Swiftpack.co - Package - Satook/sw-OpenGLLoader

Swift OpenGL Loader

This is a simple OpenGL loader library. The repo currently contains code to load a Core profiles from 3.3 to 4.6. The included profiles do not load any extensions.

This repository has been adapted from code originally written by David Turnbull. His code can be found here: https://github.com/SwiftGL/OpenGL

This fork allows generating code for multiple profiles at once and removes the implicit library loading and function binding step of the original code. By requiring an explicit call to loadGL, client code to verify if the required OpenGL profile was loaded correctly.

Using a loader

To load an OpenGL version 3.3 profile

import GLLoader33

guard GLLoader33.loadGL(getGLProc) else {
  print("Could now load GL 3.3 profile")
  exit(1)
}

The type signature of getGLProc is:

public typealias GLFuncType = @convention(c) () -> Void
public typealias GetGLFunc = @convention(c) (_ : UnsafePointer<Int8>) -> GLFuncType?

All bindings default to stub implementations and only point at the real OpenGL functions after loadGL() has returned successfully.

Generating a new loader

If you don't want functions for a Core 3.3 profile, or want to add extensions, "Tools/main.swift" is what you want.

In the repo root:

swift run glgen Tools/gl.xml loader4.6 --profile GL_VERSION_4_6

This will generate a new set of GL functions and loader func in the "loader4.6" directory. As renderers will likely depend on specific profile/extension combinations, it is recommended to fork this repo and add additional products to Package.swift or generate loaders for your desired profile/extensions combinations and add them to your own repository.

The pre-generated code in this repo is handy if you only need a vanilla Core profile.

Shortcomings

The one major issue with the current loader logic is that the load will "fail" if any of the extensions cannot be loaded. Whilst it is reasonable to fail if the any parts of the Core profile cannot be loaded, a mechanism for communicating which extensions were successfully loaded or not is likely more helpful for clients. As it is not yet a requirement for my engine, I have not implemented this.

As always, pull requests are welcome.

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