# Zig OpenGL Binding

This is a pragmatic binding to different OpenGL versions.

It uses the official [OpenGL Registry](https://github.com/KhronosGroup/OpenGL-Registry) by Khronos to generate the Zig code.

Right now, it does minimal adjustments like removing the `gl` prefix from functions or the `GL_` prefix from constants. Everything else is the same as the C API.

There is a single non-OpenGL function exported:

```zig
pub fn load(load_ctx: anytype, get_proc_address: fn(@TypeOf(load_ctx), [:0]const u8) ?*FunctionPointer) !void {
```

This function will load all OpenGL entry points with the help of `get_proc_address`. It receives the `load_ctx` as well as the function name.

**NOTE:** Please do not reference `zig-opengl` as a submodule or a package. Generate a binding and copy the output of that into your repository and update the file on demand. The OpenGL Registry is just too huge to be used conveniently.

Cloning submodules is required, so use `--recursive`:

```bash
git clone --recursive https://github.com/ikskuh/zig-opengl.git
```

## Example

This example uses [ZWL](https://github.com/Aransentin/ZWL/) by @Aransentin.

```zig
const zwl = @import("zwl");

const Platform = zwl.Platform(…);

pub fn initAndDraw(window: Platform.Window) !void {
  try gl.load(window.platform, Platform.getOpenGlProcAddress);

  while(true) {
    gl.clearColor(1, 0, 1, 1);
    gl.clear(gl.COLOR_BUFFER_BIT);

    try window.present();
  }
}
```

### Usage with mach-glfw

There is an example of `mach-glfw` + `zig-opengl` usage available here: https://github.com/hexops/mach-glfw-opengl-example

## Pregenerated Loaders

This repository contains pre-generated bindings for all extension-free OpenGL versions.

## Generating your own loader

### From source

To generate your own loader, you have to clone this repository and build the generator with `dotnet`:

```sh-session
user@machine:~/zig-opengl$ dotnet run
Usage: generator <registry> <result> <api_version> [<extension>] [<extension>] ...
user@machine:~/zig-opengl$ dotnet run OpenGL-Registry/xml/gl.xml gl3v3.zig GL_VERSION_3_3
Final API has 344 commands and 818 enums types.
user@machine:~/zig-opengl$
```

```sh-session
dotnet run \
  OpenGL-Registry/xml/gl.xml \ # path to the opengl registry
  my_binding.zig             \ # path to the generated file
  GL_VERSION_3_3             \ # feature level, options listed below
  …                            # Add your extensions here, each as a single arg. Or let them out, you don't need extensions
```

Possible feature levels (at the time of writing) are:

- `GL_VERSION_1_0`
- `GL_VERSION_1_1`
- `GL_VERSION_1_2`
- `GL_VERSION_1_3`
- `GL_VERSION_1_4`
- `GL_VERSION_1_5`
- `GL_VERSION_2_0`
- `GL_VERSION_2_1`
- `GL_VERSION_3_0`
- `GL_VERSION_3_1`
- `GL_VERSION_3_2`
- `GL_VERSION_3_3`
- `GL_VERSION_4_0`
- `GL_VERSION_4_1`
- `GL_VERSION_4_2`
- `GL_VERSION_4_3`
- `GL_VERSION_4_4`
- `GL_VERSION_4_5`
- `GL_VERSION_4_6`
- `GL_VERSION_ES_CM_1_0`
- `GL_ES_VERSION_2_0`
- `GL_ES_VERSION_3_0`
- `GL_ES_VERSION_3_1`
- `GL_ES_VERSION_3_2`
- `GL_SC_VERSION_2_0`

## Contribution

This library uses a small C# script that generates the Zig bindings. It is located in `src/Generator.cs`

## What is missing right now?

- Option to specify `core` or `compatibility` profile.