Font missing dots above lowercase 'i' and 'j' about fontdue

[mooman219]

I fixed it, I'll push the change eventually

[mooman219]

tl;dr fontdue accepts out of spec fonts, but your font is more out of spec than the usual out of spec font.

Most font rasterizers, like Fontdue, raster a glyph in scanline order. It knows when it enters or leaves a contour by the direction of the line it encounters. Specifically, this is the winding order. TTF fonts use the glyf table while OTF fonts generally use the CFF/CFF2 tables. The glyf table specifies that contours are defined clockwise, while CFF/CFF2 is counter-clockwise.

TTF glypf table example:

Fontdue accept malformed fonts to some degree. It will re-compute glyph metrics and winding order per glyph (that commit cb2e9b2), which fixes a number of issues with some moderately wrong fonts. If a font has a clockwise winding order for some glyphs, but a counter clockwise order for other, Fontdue will render them all correct.

The issue here is that this spec is not enforced, and fonts that don't follow the spec produce undefined behavior. Your font, https://nickmass.com/files/evesansneue-regular.otf, is out of spec. It's a malformed font. Your 'i' and 'j' use two different winding orders for each of its contours. I colored the subtractive and additive sections of the glyph in red and green.

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I'm open to fixing this, I'd love to support more out of spec fonts, but this issue is definitely on the font.

[nickmass]

Thank you for the detailed response, I was able to open the font in an editor and quickly fix the directions of those contours and now fontdue renders everything perfectly.

[mooman219]

No worries, I'll work on thinking of a way to handle this new edge case automatically so you won't need to hand fix the font in the future.

[mooman219]

Fixed here: 6f0cea6#diff-7c2ff0572abc69580f0e70fc67a1cbe0d6d5e94bdb96a787ed350e108ef7f3b0