Bindings for the D language to Apple's Metal Graphics API

Those bindings were created by hand and includes comments from apple.developer documentations. If you wish to contrirbute, try to stick to what was done by keeping comments for easier developer understanding on what is happening. If possible, the binding must be user friendly as a programming language to learn Metal.

The Binding has a wrapper over it to make development easier. For example, most arrays are accessed on Objective-C using objectIndexedAtSubscript. However, this API is not natural for D. So, beyond the bindings, this also includes opIndex and opIndexAssign, making the API more familiar to Objective-C.

The binding is a little bit different from Objective-C too by giving g enum short names. For example instead of using MTLPixelFormatR8Unorm, this enum is accessed by using MTLPixelFormat.R8Unorm. This will make your code shorter and easier to read. Enums that has a number after the prefix starts with an underline. For example: MTLTextureType._2D.

Another detail on this API, using NSArray as the generic type for everything is counter intuitive, so, for making the API more self descriptive, this binding defines 2 concepts:

1. NSArray_(T): This is an alias that resolves to NSArray. It does not create a type, and it is solely for documentation on function purposes. It is the type you use for interfacing with Objective-C.

2. NSArrayD(T): This is a structt that wraps a NSArray with alias arr this. It is strongly typed for keeping your code less error prone. It also wraps opIndex and opApply for being able to use the foreach and index operators.

This binding was even further extended to make Objective-C interfacing easier. Whenever needing to interface to Objective-C via NSDictionary, NSArray, NSString, NSNumber or other kind of objects that D can easily simulate, you can just append .ns to your type. The following style is used to create a macro dictionary from D side:

MTLCompileOptions opts = MTLCompileOptions.alloc.initialize;
opts.preprocessorMacros = ["ARGS_TIER2": 0].ns;

This way, there's no need to kep dealing all the time with Objective-C API.