I just spent the afternoon implementing OpenSCAD 2D path/pathlist function builtins for:

• union_paths(pathlist, pathlist, ...) -> pathlist
• union_paths(pathlists) -> pathlist
• difference_paths(pathlist, pathlist, ...) -> pathlist
• difference_paths(pathlists) -> pathlist
• intersect_paths(pathlist, pathlist, ...) -> pathlist
• intersect_paths(pathlists) -> pathlist
• minkowski_paths(pathlist, pathlist, ...) -> pathlist
• minkowski_paths(pathlists) -> pathlist

I have those done, and they are all implemented with ClipperUtils. They all can take a 2D path or a region made up of a list of 2D paths for any of the pathlist arguments. And they will all reject malformed paths/regions. I avoided naming them the same as their geometry equivalents to avoid confusion.

I'm currently working on offset_paths(), and I've run into an odd little quirk of functions in OpenSCAD:
Every single function builtin uses positional args instead of named args.  Every Single One.  This means that in search(), the num_returns_per_match= must always be the 3rd argument, and index_col_num= must always be the 4th.

For offset_paths(), I want to be able to specify r= or delta= and chamfer=.  In builtin modules, it looks like it sets up a ContextHandle<Context> to use lookup_variable() to get named args, but it is unclear to me if this is allowed in a builtin function.  IS that how it would be done?

• Revar

Okay, I got the boolean paths built-ins all working in a couple afternoons of
work.  Most of my time was trying to get OpenSCAD to compile on my OS X
system.  I gave up, created a Linux VM, and set up a build environment
there.  That was far, far easier.

Anyways, I made a PR for it at
https://github.com/openscad/openscad/pull/3288

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