fix(OGC3DTilesLayer): handle multiple views

[AnthonyGlt]

Description

Handle the 3dtiles cache in each view when multiple views are created

Motivation and Context

#2426

Modifications

Adding an id to the view. Incremented at each new view.
Adding a list of cache and queues in OGC3DTilesLayer.js, to share them if in in the same view

Improvements

@jailln @Desplandis

How to handle a View disposing ?
Also, a "viewers" constant already exist in View.js, maybe this one could be used ?

itowns/src/Core/View.js

Line 118 in a4f0d22

const viewers = [];

[jailln]

Can you add a comment saying that it stores ids of viewers where tilesets have been added and explaining why and how it is related to the cache please ? You can also link the issue I think

[jailln]

@AnthonyGlt when a view is disposed, all layers added to this view are removed and their object3Ds are removed from the scene so it should be handled automatically; but it's worth checking that everything works fine :)

[AnthonyGlt]

@AnthonyGlt when a view is disposed, all layers added to this view are removed and their object3Ds are removed from the scene so it should be handled automatically; but it's worth checking that everything works fine :)

I meant that in the viewers of OGC3DTilesLayer here

https://github.com/iTowns/itowns/pull/2435/files#diff-05568d5784ac6e47fd8c2b288edaf3965abce4a92c99c0b8bec7de4ec68a5f77R29

We will store cache & queues for each view.

Once a view is disposed, the corresponding cache & queue will still be stored in the viewers, so we never remove anything from viewers

@jailln

[jailln]

If you want to remove it from viewers I think you should do it here (called when a view holding this layer is disposed)

[AnthonyGlt]

If you want to remove it from viewers I think you should do it here (called when a view holding this layer is disposed)

@jailln it should be disposed when the view is disposed, not the layer, because we share it between all layers of a same view.
It could be linked to the disposal of the view, right ?

itowns/src/Core/View.js

Lines 283 to 292 in d73f0a1

	* Dispose viewer before delete it.
	*
	* Method dispose all viewer objects
	* - remove control
	* - remove all layers
	* - remove all frame requester
	* - remove all events
	* @param {boolean} [clearCache=false] Whether to clear all the caches or not (layers cache, style cache, tilesCache)
	*/
	dispose(clearCache = false) {

[jailln]

@jailln it should be disposed when the view is disposed, not the layer, because we share it between all layers of a same view. It could be linked to the disposal of the view, right ?

Yes you're right it should be disposed when the view is disposed. Normally, when a layer is disposed, the tiles of this layer (only) should be removed from the cache (this should be handled by 3DTilesRenderer with tilesRenderer.dispose()). When a view is disposed, all layers from this view are disposed, so the lruCache cache corresponding to this view should be emptied (also because tilesRenderer.dispose()) will be called for each layer). Therefore, in my opinion nothing more should be done for emptying the cache. WDYT? It's worth checking this out in practice though :) Can you validate it's working correctly?

What you may want to do in addition is to remove the view and its associated lruCache, downloadQueue and parseQueue from the viewers when a view is disposed? You can setup an event when a view is disposed to do that for instance?

[AnthonyGlt]

@jailln

What you may want to do in addition is to remove the view and its associated lruCache, downloadQueue and parseQueue from the viewers when a view is disposed? You can setup an event when a view is disposed to do that for instance?

That was what I was talking about :)

I've pushed some edits, maybe a bit overkill to pass the view as parameter but it works.
WDYT ?

[jailln]

thanks :)

[jailln]

Ok for me, thanks for the changes :) @Desplandis @mgermerie do you want to take a look at it or should we merge?

[Desplandis]

Okay for me, but we'll need to have a better way to handle shared ressources between layers of a given view!