Make headless-gl context aware

[dhritzkiv]

For use in workers, etc.

See

• https://nodejs.org/api/addons.html#addons_context_aware_addons
• src: add buildflag to force context-aware addons nodejs/node#29631
• [Discussion] Requiring Native Modules in the Renderer Process to be NAPI or Context Aware electron/electron#18397

To do:

• Determine if this is a blocker Add module initializer with context corresponding to NODE_MODULE_INITIALIZER nodejs/nan#844
• fix windows test (incorrect way of invoking tape with node CLI args)
• write a worker threads test this change more concretely
• (in the future) check if we need to implement any global cleanup callbacks, such as the one here.

Closes #151

[dhritzkiv]

@robertleeplummerjr with more work, is this something that'd be useful in gpu.js? In your project, I see references to workers, but they look like browser workers, and not Node.js Worker Threads.

[robertleeplummerjr]

We test against web workers currently. However, this would be a very useful addition. When this is added, we'll be sure to add tests to showcase the feature.

[dhritzkiv]

The good news is that gl works in the most basic usage of worker threads (one worker thread at a time). However, we quickly run into SIGSEGV issues when running it on many threads (main thread + a worker thread, or two worker threads at the same time). Unfortunately, I've had a hard time debugging with LLDB, as it's not revealing exactly where the segfault occurs.

I suspect part of the problem may be global/static data being accessed across threads, specifically

headless-gl/src/native/webgl.cc

Lines 7 to 10 in 8667ce0

	bool WebGLRenderingContext::HAS_DISPLAY = false;
	EGLDisplay WebGLRenderingContext::DISPLAY;
	WebGLRenderingContext* WebGLRenderingContext::ACTIVE = NULL;
	WebGLRenderingContext* WebGLRenderingContext::CONTEXT_LIST_HEAD = NULL;

If that were somehow addressed, I wonder if the Angle library itself would work as expected. Scouring the Angle project's forums, it seems that Angle (at least our version) is not thread-safe. So perhaps this feature is a fool's errand?

[lqomg]

Hello, has this plan been terminated? I want to use gl on the main process of Electron 22+, but it is currently not feasible. After consulting a lot of information, I couldn't solve it, probably because of this:
https://www.electronjs.org/docs/latest/breaking-changes#default-changed-loading-non-context-aware-native-modules-in-the-renderer-process-is-disabled-by-default
electron/electron#18397