A script to quickly copy specific kerns between fonts. A bit kludgy... be sure to use Git to know what’s happening to your fonts!

copy-kerning-in-pair_list-without-metrics_machine.py

"""
    A script to run on UFO files from a command line. Go through a pair list and 
    copy kerns from one UFO to one other UFO, if those kern pairs are in the pair list.

    What happens:
    - copy groups from ufoToCopyFrom to ufoToCopyTo
    - for each pair in the pair list, copy kern from ufoToCopyFrom to ufoToCopyTo

    Usage:

    python "DIR/PATH/copy-kerning-in-pair_list-without-metrics_machine.py" "DIR/PATH/pair_list.txt" "ufo/to/copy/from" "ufo/to/copy/to"

    Required argument: Pair list, as exported from Metrics Machine, e.g.

    ```
    #KPL:P: UC and Punc
    H hyphen
    hyphen H
    H parenleft
    # etc
    ```

    Required argument: File path of UFO to copy groups from

    Optional argument: Dir path of UFOs to copy to (if not set, this assumes 
    you wish to copy to all UFOs in the same dir as the first one given)

    Assumptions:
        - You have a single group of UFOs
        - You wish to exactly copy groups.plist from the UFO path to the other
        - You wish to exactly copy kerning data from the pair list from 
          the first UFO to the other
        - You are working with Git, so you can verify changes before 
          truly saving them

    ------------------------------------------------------------------------

    MIT License.

    Copyright 2022 Arrow Type LLC / Stephen Nixon

    Permission is hereby granted, free of charge, to any person obtaining a 
    copy of this software and associated documentation files (the "Software"), 
    to deal in the Software without restriction, including without limitation 
    the rights to use, copy, modify, merge, publish, distribute, sublicense, 
    and/or sell copies of the Software, and to permit persons to whom the 
    Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included 
    in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
    OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
    DEALINGS IN THE SOFTWARE.
"""

import sys
import os
import shutil
from fontParts.world import OpenFont, RFont
from ufonormalizer import normalizeUFO

# Deal with arguments

try:
    if sys.argv[1].endswith(".txt"):
        kerningPairFile = sys.argv[1]
    else:
        print("⚠️ You must include a kerning pair .txt file")
        exit()
except IndexError:
    print("⚠️ You must include a kerning pair .txt file")
    exit()

try:
    if sys.argv[2].endswith(".ufo"):
        ufoToCopyFrom = sys.argv[2]
    else:
        print("⚠️ The second arg must be the path of UFO to copy groups & kerning from")
        exit()
except IndexError:
    print("⚠️ The second arg must be the path of UFO to copy groups & kerning from")
    exit()

try:
    if sys.argv[3].endswith(".ufo"):
        ufoToCopyTo = sys.argv[3]
    else:
        print("⚠️ The third arg must be the path of UFO to copy groups & kerning into")
        exit()
except IndexError:
    print("⚠️ The third arg must be the path of UFO to copy groups & kerning into")
    exit()


# ----------------------------------------------------------------
# COPY GROUPS

if ufoToCopyTo != ufoToCopyFrom and ".ufo" in ufoToCopyTo and "sparse" not in ufoToCopyTo:
    print(f"Copying groups to {ufoToCopyFrom}")
    groupsPath = f"{ufoToCopyFrom}/groups.plist"
    groupsDest = f"{ufoToCopyTo}/groups.plist"
    shutil.copyfile(groupsPath, groupsDest)


# ----------------------------------------------------------------
# COPY KERNS

# READ PAIR LIST

pairList = []

pairsGrouped = {}

with open(kerningPairFile) as f:
    data = f.read()

    for line in data.split("\n"):
        if line[0] != "#":
            # maybe make line into tuple?
            pairList.append(line.split(" "))

# HELPERS

def getKernValue(font, pair):
    "Try possible combinations to find the value of a given kerning pair, if it exists"

    try:
        font.kerning[(pair[0], pair[1])]
        return font.kerning[(pair[0], pair[1])]
    except KeyError:
        pass

    try:
        return font.kerning[(f"public.kern1.{pair[0]}", pair[1])]
    except KeyError:
        pass

    try:
        return font.kerning[(pair[0], f"public.kern2.{pair[1]}")]
    except KeyError:
        pass

    try:
        return font.kerning[(f"public.kern1.{pair[0]}", f"public.kern2.{pair[1]}")]
    except:
        pass

    return None


def setKernValue(font, pair, value):

    # find if left/right of pair in groups
    leftGroup = ""
    rightGroup = ""

    for group in font.groups.keys():
        if "kern1" in group and pair[0] in font.groups[group]:
            leftGroup = group

        if "kern2" in group and pair[1] in font.groups[group]:
            rightGroup = group

    # set kerning by group if you should
    if leftGroup and rightGroup:
        font.kerning[(leftGroup, rightGroup)] = value

    elif leftGroup:
        font.kerning[(leftGroup, pair[1])] = value

    elif rightGroup:
        font.kerning[(pair[0], rightGroup)] = value

    # otherwise, just set lone pair
    else:
        font.kerning[(pair[0], pair[1])] = value


fontToCopyFrom = OpenFont(ufoToCopyFrom, showInterface=False)


if ufoToCopyTo != ufoToCopyFrom and ".ufo" in ufoToCopyTo and "sparse" not in ufoToCopyTo:
    print("Copying kerning pairs to ", ufoToCopyTo)

    fontToCopyTo = OpenFont(ufoToCopyTo, showInterface=False)

    for pair in pairList:
        valueToCopy = getKernValue(fontToCopyFrom, pair)
        if valueToCopy:
            setKernValue(fontToCopyTo, pair, valueToCopy)

    fontToCopyTo.save()

    # makes saved UFO not have changes outside of kern updates
    normalizeUFO(ufoToCopyTo, writeModTimes=False)

    fontToCopyTo.close()

print("All Done!")