Make Anchor work for Rectangle Mesh2d

[colepoirier]

What problem does this solve or what need does it fill?

Currently inserting Anchor when using a Rectangle mesh2d component has no effect (anchor will be the default - center). Given that Anchors work for sprites which IIUC are just rectangle meshes with images on them I don't see why this shouldn't also work for Rectangle mesh2d's.

What solution would you like?

Take into account the Anchor component in Mesh2d rendering for the Rectangle primitive shape and apply (the same transform logic that exists in the sprite pipeline for anchors)[https://github.com/bevyengine/bevy/blob/3f2baf8ecd7f8948fb67cf11b0f2811d7a1ca1ae/crates/bevy_sprite/src/render/mod.rs#L734].

What alternative(s) have you considered?

None.

Additional context

I'd be happy to implement this and submit a PR for it but I'd need some guidance on the implementation.

[colepoirier]

Comment about this on discord form @tychedelia "mesh primitives like Rectangle are all really just a description of how to build a mesh asset. Rectangle doesn't exist as a component / at the type level. so really you wouldn't be writing an anchoring system over rectangles but over 2d meshes in general." ... "if you just want it to work with rects that wouldn't be hard to implement, but is a reason why it would require more thought when the apis are eventually brought together."