Transverse Alignment Support

[ax3l]

Add support for non-ideal transverse alignment in elements.

This adds horizontal and vertical translation offsets per element as well as rotation in the x-y plane.

Checklist

• add new mixin helper class Alignment
• use in elements that support it
• initialize in inputs files & Python API
• document
• test case

[ax3l]

Moved forward as in WarpX: showing examples before API details feels more user-friendly :)

[cemitch99]

Made some suggestions, especially to avoid mixing variable values in new/old coordinate system.

In general, "Transversal" is usually written as "Transverse".

Don't we also need to modify InitElement.cpp? Could also be a follow-up.

[ax3l]

Thanks for the review comments!

Don't we also need to modify InitElement.cpp? Could also be a follow-up.

src/initialization/InitElement.cpp is modified, but it is a bigger change and has to be expanded manually in the Files changed tab when you click on it.

[cemitch99]

I have a test example in mind with parameters we can try. I'll copy your branch and try to get this working tomorrow morning.

[cemitch99]

This is great. In the end, the code change to each individual element is minor and easily duplicated.

[ax3l]

Thanks! Yes, that's the idea.

Another cool property of this mixin class approach is, that we see from the type of a class if it can be misaligned or not.

If we need it later on, we can also add an explicit alignment element from this mixin class, but currently this seems to a user friendly way to expose it in each element (and the calculation is nicely fused in the kernel that does the map advance).