Merge pull request #1752 from anthrotype/region-axis-count

enforce VarStore RegionAxisCount == fvar.AxisCount

Lib/fontTools/ttLib/tables/otBase.py

@@ -513,6 +513,8 @@ class CountReference(object):
 			table[name] = value
 		else:
 			assert table[name] == value, (name, table[name], value)
+	def getValue(self):
+		return self.table[self.name]
 	def getCountData(self):
 		v = self.table[self.name]
 		if v is None: v = 0
@@ -690,8 +692,16 @@ class BaseTable(object):
 				# table. We will later store it here.
 				# We add a reference: by the time the data is assembled
 				# the Count value will be filled in.
-				ref = writer.writeCountReference(table, conv.name, conv.staticSize)
+				# We ignore the current count value since it will be recomputed,
-				table[conv.name] = None
+				# unless it's a CountReference that was already initialized in a custom preWrite.
+				if isinstance(value, CountReference):
+					ref = value
+					ref.size = conv.staticSize
+					writer.writeData(ref)
+					table[conv.name] = ref.getValue()
+				else:
+					ref = writer.writeCountReference(table, conv.name, conv.staticSize)
+					table[conv.name] = None
 				if conv.isPropagated:
 					writer[conv.name] = ref
 			elif conv.isLookupType:

Lib/fontTools/ttLib/tables/otTables.py

@@ -7,7 +7,7 @@ converter objects from otConverters.py.
 """
 from fontTools.misc.py23 import *
 from fontTools.misc.textTools import pad, safeEval
-from .otBase import BaseTable, FormatSwitchingBaseTable, ValueRecord
+from .otBase import BaseTable, FormatSwitchingBaseTable, ValueRecord, CountReference
 import logging
 import struct
 
@@ -687,6 +687,25 @@ class VarIdxMap(BaseTable):
 		mapping[glyph] = (outer << 16) | inner
 
 
+class VarRegionList(BaseTable):
+
+	def preWrite(self, font):
+		# The OT spec says VarStore.VarRegionList.RegionAxisCount should always
+		# be equal to the fvar.axisCount, and OTS < v8.0.0 enforces this rule
+		# even when the VarRegionList is empty. We can't treat RegionAxisCount
+		# like a normal propagated count (== len(Region[i].VarRegionAxis)),
+		# otherwise it would default to 0 if VarRegionList is empty.
+		# Thus, we force it to always be equal to fvar.axisCount.
+		# https://github.com/khaledhosny/ots/pull/192
+		fvarTable = font.get("fvar")
+		if fvarTable:
+			self.RegionAxisCount = len(fvarTable.axes)
+		return {
+			**self.__dict__,
+			"RegionAxisCount": CountReference(self.__dict__, "RegionAxisCount")
+		}
+
+
 class SingleSubst(FormatSwitchingBaseTable):
 
 	def populateDefaults(self, propagator=None):

Lib/fontTools/varLib/__init__.py

@@ -213,15 +213,13 @@ def _add_gvar(font, masterModel, master_ttfs, tolerance=0.5, optimize=True):
 
 	log.info("Generating gvar")
 	assert "gvar" not in font
-	gvar = font["gvar"] = newTable('gvar')
-	gvar.version = 1
-	gvar.reserved = 0
-	gvar.variations = {}
 
 	glyf = font['glyf']
 
 	# use hhea.ascent of base master as default vertical origin when vmtx is missing
 	baseAscent = font['hhea'].ascent
+
+	variations = {}
 	for glyph in font.getGlyphOrder():
 
 		isComposite = glyf[glyph].isComposite()
@@ -241,7 +239,6 @@ def _add_gvar(font, masterModel, master_ttfs, tolerance=0.5, optimize=True):
 		del allControls
 
 		# Update gvar
-		gvar.variations[glyph] = []
 		deltas = model.getDeltas(allCoords)
 		supports = model.supports
 		assert len(deltas) == len(supports)
@@ -280,7 +277,14 @@ def _add_gvar(font, masterModel, master_ttfs, tolerance=0.5, optimize=True):
 					if optimized_len < unoptimized_len:
 						var = var_opt
 
-			gvar.variations[glyph].append(var)
+			variations.setdefault(glyph, []).append(var)
+
+	if variations:
+		gvar = font["gvar"] = newTable('gvar')
+		gvar.version = 1
+		gvar.reserved = 0
+		gvar.variations = {g: variations.get(g, []) for g in font.getGlyphOrder()}
+
 
 def _remove_TTHinting(font):
 	for tag in ("cvar", "cvt ", "fpgm", "prep"):
@@ -350,19 +354,21 @@ def _merge_TTHinting(font, masterModel, master_ttfs, tolerance=0.5):
 		_remove_TTHinting(font)
 		return
 
-	# We can build the cvar table now.
+	variations = []
-
-	cvar = font["cvar"] = newTable('cvar')
-	cvar.version = 1
-	cvar.variations = []
-
 	deltas, supports = masterModel.getDeltasAndSupports(all_cvs)
 	for i,(delta,support) in enumerate(zip(deltas[1:], supports[1:])):
 		delta = [otRound(d) for d in delta]
 		if all(abs(v) <= tolerance for v in delta):
 			continue
 		var = TupleVariation(support, delta)
-		cvar.variations.append(var)
+		variations.append(var)
+
+	# We can build the cvar table now.
+	if variations:
+		cvar = font["cvar"] = newTable('cvar')
+		cvar.version = 1
+		cvar.variations = variations
+
 
 _MetricsFields = namedtuple('_MetricsFields',
 	['tableTag', 'metricsTag', 'sb1', 'sb2', 'advMapping', 'vOrigMapping'])

Tests/varLib/data/SingleMaster.designspace

@@ -0,0 +1,13 @@
+<?xml version='1.0' encoding='utf-8'?>
+<designspace format="3">
+    <axes>
+        <axis default="400" maximum="400" minimum="400" name="weight" tag="wght" />
+    </axes>
+    <sources>
+        <source familyname="Test Family" filename="master_ufo/TestFamily-Master0.ufo" name="master_0">
+            <location>
+                <dimension name="weight" xvalue="400" />
+            </location>
+        </source>
+    </sources>
+</designspace>

Tests/varLib/data/test_results/SingleMaster.ttx

@@ -0,0 +1,98 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ttFont sfntVersion="\x00\x01\x00\x00" ttLibVersion="4.0">
+
+  <GDEF>
+    <Version value="0x00010003"/>
+    <GlyphClassDef Format="2">
+      <ClassDef glyph="uni0024" class="1"/>
+      <ClassDef glyph="uni0024.nostroke" class="1"/>
+      <ClassDef glyph="uni0041" class="1"/>
+      <ClassDef glyph="uni0061" class="1"/>
+    </GlyphClassDef>
+  </GDEF>
+
+  <HVAR>
+    <Version value="0x00010000"/>
+    <VarStore Format="1">
+      <Format value="1"/>
+      <VarRegionList>
+        <!-- RegionAxisCount=1 -->
+        <!-- RegionCount=0 -->
+      </VarRegionList>
+      <!-- VarDataCount=1 -->
+      <VarData index="0">
+        <!-- ItemCount=6 -->
+        <NumShorts value="0"/>
+        <!-- VarRegionCount=0 -->
+        <Item index="0" value="[]"/>
+        <Item index="1" value="[]"/>
+        <Item index="2" value="[]"/>
+        <Item index="3" value="[]"/>
+        <Item index="4" value="[]"/>
+        <Item index="5" value="[]"/>
+      </VarData>
+    </VarStore>
+  </HVAR>
+
+  <STAT>
+    <Version value="0x00010001"/>
+    <DesignAxisRecordSize value="8"/>
+    <!-- DesignAxisCount=1 -->
+    <DesignAxisRecord>
+      <Axis index="0">
+        <AxisTag value="wght"/>
+        <AxisNameID value="256"/>  <!-- Weight -->
+        <AxisOrdering value="0"/>
+      </Axis>
+    </DesignAxisRecord>
+    <!-- AxisValueCount=0 -->
+    <ElidedFallbackNameID value="2"/>  <!-- Regular -->
+  </STAT>
+
+  <fvar>
+
+    <!-- Weight -->
+    <Axis>
+      <AxisTag>wght</AxisTag>
+      <Flags>0x0</Flags>
+      <MinValue>400.0</MinValue>
+      <DefaultValue>400.0</DefaultValue>
+      <MaxValue>400.0</MaxValue>
+      <AxisNameID>256</AxisNameID>
+    </Axis>
+  </fvar>
+
+  <name>
+    <namerecord nameID="256" platformID="1" platEncID="0" langID="0x0" unicode="True">
+      Weight
+    </namerecord>
+    <namerecord nameID="1" platformID="3" platEncID="1" langID="0x409">
+      Test Family
+    </namerecord>
+    <namerecord nameID="2" platformID="3" platEncID="1" langID="0x409">
+      Regular
+    </namerecord>
+    <namerecord nameID="3" platformID="3" platEncID="1" langID="0x409">
+      Version 1.001;ADBO;Test Family Regular
+    </namerecord>
+    <namerecord nameID="4" platformID="3" platEncID="1" langID="0x409">
+      Test Family
+    </namerecord>
+    <namerecord nameID="5" platformID="3" platEncID="1" langID="0x409">
+      Version 1.001
+    </namerecord>
+    <namerecord nameID="6" platformID="3" platEncID="1" langID="0x409">
+      TestFamily-Master0
+    </namerecord>
+    <namerecord nameID="9" platformID="3" platEncID="1" langID="0x409">
+      Frank Grießhammer
+    </namerecord>
+    <namerecord nameID="17" platformID="3" platEncID="1" langID="0x409">
+      Master 0
+    </namerecord>
+    <namerecord nameID="256" platformID="3" platEncID="1" langID="0x409">
+      Weight
+    </namerecord>
+  </name>
+
+</ttFont>

Tests/varLib/varLib_test.py

@@ -584,6 +584,15 @@ class BuildTest(unittest.TestCase):
         self.expect_ttx(varfont, expected_ttx_path, tables)
         self.check_ttx_dump(varfont, expected_ttx_path, tables, suffix)
 
+    def test_varlib_build_single_master(self):
+        self._run_varlib_build_test(
+            designspace_name='SingleMaster',
+            font_name='TestFamily',
+            tables=['GDEF', 'HVAR', 'MVAR', 'STAT', 'fvar', 'cvar', 'gvar', 'name'],
+            expected_ttx_name='SingleMaster',
+            save_before_dump=True,
+        )
+
     def test_kerning_merging(self):
         """Test the correct merging of class-based pair kerning.