Moving simulation window for domain wall motion

[lamoreel]

This pull request adds the possibility for a moving simulation window, albeit not very general. The functionality is implemented for

• Magnets with no geometry
• Magnets with no regions
• Only domain wall motion is supported (1D)

The code base is kept general as to easily extend it to other cases (e.g. 2D skyrmion motion) in later PRs. The (ancient) implementation on the moving-window branch already contains some groundwork for a more general implementation, in the case we or the community would need this in the future.

[ilateur]

Sorry for the long review, but I hope it's useful and clear.

I have some general concerns as well:

• Edge charge compensation seems fairly important to a moving window. I think it should be within the same update, although not within the same pull request.
• I think there should be an example using the moving window, along with an explanation of the current restrictions (preferably on the website too).
• Don't forget to add the Window class to the documentation, via docs/api.rst I believe.
• world.center_domain_wall is now something you call once and it is then permanently enabled right? Should there be a way to disable this again? (It would also need something like ClearPostSteps() from mumax3 then.)

[ilateur]

I think this if-statement is incorrect. "not any geometry" tests whether or not the geometry is completely empty (which should never be the case). I believe not np.all(magnet.geometry) would be the correct check.

[lamoreel]

Edge charge compensation seems fairly important to a moving window. I think it should be within the same update, although not within the same pull request.

This PR is already in the making 😊 .

I think there should be an example using the moving window, along with an explanation of the current restrictions (preferably on the website too).

Yes.

Don't forget to add the Window class to the documentation, via docs/api.rst I believe.

It seems I keep forgetting this.

world.center_domain_wall is now something you call once and it is then permanently enabled right? Should there be a way to disable this again? (It would also need something like ClearPostSteps() from mumax3 then.)

Very fair. On it!