dcc.Loading flexibility enhancements

[alexcjohnson]

A couple of ideas came out of https://github.com/plotly/dash/issues/1441

• type: 'text' to allow you to display arbitrary text during loading
• Is there some way we could display certain dash components only during loading? My thought was something like a dcc.WhileLoading component, that when nested inside a dcc.Loading component, would display its contents only while loading.

[harisbal]

I would also suggest including a delay parameter for cases where loading may not last long. In such cases showing the spinner for a few milliseconds does not result in good user experience

[Jerry-Ma]

Hi, I am developing a large, modularized Dash app and I went into the same dead end as in #1441. The use case I have is that app consists of a "core" and a few "plugins". When the core does some calculation, I'd like to notify the plugin layouts the loading state of the core layout, so the plugin layouts can display the loading spinner. It would be great to have a way to subscribe to other components' loading state.

[Coding-with-Adam]

closed by #2760