[gvar] Rename gvar.decompileSharedCoords() to decompileSharedTuples()

The new name is consistent with the terminology of the OpenType 1.8
specification, which calls the decoded structure the `SharedTuples`
array.

Lib/fontTools/ttLib/tables/_g_v_a_r.py

@@ -174,7 +174,8 @@ class table__g_v_a_r(DefaultTable.DefaultTable):
 		assert len(glyphs) == self.glyphCount
 		assert len(axisTags) == self.axisCount
 		offsets = self.decompileOffsets_(data[GVAR_HEADER_SIZE:], tableFormat=(self.flags & 1), glyphCount=self.glyphCount)
-		sharedCoords = self.decompileSharedCoords_(axisTags, data)
+		sharedCoords = decompileSharedTuples_(
+			axisTags, self.sharedTupleCount, data, self.offsetToSharedTuples)
 		self.variations = {}
 		offsetToData = self.offsetToGlyphVariationData
 		for i in range(self.glyphCount):
@@ -185,10 +186,6 @@ class table__g_v_a_r(DefaultTable.DefaultTable):
 			self.variations[glyphName] = \
 				self.decompileGlyph_(numPointsInGlyph, sharedCoords, axisTags, gvarData)
 
-	def decompileSharedCoords_(self, axisTags, data):
-		result, _pos = TupleVariation.decompileCoords_(axisTags, self.sharedTupleCount, data, self.offsetToSharedTuples)
-		return result
-
 	@staticmethod
 	def decompileOffsets_(data, tableFormat, glyphCount):
 		if tableFormat == 0:
@@ -338,3 +335,11 @@ class table__g_v_a_r(DefaultTable.DefaultTable):
 		else:
 			# Empty glyphs (eg. space, nonmarkingreturn) have no "coordinates" attribute.
 			return len(getattr(glyph, "coordinates", [])) + NUM_PHANTOM_POINTS
+
+
+def decompileSharedTuples_(axisTags, sharedTupleCount, data, offset):
+    result = []
+    for _ in range(sharedTupleCount):
+        t, offset = TupleVariation.decompileCoord_(axisTags, data, offset)
+        result.append(t)
+    return result

Lib/fontTools/ttLib/tables/_g_v_a_r_test.py

@@ -1,15 +1,20 @@
 from __future__ import print_function, division, absolute_import, unicode_literals
 from fontTools.misc.py23 import *
 from fontTools.misc.textTools import deHexStr, hexStr
-from fontTools.ttLib import TTLibError
+from fontTools.ttLib import TTLibError, getTableModule
 from fontTools.ttLib.tables.TupleVariation import TupleVariation
 from fontTools.ttLib.tables._g_v_a_r import table__g_v_a_r
 import unittest
 
+
+gvar = getTableModule("gvar")
+
+
 def hexencode(s):
 	h = hexStr(s).upper()
 	return ' '.join([h[i:i+2] for i in range(0, len(h), 2)])
 
+
 # Glyph variation table of uppercase I in the Skia font, as printed in Apple's
 # TrueType spec. The actual Skia font uses a different table for uppercase I.
 # https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6gvar.html
@@ -32,8 +37,8 @@ SKIA_GVAR_I = deHexStr(
 	"01 84 91 00 80 06 07 08 08 08 08 0A 07 80 03 FE "
 	"FF FF FF 81 00 08 81 82 02 EE EE EE 8B 6D 00")
 
-# Shared coordinates in the Skia font, as printed in Apple's TrueType spec.
+# Shared tuples in the Skia font, as printed in Apple's TrueType spec.
-SKIA_SHARED_COORDS = deHexStr(
+SKIA_SHARED_TUPLES = deHexStr(
 	"40 00 00 00 C0 00 00 00 00 00 40 00 00 00 C0 00 "
 	"C0 00 C0 00 40 00 C0 00 40 00 40 00 C0 00 40 00")
 
@@ -111,12 +116,11 @@ class GVARTableTest(unittest.TestCase):
 		result = table.compileSharedCoords_(["wght", "wdth"])
 		self.assertEqual(["40 00 2C CD", "40 00 33 33"], [hexencode(c) for c in result])
 
-	def test_decompileSharedCoords_Skia(self):
+	def test_decompileSharedTuples_Skia(self):
-		table = table__g_v_a_r()
+		sharedCoords = gvar.decompileSharedTuples_(
-		table.offsetToSharedTuples = 0
+            axisTags=["wght", "wdth"], sharedTupleCount=8,
-		table.sharedTupleCount = 8
+            data=SKIA_SHARED_TUPLES, offset=0)
-		sharedCoords = table.decompileSharedCoords_(["wght", "wdth"], SKIA_SHARED_COORDS)
+		self.assertEqual(sharedCoords, [
-		self.assertEqual([
 			{"wght": 1.0, "wdth": 0.0},
 			{"wght": -1.0, "wdth": 0.0},
 			{"wght": 0.0, "wdth": 1.0},
@@ -125,13 +129,10 @@ class GVARTableTest(unittest.TestCase):
 			{"wght": 1.0, "wdth": -1.0},
 			{"wght": 1.0, "wdth": 1.0},
 			{"wght": -1.0, "wdth": 1.0}
-		], sharedCoords)
+		])
 
-	def test_decompileSharedCoords_empty(self):
+	def test_decompileSharedTuples_empty(self):
-		table = table__g_v_a_r()
+		self.assertEqual(gvar.decompileSharedTuples_(["wght"], 0, b"", 0), [])
-		table.offsetToSharedTuples = 0
-		table.sharedTupleCount = 0
-		self.assertEqual([], table.decompileSharedCoords_(["wght"], b""))
 
 	def test_decompileGlyph_Skia_I(self):
 		axes = ["wght", "wdth"]
@@ -139,8 +140,10 @@ class GVARTableTest(unittest.TestCase):
 		table.offsetToSharedTuples = 0
 		table.sharedTupleCount = 8
 		table.axisCount = len(axes)
-		sharedCoords = table.decompileSharedCoords_(axes, SKIA_SHARED_COORDS)
+		sharedTuples = gvar.decompileSharedTuples_(
-		tuples = table.decompileGlyph_(18, sharedCoords, axes, SKIA_GVAR_I)
+			axisTags=axes, sharedTupleCount=8,
+			data=SKIA_SHARED_TUPLES, offset=0)
+		tuples = table.decompileGlyph_(18, sharedTuples, axes, SKIA_GVAR_I)
 		self.assertEqual(8, len(tuples))
 		self.assertEqual({"wght": (0.0, 1.0, 1.0)}, tuples[0].axes)
 		self.assertEqual("257,0 -127,0 -128,58 -130,90 -130,62 -130,67 -130,32 -127,0 257,0 "