Avoid hardcoding a tolerance in Vello API, instead require the user to provide it #1376
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This represents shapes which can be turned into exact paths Co-Authored-By: Tom Churchman <thomas@churchman.nl>
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This was one of the key points raised for follow-up in #1360, to make this API harder to misuse.
The implementation strategy is to have a new
ExactPathElementstrait, which is implemented forShapes which don't require approximation.To allow shapes which do require a tolerance to be used without allocation, the
withinfunction can be used, which creates an exact shape from an inexact shape within the provided tolerance.This ensures that the common-case of rectangles and similar is ergonomic, whilst the case where tolerance is needed is handled by the user. This still completely avoids per-path allocations.
The
ExactPathElementsis based on code by @tomcur from #vello > Determining correct `Shape` tolerance. There are reasonable arguments thatExactPathElementsactually belongs in Kurbo, but I also think that, if this is the direction we decide to go, migrating that code into Kurbo would (relatively) straightforward.