emscripten_webgl_commit_frame black screen

[malytomas]

I have pthread with offscreen canvas and use the commit function, however, all I get is a black screen.
Using emscripten_set_main_loop instead works well.

Source code of the rendering part: https://github.com/melowntech/vts-browser-cpp/blob/9110c3d4fd4cf18dcccfa1358ae4005f73a5b84c/browser/src/vts-browser-wasm-canvas/render.cpp
Defining the RENDER_EXPLICIT_SWAP enables the commit function within an infinite loop. Am I using this correctly?

The emscripten_webgl_commit_frame returns 0 (success).
I also tried adding emscripten_current_thread_process_queued_calls into the loop in case there were any events that would need processing.

I am testing this with chrome Version 79.0.3945.130 (Official Build) (64-bit) on ubuntu.
(I cannot test with firefox because it no longer works with shared array buffers even when enabled.)

Built with sdk-releases-upstream-967836071d96d9b7894e492382f5fcb96423fc07-64bit.

Relevant build flags: -s OFFSCREENCANVAS_SUPPORT=1 -s PROXY_TO_PTHREAD=1 -s OFFSCREENCANVASES_TO_PTHREAD='#display' -s WASM=1 -s USE_PTHREADS=1 -s USE_WEBGL2=1 -s FULL_ES3=1

Thanks for any help.

[juj]

Unfortunately the latest draft of OffscreenCanvas no longer supports explicit swapping behavior. It is not clear if the final spec will, but currently it looks like it will not.

If so, explicit swapping will be restricted to the OFFSCREEN_FRAMEBUFFER feature - and in OFFSCREEN_CANVAS, to swap one will need to yield back to browser event loop.

There was a lot of contention against having a .commit() function. See w3ctag/design-reviews#141 and w3ctag/design-reviews#288 if you are interested in the conversation history.

[malytomas]

Thanks for the explanation :D