Implement building cvar tables

Lib/fontTools/ttLib/tables/_c_v_t.py

@@ -1,4 +1,5 @@
 from __future__ import print_function, division, absolute_import
+from numbers import Number
 from fontTools.misc.py23 import *
 from fontTools.misc.textTools import safeEval
 from . import DefaultTable
@@ -47,3 +48,34 @@ class table__c_v_t(DefaultTable.DefaultTable):
 
 	def __delitem__(self, index):
 		del self.values[index]
+
+
+class CVTValues(object):
+	""" This is used in varLib for calculating control value deltas"""
+
+	def __init__(self, values):
+		self.values = list(values)
+
+	def __getitem__(self, index):
+		return self.values[index]
+
+	def __len__(self):
+		return len(self.values)
+
+	def __repr__(self):
+		return u"CVTValues(%s)" % self.values
+
+	def __isub__(self, other):
+		if isinstance(other, CVTValues):
+			assert len(self.values) == len(other)
+			self.values = [self.values[i] - other.values[i] for i in range(len(self.values))]
+			return self
+		if isinstance(other, Number):
+			self.values = [v - other for v in self.values]
+			return self
+		return NotImplemented
+
+	def __mul__(self, other):
+		if isinstance(other, Number):
+			return CVTValues([v * other for v in self.values])
+		return NotImplemented

Lib/fontTools/varLib/__init__.py

@@ -23,6 +23,7 @@ from __future__ import unicode_literals
 from fontTools.misc.py23 import *
 from fontTools.ttLib import TTFont, newTable
 from fontTools.ttLib.tables._n_a_m_e import NameRecord
+from fontTools.ttLib.tables._c_v_t import CVTValues
 from fontTools.ttLib.tables._f_v_a_r import Axis, NamedInstance
 from fontTools.ttLib.tables._g_l_y_f import GlyphCoordinates
 from fontTools.ttLib.tables.TupleVariation import TupleVariation
@@ -502,6 +503,34 @@ def _add_gvar(font, model, master_ttfs, tolerance=0.5, optimize=True):
 
 			gvar.variations[glyph].append(var)
 
+def _add_cvar(font, model, master_ttfs):
+
+	log.info("Generating cvar")
+	assert "cvar" not in font
+	cvar = font["cvar"] = newTable('cvar')
+	cvar.version = 1
+	cvar.variations = []
+
+	allCVTs = [CVTValues(m["cvt "].values) for m in master_ttfs]
+	num_cvts0 = len(allCVTs[0])
+
+	if (any(len(c) != num_cvts0 for c in allCVTs)):
+		log.warning("Master has incompatible cvt table, not building cvar table.")
+		del font["cvar"]
+		return
+	print("    allCVTs:", allCVTs)
+	deltas = model.getDeltas(allCVTs)
+	supports = model.supports
+	print("    Deltas: ", deltas)
+	#print("    Supports:", supports)
+	for i,(delta,support) in enumerate(zip(deltas[1:], supports[1:])):
+		print("       ", i)
+		print("        Delta:  ", delta)
+		print("        Support:", support)
+		delta = [int(round(d)) for d in delta]
+		var = TupleVariation(support, delta)
+		cvar.variations.append(var)
+
 def _add_HVAR(font, model, master_ttfs, axisTags):
 
 	log.info("Generating HVAR")
@@ -856,6 +885,8 @@ def build(designspace_filename, master_finder=lambda s:s):
 	_merge_OTL(vf, model, master_fonts, axisTags)
 	if 'glyf' in vf:
 		_add_gvar(vf, model, master_fonts)
+	if 'cvt ' in vf:
+		_add_cvar(vf, model, master_fonts)
 
 	return vf, model, master_ttfs
 

Tests/varLib/data/test_results/BuildMain.ttx

@@ -855,18 +855,32 @@
 
   <cvar>
     <version major="1" minor="0"/>
+    <tuple>
+      <coord axis="cntr" value="1.0"/>
+      <delta cvt="0" value="0"/>
+      <delta cvt="1" value="0"/>
+    </tuple>
     <tuple>
       <coord axis="wght" value="-1.0"/>
       <delta cvt="0" value="-4"/>
+      <delta cvt="1" value="0"/>
     </tuple>
     <tuple>
       <coord axis="wght" value="1.0"/>
       <delta cvt="0" value="13"/>
+      <delta cvt="1" value="0"/>
+    </tuple>
+    <tuple>
+      <coord axis="wght" value="-1.0"/>
+      <coord axis="cntr" value="1.0"/>
+      <delta cvt="0" value="0"/>
+      <delta cvt="1" value="0"/>
     </tuple>
     <tuple>
       <coord axis="wght" value="1.0"/>
       <coord axis="cntr" value="1.0"/>
-      <delta cvt="0" value="13"/>
+      <delta cvt="0" value="0"/>
+      <delta cvt="1" value="0"/>
     </tuple>
   </cvar>