Rendering in pthread by offscreen canvas without PROXY_TO_PTHREAD

[aharondavid]

Hi,
My main thread do a rendering job (in some reasons I can't use in PROXY_TO_PTHREAD).
I have an others pthreads that I want them to do also a rendering job on the same canvas (by an offscreen canvas).
By debugging into emscripten, I realized that those pthreads are proxy the rendering job to the webgl main thread context and they are not executed on the pthread. also I got this warning:
what is the efficient way to do a rendering in pthread and main thread without PROXY_TO_PTHREAD flag?

here is the emscripten js error:

Link flags:
-s NO_DISABLE_EXCEPTION_CATCHING -s ALLOW_TABLE_GROWTH -s WASM_BIGINT -s OFFSCREEN_FRAMEBUFFER=1 -s OFFSCREENCANVAS_SUPPORT=1 -g --bind -s USE_PTHREADS -s ALLOW_MEMORY_GROWTH=1 -s PTHREAD_POOL_SIZE=40

Emcc version: 3.1.9