List GSUB Features in SFNT

listGSUBFeatures.py

import sys
from fontTools.ttLib import TTFont

'''
usage:
$ python listGSUBFeatures.py path/to/font.otf
'''

def main():
    if len(sys.argv) < 2:
        print("Please supply (atleast) one sfnt.")
        sys.exit(1)
    else:
        featureTags = {"aalt":"Access All Alternates","abvf":"Above-base Forms","abvm":"Above-base Mark Positioning","abvs":"Above-base Substitutions","afrc":"Alternative Fractions","akhn":"Akhands","blwf":"Below-base Forms","blwm":"Below-base Mark Positioning","blws":"Below-base Substitutions","calt":"Contextual Alternates","case":"Case-Sensitive Forms","ccmp":"Glyph Composition / Decomposition","cfar":"Conjunct Form After Ro","cjct":"Conjunct Forms","clig":"Contextual Ligatures","cpct":"Centered CJK Punctuation","cpsp":"Capital Spacing","cswh":"Contextual Swash","curs":"Cursive Positioning","cv01":"Character Variants","c2pc":"Petite Capitals From Capitals","c2sc":"Small Capitals From Capitals","dist":"Distances","dlig":"Discretionary Ligatures","dnom":"Denominators","dtls":"Dotless Forms","expt":"Expert Forms","falt":"Final Glyph on Line Alternates","fin2":"Terminal Forms #2","fin3":"Terminal Forms #3","fina":"Terminal Forms","flac":"Flattened accent forms","frac":"Fractions","fwid":"Full Widths","half":"Half Forms","haln":"Halant Forms","halt":"Alternate Half Widths","hist":"Historical Forms","hkna":"Horizontal Kana Alternates","hlig":"Historical Ligatures","hngl":"Hangul","hojo":"Hojo Kanji Forms (JIS X 0212-1990 Kanji Forms)","hwid":"Half Widths","init":"Initial Forms","isol":"Isolated Forms","ital":"Italics","jalt":"Justification Alternates","jp78":"JIS78 Forms","jp83":"JIS83 Forms","jp90":"JIS90 Forms","jp04":"JIS2004 Forms","kern":"Kerning","lfbd":"Left Bounds","liga":"Standard Ligatures","ljmo":"Leading Jamo Forms","lnum":"Lining Figures","locl":"Localized Forms","ltra":"Left-to-right alternates","ltrm":"Left-to-right mirrored forms","mark":"Mark Positioning","med2":"Medial Forms #2","medi":"Medial Forms","mgrk":"Mathematical Greek","mkmk":"Mark to Mark Positioning","mset":"Mark Positioning via Substitution","nalt":"Alternate Annotation Forms","nlck":"NLC Kanji Forms","nukt":"Nukta Forms","numr":"Numerators","onum":"Oldstyle Figures","opbd":"Optical Bounds","ordn":"Ordinals","ornm":"Ornaments","palt":"Proportional Alternate Widths","pcap":"Petite Capitals","pkna":"Proportional Kana","pnum":"Proportional Figures","pref":"Pre-Base Forms","pres":"Pre-base Substitutions","pstf":"Post-base Forms","psts":"Post-base Substitutions","pwid":"Proportional Widths","qwid":"Quarter Widths","rand":"Randomize","rclt":"Required Contextual Alternates","rkrf":"Rakar Forms","rlig":"Required Ligatures","rphf":"Reph Forms","rtbd":"Right Bounds","rtla":"Right-to-left alternates","rtlm":"Right-to-left mirrored forms","ruby":"Ruby Notation Forms","rvrn":"Required Variation Alternates","salt":"Stylistic Alternates","sinf":"Scientific Inferiors","size":"Optical size","smcp":"Small Capitals","smpl":"Simplified Forms","ss01":"Stylistic Set 1","ss02":"Stylistic Set 2","ss03":"Stylistic Set 3","ss04":"Stylistic Set 4","ss05":"Stylistic Set 5","ss06":"Stylistic Set 6","ss07":"Stylistic Set 7","ss08":"Stylistic Set 8","ss09":"Stylistic Set 9","ss10":"Stylistic Set 10","ss11":"Stylistic Set 11","ss12":"Stylistic Set 12","ss13":"Stylistic Set 13","ss14":"Stylistic Set 14","ss15":"Stylistic Set 15","ss16":"Stylistic Set 16","ss17":"Stylistic Set 17","ss18":"Stylistic Set 18","ss19":"Stylistic Set 19","ss20":"Stylistic Set 20","ssty":"Math script style alternates","stch":"Stretching Glyph Decomposition","subs":"Subscript","sups":"Superscript","swsh":"Swash","titl":"Titling","tjmo":"Trailing Jamo Forms","tnam":"Traditional Name Forms","tnum":"Tabular Figures","trad":"Traditional Forms","twid":"Third Widths","unic":"Unicase","valt":"Alternate Vertical Metrics","vatu":"Vattu Variants","vert":"Vertical Writing","vhal":"Alternate Vertical Half Metrics","vjmo":"Vowel Jamo Forms","vkna":"Vertical Kana Alternates","vkrn":"Vertical Kerning","vpal":"Proportional Alternate Vertical Metrics","vrt2":"Vertical Alternates and Rotation","vrtr":"Vertical Alternates for Rotation","zero":"Slashed Zero"}
        for path in sys.argv[1:]:
            f = TTFont(path)
            print("--------------------")
            print(f["name"].getName(4,1,0,0))
            print("------- GSUB -------")
            GSUB = f["GSUB"]
            i = []
            for r in GSUB.table.FeatureList.FeatureRecord:
                i.append(r.FeatureTag)
            features = sorted(list(set(i)))
            for fea in features:
                # changing this to .get() in the case of a custom tag
                print(f"({fea}) {featureTags.get(fea)}")
        
if __name__ == "__main__":
    main()