[OpenGL] use GLAD as API loader (replace GLEW)

[archibate]

Related issue = #664

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[archibate]

glad is not a library, it's a python package that generate codes.
We can generate our own external/glad, without any library loading required.
(If I got its point correctly)

[archibate]

Local test passing. Do you have a win environment?

[yuanming-hu]

Thanks! Let's see if glad is more portable than glew (I believe so). Only major thing to fix here: the glad files are too big (1.6 MB) in total - could you please use a submodule (just like https://github.com/taichi-dev/glew-ready)?

[yuanming-hu]

Local test passing. Do you have a win environment?

I do. I can help test on Windows once this is merged.

[archibate]

Thanks! Let's see if glad is more portable than glew (I believe so). Only major thing to fix here: the glad files are too big (1.6 MB) in total - could you please use a submodule (just like https://github.com/taichi-dev/glew-ready)?

To be clear this is not a repo, glad is a command line tool that generates this dir (glad --out-path=external/glad). So two choices:

1. taichi-dev/glad-ready as submodule
2. let user run glad themselves (may harm gfw users since it downloads a huge xml file from khr's offical repo)

1 sounds far more better but I'm not sure if the external/glad generated in Linux can work on Windows (and other Linux dist) too, if you could do me a favor...

[yuanming-hu]

To be clear this is not a repo, glad is a command line tool that generates this dir (glad --out-path=external/glad).

I know, we should probably just include the generated files instead of the glad source in the submodule, and update the submodule when necessary.

You might need to generate both GLX (Linux) and WGL (Windows) versions using https://glad.dav1d.de/ or a downloaded glad.

I'm happy to test for you on Windows when you are ready.

[archibate]

You might need to generate both GLX (Linux) and WGL (Windows) versions using https://glad.dav1d.de/ or a downloaded glad.

It seems like current glad.c already includes WGL support:

https://github.com/taichi-dev/glad-ready/blob/6e0265ca71db319da02fe4bdfead2430e089d510/src/glad.c#L670

It detects _MSC_VER and _WIN32, so it's generic if no --spec specified.

We only need glad_wgl.c when we want some opengl+win32 specific glue functions like HWND &PRECT paintings&bindings or whatever... And we didn't use that, we only use compute shaders.

[yuanming-hu]

Now it works on Windows and all tests pass :-) Great job!

[yuanming-hu]

This looks great! Thank you. This is a great step towards v0.6.

Just a few very minor things:

• Rename https://github.com/taichi-dev/glad-ready to https://github.com/taichi-dev/taichi_glad_ready We want to all repos under taichi-dev to have consistent names
• Hide/remove https://github.com/taichi-dev/glew-ready from taichi-dev
• Skip testing OpenGL on AppVeyor (but we should build the OpenGL backend)
• Remove the ... WIP, MAY NOT WORK warning

I'll merge this after these are resolved.

[archibate]

All done! Except for:

Hide/remove https://github.com/taichi-dev/glew-ready from taichi-dev

Sadly I can't find the Settings section in this repo... maybe I don't have admin access to it? Could you remove it or transfer ownership to me? Thanks!

[yuanming-hu]

All done! Except for:

Hide/remove https://github.com/taichi-dev/glew-ready from taichi-dev

Sadly I can't find the Settings section in this repo... maybe I don't have admin access to it? Could you remove it or transfer ownership to me? Thanks!

Thanks for fixing everything. Now you are the admin of glew-ready. Could you try again?

[yuanming-hu]

Thanks for your patience. I'll merge this once CI passes. I plan to release v0.5.15 today or tomorrow with OpenGL shipped experimentally and then release v0.6 later this week.

[archibate]

CI is passed!