Skateboard chokes on kerning?



  • I've been using Skateboard in design of a two-axes variable font. So far all is well, but now I'm adding kerning to my ufo's and Skateboard is not liking it. I can visualize the fonts in the text window throughout the design space, but trying to create a Preview UFO gets the following error:

    Something went wrong. At this time it may not be possible to assign blame and point fingers. So, pardon the traceback posted below, it may be helpful in a report. Thanks!
    
    Traceback (most recent call last):
      File "/Users/gregory/Library/Application Support/RoboFont/plugins/Skateboard.roboFontExt/lib/skateboard.py", line 3992, in export_generateUFOCallback
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/ufoProcessor/__init__.py", line 669, in makeInstance
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/ufoProcessor/__init__.py", line 393, in getKerningMutator
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontMath/mathKerning.py", line 27, in __init__
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontMath/mathKerning.py", line 35, in update
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/kerning.py", line 396, in keys
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/base.py", line 278, in keys
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/base.py", line 287, in _keys
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/kerning.py", line 386, in items
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/base.py", line 295, in items
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/base.py", line 295, in <listcomp>
      File "/Applications/RoboFont.app/Contents/Resources/lib/python3.7/fontParts/base/normalizers.py", line 131, in normalizeKerningKey
    ValueError: Kerning key items must be one character long
    


  • @GregThompson More detail on my situation.

    • There are four ufo sources

    • Each ufo has identical kerning groups, pairs, and values

    • 859 pairs, 143 groups, 399 glyphs in each ufo

    • Robofont 3.4, Skateboard 1.6.1, MetricsMachine 1.1.0

    • otf and variable fonts generate with no errors



  • Found the problem. It was a kerning pair without a Side 1 glyph. And only in one ufo, the first ufo I kerned. I then copied that kerning info into the other three ufo's but the error didn't copy.


  • admin

    good you found it!
    kerning values has to be set very precise.

    Did the extension DesignSpaceEditor show this kern error in the report?

    good luck!


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