Patching Iosevka breaks some subtables

[Finii]

🗹 Requirements

• [x] I have searched the issues for my issue and found nothing related and/or helpful
• [x] I have searched the FAQ for help
• [x] I have searched the Wiki for help

🎯 Subject of the issue

Done with Patch Sets, generating font...
WARNING: Have only minimal naming information, check resulting name. Maybe specify --makegroups 0
Lookup subtable contains unused glyph POWER making the whole subtable invalid
Lookup subtable contains unused glyph POWER making the whole subtable invalid
Lookup subtable contains unused glyph POWER making the whole subtable invalid
Lookup subtable contains unused glyph POWER making the whole subtable invalid
Lookup subtable contains unused glyph HEAVY making the whole subtable invalid
Lookup subtable contains unused glyph POWER making the whole subtable invalid
Lookup subtable contains unused glyph POWER making the whole subtable invalid
Lookup subtable contains unused glyph POWER making the whole subtable invalid
Lookup subtable contains unused glyph POWER making the whole subtable invalid
Lookup subtable contains unused glyph HEAVY making the whole subtable invalid
   Iosevka Nerd Font
   \===> 'IosevkaNerdFont-Regular.ttf'

Experienced behavior:

Expected behavior:

Example symbols:

🔧 Your Setup

• Which font are you using (e.g. Anonymice Powerline Nerd Font Complete.ttf)?
  • Please give the full filename
• Where did you get the file from (download link, self patched, source downloaded from link...)
• Which terminal emulator are you using (e.g. iterm2, urxvt, gnome, konsole)?
• Are you using OS X, Linux or Windows? And which specific version or distribution?

★ Screenshots (Optional)

[Finii]

Well, this happens just for the PfaEdit table, subtable lookup names:

As Nerd Font is not writing these, ignore the fontforge problem :grimacing:

[Finii]

lookup 6 data 0 :thinking:

[Finii]

$ cat config.json
[Subtables]
    ligatures: [
        "Single Substitution lookup 6 per glyph data 1",
        "Single Substitution lookup 6 per glyph data 0" ]

[Finii]

Checked the output and the fontforge message is wrong (or sounds wrong).

For example

• 21E1 is glyph "uni21E1.WWID"
• One single substitution table contains "uni21E1.WWID" -> "uni21E1.NWID" (table A)
• Another single substitution table contains "uni21E1.NWID" -> "uni21E1.WWID" (table B)

When we overwrite 21E1 and thus "uni21E1.WWID" we remove the entry in table A because it is a rule for the modified glyph. But we do not remove the entry in table B, because destinations of rules can not be easily checked and removed in Fontforge Python code. When the font is finally exported Fontforge notices that the rule in table B has no valid destination anymore and removes just that one rule (and not the whole subtable).

All good.