Adding Subtables for Large Kerning Lookups

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Bhikkhu Pesala
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Adding Subtables for Large Kerning Lookups

Post by Bhikkhu Pesala » Sun May 26, 2019 11:25 am

Large fonts like my font Pali have a lot of kerning pairs. It is much easier to manage them by splitting the single PairAdjustment_0 subtable into several others. I renamed mine for greater ease of use.
Subtables and afrc.png
Subtables and afrc.png (11.92 KiB) Viewed 283 times
I arranged Subtable_hyphen at the top so that it appears by default when selecting the Pair Adjustment lookup, because pairs with hyphen are often problematic when generating kerning values with autokern.

Adding a New Subtable for Alternative Fractions
Click on the gears icon to open the Subtable manager, where one can add or sort subtables. I added Subtable_afrc for a simple demonstration.
Subtable Manager.png
Subtable Manager.png (5.62 KiB) Viewed 283 times
Editing the Pair Adjustment Lookup
Find Next afrc.png
Find Next afrc.png (12.72 KiB) Viewed 283 times
  1. Close the subtable manager and open the Pair Adjustment lookup in the code editor.
  2. Search for "afrc" to find any pairs using alternative fractions.
  3. Select the lookup pairs and cut them to the clipboard
  4. Go to the end of the lookup and paste them into the new subtable
Paste kerning pairs.png
Paste kerning pairs.png (11.7 KiB) Viewed 283 times
Adjusting the Kerning Pairs for afrc

Close the Pair Adjustment lookup and select Subtable_afrc to inspect those pairs. Use the shortcuts Left/Right cursor, Shift+Left/Right cursor, or Ctrl+Left/Right cursor to adjust the selected kerning pair’s value by 10, 100, or 1 funit respectively.
Subtable afrc.png
Subtable afrc.png (6.41 KiB) Viewed 283 times
Note that actions like autokern or trim work on the entire lookup, not just on the selected subtable.

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