Compare map widget sometimes fails

[batpad]

There's some weird timing bug with lonboard / DeckGL during the layer construction when two maps are initted at the same time that causes the static output of the Map Compare widget to "sometimes" fail - it's a bit random and hard to reproduce, but creating this issue to dump notes with some further digging.

[batpad]

Going to try and write out a blathering of what I think I know about this issue --

deck.gl sometimes seems to get / generate "duplicate ids" for layers, and that throws an error that causes map rendering to fail. This seems to be caused by the lonboard React component render method being called many times in quick succession when rendering many layers on the map, and some-how seems worse when there are two maps?

The errors in console look something like:

deck: Multiple new layers with same id 21a3a64f9e9f40dda0a4a1b09f3bbbae
  deck: Multiple old layers with same id 21a3a64f9e9f40dda0a4a1b09f3bbbae
  deck: initialization of BitmapLayer({id: '21a3a64f9e9f40dda0a4a1b09f3bbbae'}): deck.gl: assertion failed. Error: deck.gl: assertion failed.

This seems like it could be related to developmentseed/lonboard#994

There's this issue in deck.gl that might be similar, but there it seemed the problem was with the caller setting duplicate ids: visgl/deck.gl#2603. Am fairly certain I've verified in this case we are not sending duplicate ids, and this is some-how getting generated in deck.gl iteself, but honestly I also don't really know what's going on, and the bug appears only sometimes, so it's very hard to reproduce.

It's very weird - @kylebarron lemme know if there's anything here that feels jumps out or feels familiar? To try and reproduce the issue: https://developmentseed.org/manywidgets/map-compare-1/

Will be very useful to know if other folks are bumping up against this or if the compare map just works (like it does for me, most of the time?) - I'll look at this again on Monday with a fresh head.

[kylebarron]

I mean looking at your example I get a lot of console errors in the form of

It looks like this line is erroring:

https://github.com/visgl/deck.gl/blob/7a9d5ea49f6647ee6207b8821007a9c4ed572499/modules/core/src/lib/layer.ts#L919

This is not related to developmentseed/lonboard#994. I don't think this is related to visgl/deck.gl#2603.

Honestly most likely this is due to somehow using the same id across multiple layers.

We can talk more on Monday