Validate winding of sketches

[hannobraun]

Sketches each contain multiple Regions. The exterior cycle of those regions should have counter-clockwise winding, their interior cycles should have clockwise winding. I believe that the sweep code already assumes this, but currently, this is not documented nor enforced.

Implementation

This new validation check would go into the validate module, specifically validate::sketch. You can use the structure of the existing validation check (for Sketch and other objects) as a guideline for the implementation.

The check itself should be rather straight-forward, as it could just use Cycle::winding. Please note that this method is buggy (#2130), but as long as we make sure not to use any complicated cycles in the unit test for this validation check, we'll be fine (just stick to polygons).

Since this should be relatively straight-forward, and there are already numerous validation checks to serve as inspiration, I'm designating this as a good first issue Good for newcomers .

Related Issues

There are two related issues:

• Consider removing region interiors #2132, which would change the structure of regions (implementing that first would simplify this issue).
• Improve validation infrastructure #2157, which would restructure the validation infrastructure (implementing that first would change where this check would go, and some details about how it would be implemented).

Neither of those issues are blockers for this one, but work would need to be coordinated. If you're interested in picking this up, I suggest you check out those issues to see if anybody is already working on them.

[hannobraun]

Addressed by @emka in #2256.