[varLib] Add temporary file interpolate-layout.py

Just here while implementing GPOS / GSUB merging and then figure
out where the code should live.

Lib/fontTools/varLib/interpolate-layout.py

@@ -0,0 +1,142 @@
+"""
+Interpolate OpenType Layout tables (GDEF / GPOS / GSUB).
+"""
+from __future__ import print_function, division, absolute_import
+from fontTools.misc.py23 import *
+from fontTools.ttLib import TTFont
+from fontTools.ttLib.tables import otTables as ot
+from fontTools.varLib import designspace, models, builder
+import os.path
+
+
+def _all_equal(lst):
+	it = iter(lst)
+	v0 = next(it)
+	for v in it:
+		if v0 != v:
+			return False
+	return True
+
+def buildVarDevTable(store, master_values):
+	if _all_equal(master_values):
+		return None
+	deltas = master_values
+	return builder.buildVarDevTable(0xdeadbeef)
+
+def _merge_OTL(font, model, master_ttfs, axes, base_idx):
+
+	print("Merging OpenType Layout tables")
+
+	GDEFs = [m['GDEF'].table for m in master_ttfs]
+	GPOSs = [m['GPOS'].table for m in master_ttfs]
+	GSUBs = [m['GSUB'].table for m in master_ttfs]
+
+	# Reuse the base font's tables
+	for tag in 'GDEF', 'GPOS', 'GSUB':
+		font[tag] = master_ttfs[base_idx][tag]
+
+	GPOS = font['GPOS'].table
+
+	getAnchor = lambda GPOS: GPOS.LookupList.Lookup[4].SubTable[0].MarkArray.MarkRecord[28].MarkAnchor
+	store_builder = builder.OnlineVarStoreBuilder(axes.keys())
+	store_builder.setModel(model)
+
+	anchors = [getAnchor(G) for G in GPOSs]
+	anchor = getAnchor(GPOS)
+
+	XDeviceTable = buildVarDevTable(store_builder, [a.XCoordinate for a in anchors])
+	YDeviceTable = buildVarDevTable(store_builder, [a.YCoordinate for a in anchors])
+	if XDeviceTable or YDeviceTable:
+		anchor.Format = 3
+		anchor.XDeviceTable = XDeviceTable
+		anchor.YDeviceTable = YDeviceTable
+
+	store = store_builder.finish()
+	# TODO insert in GDEF
+
+
+def main(args=None):
+
+	import sys
+	if args is None:
+		args = sys.argv[1:]
+
+	designspace_filename = args[0]
+	locargs = args[1:]
+	outfile = os.path.splitext(designspace_filename)[0] + '-instance.ttf'
+
+	finder = lambda s: s.replace('master_ufo', 'master_ttf_interpolatable').replace('.ufo', '.ttf')
+
+	loc = {}
+	for arg in locargs:
+		tag,val = arg.split('=')
+		loc[tag] = float(val)
+	print("Location:", loc)
+
+	masters, instances = designspace.load(designspace_filename)
+	base_idx = None
+	for i,m in enumerate(masters):
+		if 'info' in m and m['info']['copy']:
+			assert base_idx is None
+			base_idx = i
+	assert base_idx is not None, "Cannot find 'base' master; Add <info> element to one of the masters in the .designspace document."
+
+	from pprint import pprint
+	print("Masters:")
+	pprint(masters)
+	print("Index of base master:", base_idx)
+
+	print("Building GX")
+	print("Loading TTF masters")
+	basedir = os.path.dirname(designspace_filename)
+	master_ttfs = [finder(os.path.join(basedir, m['filename'])) for m in masters]
+	master_fonts = [TTFont(ttf_path) for ttf_path in master_ttfs]
+
+	#font = master_fonts[base_idx]
+	font = TTFont(master_ttfs[base_idx])
+
+	master_locs = [o['location'] for o in masters]
+
+	axis_tags = set(master_locs[0].keys())
+	assert all(axis_tags == set(m.keys()) for m in master_locs)
+	print("Axis tags:", axis_tags)
+	print("Master positions:")
+	pprint(master_locs)
+
+	# Set up axes
+	axes = {}
+	for tag in axis_tags:
+		default = master_locs[base_idx][tag]
+		lower = min(m[tag] for m in master_locs)
+		upper = max(m[tag] for m in master_locs)
+		axes[tag] = (lower, default, upper)
+	print("Axes:")
+	pprint(axes)
+
+	loc = models.normalizeLocation(loc, axes)
+	# Location is normalized now
+	print("Normalized location:", loc)
+
+	# Normalize master locations
+	master_locs = [models.normalizeLocation(m, axes) for m in master_locs]
+	print("Normalized master positions:")
+	print(master_locs)
+
+	# Assume single-model for now.
+	model = models.VariationModel(master_locs)
+	assert 0 == model.mapping[base_idx]
+
+	print("Building variations tables")
+	_merge_OTL(font, model, master_fonts, axes, base_idx)
+
+	print("Saving GX font", outfile)
+	font.save(outfile)
+
+
+if __name__ == "__main__":
+	import sys
+	if len(sys.argv) > 1:
+		main()
+		#sys.exit(0)
+	import doctest, sys
+	sys.exit(doctest.testmod().failed)