Custom Layers: correct layer z-order behaviour

[carderne]

I've written a little utility zarr-gl for loading Zara (multi-dimensional raster-y) data as a CustomLayer.

It mostly works, but one thing doesn't: no matter where I place it in the layer order, it's always effectively at the top (but underneath symbols). Eg if I set opacity to 50% and place it underneath a fully opaque layer, it blends with that layer rather than being obscured/masked by it.

In this image, the blue layer is right at the top and should mask anything underneath it, including the orange/green Zarr layer.

These are my blending options (though I've tried tons):

gl.enable(gl.BLEND);
gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);

The docs for CustomLayerInterface hint that maybe I should use an off-screen framebuffer with the prerender method to achieve this? But I might be misunderstanding...

Appreciate any help or tips on how to make this work! Or just pointers to examples that achieve this layering, or using the prerender method...

[carderne]

Figured it out. It was because my render() method had an await, which I guess messes with the WebGL stuff in ways I don't yet understand.