[Epic] Core Updates - Fix and update out-of-date native cores

[JoeMatt]

Overview

Several native emulator cores are out of date, have bugs, or are disabled. Updating these is critical for competing with Delta, Manic EMU, and RetroArch.

Cores Needing Work

PVDosBox

• Status: Compiles, keyboard+mouse recently added ([Agent] DosBox keyboard and mouse mapping support #2457)
• Issues: Mouse touch input buggy, graphics completely glitched
• Note: RetroArch dosbox-pure works but native version preferred

PVDuckStation (PSX)

• Status: Unknown/forgotten, core code is years out of date
• Value: Native PSX with upscaling would differentiate from Mednafen/RetroArch PSX cores
• Note: Cheats exist but disabled

PVMupen64Plus (N64)

• Status: Core out of date, plugins (GLideN64, Rice, RDP) mostly current
• Tasks: Update core, verify large ROM hack patch (may be in mainline now)
• Variants: Mupen64Plus and Mupen64Plus-NX

PVBeetlePSX

• Status: Left off moving to makefile build with dylib linking + dummy .framework
• Note: Alternative build method for PVCoreBridgeRetro wrapped cores

PVDesmume2015 (DS)

• Status: Basically working with touch support
• Issues: Core code out of date, dual-screen skins disabled
• Note: Manic EMU and Delta support dual-screen DS skins (screens resize/move)

PVMelonDS (DS)

• Status: Basically working with touch support
• Issues: Colors out of whack, core code out of date, dual-screen skins disabled
• Note: Getting colors fixed + dual-screen skins would be a big win

Cross-Cutting: Dual-Screen Skin System

• Delta and Manic EMU support dual-screen DS skins where screens move and resize
• Never got this working in Provenance
• Impossible with RetroArch wrapped dylib cores
• Requires native cores (Desmume2015, MelonDS) to be working properly first

Priority Order

1. MelonDS color fix (user-visible bug)
2. DuckStation revival (high-value PSX upscaling)
3. Mupen64Plus core update
4. Dual-screen skin system
5. DosBox graphics fix
6. BeetlePSX build method

[github-actions]

Audit of PR #2373 (feature/new-cores/libretrogles) vs develop

Completed a full diff analysis of the stale feature/new-cores/libretrogles branch (PR #2373) against current develop. Here's the comprehensive status update:

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What develop has already absorbed (from the past year)

3D GLES/GL Core Support ✅

• a20b7c788 — "RA core allow 3d gles cores now, vecx gliden" — RetroArch wrapper now supports 3D GLES cores. VecX switched from forced-software to hardware rendering.
• GL pixel format pipeline improvements (several commits)
• DosBox GL/video/mouse fixes

Virtual Keyboard + Mouse Overlay ✅ (Full system)

• supportsVirtualKeyboard / supportsVirtualMouse added to PVEmulatorCore ([Agent] feat: Add supportsVirtualKeyboard/Mouse to PVEmulatorCore #2587)
• SwiftUI QWERTY keyboard overlay ([Agent] feat: VirtualKeyboardView — SwiftUI QWERTY overlay with haptics and dismiss gesture #2591)
• Mouse cursor overlay for pointer-based cores ([Agent] PVUI: Mouse cursor overlay for pointer-based cores #2590)
• Platform-specific layouts: C64, ZX Spectrum, Amstrad CPC ([Agent] feat(PVUI): Platform-specific keyboard layouts: C64, ZX Spectrum, Amstrad CPC #2595)
• Wired into PVEmulatorViewController ([Agent] feat: Wire virtual keyboard and cursor into PVEmulatorViewController #2594)
• Hardened keyboard event pipeline for libretro cores ([Agent] feat: Harden keyboard event pipeline for libretro cores #2589)
• tvOS Siri Remote keyboard/mouse passthrough ([Agent] tvOS: Siri Remote keyboard/mouse passthrough + D-pad virtual keyboard #2593)
• Compact keyboard + function-row-only variants ([Agent] feat(PVUI): Compact keyboard + function-row-only virtual keyboard variants #2588)

DS Dual-Screen Skin System ✅

• 3fdbdd905 — Phases 1-3 merged — screens can resize/move for DS games

DuckStation Cheats ✅

• GameShark cheat support enabled and working

Dolphin ✅ (partial)

• Landscape Vulkan fixed (f595ca97c)
• Shaders working (61d5e14aa)
• Dolphin libretro core added to RetroArch (not yet used due to GL issues)

Desmume2015 (partial) ✅

• Touch/mouse inputs added to libretro.h wrapper
• Core options wired

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What's still in PR #2373 that hasn't landed (and is worth saving)

Flycast — Libretro Mode Scaffold

The PR set up #ifdef LIBRETRO guards throughout the Flycast bridge to support running Flycast as a pure libretro core (without the full upstream Flycast native codebase). Key pieces:

• PVFlycastEmuCore.swift: Added didMoveJoystick forwarding (only button press/release existed before)
• PVFlycastCore+Controls.mm: extern declarations for controller arrays in libretro mode
• PVFlycastCore.h: Updated base class to PVLibRetroGLESCoreBridge
  Blocker: retro_hw_render_callback not wired to Metal/MoltenVK — no video output.
  Status: [Core] Flycast Redo 1 #2369

BeetlePSX — Swift Core Scaffold

New Swift/ObjC files that structure the core cleanly:

• CoreOptions.swift, CorePlist.swift, CorePlist-Generated.swift, PVBeetlePSXCore.swift, PVBeetlePSXCoreBridge.mm
  Blocker: Same hw_render + semaphore lock issue as Flycast.
  Status: [Core] Beetle PSX #2368

Dolphin — Experimental Config Tuning

The PR had several experimental Dolphin config changes that may or may not be improvements:

• bMMU = true
• bDSPThread = true
• bCPUThread = false (split CPU/GPU thread)
• bJITOff = true for non-jailbroken devices
• SConfig::GetInstance().SaveSettings() called after init
• Ubershader mode set to SynchronousUberShaders on WMUserCreate
• g_Config.aspect_mode = AspectMode::Stretch
  These are in the PR but not merged — would need testing to validate.

DuckStation — MoltenVK Path Fix

Critical path fix: bundle.bundlePath + "/Frameworks/MoltenVK.framework/MoltenVK" instead of bundle.sharedFrameworksPath. If Vulkan is broken in DuckStation, this is likely why.
See also: #2543

fMSX — Video Format

Video renders but in the wrong format. May be partially addressed by GL pixel format pipeline improvements on develop. Worth retesting.
Status: #2372

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The shared blocker: retro_hw_render_callback

For Flycast, BeetlePSX, and any other libretro core using hardware rendering (RETRO_ENVIRONMENT_SET_HW_RENDER), the core requests a GL/Vulkan context via retro_hw_render_callback. The Provenance libretro bridge needs to:

1. Intercept this environment callback
2. Create/provide a real OpenGL ES or Vulkan context (via MoltenVK)
3. Make it current before each retro_run() call
4. Pass the framebuffer back to the Metal render pipeline

This is the single biggest unresolved piece for native hw-render libretro cores. Solving it once would unblock Flycast, BeetlePSX, and potentially Play! (PS2), FreeIntv, and others.

This deserves its own issue/spike.

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Recommended new issues

1. [Spike] libretro RETRO_ENVIRONMENT_SET_HW_RENDER bridge for OpenGL/Vulkan cores — shared blocker for Flycast + BeetlePSX
2. [Core] Flycast: Complete video output for native libretro mode — Part of [Core] Flycast Redo 1 #2369
3. [Core] Dolphin: Evaluate experimental config from PR Feature/new cores/libretrogles #2373 — bMMU, bDSPThread, bCPUThread settings