From 7494943c1bb0a4312dbd89c45774bbbc883565fe Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Fri, 20 Oct 2017 13:50:08 -0400
Subject: [PATCH] [varLib.varStore] Add VarStoreInstancer

---
 Lib/fontTools/varLib/mutator.py  | 25 ++++----------------
 Lib/fontTools/varLib/varStore.py | 39 ++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/Lib/fontTools/varLib/mutator.py b/Lib/fontTools/varLib/mutator.py
index 37adbf9aa..c8cbc9e31 100644
--- a/Lib/fontTools/varLib/mutator.py
+++ b/Lib/fontTools/varLib/mutator.py
@@ -10,6 +10,7 @@ from fontTools.ttLib import TTFont
 from fontTools.ttLib.tables._g_l_y_f import GlyphCoordinates
 from fontTools.varLib import _GetCoordinates, _SetCoordinates, _DesignspaceAxis
 from fontTools.varLib.models import supportScalar, normalizeLocation
+from fontTools.varLib.varStore import VarStoreInstancer
 from fontTools.varLib.mvar import MVAR_entries
 from fontTools.varLib.iup import iup_delta
 import os.path
@@ -87,34 +88,18 @@ def instantiateVariableFont(varfont, location, inplace=False):
 
 	if 'MVAR' in varfont:
 		mvar = varfont['MVAR'].table
-		varstore = mvar.VarStore
+		varStoreInstancer = VarStoreInstancer(mvar.VarStore, fvar.axes, loc)
 		records = mvar.ValueRecord
 		for rec in records:
 			mvarTag = rec.ValueTag
 			if mvarTag not in MVAR_entries:
 				continue
 			tableTag, itemName = MVAR_entries[mvarTag]
-
-			varIdx = rec.VarIdx
-			major,minor = varIdx >> 16, varIdx & 0xFFFF
-
-			assert varstore.Format == 1
-			deltas = varstore.VarData[major].Item[minor]
-			def VarRegion_get_support(self, fvar):
-				axes = fvar.axes
-				return {axes[i].axisTag: (reg.StartCoord,reg.PeakCoord,reg.EndCoord)
-					for i,reg in enumerate(self.VarRegionAxis)}
-			supports = [VarRegion_get_support(varstore.VarRegionList.Region[ri], fvar)
-				    for ri in varstore.VarData[major].VarRegionIndex]
-			delta = 0.
-			for d,s in zip(deltas, supports):
-				if not d: continue
-				scalar = supportScalar(loc, s)
-				delta += d * scalar
-			delta = int(round(delta))
+			delta = int(round(varStoreInstancer[rec.VarIdx]))
 			if not delta:
 				continue
-			setattr(varfont[tableTag], itemName, getattr(varfont[tableTag], itemName) + delta)
+			setattr(varfont[tableTag], itemName,
+				getattr(varfont[tableTag], itemName) + delta)
 
 	log.info("Removing variable tables")
 	for tag in ('avar','cvar','fvar','gvar','HVAR','MVAR','VVAR','STAT'):
diff --git a/Lib/fontTools/varLib/varStore.py b/Lib/fontTools/varLib/varStore.py
index aad753735..e75596927 100644
--- a/Lib/fontTools/varLib/varStore.py
+++ b/Lib/fontTools/varLib/varStore.py
@@ -1,6 +1,7 @@
 from __future__ import print_function, division, absolute_import
 from __future__ import unicode_literals
 from fontTools.misc.py23 import *
+from fontTools.varLib.models import supportScalar
 from fontTools.varLib.builder import (buildVarRegionList, buildVarStore,
 				      buildVarRegion, buildVarData,
 				      varDataCalculateNumShorts)
@@ -56,3 +57,41 @@ class OnlineVarStoreBuilder(object):
 		return base, (self._outer << 16) + inner
 
 
+def VarRegion_get_support(self, fvar_axes):
+	return {fvar_axes[i].axisTag: (reg.StartCoord,reg.PeakCoord,reg.EndCoord)
+		for i,reg in enumerate(self.VarRegionAxis)}
+
+class VarStoreInstancer(object):
+
+	def __init__(self, varstore, fvar_axes, location={}):
+		assert varstore.Format == 1
+		self.varstore = varstore
+		self.fvar_axes = fvar_axes
+		self._varData = varstore.VarData
+		self._regions = varstore.VarRegionList.Region
+		self.setLocation(location)
+
+	def setLocation(self, location):
+		self.location = dict(location)
+		self._clearCaches()
+
+	def _clearCaches(self):
+		pass
+		#self._scalars = {}
+
+	def __getitem__(self, varidx):
+
+		major, minor = varidx >> 16, varidx & 0xFFFF
+
+		varData = self._varData
+		supports = [VarRegion_get_support(self._regions[ri], self.fvar_axes)
+			    for ri in varData[major].VarRegionIndex]
+
+		deltas = varData[major].Item[minor]
+		delta = 0.
+		for d,s in zip(deltas, supports):
+			if not d: continue
+			scalar = supportScalar(self.location, s)
+			delta += d * scalar
+		return delta
+