Axis mappings completely upside down

[simoncozens]

Let's take Nunito.glyphs which is a Glyphs 2 file and convert it to designspace. The weight axis mappings look like this:

    <axis tag="wght" name="Weight" minimum="200" maximum="1000" default="200">
      <map input="200" output="42"/>
      <map input="300" output="61"/>
      <map input="400" output="81"/>
      <map input="500" output="91"/>
      <map input="600" output="101"/>
      <map input="700" output="125"/>
      <map input="800" output="151"/>
      <map input="900" output="178"/>
      <map input="1000" output="208"/>
    </axis>

In Glyphs, I open the file, change it to file format 3 and save it. When run through glyphs2ufo, the axis mapping now looks like this:

    <axis tag="wght" name="Weight" minimum="42" maximum="208" default="42">
      <map input="42" output="200"/>
      <map input="61" output="300"/>
      <map input="81" output="400"/>
      <map input="91" output="500"/>
      <map input="101" output="600"/>
      <map input="125" output="700"/>
      <map input="151" output="800"/>
      <map input="178" output="900"/>
      <map input="208" output="1000"/>
    </axis>

I think this is because Glyphs changed its understanding of the Axis Mapping custom parameter, so that's a pain but it probably can't be helped.

Let's get rid of the Axis Mapping custom parameter, save the Glyphs file, and try again, relying on the axis coordinates in the instances to provide the mapping.

 <axis tag="wght" name="Weight" minimum="1" maximum="1000" default="200">
      <map input="1" output="208"/>
      <map input="200" output="42"/>
      <map input="300" output="61"/>
      <map input="400" output="91"/>
      <map input="500" output="91"/>
      <map input="600" output="101"/>
      <map input="700" output="125"/>
      <map input="800" output="151"/>
      <map input="900" output="178"/>
      <map input="1000" output="208"/>
    </axis>

Where did that "1" come from?

[schriftgestalt]

That was changed after this discussion: https://github.com/googlefonts/glyphsLib/issues/745#issuecomment-1380367686

[schriftgestalt]

I’ll look into the "1".

[simoncozens]

Just hit some weird issues in fontmake with the compatibility checker dying:

% fontmake -o variable -g sources/AndadaPro.glyphs
    if not CompatibilityChecker(source_fonts).check():
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/simon/others-repos/fontmake/Lib/fontmake/compatibility.py", line 26, in check
    first = self.fonts[0]
            ~~~~~~~~~~^^^
IndexError: list index out of range

This turns out to be the same issue! Because the axis mappings are upside down, we produce designspace files like so:

    <axes>
        <axis tag="wght" name="Weight" minimum="96" maximum="140" default="96">
            <map input="96" output="400" />
            <map input="140" output="840" />
        </axis>
    </axes>
    <sources>
        <source filename="AndadaPro-Regular.ufo">
        <location>
            <dimension name="Weight" xvalue="96" />
        </location>
        </source>
        <source filename="AndadaPro-XBold.ufo">
        <location>
            <dimension name="Weight" xvalue="140" />
        </location>
        </source>
    </sources>

and when splitInterpolable runs on this, it produces a designspace with no sources, which gets handed to the compatibility checker, and self.fonts is empty.