Add loading screen for crystal visualization

[franflame]

Meant to implement a loading screen for the crystal visualization tool in place of the blank screen.

Using Loading() with no further changes results in a loading screen that is preceded by a blank white screen for longer loading times.

[mkhorton]

Hi @franflame, can you clarify? Are you saying the change you are suggesting does not work as you intend?

If I recall, the issue with putting the structure viewer within a Loading component is that it will flash the loading spinner each time a setting is changed, which also temporarily hides the controls, leading to a confusing user experience. However, I have not tried this recently!

Thank you for opening the PR.

[franflame]

Hi @mkhorton,

Thanks for reaching out! Yes, unfortunately the loading screen does not fully work as intended. I don't recall encountering the issue you described, but I haven't looked into it specifically, so I can't say for sure whether it's still happening.

The current issue is a little different - instead of the spinner always being present when the screen is in a loading state, the screen will sometimes stay blank for a few seconds before the spinner is displayed. This tends to happen for visualizations with longer loading times. I've tried many permutations of where to place Loading(), but unfortunately the issue still persists.

Let me know if this helps, and if I can provide any further clarification.