[Feature request] Implement delegate for when all HTTPRequests are finished

[Naphier]

Currently there's no built-in way to determine when all HTTPRequests are completed.

Developers can, of course, put in their own method, but this requires modifying the internal HTTPRequest class.

Consider adding a class with a delegate that will fire when all requests have completed. I did this with a simple static Action and int where the int increments with every HTTPRequest construction then decrements in the end of the DoRequest coroutine and when the int is 0 it fires the delegate. However, there's probably a more elegant way of doing this (I was in a rush ;)).

Thanks!

[david-rhodes]

@Naphier Great request! This is similar to: #35. We're thinking of creating an IProgressReporter interface and implementing that throughout the SDK, starting with the originating request (HTTPRequest or MapboxAccess, in this case).

In the meantime, please be encouraged to fork and submit pull requests!

/cc @BergWerkGIS something to think about for threaded requests

[Naphier]

What I did was not worthy of a PR. ;)
I think #35 is overall a better plan. Progress would be perfect. Feel free to close this if you like.

[wilhelmberg]

@david-rhodes @Naphier

First idea:

• callback when a request has finished, has the number of remaining requests as parameter
• callback when the request queue has finished

https://github.com/mapbox/mapbox-sdk-cs/blob/d2f632ef8ddc65d4217bf8b0679de9f9f876151f/test/UnitTest/FileSourceMockApiTest.cs#L166-L177

Would that work?

[Naphier]

My problem with this is that you'd need to hook in to every request's callback. Likely more elegant, but might be sort of complex to newer Unity devs as it requires a bit of work to set up a custom callback. My idea was just a static class that retains the request count:

https://gist.github.com/Naphier/44a63d8d07be52e589e387c642e572fd

Of course, this doesn't have progress, but it would be simple to implement. And I'd ultimately think this should be done at a higher level (maybe at Mapbox.Map.Tile.Initialize() ?). Each MapController.Execute() would reset the static total requests, a new count of requests would get registered via each Mapbox.Map.Tile.Initialize(). Each Mapbox.Map.Tile.HandleResponse() would increment a static number of responses. Then a static action could be used to report progress. Just my thoughts on it and what I think would be simplest for the developer to interface with.

[david-rhodes]

@BergWerkGIS As mentioned, I was thinking we could have an IProgressReporter. IAsyncRequest could implement this (as well as all our mesh factories and visualizers), and this could report a normalized value of completion (maybe as an event?). Then, as a developer, you get a reference to whatever IProgressReporter you want and handle its notifications.

Using this approach would also let us build composite progress reporters to chain progress all the way through a complex map generation.

[david-rhodes]

First pass progress reporting has been implemented: #89.

The AbstractMap has an initialized event, but this is used for doing conversions that require specific map attributes (reference tile and world scale, etc.). The MapVisualizer now has state changed events, as well as all the TileFactories. Use these to know when specific factories, or the entire map are done loading.