[Snippets/interpolatable.py] Add preliminary script for detecting interpolation errors

Very basic.  Right now detects if glyphs have wrong order of contours / components.

Lib/fontTools/varLib/__init__.py

@@ -494,6 +494,7 @@ def main(args=None):
 		'width':   ('wdth', 'Width'),
 		'slant':   ('slnt', 'Slant'),
 		'optical': ('opsz', 'Optical Size'),
+		'custom':  ('xxxx', 'Custom'),
 	}
 
 	axis_map = standard_axis_map

Snippets/interpolatable.py

@@ -0,0 +1,140 @@
+#! /usr/bin/env python
+
+"""
+Tool to find wront contour order between different masters, and
+other interpolatability (or lack thereof) issues.
+"""
+
+from __future__ import print_function, division, absolute_import
+from fontTools.misc.py23 import *
+
+from fontTools.pens.basePen import BasePen
+from symfont import GlyphStatistics
+from itertools import product
+
+class PerContourOrComponentPen(BasePen):
+	def __init__(self, Pen, glyphset=None):
+		BasePen.__init__(self, glyphset)
+		self._glyphset = glyphset
+		self._Pen = Pen
+		self.value = []
+	def _moveTo(self, p0):
+		self._newItem()
+		self.value[-1].moveTo(p0)
+	def _lineTo(self, p1):
+		self.value[-1].lineTo(p1)
+	def _qCurveToOne(self, p1, p2):
+		self.value[-1].qCurveTo(p1, p2)
+	def _curveToOne(self, p1, p2, p3):
+		self.value[-1].curveTo(p1, p2, p3)
+	def _closePath(self):
+		self.value[-1].closePath()
+	def _endPath(self):
+		self.value[-1].endPath()
+	def addComponent(self, glyphName, transformation):
+		self._newItem()
+		self.value[-1].addComponent(glyphName, transformation)
+
+	def _newItem(self):
+		self.value.append(self._Pen(glyphset=self._glyphset))
+
+class RecordingPen(BasePen):
+	def __init__(self, glyphset):
+		BasePen.__init__(self, glyphset)
+		self._glyphset = glyphset
+		self.value = []
+	def _moveTo(self, p0):
+		self.value.append(('moveTo', (p0,)))
+	def _lineTo(self, p1):
+		self.value.append(('lineTo', (p1,)))
+	def _qCurveToOne(self, p1, p2):
+		self.value.append(('qCurveTo', (p1,p2)))
+	def _curveToOne(self, p1, p2, p3):
+		self.value.append(('curveTo', (p1,p2,p3)))
+	def _closePath(self):
+		self.value.append(('closePath', ()))
+	def _endPath(self):
+		self.value.append(('endPath', ()))
+	# Humm, adding the following method slows things down some 20%.
+	# We don't have as much control as we like currently.
+	#def addComponent(self, glyphName, transformation):
+	#	self.value.append(('addComponent', (glyphName, transformation)))
+
+	def draw(self, pen):
+		for operator,operands in self.value:
+			getattr(pen, operator)(*operands)
+
+def _dot(v0, v1):
+	v = 0
+	for p,q in zip(v0,v1):
+		v += p*q
+	return v
+
+def test(glyphsets, glyphs=None):
+
+	if glyphs is None:
+		glyphs = glyphsets[0].keys()
+
+	for glyph_name in glyphs:
+		#print()
+		#print("glyph:", glyph_name, end='')
+
+		try:
+			allVectors = []
+			for glyphset in glyphsets:
+				#print('.', end='')
+				glyph = glyphset[glyph_name]
+
+				perContourPen = PerContourOrComponentPen(RecordingPen, glyphset=glyphset)
+				glyph.draw(perContourPen)
+				contourPens = perContourPen.value
+				del perContourPen
+
+				contourVectors = []
+				allVectors.append(contourVectors)
+				for contour in contourPens:
+					stats = GlyphStatistics(contour, glyphset=glyphset)
+					vector = (
+						#int(stats.Perimeter * .125),
+						int(abs(stats.Area) ** .5 * .5),
+						int(stats.MeanX),
+						int(stats.MeanY),
+						#int(stats.StdDevX * 2),
+						#int(stats.StdDevY * 2),
+						#int(stats.Covariance/(stats.StdDevX*stats.StdDevY)**.5),
+					)
+					contourVectors.append(vector)
+					#print(vector)
+
+			# Check each master against the next one in the list.
+			for m0,m1 in zip(allVectors[:-1],allVectors[1:]):
+				assert len(m0) == len(m1)
+				# TODO Implement proper weighted bipartite matching
+				while m0:
+					n = len(m0)
+					weights = [_dot(v0,v1) for v0,v1 in product(m0,m1)]
+					maxWeight = max(weights)
+					arg = weights.index(maxWeight)
+					# Expect it to be on the diagonal
+					row, col = arg // n, arg % n
+					if row != col:
+						print('Glyph has wrong contour/component order', glyph_name)#, m0, m1)
+						break
+					del m0[row], m1[col]
+
+
+		except ValueError as e:
+			print(' math error; skipping glyph', e)
+
+def main(args):
+	filenames = args
+	glyphs = None
+	#glyphs = ['uni08DB', 'uniFD76']
+	from fontTools.ttLib import TTFont
+	fonts = [TTFont(filename) for filename in filenames]
+	glyphsets = [font.getGlyphSet() for font in fonts]
+	test(glyphsets, glyphs=glyphs)
+
+if __name__ == '__main__':
+	import sys
+	main(sys.argv[1:])