odin-lang.Odin/vendor/darwin/Metal

About

metal-odin is a low overhead Odin interface for Metal that helps developers add Metal functionality to graphics applications that are written in Odin. metal-odin removes the need to create a shim and allows developers to call Metal functions directly from anywhere in their existing Odin code.

Highlights

• Drop in Odin alternative interface to the Metal Objective-C headers.
• Direct mapping of all Metal Objective-C classes, constants, enums and bit_sets to Odin
• No measurable overhead compared to calling Metal Objective-C headers, due to inlining of Odin procedure calls.
• No usage of wrapper containers that require additional allocations.
• Identical header files and procedure/constant/enum availability for iOS, macOS and tvOS.
• Backwards compatibility: All MTL.Device.supports...() procedure check if their required selectors exist and automatically return false if not.
• String (ErrorDomain) constants are @(linkage="weak") and automatically set to nil if not available.

Memory Allocation Policy

metal-odin follows the object allocation policies of Cocoa and Cocoa Touch. Understanding those rules is especially important when using metal-odin, as Odin values are not eligible for automatic reference counting (ARC).

metal-odin objects are reference counted. To help convey and manage object lifecycles, the following conventions are observed:

AutoreleasePools and Objects

Several methods that create temporary objects in metal-odin add them to an AutoreleasePool to help manage their lifetimes. In these situations, after metal-odin creates the object, it adds it to an AutoreleasePool, which will release its objects when you release (or drain) it.

By adding temporary objects to an AutoreleasePool, you do not need to explicitly call release() to deallocate them. Instead, you can rely on the AutoreleasePool to implicitly manage those lifetimes.

If you create an object with a method that does not begin with alloc, or copy, the creating method adds the object to an autorelease pool.

The typical scope of an AutoreleasePool is one frame of rendering for the main thread of the program. When the thread returns control to the RunLoop (an object responsible for receiving input and events from the windowing system), the pool is drained, releasing its objects.

You can create and manage additional AutoreleasePools at smaller scopes to reduce your program's working set, and you are required to do so for any additional threads your program creates.

If an object's lifecycle needs to be extended beyond the AutoreleasePool's scope, you can claim ownership of it (avoiding its release beyond the pool's scope) by calling its retain() method before its pool is drained. In these cases, you will be responsible for making the appropriate release() call on the object after you no longer need it.

You can find a more-detailed introduction to the memory management rules here: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmRules.html.

For more details about the application's RunLoop, please find its documentation here: https://developer.apple.com/documentation/foundation/nsrunloop

Use and debug AutoreleasePools

When you create an autoreleased object and there is no enclosing AutoreleasePool, the object is leaked.

To prevent this, you normally create an AutoreleasePool in your program's main procedure, and in the entry procedure for every thread you create. You may also create additional AutoreleasePools to avoid growing your program's high memory watermark when you create several autoreleased objects, such as when rendering.

Use the Environment Variable OBJC_DEBUG_MISSING_POOLS=YES to print a runtime warning when an autoreleased object is leaked because no enclosing AutoreleasePool is available for its thread.

You can also run leaks --autoreleasePools on a memgraph file or a process ID (macOS only) to view a listing of your program's AutoreleasePools and all objects they contain.

nil

Similar to Objective-C, it is legal to call any method, including retain() and release(), on nil "objects". While calling methods on nil still does incur in procedure call overhead, the effective result is equivalent of a NOP.

Conversely, do not assume that because calling a method on a pointer did not result in a crash, that the pointed-to object is valid.

Adding metal-odin to a Project

Simply import MTL "core:sys/darwin/Metal". To ensure that the selector and class symbols are linked.

import MTL "core:sys/darwin/Metal"

Examples

Creating the device

Objective-C (with automatic reference counting)

id< MTLDevice > device = MTLCreateSystemDefaultDevice();

// ...

Objective-C

id< MTLDevice > device = MTLCreateSystemDefaultDevice();

// ...

[device release];

Odin

device := MTL.CreateSystemDefaultDevice()

// ...

device->release()

Metal function calls map directly to Odin

Objective-C (with automatic reference counting)

MTLSamplerDescriptor* samplerDescriptor = [[MTLSamplerDescriptor alloc] init];

[samplerDescriptor setSAddressMode: MTLSamplerAddressModeRepeat];
[samplerDescriptor setTAddressMode: MTLSamplerAddressModeRepeat];
[samplerDescriptor setRAddressMode: MTLSamplerAddressModeRepeat];
[samplerDescriptor setMagFilter: MTLSamplerMinMagFilterLinear];
[samplerDescriptor setMinFilter: MTLSamplerMinMagFilterLinear];
[samplerDescriptor setMipFilter: MTLSamplerMipFilterLinear];
[samplerDescriptor setSupportArgumentBuffers: YES];

id< MTLSamplerState > samplerState = [device newSamplerStateWithDescriptor:samplerDescriptor];

Objective-C

MTLSamplerDescriptor* samplerDescriptor = [[MTLSamplerDescriptor alloc] init];

[samplerDescriptor setSAddressMode: MTLSamplerAddressModeRepeat];
[samplerDescriptor setTAddressMode: MTLSamplerAddressModeRepeat];
[samplerDescriptor setRAddressMode: MTLSamplerAddressModeRepeat];
[samplerDescriptor setMagFilter: MTLSamplerMinMagFilterLinear];
[samplerDescriptor setMinFilter: MTLSamplerMinMagFilterLinear];
[samplerDescriptor setMipFilter: MTLSamplerMipFilterLinear];
[samplerDescriptor setSupportArgumentBuffers: YES];

id< MTLSamplerState > samplerState = [device newSamplerStateWithDescriptor:samplerDescriptor];

[samplerDescriptor release];

// ...

[samplerState release];

Odin

samplerDescriptor := MTL.SamplerDescriptor.alloc()->init()

samplerDescriptor->setSAddressMode(.Repeat)
samplerDescriptor->setTAddressMode(.Repeat)
samplerDescriptor->setRAddressMode(.Repeat)
samplerDescriptor->setMagFilter(.Linear)
samplerDescriptor->setMinFilter(.Linear)
samplerDescriptor->setMipFilter(.Linear)
samplerDescriptor->setSupportArgumentBuffers(true)

samplerState := device->newSamplerState(samplerDescriptor)

samplerDescriptor->release()

// ...

samplerState->release()