogic is NotImplemented:
+			continue
+		value = mergeLogic(getattr(table, key, NotImplemented) for table in lst)
+		if value is not NotImplemented:
+			returnDict[key] = value
+
+	returnTable.__dict__ = returnDict
+
+	return returnTable
+
+@add_method(DefaultTable, allowDefaultTable=True)
+def merge(self, m, tables):
+	if not hasattr(self, 'mergeMap'):
+		log.info("Don't know how to merge '%s'.", self.tableTag)
+		return NotImplemented
+
+	logic = self.mergeMap
+
+	if isinstance(logic, dict):
+		return m.mergeObjects(self, self.mergeMap, tables)
+	else:
+		return logic(tables)
+
+