From ff01e27763e1ca582335c1eb86c92033a569dc1b Mon Sep 17 00:00:00 2001
From: Tal Leming <tal@typesupply.com>
Date: Tue, 6 Dec 2011 18:46:31 +0000
Subject: [PATCH] Added a kerning validator. This must be run by the caller
 since groups are required. This should resolve ticket #8.

git-svn-id: http://svn.robofab.com/branches/ufo3k@507 b5fa9d6c-a76f-4ffd-b3cb-f825fc41095c
---
 Lib/ufoLib/__init__.py   | 12 ++++++
 Lib/ufoLib/validators.py | 87 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 98 insertions(+), 1 deletion(-)

diff --git a/Lib/ufoLib/__init__.py b/Lib/ufoLib/__init__.py
index a22d95edf..fa0259530 100755
--- a/Lib/ufoLib/__init__.py
+++ b/Lib/ufoLib/__init__.py
@@ -352,6 +352,13 @@ class UFOReader(object):
 	def readKerning(self):
 		"""
 		Read kerning.plist. Returns a dict.
+
+		This performs structural validation of the kerning data,
+		but it does not check the validity of the kerning as
+		dictated in the UFO spec. To do that, pass the kerning
+		obtained from this method and the groups obtained from
+		readGroups to the kerningvalidator function in the
+		validators module.
 		"""
 		# handle up conversion
 		if self._formatVersion < 3:
@@ -834,6 +841,11 @@ class UFOWriter(object):
 		"""
 		Write kerning.plist. This method requires a
 		dict of kerning pairs as an argument.
+
+		This performs basic structural validation of the kerning,
+		but it does not check for compliance with the spec in
+		regards to conflicting pairs. The assumption is that the
+		kerning data being passed is standards compliant.
 		"""
 		invalidFormatMessage = "The kerning is not properly formatted."
 		if not isDictEnough(kerning):
diff --git a/Lib/ufoLib/validators.py b/Lib/ufoLib/validators.py
index 05d5e786d..d1594fa13 100644
--- a/Lib/ufoLib/validators.py
+++ b/Lib/ufoLib/validators.py
@@ -3,7 +3,6 @@
 import os
 import calendar
 
-
 # -------
 # Generic
 # -------
@@ -887,6 +886,92 @@ def groupsValidator(value):
 				d[glyphName] = groupName
 	return True, None
 
+# -------------
+# kerning.plist
+# -------------
+
+def kerningValidator(kerning, groups):
+	"""
+	This validates a passed kerning dictionary
+	using the provided groups. The validation
+	checks to make sure that there are no conflicting
+	glyph + group and group + glyph exceptions.
+
+	>>> groups = {
+	...     "public.kern1.O" : ["O", "D", "Q"],
+	...     "public.kern2.E" : ["E", "F"]
+	... }
+	>>> kerning = {
+	...     ("public.kern1.O", "public.kern2.E") : -100,
+	...     ("public.kern1.O", "F") : -200,
+	...     ("D", "F") : -300,
+	... }
+	>>> kerningValidator(kerning, groups)
+	True
+	>>> kerning = {
+	...     ("public.kern1.O", "public.kern2.E") : -100,
+	...     ("public.kern1.O", "F") : -200,
+	...     ("Q", "public.kern2.E") : -250,
+	...     ("D", "F") : -300,
+	... }
+	>>> kerningValidator(kerning, groups)
+	False
+	"""
+	# flatten the groups
+	flatFirstGroups = {}
+	flatSecondGroups = {}
+	for groupName, glyphList in groups.items():
+		if not groupName.startswith("public.kern1.") and not groupName.startswith("public.kern2."):
+			continue
+		if groupName.startswith("public.kern1."):
+			d = flatFirstGroups
+		elif groupName.startswith("public.kern2."):
+			d = flatSecondGroups
+		for glyphName in glyphList:
+			d[glyphName] = groupName
+	# search for conflicts
+	for first, second in kerning.keys():
+		firstIsGroup = first.startswith("public.kern1.")
+		secondIsGroup = second.startswith("public.kern2.")
+		# skip anything other than glyph + group and group + glyph
+		if firstIsGroup and secondIsGroup:
+			continue
+		if not firstIsGroup and not secondIsGroup:
+			continue
+		# if the first is a glyph and it isn't in a group, skip
+		if not firstIsGroup:
+			if first not in flatFirstGroups:
+				continue
+		# if the second is a glyph and it isn't in a group, skip
+		if not secondIsGroup:
+			if second not in flatSecondGroups:
+				continue
+		# skip unknown things
+		if firstIsGroup and first not in groups:
+			continue
+		if firstIsGroup and second not in flatSecondGroups:
+			continue
+		if secondIsGroup and second not in groups:
+			continue
+		if secondIsGroup and first not in flatFirstGroups:
+			continue
+		# validate group + glyph
+		if firstIsGroup:
+			firstOptions = groups[first]
+			secondGroup = flatSecondGroups[second]
+			for glyph in firstOptions:
+				if (glyph, secondGroup) in kerning:
+					return False
+		# validate glyph + group
+		if secondIsGroup:
+			secondOptions = groups[second]
+			firstGroup = flatFirstGroups[first]
+			for glyph in secondOptions:
+				if (firstGroup, glyph) in kerning:
+					return False
+	# fallback
+	return True
+
 # -------------
 # lib.plist/lib
 # -------------