Getting started with Metal-cpp

Metal-cpp is a low-overhead C++ interface for Metal that helps you add Metal functionality to graphics apps, games, and game engines that are written in C++.

Highlights

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

Installation instructions

1. Prepare your Mac.

• Open Xcode on your Mac. Xcode 9.3 or later includes C++17, which is the minimum required by Metal-cpp because of the use of constexpr in NS::Object.
• Download and extract the contents of this ZIP file.

  metal-cpp_macOS12_iOS15.zip
  metal-cpp_macOS13_iOS16.zip
  metal-cpp_macOS13.3_iOS16.4.zip
  metal-cpp_macOS14_iOS17-beta.zip
  metal-cpp_macOS14.2_iOS17.2.zip

2. Add the metal-cpp folder to your build system’s header search path.

In Xcode:

• Click the Project Navigator.
• Click the Project.
• Click Build Settings.
• Search for Header Search Paths.
• Add the path to the extracted folder, metal-cpp/.
• Search for C++ Language Dialect and make sure it's set to C++17 or higher.
• Make sure to add the Foundation, QuartzCore, and Metal frameworks to the list of frameworks to be linked in the Build Phases tab.

3. Generate the implementation.

metal-cpp is a header-only library. To generate the implementation, add the following code in one of your .cpp files:

#define NS_PRIVATE_IMPLEMENTATION
#define CA_PRIVATE_IMPLEMENTATION
#define MTL_PRIVATE_IMPLEMENTATION
#include <Foundation/Foundation.hpp>
#include <Metal/Metal.hpp>
#include <QuartzCore/QuartzCore.hpp>

Note: It's also possible to include the metal-cpp headers with quotation marks.

4. Use metal-cpp.

From any files that need to reference metal-cpp objects or types, simply include the headers to make the symbols available.

#include <Foundation/Foundation.hpp>
#include <Metal/Metal.hpp>
#include <QuartzCore/QuartzCore.hpp>

Important: Don't define the NS, MTL, or CA _PRIVATE_IMPLEMENTATION macros more than once.

Metal-cpp single header alternative

For convenience, you can alternatively use metal-cpp as a single-header include in your project.

After you extract the ZIP file contents, run the following command from the terminal to generate a single include header.

./SingleHeader/MakeSingleHeader.py Foundation/Foundation.hpp QuartzCore/QuartzCore.hpp Metal/Metal.hpp

Once completed, the command will have generated a single file: ./SingleHeader/Metal.hpp. This file includes everything you need to use metal-cpp in your project.

Remember to generate the implementation in one CPP file.

#define NS_PRIVATE_IMPLEMENTATION
#define CA_PRIVATE_IMPLEMENTATION
#define MTL_PRIVATE_IMPLEMENTATION
#include <Metal/Metal.hpp>

Memory management considerations

Metal-cpp follows the object allocation policies of Cocoa and Cocoa Touch. Understanding those rules is especially important when using metal-cpp because C++ objects aren't eligible for automatic reference counting (ARC). For more information, refer to the Read Me file in the metal-cpp download.