Based on Miguel Sousa's original PR and the following discussion:
https://github.com/googlei18n/cu2qu/pull/114
Instead of raising an error at the first incompatible glyph, we
let it continue (keeping the original contours unmodified when
that happens), and use logging to print error messages.
A new `IncompatibleFontsError` exception is raised at the end of
`fonts_to_quadratic` if any glyph has incompatible number or types
of segments. The exception instance has a `glyph_errors` attribute
(dict) which collects all the individual IncompatibleGlyphsError
keyed by glyph name.
When the 'max_err_em' argument is a float, we multiply it
by the font.info.unitsPerEm. However we were not doing it when
the argument is a list of floats...
We dropped robofab support. There is no reason to arbitrarily
drop any contour points. Anchors are handled as anchors in
latest ufoLib+defcon, also for UFO2. No more need to special-case.
otherwise, the direction would only flipped if the glyph contains at least one cubic curve; whereas, we want to reverse the contour direction of all the glyphs in the font, even if they are just made of straight lines.
Don't use zip(*fonts) as defcon fonts are dictionary-like objects and the ordering of the glyphs returned by __iter__ method is undefined.
Should fix#48
This was requested in https://github.com/googlei18n/cu2qu/issues/26
Plus:
- do not modify input glyphs unless they contain one cubic curve;
- make public functions return True/False to signal that the input
was modified or not (eg. no curves, or all quadratic)
For some reason, I was subtracting 1 from the spline lengths in the
test report. Not sure why that is, so I've assumed it was wrong (and
now we subtract 2 to get the length in number of segments).
