Should geom::Polygon.points be closed or not?

I wanted to test out some new georust/geo features in the context of abstreet, and consequently I've been spelunking in abstreet::geom.

I ran into some inconsistencies while trying to roundtrip some abstreet::geom::Polygyon to/from geo::Polygon - it resulted in some corrupt rendering like this:

My unverified hunch is that this some problem with one or more of:
- a mismatch in the `points` array and the precomputed triangulation `indices`
- an issue with the vertex uploading assuming closed vs open
- an issue with earcutr assuming closed vs open

While digging into that, I noticed that some (but not all) of the abstreet:geom::Polygon.points are closed. Do you have any strong feelings on whether abstreet::geom::Polygon.points should be closed?

Full disclosure is that more broadly I'm interested in making abstreet/geom more semantically consistent with georust/geo, in hopes of make future inter-op easier, but I'm also aware that these are the kinds of changes with no immediate benefit that could have a long tail of bugs in a system which is more or less currently working.

查看 geom crate 中的 geom::Polygon 结构，重点关注 points 字段和三角剖分索引。将其与 geo::Polygon 的环表示进行比较，以了解关于闭环与开环的假设。在这两种类型之间测试往返转换，并检查 earcutr 的三角剖分输出。该 issue 提到了渲染损坏，因此检查 graphics pipeline 中上传顶点的代码。

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