GPU Aggregation (1/8): Aggregator and AggregationLayer

[Pessimistress]

For #7457

The goals of this refactor:

• Unified Aggregator interface for both GPU aggregation and CPU aggregation
• Simplified Aggregator and AggregationLayer classes that no longer concern:
  • Different props.data formats (iterable, non-iterable, binary...)
  • Projection systems
  • Specific prop names and update triggers
• Fully typed and extensively documented

Planned PRs:

• Aggregator and AggregationLayer
• GPUAggregator
• CPUAggregator
• ScreenGridLayer
• GridLayer
• HexagonLayer
• ContourLayer
• Remove legacy code

Change List

• New Aggregator interface
• New AggregationLayer abstract class
• Add isDrawable to Layer class to decouple isComposite from drawing behavior. AggregationLayer is a composite layer (renders sublayers) but also participate in the draw cycle.

[coveralls]

coverage: 89.672% (-0.2%) from 89.901%
when pulling 0dc11d4 on x/aggregation-1
into 49131c1 on master.

[donmccurdy]

I like this direction a lot! 👏🏻

Left a few questions, nothing critical.

[ibgreen]

Very nice. Being able to reason about and define Aggregators separately and have a layer that accepts them follows the true spirit of vis.gl composability

I would mostly encourage another pass to remove differences between GPUAggregator and CPUAggregator from being visible in the AggregationLayer. I think you are almost there, see detailed notes.

[ibgreen]

Nit: TSDoc on the type as well.

[ibgreen]

Nit: Is this extra wrinkle worth it? Should we just start calling draw on composite layers and just make sure we provide an empty implementation?

[Pessimistress]

We have limited slots (255) in picking and including composite layers could be breaking to tiled use cases.

[ibgreen]

and extensively documented

The Aggregator class deserves extensive user facing documentation, to help end-users define their own aggregators and that could probably be copy pasted from your voluminous comments in the source.

[Pessimistress]

@ibgreen I will add markdown documentation once the API discussion settles. I didn't want to write them prematurely as you can't type check those.

[felixpalmer]

Have you thought about how this could work with a TileLayer? I'm working on a cluster layer right now which works with a tiled data source, and aggregates whenever the visible data changes (outputting a single ScatterplotLayer)