<![CDATA[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
]]>https://forum.robofont.com/topic/886/skateboard-chokes-on-kerningRSS for NodeThu, 14 May 2026 04:40:17 GMTThu, 16 Jul 2020 23:53:45 GMT60<![CDATA[Reply to Skateboard chokes on kerning? on Fri, 24 Jul 2020 14:20:58 GMT]]>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
]]>https://forum.robofont.com/post/3448https://forum.robofont.com/post/3448Fri, 24 Jul 2020 14:20:58 GMT<![CDATA[Reply to Skateboard chokes on kerning? on Fri, 17 Jul 2020 00:10:17 GMT]]>@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

]]>https://forum.robofont.com/post/3449https://forum.robofont.com/post/3449Fri, 17 Jul 2020 00:10:17 GMT<![CDATA[Reply to Skateboard chokes on kerning? on Fri, 17 Jul 2020 01:51:49 GMT]]>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.

]]>https://forum.robofont.com/post/3450https://forum.robofont.com/post/3450Fri, 17 Jul 2020 01:51:49 GMT<![CDATA[Reply to Skateboard chokes on kerning? on Fri, 17 Jul 2020 20:48:15 GMT]]>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!

]]>https://forum.robofont.com/post/3451https://forum.robofont.com/post/3451Fri, 17 Jul 2020 20:48:15 GMT