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zglgen

Zig cron build

OpenGL bindings generator fully written in Zig.

Supports generating bindings for all versions of:

  • OpenGL
  • OpenGL Core
  • OpenGL ES
  • OpenGL SC

hello world triangle

Usage

The main branch of zglgen tries to work with latest official release of Zig.

Command line

Up-to-date documentation on command line options can be found by running zglgen -h.

[-hc] [-o <file>] [--api <apispec>] [--registry <file>] <extension>...
    -h, --help
            Show this help message

    -o, --output <file>
            Destination path for the generated module (default: prints to stdout)

        --api <apispec>
            Api to generate

        --registry <file>
            File path to OpenGL registry (default: downloads https://raw.githubusercontent.com/KhronosGroup/OpenGL-Registry/main/xml/gl.xml)

    -c, --no-cache
            Disables caching of GL registry

    <extension>...
            Additional extensions

Generating bindings

You can use zglgen to generate bindings on the command line or as part of your build process. See examples/build.zig.

NOTE: Consider building zglgen with ReleaseSafe optimization. In Debug, zglgen uses std.GeneralPurposeAllocator which is really slow but is necessary to fix bugs. In ReleaseSafe mode, zglgen will link with C standard library and use std.heap.c_allocator which is substantially faster.

FAQ

Why the procedure table is thread_local?

As per Khronos OpenGL Wiki:

The current context is a thread-local variable, so a single process can have several threads each of which has its own current context. However, a single context cannot be current in multiple threads at the same time.

A non-thread-local procedure table is unusable for people that want to have multiple GL contexts.

  1. Multiple contexts may refer to different APIs.
  2. Changing contexts does not guarantee that function pointers stay the same.

Why OpenGL constants aren't Zig enums?

Reason no. 1: Aliases. In Zig multiple tag names cannot refer to the same value. I've experimented with making them as public declerations but ultimately decided to keep API consistant and opted out to include a comment near a constant about the enum groups it belongs to. Using LSP's goto reference you can find constants that uniquely belong to a single enum group.

I've also experimented with representing bitmasks as packed structs. The upside is that bitfield values were easly discoverable. The downside is that we lost the ability to perform tail calls. Considering the bindings can potentialy be a part of a hot code path (which they most likely are), I removed them.