406 lines
14 KiB
Python
406 lines
14 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.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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import itertools
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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 Spaces. A Space is a dict mapping axisTags to
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(minValue, maxValue) tuples. Irrelevant axes may be omitted.
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A Space represents a '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 Spaces in the Region.
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For efficiency, Spaces 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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"""
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# Example:
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#
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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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# ... ([{"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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# >>> addFeatureVariations(f, condSubst)
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# >>> f.save(dstPath)
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# Since the FeatureVariations table will only ever match one rule at a time,
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# we will make new rules for all possible combinations of our input, so we
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# can indirectly support overlapping rules.
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# Merge duplicate region rules before combinatorial explosion.
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merged = OrderedDict()
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for key,value in conditionalSubstitutions:
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key = tuple(sorted(tuple(sorted(k.items())) 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] = value
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conditionalSubstitutions = [([dict(k) for k in key],value) for key,value in merged.items()]
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explodedConditionalSubstitutions = []
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for combination in iterAllCombinations(len(conditionalSubstitutions)):
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regions = []
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lookups = []
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for index in combination:
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regions.append(conditionalSubstitutions[index][0])
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lookups.append(conditionalSubstitutions[index][1])
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if not regions:
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continue
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intersection = regions[0]
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for region in regions[1:]:
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intersection = intersectRegions(intersection, region)
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for space in intersection:
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# Remove default values, so we don't generate redundant ConditionSets
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space = cleanupSpace(space)
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if space:
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explodedConditionalSubstitutions.append((space, lookups))
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addFeatureVariationsRaw(font, explodedConditionalSubstitutions)
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def iterAllCombinations(numRules):
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"""Given a number of rules, yield all the combinations of indices, sorted
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by decreasing length, so we get the most specialized rules first.
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>>> list(iterAllCombinations(0))
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[]
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>>> list(iterAllCombinations(1))
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[(0,)]
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>>> list(iterAllCombinations(2))
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[(0, 1), (0,), (1,)]
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>>> list(iterAllCombinations(3))
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[(0, 1, 2), (0, 1), (0, 2), (1, 2), (0,), (1,), (2,)]
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"""
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indices = range(numRules)
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for length in range(numRules, 0, -1):
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for combinations in itertools.combinations(indices, length):
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yield combinations
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#
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# Region and Space support
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#
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# Terminology:
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#
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# A 'Space' is a dict representing a "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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# A 'Region' is a list of Space dicts, representing the union of the Spaces,
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# therefore representing a more complex subset of design space.
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#
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def intersectRegions(region1, region2):
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"""Return the region intersecting `region1` and `region2`.
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>>> intersectRegions([], [])
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[]
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>>> intersectRegions([{'wdth': (0.0, 1.0)}], [])
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[]
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>>> expected = [{'wdth': (0.0, 1.0), 'wght': (-1.0, 0.0)}]
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>>> expected == intersectRegions([{'wdth': (0.0, 1.0)}], [{'wght': (-1.0, 0.0)}])
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True
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>>> expected = [{'wdth': (0.0, 1.0), 'wght': (-0.5, 0.0)}]
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>>> expected == intersectRegions([{'wdth': (0.0, 1.0), 'wght': (-0.5, 0.5)}], [{'wght': (-1.0, 0.0)}])
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True
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>>> intersectRegions(
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... [{'wdth': (0.0, 1.0), 'wght': (-0.5, 0.5)}],
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... [{'wdth': (-1.0, 0.0), 'wght': (-1.0, 0.0)}])
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[]
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"""
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region = []
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for space1 in region1:
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for space2 in region2:
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space = intersectSpaces(space1, space2)
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if space is not None:
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region.append(space)
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return region
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def intersectSpaces(space1, space2):
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"""Return the space intersected by `space1` and `space2`, or None if there
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is no intersection.
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>>> intersectSpaces({}, {})
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{}
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>>> intersectSpaces({'wdth': (-0.5, 0.5)}, {})
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{'wdth': (-0.5, 0.5)}
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>>> intersectSpaces({'wdth': (-0.5, 0.5)}, {'wdth': (0.0, 1.0)})
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{'wdth': (0.0, 0.5)}
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>>> expected = {'wdth': (0.0, 0.5), 'wght': (0.25, 0.5)}
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>>> expected == intersectSpaces({'wdth': (-0.5, 0.5), 'wght': (0.0, 0.5)}, {'wdth': (0.0, 1.0), 'wght': (0.25, 0.75)})
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True
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>>> expected = {'wdth': (-0.5, 0.5), 'wght': (0.0, 1.0)}
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>>> expected == intersectSpaces({'wdth': (-0.5, 0.5)}, {'wght': (0.0, 1.0)})
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True
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>>> intersectSpaces({'wdth': (-0.5, 0)}, {'wdth': (0.1, 0.5)})
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"""
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space = {}
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space.update(space1)
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space.update(space2)
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for axisTag in set(space1) & set(space2):
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min1, max1 = space1[axisTag]
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min2, max2 = space2[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
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space[axisTag] = minimum, maximum
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return space
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def cleanupSpace(space):
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"""Return a sparse copy of `space`, without redundant (default) values.
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>>> cleanupSpace({})
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{}
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>>> cleanupSpace({'wdth': (0.0, 1.0)})
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{'wdth': (0.0, 1.0)}
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>>> cleanupSpace({'wdth': (-1.0, 1.0)})
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{}
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"""
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return {tag: limit for tag, limit in space.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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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 = [0]
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srec.Script.DefaultLangSys = langrec.LangSys
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gsub.ScriptList.ScriptRecord.append(srec)
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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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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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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
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doctest.testmod()
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