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commontype-standard / commontype

Annotated OpenType Specification
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slnt range greater than -91 and less than +91? #24

Open davelab6 opened 3 years ago

davelab6 commented 3 years ago

https://docs.microsoft.com/en-us/typography/opentype/spec/dvaraxistag_slnt says

Values must be greater than -90 and less than +90.

That's non-inclusive (doesn't say 'greater than or equal to' which means we can't "slant things away" to nothing, with a value of 90.

alerque commented 3 years ago

I presume they were trying to avoid having to do a bunch of value checking before doing math to make sure to avoid divide-by-zero type errors. That in itself might not be wrong, but what the goal is should be documented more explicitly. The same issue would be introduced making shapers difficult to implement if say a width axis was allowed to go to zero instead of starting at 25% or weight could be 0 instead of starting at 100 or whatever.

At least there however it isn't noted whether this is an integer value or a float. Could 89.999° be a valid value? Or is 89° as far as you can lean over before falling?