fix TypeError when converting pathops.Path to svg #305
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Fixes #304 Fixes googlefonts/nanoemoji#455 Fixes googlefonts/noto-emoji#429 since skia-pathops v0.8.0, the Path.segments (SegmentPenIterator) may yield segments with an on-curve point set to None when closed contour is only comprised of quadratic beziers and all the on-curve points can be implied as in-between consecutive off-curve points (special TrueType quadratic spline), this was to match FontTools pen protocol, which the SegmentPenIterator is supposed to work with. Picosvg was using this interface for converting from pathops.Path to SVG path.d strings, and uncaught TypeError was being raised when that happened. However, it turns out picosvg can avoid the SegmentPenIterator altogether when converting from pathops.Path to SVG, because the Path's RawPathIterator (i.e. iterating over the path itself as opposed to Path.segments) already yields (verb, points) for individual segment that matches what SVG expects (in this particular case, a move, a list of quadratic bezier segments each with one off-curve point, and a close command, no fonttools-style implied points anywhere). This way we can translate between SVG<=>pathops.Path in a more straightforward way (since they are closed to one another than to fonttools pen protocol more geared to font format specifics).
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Fixes #304
Fixes googlefonts/nanoemoji#455
Fixes googlefonts/noto-emoji#429
since skia-pathops v0.8.0, the Path.segments (aka SegmentPenIterator) may yield segments where the on-curve point is set to None, which happens when a closed contour is only comprised of quadratic beziers and all the on-curve points can be implied as in-between consecutive off-curve points (i.e. special TrueType quadratic spline). This was to match FontTools pen protocol, which the SegmentPenIterator is supposed to work with, allowing to round-trip these oncurve-less contours through pathops.
Picosvg happens to be using this Path.segments interface when converting from pathops.Path to SVG path.d strings, and an uncaught TypeError was being raised when that happened. However, it turns out that picosvg can avoid using the SegmentPenIterator altogether when converting from pathops.Path to SVG, because the Path's
RawPathIterator(i.e. used for iterating over the Path itself, as opposed to its Path.segments) already yields (verb, points) for individual curve segments that match what SVG expects: in this particular case, an explicit move, a list of quadratic bezier segments each with one off-curve point, and a close command, and no fonttools-style None-implied points.This way we can translate between SVG<=>pathops.Path in a more straightforward way, since they are closer to one another than to fonttools pen protocol, more geared towards font format specifics.