Add "skipWorker" option to GeoJSON sources [DO NOT MERGE]

[lucaswoj]

Many users, especially mapbox-gl-draw, have demonstrated a need for high responsiveness in updating GeoJSON sources. One potential solution is to do GeoJSON parsing / tiling in the main thread rather than the worker.

mapbox/mapbox-gl-draw#185

Next Steps

• quantify performance change
• quantify bundle size change
• DRY up code
• fix featuresIn / featuresAt
• add integration tests for GeoJSON sources (or ticket out separately)

[mcwhittemore]

Assuming this is faster for X features and less, why make it a flag? Why not just always do it for that number of features?

I'm guessing number of features will be too simple. The size of the geometry might mater more. Either way, if this gets into gl-js, we should have a recommendation of when to use which mode.

[lucaswoj]

Assuming this is faster for X features and less, why make it a flag? Why not just always do it for that number of features?

I'm guessing number of features will be too simple. The size of the geometry might mater more. Either way, if this gets into gl-js, we should have a recommendation of when to use which mode.

These are all great questions for which I don't yet have good answers. I think the answer will be one of:

• "this is faster for X verticies or less"
• "this has different performance characteristics that are well suited for the the animation of simple geometries."
• "this is a bad idea"

[lucaswoj]

ref #1180
ref mapbox/DEPRECATED-mapbox-gl#7

[lucaswoj]

As an added bonus, this would also allow for easier integration testing (ref #1987 (comment))

[mourner]

@lucaswoj I'm 👍 on such an option (off by default, no smart heuristics for now). The main tricky thing here is how to DRY up the code. :) Will probably require moving out GeoJSON handling into a separate file.

[lucaswoj]

My plan for DRYing this code is to refactor the Dispatcher and Actor to optionally run operations on the same thread instead of in a Worker.

[lucaswoj]

We might be able to get similar performance characteristics using a transferrable byte array containing stringified GeoJSON or geobuf. #1504

[lucaswoj]

Closing while we consider other solutions to this problem in #1504

[lucaswoj]

#2224 is a much better solution than this PR.