Empty name entry generated if elidable="true" in Designspace v5 <label>

Context

I’m building a family that has two variable fonts: a roman and an italic, each with 5 weight instances.

I’m using Designspace version 5.0 to setup both subfamilies in one document, including STAT information. This is amazing, and FontMake is handling it wonderfully overall.

I have a labels element set up in my Weight axis, which is built into a STAT table that looks good. Here’s from my designspace:

  <axes>
    <axis tag="wght" name="Weight" minimum="300" maximum="700" default="300">
      <map input="300" output="0"/>
      <map input="400" output="230"/>
      <map input="500" output="420"/>
      <map input="600" output="543"/>
      <map input="700" output="668"/>
      <labels>
        <label uservalue="300" name="Light" />
        <label uservalue="400" name="Regular" linkeduservalue="700" elidable="true"/>
        <label uservalue="500" name="Medium"  />
        <label uservalue="600" name="Semibold" />
        <label uservalue="700" name="Bold" />
      </labels>
    </axis>
    <axis name="Italic" tag="ital" default="0" values="0 1">
        <labels>
            <label uservalue="0" name="Roman" elidable="true" />
            <label uservalue="1" name="Italic" />
        </labels>
    </axis>
  </axes>

This results in a STAT table that seems to look great, including this entry for the Regular weight instance:

    <AxisValue index="1" Format="3">
        <AxisIndex value="0"/>
        <Flags value="2"/>  <!-- ElidableAxisValueName -->
        <ValueNameID value="280"/>  <!-- Regular -->
        <Value value="400.0"/>
        <LinkedValue value="700.0"/>
      </AxisValue>

In my Designspace, I’m specifying two variable fonts:

  <variable-fonts>
    <variable-font name="Familyname-Variable">
        <axis-subsets>
            <axis-subset name="Weight"/>
            <axis-subset name="Italic" uservalue="0"/>
        </axis-subsets>
    </variable-font>
    <variable-font name="FamilynameItalic-Variable">
        <axis-subsets>
            <axis-subset name="Weight"/>
            <axis-subset name="Italic" uservalue="1"/>
        </axis-subsets>
    </variable-font>
  </variable-fonts>

However, I may have found one glitch.

Problem

If I include elidable="true" in the label element for the Regular instance at 400, an empty entry appears in the resulting font’s name table:

    <namerecord nameID="270" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Light
    </namerecord>
    <namerecord nameID="271" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Familyname-Light
    </namerecord>
    <namerecord nameID="272" platformID="1" platEncID="0" langID="0x0" unicode="True">
      
    </namerecord>
    <namerecord nameID="273" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Familyname-Regular
    </namerecord>
    <namerecord nameID="274" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Medium
    </namerecord>
    <namerecord nameID="275" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Familyname-Medium
    </namerecord>
    <namerecord nameID="276" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Semibold
    </namerecord>
    <namerecord nameID="277" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Familyname-Semibold
    </namerecord>
    <namerecord nameID="278" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Bold
    </namerecord>
    <namerecord nameID="279" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Familyname-Bold
    </namerecord>

Further, the fvar table looks like this (notice the missing <!-- Regular --> comment – this is copied directly from a ttx output):

  <fvar>

    <!-- Weight -->
    <Axis>
      <AxisTag>wght</AxisTag>
      <Flags>0x0</Flags>
      <MinValue>300.0</MinValue>
      <DefaultValue>300.0</DefaultValue>
      <MaxValue>700.0</MaxValue>
      <AxisNameID>269</AxisNameID>
    </Axis>

    <!-- Light -->
    <!-- PostScript: Familyname-Light -->
    <NamedInstance flags="0x0" postscriptNameID="271" subfamilyNameID="270">
      <coord axis="wght" value="300.0"/>
    </NamedInstance>
    <!-- PostScript: Familyname-Regular -->
    <NamedInstance flags="0x0" postscriptNameID="273" subfamilyNameID="272">
      <coord axis="wght" value="400.0"/>
    </NamedInstance>

    <!-- Medium -->
    <!-- PostScript: Familyname-Medium -->
    <NamedInstance flags="0x0" postscriptNameID="275" subfamilyNameID="274">
      <coord axis="wght" value="500.0"/>
    </NamedInstance>

    <!-- Semibold -->
    <!-- PostScript: Familyname-Semibold -->
    <NamedInstance flags="0x0" postscriptNameID="277" subfamilyNameID="276">
      <coord axis="wght" value="600.0"/>
    </NamedInstance>

    <!-- Bold -->
    <!-- PostScript: Familyname-Bold -->
    <NamedInstance flags="0x0" postscriptNameID="279" subfamilyNameID="278">
      <coord axis="wght" value="700.0"/>
    </NamedInstance>
  </fvar>

If I simply remove the elidable attribute from the Regular label, name 272 changes to Regular, and the fvar table outputs in an expected way.

    <!-- Regular -->
    <!-- PostScript: Familyname-Regular -->
    <NamedInstance flags="0x0" postscriptNameID="273" subfamilyNameID="272">
      <coord axis="wght" value="400.0"/>
    </NamedInstance>

    <namerecord nameID="272" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Regular
    </namerecord>
    <namerecord nameID="273" platformID="1" platEncID="0" langID="0x0" unicode="True">
      Familyname-Regular
    </namerecord>

In FontBakery, including elidable="true" in the designspace label triggers the following FAILs (these don’t happen without elidable="true"):

🔥 FAIL: Check name table for empty records. (com.adobe.fonts/check/name/empty_records)

<div>

Check the name table for empty records, as this can cause problems in Adobe apps.

• 🔥 FAIL “name” table record with key=(1, 0, 0, 272) is empty and should be removed. [code: empty-record]
• 🔥 FAIL “name” table record with key=(3, 1, 1033, 272) is empty and should be removed. [code: empty-record]

</div>

🔥 FAIL: The variable font 'wght' (Weight) axis coordinate must be 400 on the 'Regular' instance. (com.google.fonts/check/varfont/regular_wght_coord)

<div>

According to the Open-Type spec’s registered design-variation tag ‘wght’ available at https://docs.microsoft.com/en-gb/typography/opentype/spec/dvaraxistag_wght

If a variable font has a ‘wght’ (Weight) axis, then the coordinate of its ‘Regular’ instance is required to be 400.

• 🔥 FAIL The “wght” axis coordinate of the “Regular” instance must be 400. Got None instead. [code: wght-not-400]

</div>

Expectation

As far as I understand it, the only change I should expect from including elidable="true" should be a flag in the AxisValue entry of the STAT table. Indeed, this does work well for the STAT table.

…but I doubt it should create the empty name table entry.

Perhaps making Regular elidable isn’t actually necessary, or expected on FontMake’s end? I don’t get FontBakery fails when I don’t set the elidable flag, even though I was under the impression that it was a good flag to set for the Regular instance. For now, I will skip it.

If I am doing something wrong, I will very much appreciate learning about it! Otherwise, hopefully this helps improve FontMake a little further.

[anthrotype]

a link would suffice, thank you

[anthrotype]

it does look like a bug in fonttools designspaceLib or varLib, we should move/file this over there, fontmake is simply handing off the designspace to varLib when making the STAT table.