iOS support test branch

[untoldengine]

Hi Javier, this is the branch I referred to in your PR.

It is called:
feature/enable_ios_support_test

Again, if you feel that it will be helpful, please use it as a reference.
The only thing that it is missing is essentially the dimensions for the mtkview. I hardcoded those values during the test and the engine worked on my iOS device.

Here is a rundown of what I did.

TL;DR:

• Editor/AppKit code is gated for macOS only;
• input was abstracted;
• Package.swift links frameworks conditionally and ships platform metallibs.

What changed

• Swift conditionals

  • Wrapped all Editor sources with Swift conditional compilation:

    #if canImport(AppKit)
    // Editor (AppKit) code
    #endif

  • Used #if os(macOS) where behavior is OS-specific (e.g., NSApplication/window setup).
  • Goal: keep AppKit code out of iOS/visionOS/tvOS/Catalyst builds.

• InputSystem abstraction

  • Kept a platform-agnostic core API.
  • Added AppKit-specific handlers on macOS and a UIKit path for iOS (same engine callbacks).
  • Ensured no NS* / UI* types leak into the core.

• Package.swift

  • Declared iOS support:

    platforms: [
      .macOS(.v14),
      .iOS(.v17),
    ]

  • Switched to conditional linking (removed unsafeFlags):

    .linkedFramework("Metal"),
    .linkedFramework("QuartzCore", .when(platforms: [.macOS, .iOS])),
    .linkedFramework("AppKit", .when(platforms: [.macOS])),
    .linkedFramework("UIKit", .when(platforms: [.iOS])),

  • Included platform metallibs as resources:
    • UntoldEngineKernels.metallib (macOS)
    • UntoldEngineKernels-ios.metallib (iOS device)
    • UntoldEngineKernels-iphonesim.metallib (iOS Simulator)

• Metallib loading

  • Runtime selection based on platform/simulator:

    #if os(iOS)
      #if targetEnvironment(simulator)
      let name = "UntoldEngineKernels-iphonesim"
      #else
      let name = "UntoldEngineKernels-ios"
      #endif
    #else
      let name = "UntoldEngineKernels"
    #endif
    let url = Bundle.module.url(forResource: name, withExtension: "metallib")!

• Logger

  • Sink/backlog/broadcast machinery behind:

    #if canImport(AppKit)
    // sink storage + replay
    #endif

  • Simple console logging remains cross-platform (option to use os.Logger on iOS later).

• Executables

  • Wrapped DemoGame / StarterGame sources with #if os(macOS) so choosing an iOS destination in Xcode doesn’t attempt to link AppKit.
  • For iOS, run via a small host app (SwiftUI/UIViewController) that depends on the UntoldEngine package and embeds the engine’s MTKView.

Quick iOS smoke test

For a quick test, I hardcoded the dimension values. This is not present in the branch.

let defaultSize = CGSize(width: 1920, height: 1080) // pixels
renderer.metalView.autoResizeDrawable = false
renderer.metalView.drawableSize = defaultSize

I tried to keep the commit history as clean as possible so you can follow my changes.

thanks. Again, feel free to use if you think it will be helpful.

[miogds]

I think this branch is a better starting point for the cross-platform compilation on all Apple OSes. Also, it’s better to push this version to the develop branch and after apply my PR, so we will have also a native SwiftUI version without the need to create a hosting app for every platform.

Maybe my pull request will not work after this branch. If this is the case, I can get your branch first and do the merge in my branch and do the pull request again. Just tell me if you can't merge.

[untoldengine]

Ok. I'll merge this branch to develop tomorrow morning. I also think the conflicts will be minimal with your pr.

Thanks.

[miogds]

I reviewed the branch, and maybe the only conflict we can have is that I made some changes in the SceneView to make it compatible with both macOS and iOS. The rest of the changes should be trivial to merge.

[miogds]

I tested the develop version and it works on iOS and macOS but not in the simulators.

Do you want me to check the simulators? I think I prefer to keep working on all simulators first, make it compile and run, because it’s faster to try all the devices like watchOS, tvOS and VisionOS instead of testing in the device, especially VisionOS because I need to put the glasses on and off all the time.

I'm guessing the problem of not running on the simulators could be because the metal lib is not compiled for that, but I need to dig deeper to check what the issue is.

[miogds]

I just checked and there were 2 problems. First, I had to compile the metal lib, which was easy, and I added the option in the build script.

The other problem was when creating some depth textures, in the simulator they can't be .shared, it's forbidden in the Simulators, but not in the devices. They should be private, most of the common cases, or memoryless if they’re temporary.

To make it run in the simulator, I added an ifdef macro to change the storage option to .private if it’s the simulator and left the .shared for the actual devices, but maybe you should look at the storage option because Metal documents say it's not recommended for depth, stencil, or depth stencil textures.

[untoldengine]

Metal recommends the depth texture to be private?

[miogds]

Yes, at least that's what the error says in the simulator. On the device I don't get any error.

In the documentation https://developer.apple.com/documentation/metalkit/mtkview/depthstencilstoragemode/ the default value is .private

But maybe we should initialize the values from the metal view, which is the recommended approach, instead of setting directly a fixed value because it depends on the device and could be different, but that is something I leave to you to check because at this moment you know more than me about metal.