This isn't even a regular SPI. It's not even present in the Metal framework. It's exposed by the driver. Only AMD drivers support the method we need for now.
486 lines
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486 lines
24 KiB
Markdown
<a class="site-logo" href="https://github.com/KhronosGroup/MoltenVK" title="MoltenVK">
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<img src="Docs/images/MoltenVK-Logo-Banner.png" alt="MoltenVK" style="width:256px;height:auto">
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</a>
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MoltenVK
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========
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Copyright (c) 2015-2024 [The Brenwill Workshop Ltd.](http://www.brenwill.com)
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[comment]: # "This document is written in Markdown (http://en.wikipedia.org/wiki/Markdown) format."
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[comment]: # "For best results, use a Markdown reader."
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
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Table of Contents
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-----------------
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- [Introduction to **MoltenVK**](#intro)
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- [Developing Vulkan Applications on *macOS, iOS, tvOS, and visionOS*](#developing_vulkan)
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- [Using the *Vulkan SDK*](#sdk)
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- [Using MoltenVK Directly](#download)
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- [Fetching **MoltenVK** Source Code](#install)
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- [Building **MoltenVK**](#building)
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- [Building from the Command Line](#command_line_build)
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- [Hiding _Vulkan_ API Symbols](#hiding_vulkan_symbols)
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- [Accessing _Metal_ Private API calls](#metal_private_api)
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- [Running **MoltenVK** Demo Applications](#demos)
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- [Using **MoltenVK** in Your Application](#using)
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- [**MoltenVK** and *Vulkan* Compliance](#compliance)
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- [Getting Support](#support)
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- [Contributing to **MoltenVK** Development](#contributing)
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<a name="intro"></a>
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Introduction to MoltenVK
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------------------------
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**MoltenVK** is a layered implementation of [*Vulkan 1.2*](https://www.khronos.org/vulkan)
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graphics and compute functionality, that is built on Apple's [*Metal*](https://developer.apple.com/metal)
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graphics and compute framework on *macOS*, *iOS*, *tvOS*, and *visionOS*. **MoltenVK** allows
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you to use *Vulkan* graphics and compute functionality to develop modern, cross-platform,
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high-performance graphical games and applications, and to run them across many platforms,
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including *macOS*, *iOS*, *tvOS*, *visionOS*, *Simulators*, and *Mac Catalyst* on *macOS 11.0+*,
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and all *Apple* architectures, including *Apple Silicon*.
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*Metal* uses a different shading language, the *Metal Shading Language (MSL)*, than
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*Vulkan*, which uses *SPIR-V*. **MoltenVK** automatically converts your *SPIR-V* shaders
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to their *MSL* equivalents.
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To provide *Vulkan* capability to the *macOS*, *iOS*, *tvOS*, and *visionOS* platforms,
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**MoltenVK** uses *Apple's* publicly available API's, including *Metal*. **MoltenVK**
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does **_not_** use any private or undocumented API calls or features, so your app will
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be compatible with all standard distribution channels, including *Apple's App Store*.
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The **MoltenVK** runtime package contains two products:
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- **MoltenVK** is a implementation of an almost-complete subset of the
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[*Vulkan 1.2*](https://www.khronos.org/vulkan) graphics and compute API.
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- **MoltenVKShaderConverter** converts *SPIR-V* shader code to *Metal Shading Language (MSL)*
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shader code, and converts *GLSL* shader source code to *SPIR-V* shader code and/or
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*Metal Shading Language (MSL)* shader code. The converter is embedded in the **MoltenVK**
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runtime to automatically convert *SPIR-V* shaders to their *MSL* equivalents. In addition,
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both the *SPIR-V* and *GLSL* converters are packaged into a stand-alone command-line
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`MoltenVKShaderConverter` *macOS* tool for converting shaders at development time from the command line.
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<a name="developing_vulkan"></a>
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Developing *Vulkan* Applications for *macOS, iOS, tvOS, and visionOS*
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---------------------------------------------------------------------
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<a name="sdk"></a>
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### Using the *Vulkan SDK*
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The recommended method for developing a *Vulkan* application for *macOS* is to use the
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[*Vulkan SDK*](https://vulkan.lunarg.com/sdk/home).
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The *Vulkan SDK* includes a **MoltenVK** runtime library for *macOS*. *Vulkan* is a layered
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architecture that allows applications to add additional functionality without modifying the
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application itself. The *Validation Layers* included in the *Vulkan SDK* are an essential debugging
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tool for application developers because they identify inappropriate use of the *Vulkan API*.
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If you are developing a *Vulkan* application for *macOS*, it is highly recommended that you use the
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[*Vulkan SDK*](https://vulkan.lunarg.com/sdk/home) and the **MoltenVK** library included in it.
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Refer to the *Vulkan SDK [Getting Started](https://vulkan.lunarg.com/doc/sdk/latest/mac/getting_started.html)*
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document for more info.
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Because **MoltenVK** supports the `VK_KHR_portability_subset` extension, when using the
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*Vulkan Loader* from the *Vulkan SDK* to run **MoltenVK** on *macOS*, the *Vulkan Loader*
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will only include **MoltenVK** `VkPhysicalDevices` in the list returned by
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`vkEnumeratePhysicalDevices()` if the `VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR`
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flag is enabled in `vkCreateInstance()`. See the description of the `VK_KHR_portability_enumeration`
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extension in the *Vulkan* specification for more information about the use of the
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`VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR` flag.
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<a name="download"></a>
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### Using MoltenVK Directly
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If you are developing a *Vulkan* application for *iOS*, *tvOS*, or *visionOS*, or are
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developing a *Vulkan* application for *macOS* and want to use a different version or
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build of the **MoltenVK** runtime library than provided in the *macOS Vulkan SDK*,
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you can access a pre-built MoltenVK binary library from the **MoltenVK** repository, by
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[selecting a repository commit from the list](https://github.com/KhronosGroup/MoltenVK/actions),
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and downloading the associated **MoltenVK** runtime library artifact.
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Finally, if you want a customized build of **MoltenVK**, you can follow the [instructions below](#install)
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to create a **MoltenVK** runtime library by fetching and building the **MoltenVK** source code.
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To learn how to integrate the **MoltenVK** runtime library into a game or application,
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see the [`MoltenVK_Runtime_UserGuide.md `](Docs/MoltenVK_Runtime_UserGuide.md)
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document in the `Docs` directory.
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<a name="install"></a>
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Fetching **MoltenVK** Source Code
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---------------------------------
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To fetch **MoltenVK** source code, clone this `MoltenVK` repository, and then run the
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`fetchDependencies` script to retrieve and build several external open-source libraries
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on which **MoltenVK** relies:
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1. Ensure you have `cmake` and `python3` installed:
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brew install cmake
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brew install python3
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For faster dependency builds, you can also optionally install `ninja`:
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brew install ninja
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2. Clone the `MoltenVK` repository:
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git clone https://github.com/KhronosGroup/MoltenVK.git
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3. Retrieve and build the external libraries:
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cd MoltenVK
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./fetchDependencies [platform...]
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When running the `fetchDependencies` script, you must specify one or more platforms
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for which to build the external libraries. The platform choices include:
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--all
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--macos
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--ios
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--iossim
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--maccat
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--tvos
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--tvossim
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You can specify multiple of these selections. The result is a single `XCFramework`
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for each external dependency library, with each `XCFramework` containing binaries for
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each of the requested platforms.
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The `--all` selection is the same as entering all of the other platform choices,
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and will result in a single `XCFramework` for each external dependency library,
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with each `XCFramework` containing binaries for all supported platforms and simulators.
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Running `fetchDependencies` repeatedly with different platforms will accumulate targets
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in the `XCFramework`, if the `--keep-cache` option is used on each invocation.
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For more information about the external open-source libraries used by **MoltenVK**,
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see the [`ExternalRevisions/README.md`](ExternalRevisions/README.md) document.
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<a name="building"></a>
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Building **MoltenVK**
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-------------------
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During building, **MoltenVK** references the latest *Apple SDK* frameworks. To access these frameworks,
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and to avoid build errors, be sure to use the latest publicly available version of *Xcode*.
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> ***Note:*** *Xcode 14* introduced a new static linkage model that is not compatible with previous
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versions of *Xcode*. If you link to a `MoltenVK.xcframework` that was built with *Xcode 14* or later,
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also use *Xcode 14* or later to link it to your app or game.
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>
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> If you need to use *Xcode 13* or earlier to link `MoltenVK.xcframework` to your app or game,
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first build **MoltenVK** with *Xcode 13* or earlier.
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>
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> Or, if you want to use *Xcode 14* or later to build **MoltenVK**, in order to be able to use the
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latest *Metal* capabilities, but need to use *Xcode 13* or earlier to link `MoltenVK.xcframework`
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to your app or game, first add the value `-fno-objc-msgsend-selector-stubs` to the `OTHER_CFLAGS`
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*Xcode* build setting in the `MoltenVK.xcodeproj` and `MoltenVKShaderConverter.xcodeproj` *Xcode*
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projects, build **MoltenVK** with *Xcode 14* or later, and then link `MoltenVK.xcframework`
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to your app or game using *Xcode 13* or earlier.
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**MoltenVK** can be built to support at least *macOS 10.11*, *iOS 9*, or *tvOS 9*, but the default
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_Xcode_ build settings in the included _Xcode_ projects are set to a minimum deployment target of
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*macOS 10.13*, *iOS 11*, and *tvOS 11*, which are the oldest OS versions supported by the current
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_Xcode_ version. If you require support for earlier OS versions, modify the `MACOSX_DEPLOYMENT_TARGET`,
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`IPHONEOS_DEPLOYMENT_TARGET`, or `TVOS_DEPLOYMENT_TARGET` build settings in _Xcode_ before building **MoltenVK**.
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>***Note:*** To support `IOSurfaces` on *iOS* or *tvOS*, **MoltenVK**, and any app that uses
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**MoltenVK**, must be built with a minimum **iOS Deployment Target** (aka `IPHONEOS_DEPLOYMENT_TARGET `)
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build setting of `iOS 11.0` or greater, or a minimum **tvOS Deployment Target** (aka `TVOS_DEPLOYMENT_TARGET `)
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build setting of `tvOS 11.0` or greater.
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Once built, the **MoltenVK** libraries can be run on *macOS*, *iOS*, *tvOS*, or *visionOS* devices
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that support *Metal*,or on the *Xcode* *iOS Simulator*, *tvOS Simulator*, or *visionOS Simulator*.
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- At runtime, **MoltenVK** requires at least *macOS 10.11*, *iOS 9.0*, *tvOS 9.0*,
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or *visionOS 1.0* (or *iOS 11* or *tvOS 11* if using `IOSurfaces`).
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- Information on *macOS* devices that are compatible with *Metal* can be found in
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[this article](http://www.idownloadblog.com/2015/06/22/how-to-find-mac-el-capitan-metal-compatible).
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- Information on *iOS* devices that are compatible with *Metal* can be found in
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[this article](https://developer.apple.com/library/content/documentation/DeviceInformation/Reference/iOSDeviceCompatibility/HardwareGPUInformation/HardwareGPUInformation.html).
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The `MoltenVKPackaging.xcodeproj` *Xcode* project contains targets and schemes to build
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and package the entire **MoltenVK** runtime distribution package, or to build individual
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**MoltenVK** or **MoltenVKShaderConverter** components.
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To build a **MoltenVK** runtime distribution package, suitable for testing and integrating into an app,
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open `MoltenVKPackaging.xcodeproj` in *Xcode*, and use one of the following *Xcode Schemes*, depending
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on whether you want a **_Release_** or **_Debug_** configuration, and whether you want to build for all
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platforms, or just one platform (in **_Release_** configuration):
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- **MoltenVK Package**
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- **MoltenVK Package (Debug)**
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- **MoltenVK Package (macOS only)**
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- **MoltenVK Package (iOS only)**
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- **MoltenVK Package (tvOS only)**
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- **MoltenVK Package (visionOS only)** _(requires Xcode 15+)_
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Each of these`MoltenVKPackaging.xcodeproj` *Xcode* project *Schemes* puts the resulting packages in the
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`Package` directory, creating it if necessary. This directory contains separate `Release` and `Debug`
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directories, holding the most recent **_Release_** and **_Debug_** builds, respectively.
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A separate `Latest` directory links to the most recent build, regardless of whether it was a **_Release_**
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or **_Debug_** build. Effectively, the `Package/Latest` directory points to whichever of the `Package/Release`
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or `Package/Debug` directories was most recently updated.
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With this packaging structure, you can follow the [instructions below](#using) to link your application
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to the **MoltenVK** libraries and frameworks in the `Package/Latest` directory, to provide the flexibility
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to test your app with either a **_Debug_** build, or a higher-performance **_Release_** build.
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<a name="command_line_build"></a>
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### Building from the Command Line
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If you prefer to build **MoltenVK** from the command line, or to include the activity in a larger build script,
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you can do so by executing a command similar to the following command within the `MoltenVK` repository folder,
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and identifying one of the *Xcode Schemes* from the list above. For example, the following command will build
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**MoltenVK** in the **_Debug_** configuration for *macOS* only:
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xcodebuild build -quiet -project MoltenVKPackaging.xcodeproj -scheme "MoltenVK Package (macOS only)" -configuration "Debug"
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Alternately, you can use the basic `Makefile` in the `MoltenVK` repository folder to build **MoltenVK**
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from the command line. The following `make` targets are provided:
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make
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make all
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make macos
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make ios
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make iossim
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make maccat
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make tvos
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make tvossim
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make all-debug
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make macos-debug
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make ios-debug
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make iossim-debug
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make maccat-debug
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make tvos-debug
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make tvossim-debug
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make clean
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make install
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- Running `make` repeatedly with different targets will accumulate binaries for these different targets.
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- The `all` target executes all platform targets.
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- The `all` target is the default target. Running `make` with no arguments is the same as running `make all`.
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- The `*-debug` targets build the binaries using the **_Debug_** configuration.
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- The `install` target will copy the most recently built `MoltenVK.xcframework` into the
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`/Library/Frameworks` folder of your computer. Since `/Library/Frameworks` is protected,
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you will generally need to run it as `sudo make install` and enter your password.
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The `install` target just installs the built framework, it does not first build the framework.
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You will first need to at least run `make macos` first.
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The `make` targets all require that *Xcode* is installed on your system.
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Building from the command line creates the same `Package` folder structure described above when
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building from within *Xcode*.
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When building from the command line, you can set any of the build settings documented
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in the `MoltenVK_Configuration_Parameters.md` file, by passing them in the command line,
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as in the following examples:
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make MVK_CONFIG_LOG_LEVEL=0
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or
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make macos MVK_CONFIG_USE_METAL_ARGUMENT_BUFFERS=2
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...etc.
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<a name="hiding_vulkan_symbols"></a>
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### Hiding _Vulkan_ API Symbols
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You can optionally build **MoltenVK** with the _Vulkan_ API static call symbols (`vk*`) hidden, to avoid
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library linking conflicts when statically bound to a _Vulkan_ loader that also exports identical symbols.
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To do so, when building **MoltenVK**, set the build setting `MVK_HIDE_VULKAN_SYMBOLS=1`.
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This build setting can be set in the `MoltenVK.xcodeproj` *Xcode* project, or it can be
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included in any of the `make` command-line build commands [mentioned above](#command_line_build).
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With `MVK_HIDE_VULKAN_SYMBOLS=1`, the _Vulkan_ `vkGetInstanceProcAddr()` call remains
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statically bound, to provide the application with the ability to retrieve the remaining
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_Vulkan_ API calls as function pointers.
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<a name="metal_private_api"></a>
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### Accessing _Metal_ Private API calls
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You can optionally build **MoltenVK** with access to private _Metal_ API calls, also known
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as "Service Provider Interfaces" (SPIs). Doing so will allow **MoltenVK** to extend its
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functionality by using certain private _Metal_ API calls, but it will also disqualify the
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app from being distributed via _Apple_ App Stores.
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To do so, when building **MoltenVK**, set the build setting `MVK_USE_METAL_PRIVATE_API=1`.
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This build setting can be set in the `MoltenVK.xcodeproj` *Xcode* project, or it can be
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included in any of the `make` command-line build commands [mentioned above](#command_line_build).
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Functionality added with `MVK_USE_METAL_PRIVATE_API` enabled includes:
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- `VkPhysicalDeviceFeatures::wideLines`
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- `VkPhysicalDeviceFeatures::logicOp`
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- `VkPhysicalDeviceFeatures::depthBounds` *(requires an AMD GPU)*
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- `VkPhysicalDevicePortabilitySubsetFeaturesKHR::samplerMipLodBias`
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- `VkGraphicsPipelineRasterizationCreateInfo::sampleMask`, using `MTLRenderPipelineDescriptor.sampleMask` instead of emulating it in the fragment shader
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<a name="demos"></a>
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Running **MoltenVK** Demo Applications
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--------------------------------------
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Once you have compiled and built the **MoltenVK** runtime distribution package from this **MoltenVK** repository,
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as described in the [Building **MoltenVK**](#building) section, you can explore how **MoltenVK** provides *Vulkan*
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support on *macOS*, *iOS*, and *tvOS* by investigating and running the demo application that is included in **MoltenVK**.
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The **MoltenVK** _Cube_ demo app is located in the `Demos` folder. The demo app is available as an *Xcode* project.
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To review and run the included demo app, open the `Demos/Demos.xcworkspace` workspace in *Xcode*.
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Please read the [`Demos/README.md`](Demos/README.md) document for a description and instructions for running the
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included *Cube* demo app, and for external links to more sophisticated demo applications that can be run on **MoltenVK**.
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<a name="using"></a>
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Using **MoltenVK** in Your Application
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--------------------------------------
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Once you have compiled and built the **MoltenVK** runtime distribution package from this **MoltenVK** repository,
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as described in the [Building **MoltenVK**](#building) section, follow the instructions in the Installation
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section of the [`Docs/MoltenVK_Runtime_UserGuide.md`](Docs/MoltenVK_Runtime_UserGuide.md#install) document
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in the `Docs` directory, to link the **MoltenVK** libraries and frameworks to your application.
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The runtime distribution package in the `Package/Latest` directory is a stand-alone package, and you can copy
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the contents of that directory out of this **MoltenVK** repository into your own application building environment.
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<a name="compliance"></a>
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**MoltenVK** and *Vulkan* Compliance
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------------------------------------
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**MoltenVK** is designed to be an implementation of a *Vulkan 1.2* subset that runs on *macOS*, *iOS*,
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*tvOS*, and *visionOS* platforms by mapping *Vulkan* capability to native *Metal* capability.
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The fundamental design and development goal of **MoltenVK** is to provide this capability in a way that
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is both maximally compliant with the *Vulkan 1.2* specification, and maximally performant.
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Such compliance and performance is inherently affected by the capability available through *Metal*,
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as the native graphics driver on *macOS*, *iOS*, *tvOS*, and *visionOS* platforms. *Vulkan*
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compliance may fall into one of the following categories:
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- Direct mapping between *Vulkan* capabilities and *Metal* capabilities. Within **MoltenVK**, the vast
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majority of *Vulkan* capability is the result of this type of direct mapping.
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- Synthesized compliance through alternate implementation. A small amount of capability is provided using
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this mechanism, such as via an extra render or compute shader stage.
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- Non-compliance. This appears where the capabilities of *Vulkan* and *Metal* are sufficiently different, that
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there is no practical, or reasonably performant, mechanism to implement a *Vulkan* capability in *Metal*.
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Because of design differences between *Vulkan* and *Metal*, a very small amount of capability falls into this
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category, and at present **MoltenVK** is **_not_** fully compliant with the *Vulkan* specification. A list of
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known limitations is documented in the [`MoltenVK_Runtime_UserGuide.md`](Docs/MoltenVK_Runtime_UserGuide.md#limitations)
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document in the `Docs` directory.
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The **MoltenVK** development team welcomes you to [post Issues](https://github.com/KhronosGroup/MoltenVK/issues)
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of non-compliance, and engage in discussions about how compliance can be improved, and non-compliant features can
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|
be implemented or worked around.
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**MoltenVK** is a key component of the
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[*Khronos Vulkan Portability Initiative*](https://www.khronos.org/vulkan/portability-initiative),
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|
whose intention is to provide specifications, resources, and tools to allow developers to understand and design
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their *Vulkan* apps for maximum cross-platform compatibility and portability, including on platforms, such as
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*macOS*, *iOS*, *tvOS*, and *visionOS*, where a native *Vulkan* driver is not available.
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<a name="support"></a>
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Getting Support
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|
----------------
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|
|
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- If you have a question about using **MoltenVK**, you can ask it in
|
|
[*MoltenVK Discussions*](https://github.com/KhronosGroup/MoltenVK/discussions).
|
|
This forum is monitored by **MoltenVK** contributors and users.
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|
|
|
- If you encounter an issue with the behavior of **MoltenVK**, or want to request an enhancement,
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|
you can report it in the [*MoltenVK Issues List*](https://github.com/KhronosGroup/MoltenVK/issues).
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|
|
|
- If you encounter an issue with the *Vulkan SDK*, including the *Validation Layers*, you can report it in the
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|
[*Vulkan SDK Issues List*](https://vulkan.lunarg.com/issue/home).
|
|
|
|
- If you explore **MoltenVK** and determine that it does not meet your requirements at this time, we would appreciate
|
|
hearing why that is so, in [*MoltenVK Discussions*](https://github.com/KhronosGroup/MoltenVK/discussions).
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|
The goal of **MoltenVK** is to increase the value of *Vulkan* as a true cross-platform ecosystem, by providing
|
|
*Vulkan* on *Apple* platforms. Hearing why this is currently not working for you will help us in that goal.
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|
<a name="contributing"></a>
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|
|
Contributing to **MoltenVK** Development
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|
----------------------------------------
|
|
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|
As a public open-source project, **MoltenVK** benefits from code contributions from a wide range of developers,
|
|
and we encourage you to get involved and contribute code to this **MoltenVK** repository.
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|
|
|
To contribute your code, submit a [Pull Request](https://github.com/KhronosGroup/MoltenVK/pulls)
|
|
to this repository. The first time you do this, you will be asked to agree to the **MoltenVK**
|
|
[Contributor License Agreement](https://cla-assistant.io/KhronosGroup/MoltenVK).
|
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|
|
|
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### Licensing
|
|
|
|
**MoltenVK** is licensed under the Apache 2.0 license. All new source code files should include a
|
|
copyright header at the top, containing your authorship copyright and the Apache 2.0 licensing stub.
|
|
You may copy the text from an existing source code file as a template.
|
|
|
|
The Apache 2.0 license guarantees that code in the **MoltenVK** repository is free of Intellectual Property
|
|
encumbrances. In submitting code to this repository, you are agreeing that the code is free of any Intellectual
|
|
Property claims.
|
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|
|
|
|
### *Vulkan* Validation
|
|
|
|
Despite running on top of *Metal*, **MoltenVK** operates as a *Vulkan* core layer. As such, as per the
|
|
error handling guidelines of the [*Vulkan* specification](https://www.khronos.org/registry/vulkan/specs/1.2/html/vkspec.html#fundamentals-errors), **MoltenVK** should not perform *Vulkan* validation. When adding functionality
|
|
to **MoltenVK**, avoid adding unnecessary validation code.
|
|
|
|
Validation and error generation **_is_** appropriate within **MoltenVK** in cases where **MoltenVK** deviates
|
|
from behavior defined by the *Vulkan* specification. This most commonly occurs when required behavior cannot
|
|
be mapped to functionality available within *Metal*. In that situation, it is important to provide feedback to
|
|
the application developer to that effect, by performing the necessary validation, and reporting an error.
|
|
|
|
Currently, there is some excess *Vulkan* validation and error reporting code within **MoltenVK**, added before
|
|
this guideline was introduced. You are encouraged to remove such code if you encounter it while performing other
|
|
**MoltenVK** development. Do not remove validation and error reporting code that is covering a deviation in
|
|
behavior from the *Vulkan* specification.
|
|
|
|
|
|
### Memory Management
|
|
|
|
*Metal*, and other *Objective-C* objects in *Apple's SDK* frameworks, use reference counting for memory management.
|
|
As a contributor to **MoltenVK**, when instantiating *Objective-C* objects, it is important that you do not rely on
|
|
the app providing *autorelease pools* to do memory management for you. Because many *Vulkan* games and apps may be
|
|
ported from other platforms, they will often not automatically include autorelease pools in their threading models.
|
|
|
|
As a contributor to **MoltenVK**, avoid the use of the *Metal* `autorelease` method, or any object *Metal* creation
|
|
methods that imply internal use of `autorelease`, (eg- `[NSString stringWithFormat: ]`, etc). Instead, favor object
|
|
creation methods that return a retained object (eg- `[[NSString alloc] initWithFormat: ]`, etc), and manually track
|
|
and release those objects. If you need to use autoreleased objects, wrap your code in an `@autoreleasepool {...}` block.
|
|
|
|
|
|
### Code Formatting
|
|
|
|
When contributing code, please honour the code formatting style found in existing **MoltenVK** source code.
|
|
In future, this will formally be enforced using `clang-format`.
|