iOS port

[Markos-Th09]

Overview

I am working on porting Unleashed Recompiled to iOS. Since this is currently early stage I am opening this for feedback and evaluating the possibility of including this upstream. technical review, testing, and collaborative debugging. This is currently not in a mergeable state and is intended for technical review, testing, and collaborative debugging.

This also requires modifications to submodules. I am already working on upstreaming the changes to plume to make it compatible with iOS (renderbag/plume#102). However, for nativefiledialog-extended, it would be unlikely that this could be upstreamed or accepted as the current implementation is very much incomplete and mobile operating systems don't seem to be within the scope of the library. How should this be handled? I have identified the following options

1. Strip the iOS-specific NFD API implementation out of the submodule tree completely and compile it directly as part of this project's core source directories instead of linking against the actual NFD for iOS.
2. Fork nativefiledialog-extended and include these changes
3. Use an iOS specific implementation instead completely bypassing NFD

Known Blocking Issues

I have outlined all currently known in detail at my fork's issues page but to summarize:

• Synchronization issues in critical sections that cause deadlock and thread starvation issues specific only to iOS (Synchronization bugs in RtlEnterCriticalSection/RtlLeaveCriticalSection Markos-Th09/UnleashedRecomp#1)
• Broken depth buffer (The depth buffer is broken on iOS Markos-Th09/UnleashedRecomp#2)
• Major performance degradation compared to macOS (Major performance degradation compared to macOS Markos-Th09/UnleashedRecomp#3)

Compatibility

Since the game utilizes DXT/BC compressed textures, only very recent iOS devices natively support them. Specifically according to the Metal feature set tables:

• A17 Pro or later, A18-series or later (Apple9 Family GPUs or later)
• Apple M-series chips (M1, M2, M3, M4 or newer)

This corresponds to:

• iPhone 15 Pro / 15 Pro Max and newer
• iPhone 16 / 16 Plus / 16 Pro / 16 Pro Max / 16e and newer
• iPad mini (A17 Pro) and newer
• iPad Pro models with M-series chips (M1 / 11-inch 3rd gen / 12.9-inch 5th gen or newer)
• iPad Air models with M-series chips (M1 / 5th gen or newer)

The possibility of transcoding textures at installation time to another format like ASTC to improve compatibility could be considered in the future, but this adds significant complexity.