afc194db19
this is done automatically upon compiling; however it's good to do it here as well, in case one wants to pass the updated font directly to other modules like 'subset' which requires these fields to be present -- without having to first compile and decompile.
476 lines
17 KiB
Python
476 lines
17 KiB
Python
"""Module to build FeatureVariation tables:
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https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#featurevariations-table
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NOTE: The API is experimental and subject to change.
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"""
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from __future__ import print_function, absolute_import, division
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from fontTools.misc.py23 import *
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from fontTools.misc.dictTools import hashdict
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from fontTools.misc.intTools import popCount
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from fontTools.ttLib import newTable
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from fontTools.ttLib.tables import otTables as ot
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from fontTools.otlLib.builder import buildLookup, buildSingleSubstSubtable
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from collections import OrderedDict
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def addFeatureVariations(font, conditionalSubstitutions):
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"""Add conditional substitutions to a Variable Font.
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The `conditionalSubstitutions` argument is a list of (Region, Substitutions)
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tuples.
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A Region is a list of Boxes. A Box is a dict mapping axisTags to
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(minValue, maxValue) tuples. Irrelevant axes may be omitted and they are
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interpretted as extending to end of axis in each direction. A Box represents
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an orthogonal 'rectangular' subset of an N-dimensional design space.
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A Region represents a more complex subset of an N-dimensional design space,
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ie. the union of all the Boxes in the Region.
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For efficiency, Boxes within a Region should ideally not overlap, but
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functionality is not compromised if they do.
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The minimum and maximum values are expressed in normalized coordinates.
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A Substitution is a dict mapping source glyph names to substitute glyph names.
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Example:
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# >>> f = TTFont(srcPath)
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# >>> condSubst = [
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# ... # A list of (Region, Substitution) tuples.
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# ... ([{"wdth": (0.5, 1.0)}], {"cent": "cent.rvrn"}),
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# ... ([{"wght": (0.5, 1.0)}], {"dollar": "dollar.rvrn"}),
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# ... ]
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# >>> addFeatureVariations(f, condSubst)
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# >>> f.save(dstPath)
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"""
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addFeatureVariationsRaw(font,
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overlayFeatureVariations(conditionalSubstitutions))
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def overlayFeatureVariations(conditionalSubstitutions):
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"""Compute overlaps between all conditional substitutions.
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The `conditionalSubstitutions` argument is a list of (Region, Substitutions)
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tuples.
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A Region is a list of Boxes. A Box is a dict mapping axisTags to
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(minValue, maxValue) tuples. Irrelevant axes may be omitted and they are
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interpretted as extending to end of axis in each direction. A Box represents
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an orthogonal 'rectangular' subset of an N-dimensional design space.
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A Region represents a more complex subset of an N-dimensional design space,
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ie. the union of all the Boxes in the Region.
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For efficiency, Boxes within a Region should ideally not overlap, but
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functionality is not compromised if they do.
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The minimum and maximum values are expressed in normalized coordinates.
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A Substitution is a dict mapping source glyph names to substitute glyph names.
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Returns data is in similar but different format. Overlaps of distinct
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substitution Boxes (*not* Regions) are explicitly listed as distinct rules,
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and rules with the same Box merged. The more specific rules appear earlier
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in the resulting list. Moreover, instead of just a dictionary of substitutions,
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a list of dictionaries is returned for substitutions corresponding to each
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uniq space, with each dictionary being identical to one of the input
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substitution dictionaries. These dictionaries are not merged to allow data
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sharing when they are converted into font tables.
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Example:
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>>> condSubst = [
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... # A list of (Region, Substitution) tuples.
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... ([{"wght": (0.5, 1.0)}], {"dollar": "dollar.rvrn"}),
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... ([{"wdth": (0.5, 1.0)}], {"cent": "cent.rvrn"}),
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... ]
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>>> from pprint import pprint
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>>> pprint(overlayFeatureVariations(condSubst))
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[({'wdth': (0.5, 1.0), 'wght': (0.5, 1.0)},
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[{'dollar': 'dollar.rvrn'}, {'cent': 'cent.rvrn'}]),
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({'wdth': (0.5, 1.0)}, [{'cent': 'cent.rvrn'}]),
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({'wght': (0.5, 1.0)}, [{'dollar': 'dollar.rvrn'}])]
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"""
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# Merge same-substitutions rules, as this creates fewer number oflookups.
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merged = OrderedDict()
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for value,key in conditionalSubstitutions:
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key = hashdict(key)
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if key in merged:
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merged[key].extend(value)
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else:
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merged[key] = value
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conditionalSubstitutions = [(v,dict(k)) for k,v in merged.items()]
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del merged
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# Merge same-region rules, as this is cheaper.
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# Also convert boxes to hashdict()
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#
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# Reversing is such that earlier entries win in case of conflicting substitution
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# rules for the same region.
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merged = OrderedDict()
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for key,value in reversed(conditionalSubstitutions):
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key = tuple(sorted(hashdict(cleanupBox(k)) for k in key))
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if key in merged:
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merged[key].update(value)
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else:
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merged[key] = dict(value)
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conditionalSubstitutions = list(reversed(merged.items()))
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del merged
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# Overlay
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#
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# Rank is the bit-set of the index of all contributing layers.
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initMapInit = ((hashdict(),0),) # Initializer representing the entire space
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boxMap = OrderedDict(initMapInit) # Map from Box to Rank
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for i,(currRegion,_) in enumerate(conditionalSubstitutions):
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newMap = OrderedDict(initMapInit)
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currRank = 1<<i
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for box,rank in boxMap.items():
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for currBox in currRegion:
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intersection, remainder = overlayBox(currBox, box)
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if intersection is not None:
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intersection = hashdict(intersection)
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newMap[intersection] = newMap.get(intersection, 0) | rank|currRank
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if remainder is not None:
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remainder = hashdict(remainder)
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newMap[remainder] = newMap.get(remainder, 0) | rank
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boxMap = newMap
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del boxMap[hashdict()]
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# Generate output
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items = []
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for box,rank in sorted(boxMap.items(),
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key=(lambda BoxAndRank: -popCount(BoxAndRank[1]))):
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substsList = []
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i = 0
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while rank:
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if rank & 1:
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substsList.append(conditionalSubstitutions[i][1])
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rank >>= 1
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i += 1
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items.append((dict(box),substsList))
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return items
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#
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# Terminology:
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#
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# A 'Box' is a dict representing an orthogonal "rectangular" bit of N-dimensional space.
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# The keys in the dict are axis tags, the values are (minValue, maxValue) tuples.
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# Missing dimensions (keys) are substituted by the default min and max values
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# from the corresponding axes.
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#
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def overlayBox(top, bot):
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"""Overlays `top` box on top of `bot` box.
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Returns two items:
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- Box for intersection of `top` and `bot`, or None if they don't intersect.
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- Box for remainder of `bot`. Remainder box might not be exact (since the
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remainder might not be a simple box), but is inclusive of the exact
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remainder.
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"""
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# Intersection
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intersection = {}
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intersection.update(top)
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intersection.update(bot)
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for axisTag in set(top) & set(bot):
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min1, max1 = top[axisTag]
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min2, max2 = bot[axisTag]
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minimum = max(min1, min2)
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maximum = min(max1, max2)
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if not minimum < maximum:
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return None, bot # Do not intersect
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intersection[axisTag] = minimum,maximum
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# Remainder
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#
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# Remainder is empty if bot's each axis range lies within that of intersection.
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#
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# Remainder is shrank if bot's each, except for exactly one, axis range lies
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# within that of intersection, and that one axis, it spills out of the
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# intersection only on one side.
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#
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# Bot is returned in full as remainder otherwise, as true remainder is not
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# representable as a single box.
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remainder = dict(bot)
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exactlyOne = False
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fullyInside = False
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for axisTag in bot:
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if axisTag not in intersection:
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fullyInside = False
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continue # Axis range lies fully within
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min1, max1 = intersection[axisTag]
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min2, max2 = bot[axisTag]
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if min1 <= min2 and max2 <= max1:
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continue # Axis range lies fully within
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# Bot's range doesn't fully lie within that of top's for this axis.
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# We know they intersect, so it cannot lie fully without either; so they
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# overlap.
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# If we have had an overlapping axis before, remainder is not
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# representable as a box, so return full bottom and go home.
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if exactlyOne:
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return intersection, bot
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exactlyOne = True
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fullyInside = False
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# Otherwise, cut remainder on this axis and continue.
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if min1 <= min2:
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# Right side survives.
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minimum = max(max1, min2)
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maximum = max2
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elif max2 <= max1:
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# Left side survives.
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minimum = min2
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maximum = min(min1, max2)
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else:
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# Remainder leaks out from both sides. Can't cut either.
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return intersection, bot
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remainder[axisTag] = minimum,maximum
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if fullyInside:
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# bot is fully within intersection. Remainder is empty.
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return intersection, None
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return intersection, remainder
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def cleanupBox(box):
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"""Return a sparse copy of `box`, without redundant (default) values.
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>>> cleanupBox({})
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{}
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>>> cleanupBox({'wdth': (0.0, 1.0)})
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{'wdth': (0.0, 1.0)}
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>>> cleanupBox({'wdth': (-1.0, 1.0)})
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{}
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"""
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return {tag: limit for tag, limit in box.items() if limit != (-1.0, 1.0)}
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#
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# Low level implementation
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#
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def addFeatureVariationsRaw(font, conditionalSubstitutions):
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"""Low level implementation of addFeatureVariations that directly
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models the possibilities of the FeatureVariations table."""
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#
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# assert there is no 'rvrn' feature
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# make dummy 'rvrn' feature with no lookups
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# sort features, get 'rvrn' feature index
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# add 'rvrn' feature to all scripts
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# make lookups
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# add feature variations
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#
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if "GSUB" not in font:
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font["GSUB"] = buildGSUB()
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gsub = font["GSUB"].table
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if gsub.Version < 0x00010001:
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gsub.Version = 0x00010001 # allow gsub.FeatureVariations
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gsub.FeatureVariations = None # delete any existing FeatureVariations
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for feature in gsub.FeatureList.FeatureRecord:
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assert feature.FeatureTag != 'rvrn'
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rvrnFeature = buildFeatureRecord('rvrn', [])
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gsub.FeatureList.FeatureRecord.append(rvrnFeature)
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gsub.FeatureList.FeatureCount = len(gsub.FeatureList.FeatureRecord)
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sortFeatureList(gsub)
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rvrnFeatureIndex = gsub.FeatureList.FeatureRecord.index(rvrnFeature)
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for scriptRecord in gsub.ScriptList.ScriptRecord:
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langSystems = [lsr.LangSys for lsr in scriptRecord.Script.LangSysRecord]
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for langSys in [scriptRecord.Script.DefaultLangSys] + langSystems:
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langSys.FeatureIndex.append(rvrnFeatureIndex)
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# setup lookups
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# turn substitution dicts into tuples of tuples, so they are hashable
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conditionalSubstitutions, allSubstitutions = makeSubstitutionsHashable(conditionalSubstitutions)
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lookupMap = buildSubstitutionLookups(gsub, allSubstitutions)
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axisIndices = {axis.axisTag: axisIndex for axisIndex, axis in enumerate(font["fvar"].axes)}
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featureVariationRecords = []
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for conditionSet, substitutions in conditionalSubstitutions:
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conditionTable = []
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for axisTag, (minValue, maxValue) in sorted(conditionSet.items()):
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assert minValue < maxValue
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ct = buildConditionTable(axisIndices[axisTag], minValue, maxValue)
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conditionTable.append(ct)
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lookupIndices = [lookupMap[subst] for subst in substitutions]
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record = buildFeatureTableSubstitutionRecord(rvrnFeatureIndex, lookupIndices)
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featureVariationRecords.append(buildFeatureVariationRecord(conditionTable, [record]))
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gsub.FeatureVariations = buildFeatureVariations(featureVariationRecords)
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#
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# Building GSUB/FeatureVariations internals
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#
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def buildGSUB():
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"""Build a GSUB table from scratch."""
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fontTable = newTable("GSUB")
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gsub = fontTable.table = ot.GSUB()
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gsub.Version = 0x00010001 # allow gsub.FeatureVariations
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gsub.ScriptList = ot.ScriptList()
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gsub.ScriptList.ScriptRecord = []
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gsub.FeatureList = ot.FeatureList()
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gsub.FeatureList.FeatureRecord = []
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gsub.LookupList = ot.LookupList()
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gsub.LookupList.Lookup = []
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srec = ot.ScriptRecord()
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srec.ScriptTag = 'DFLT'
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srec.Script = ot.Script()
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srec.Script.DefaultLangSys = None
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srec.Script.LangSysRecord = []
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langrec = ot.LangSysRecord()
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langrec.LangSys = ot.LangSys()
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langrec.LangSys.ReqFeatureIndex = 0xFFFF
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langrec.LangSys.FeatureIndex = []
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srec.Script.DefaultLangSys = langrec.LangSys
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gsub.ScriptList.ScriptRecord.append(srec)
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gsub.ScriptList.ScriptCount = 1
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gsub.FeatureVariations = None
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return fontTable
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def makeSubstitutionsHashable(conditionalSubstitutions):
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"""Turn all the substitution dictionaries in sorted tuples of tuples so
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they are hashable, to detect duplicates so we don't write out redundant
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data."""
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allSubstitutions = set()
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condSubst = []
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for conditionSet, substitutionMaps in conditionalSubstitutions:
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substitutions = []
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for substitutionMap in substitutionMaps:
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subst = tuple(sorted(substitutionMap.items()))
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substitutions.append(subst)
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allSubstitutions.add(subst)
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condSubst.append((conditionSet, substitutions))
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return condSubst, sorted(allSubstitutions)
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def buildSubstitutionLookups(gsub, allSubstitutions):
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"""Build the lookups for the glyph substitutions, return a dict mapping
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the substitution to lookup indices."""
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firstIndex = len(gsub.LookupList.Lookup)
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lookupMap = {}
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for i, substitutionMap in enumerate(allSubstitutions):
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lookupMap[substitutionMap] = i + firstIndex
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for subst in allSubstitutions:
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substMap = dict(subst)
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lookup = buildLookup([buildSingleSubstSubtable(substMap)])
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gsub.LookupList.Lookup.append(lookup)
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assert gsub.LookupList.Lookup[lookupMap[subst]] is lookup
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gsub.LookupList.LookupCount = len(gsub.LookupList.Lookup)
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return lookupMap
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def buildFeatureVariations(featureVariationRecords):
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"""Build the FeatureVariations subtable."""
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fv = ot.FeatureVariations()
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fv.Version = 0x00010000
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fv.FeatureVariationRecord = featureVariationRecords
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return fv
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def buildFeatureRecord(featureTag, lookupListIndices):
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"""Build a FeatureRecord."""
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fr = ot.FeatureRecord()
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fr.FeatureTag = featureTag
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fr.Feature = ot.Feature()
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fr.Feature.LookupListIndex = lookupListIndices
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fr.Feature.populateDefaults()
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return fr
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def buildFeatureVariationRecord(conditionTable, substitutionRecords):
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"""Build a FeatureVariationRecord."""
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fvr = ot.FeatureVariationRecord()
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fvr.ConditionSet = ot.ConditionSet()
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fvr.ConditionSet.ConditionTable = conditionTable
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fvr.FeatureTableSubstitution = ot.FeatureTableSubstitution()
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fvr.FeatureTableSubstitution.Version = 0x00010000
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fvr.FeatureTableSubstitution.SubstitutionRecord = substitutionRecords
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return fvr
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def buildFeatureTableSubstitutionRecord(featureIndex, lookupListIndices):
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"""Build a FeatureTableSubstitutionRecord."""
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ftsr = ot.FeatureTableSubstitutionRecord()
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ftsr.FeatureIndex = featureIndex
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ftsr.Feature = ot.Feature()
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ftsr.Feature.LookupListIndex = lookupListIndices
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return ftsr
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def buildConditionTable(axisIndex, filterRangeMinValue, filterRangeMaxValue):
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"""Build a ConditionTable."""
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ct = ot.ConditionTable()
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ct.Format = 1
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ct.AxisIndex = axisIndex
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ct.FilterRangeMinValue = filterRangeMinValue
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ct.FilterRangeMaxValue = filterRangeMaxValue
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return ct
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def sortFeatureList(table):
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"""Sort the feature list by feature tag, and remap the feature indices
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elsewhere. This is needed after the feature list has been modified.
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"""
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# decorate, sort, undecorate, because we need to make an index remapping table
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tagIndexFea = [(fea.FeatureTag, index, fea) for index, fea in enumerate(table.FeatureList.FeatureRecord)]
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tagIndexFea.sort()
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table.FeatureList.FeatureRecord = [fea for tag, index, fea in tagIndexFea]
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featureRemap = dict(zip([index for tag, index, fea in tagIndexFea], range(len(tagIndexFea))))
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# Remap the feature indices
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remapFeatures(table, featureRemap)
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def remapFeatures(table, featureRemap):
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"""Go through the scripts list, and remap feature indices."""
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for scriptIndex, script in enumerate(table.ScriptList.ScriptRecord):
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defaultLangSys = script.Script.DefaultLangSys
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if defaultLangSys is not None:
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_remapLangSys(defaultLangSys, featureRemap)
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for langSysRecordIndex, langSysRec in enumerate(script.Script.LangSysRecord):
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langSys = langSysRec.LangSys
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_remapLangSys(langSys, featureRemap)
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if hasattr(table, "FeatureVariations") and table.FeatureVariations is not None:
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for fvr in table.FeatureVariations.FeatureVariationRecord:
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for ftsr in fvr.FeatureTableSubstitution.SubstitutionRecord:
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ftsr.FeatureIndex = featureRemap[ftsr.FeatureIndex]
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def _remapLangSys(langSys, featureRemap):
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if langSys.ReqFeatureIndex != 0xffff:
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langSys.ReqFeatureIndex = featureRemap[langSys.ReqFeatureIndex]
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langSys.FeatureIndex = [featureRemap[index] for index in langSys.FeatureIndex]
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if __name__ == "__main__":
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import doctest, sys
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sys.exit(doctest.testmod().failed)
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