Variable Font Validation

Jeremy Dooley

Is there a validator tool?

Obviously overlaps are ok, but do winding directions make a difference in variable fonts? I ask because I believe that flipped composites are ok. (?)

John Hudson

Flipped and scaled composites were supposed to be technically okay in TrueType since the beginning, but in fact they tended to cause rendering problems, so I long ago made a point of only using composites unflipped and unscaled.

Adam Jagosz

I wanted to ask the same question. So I assume it is safer to care about winding directions? Is there a reasonable way to test for them in FontLab 7? (FontAudit doesn't include it, since it's supposed to be fixed upon export, but variable fonts seemingly can't be manipulated with predictable results this way). I tried scripting, but the function I tried to use doesn't work:

<div>from FL import *;<br>f = fl.font;<br>for g in f.glyphs:<br>&nbsp; n = g.GetContoursNumber();<br>&nbsp; for i in range(0,n):<br>&nbsp;&nbsp;&nbsp; cc = g.isContourClockwise(i);<br>&nbsp;&nbsp;&nbsp; print g.name;<br>&nbsp;&nbsp;&nbsp; print cc; # returns None for all glyphs, instead of a boolean<br>&nbsp;&nbsp;&nbsp; if cc:<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; print g.name + "has counter-clockwise contour " + str(i);<br></div>

Jeremy Dooley

Some context: https://forum.fontlab.com/fontlab-7/correct-winding-directions-in-fl7-variable-font/

Viktor Rubenko

@Adam Jagosz

import fontlab as fl


for glyph in (fl.flGlyph(glyph) for glyph in fl.CurrentFont().glyphs):
    if glyph.activeLayer.getContours():
        print(
            "{}: {}".format(
                glyph.name,
                [
                    contour.clockwise
                    for contour in glyph.activeLayer.getContours()
                ],
            )
        )

Dave Crossland

Contributors to the FontBakery project are developing a set of checks for variable fonts. You are welcome to contribute ideas or code!

GitHub.com/googlefonts/FontBakery