Confused about wasm_examples/vector_tiles/vt_worker.js

[andrew-shc]

Currently trying to test out Galileo with a Rust frontend framework, Leptos, which uses Trunk to build its website, not wasm-pack. I was as far as getting something running in the code (??), but got nothing to render presumably because of some error in vt_worker.js.

This is the output from the console four times: vt_worker.js:1 Uncaught SyntaxError: Unexpected token '<' (at vt_worker.js:1:1)

Regardless, I am looking at the vector tiles in the wasm examples to try utilizing Galileo inside Leptos, but confused as what this file vt_worker.js does, especially with a mysterious import statement from "./pkg/vector_tiles_example.js" (and its corresponding wasm file).

[Maximkaaa]

Hi, @AndrewHC36 . The file vt_worker.js is needed to initialize web workers that are used to prepare vector tiles for rendering. Without web workers rendering would be lagging as it takes up to 150ms to tessellate a single tile.

This being said, the error you see seems strange as there is not single < symbol in the file. It seems like something inserts a tag in the beginning of it, hence the <... as the first symbol. I'm not familiar with Trunk but I would expect that only a build system would do something like this, so you probably can investigate how this file is being used by the build system.

Another possibility is that your dev-server does not serve vt_worker.js at all, and you get an html error in return, which produces the error you see. Check out the network page in the devtools.

One more thing to keep in mind is that the vector_tiles example is written to be compiled with --target no-modules option of wasm-pack, e.g. with no use of ES modules. This is because only Chrome supports using modules in web workers. Make sure that your build system does the same, or you would have to redesign how vt_worker.js is loaded and initialized.