feat(input): Implement SDL3 input and window management

[githubawn]

SDL3 Input Backend
This PR implements an SDL3-based input and windowing backend as a modern alternative to DirectInput and Win32 window creation. By utilizing SDL3, we bypass DirectInput emulation layers on modern systems, providing a lower-latency pipeline for Windows 11 and Wine/Linux users.

Input handling
Unified event manager that centralizes keyboard, mouse, and gamepad events into a thread-safe buffer

Gamepad Support (v0.1)
This is an initial baseline implementation focused on providing functional out-of-the-box playability. Feedback is encouraged regarding the ergonomics and logic of these default mappings.

Input	Action
Left Stick	Virtual mouse cursor
Right Stick	Camera pan (arrow keys)
LT (hold)	Currently unmapped
RT (hold)	Force Attack (LCTRL)
LB	Select All (Q)
RB	Queue Orders (LSHIFT)
A	Left click
AA	Guard mode
B	Right click
X	Attack Move (A)
Y	Stop (S)
D-Pad	Control groups 1–4
Start	Menu (ESC)
Back	Last radar event (SPACE)
L3	Next idle worker
R3	Snap to command center

Scope Note: This implementation provides a hardcoded default layout to establish core functionality. Advanced features, such as input remapping, radial menus, adjustable deadzones, are currently out of scope for this PR and may be addressed in future iterations.

The foundation of this backend was built using the SDL3 input work from the generalsX fork by fbraz3.

todo:
properly attribute all forks that have inspired this.

[greptile-apps]

Greptile Summary

This PR introduces a complete SDL3-based input and window management backend for both Generals and Zero Hour, providing a unified keyboard/mouse/gamepad event pipeline that bypasses DirectInput emulation on Windows 11 and Wine/Linux. Application startup logic is also consolidated into a new AppMain helper shared by both the Win32 and SDL3 entry points.

• SDL3 input stack: SDL3InputManager drives a ring-buffered event queue fed by SDL_PollEvent; SDL3Mouse and SDL3Keyboard drain it each frame; processGamepadInput() synthesises virtual key and mouse events from stick/button state and injects them into the same queues.
• Cursor rendering: SDL3CursorManager loads .ani files via SDL3_image and creates SDL3 animated cursors; direction bounds are loop-guarded and hotspots are read from surface properties.
• Controller-aware scrolling: LookAtTranslator gains setControllerInputActive() and getControllerScrollScale() to suppress screen-edge scroll and proportionally reduce key-scroll speed while a stick is active; all TheInGameUI/TheTacticalView/TheMouse calls are now null-guarded.

Confidence Score: 5/5

The SDL3 backend is self-contained behind compile-time guards and does not alter the Win32 path; the changes to LookAtXlat.cpp are defensive improvements (null guards, idempotent scroll state) that apply to both backends equally.

The numerous functional issues raised in earlier review rounds — window ID missing from synthetic events, scancode truncation, direction-count bounds, sentinel mismatch in event queues, TheMessageStream null checks, setScrolling side-effect loss, and headless init skip — are all addressed in this version. The remaining findings are style-level concerns that do not affect runtime behaviour.

Files Needing Attention: Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Input.cpp — the closeGamepad() cleanup block and the redundant axis reads are worth tidying before merge.

Important Files Changed

Filename	Overview
Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Input.cpp	Core of the SDL3 input backend — implements SDL3Mouse, SDL3Keyboard, and SDL3InputManager with a ring-buffer event queue, gamepad support, and virtual event injection; has minor style issues in closeGamepad() (if-bodies on same line) and a redundant left-stick axis read, but all previously flagged functional bugs appear fixed.
Core/GameEngineDevice/Include/SDL3Device/GameClient/SDL3Input.h	Header for SDL3 input classes; previously flagged scancode truncation and missing m_SDLWindow member are now fixed; dead-code field m_IsCaptured is the only remaining issue.
Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Cursor.cpp	ANI cursor loader using SDL3_image; previous direction-count bounds issue is fixed with the loop guard; now uses SDL3's native SDL_CreateAnimatedCursor instead of a hand-rolled frame array.
Core/GameEngineDevice/Source/SDL3Device/Common/SDL3GameEngine.cpp	SDL3 game-engine lifecycle: window/input-manager setup, minimized-loop with throttle and LAN keep-alive, and UTF-8 text input forwarding; headless path now correctly falls through to GameEngine::init().
Core/Main/SDL3Main.cpp	SDL3 entry point: SDL_Init, window creation, splash-screen blit, and game main loop; SDL_Init failure correctly returns early; headless path skips SDL entirely.
Core/Main/AppMain.cpp	New shared application lifecycle helper (initBeforeWindow, initAfterWindow, run, shutdown) refactored out of both WinMain files; centralises critical-section setup, version management, and instance-mutex logic.
Core/GameEngine/Source/GameClient/MessageStream/LookAtXlat.cpp	Extended with controller-aware scrolling: setControllerInputActive() stops screen-edge scroll when the stick is active, getControllerScrollScale() slows key-scroll relative to zoom; setScrolling/stopScrolling null-guards for all global pointers now added; previously flagged side-effect regressions are resolved.
Generals/Code/Main/WinMain.cpp	Refactored to delegate lifecycle calls to AppMain; removes duplicate startup code; no functional regressions visible.
GeneralsMD/Code/Main/WinMain.cpp	Same AppMain refactor as the Generals WinMain; stub SDL3 surface variable added under RTS_SDL3_ENABLE guard for future splash support.

Sequence Diagram

sequenceDiagram
    participant OS as OS / Hardware
    participant SDL3 as SDL3 Event Pump
    participant IM as SDL3InputManager
    participant KB as SDL3Keyboard
    participant MS as SDL3Mouse
    participant GP as Gamepad subsystem
    participant GE as SDL3GameEngine
    participant LX as LookAtTranslator
    participant GC as GameClient

    OS->>SDL3: Raw input (keyboard/mouse/gamepad)
    GE->>IM: update() [each frame via pollSDL3Events]
    IM->>SDL3: SDL_PollEvent loop
    SDL3-->>IM: SDL_Event
    IM->>IM: Route: key → addKeyboardSDLEvent mouse → addMouseSDLEvent
    IM->>GP: processGamepadInput()
    GP->>GP: Read axes and buttons
    GP->>IM: virtualPulseKey() / virtualPulseMouse()
    GP->>LX: setControllerInputActive(bool)
    LX->>LX: Suppress edge-scroll, scale key-scroll
    GC->>KB: getKey() [keyboard poll]
    KB->>IM: getNextKeyboardEvent()
    IM-->>KB: SDL_KeyboardEvent
    KB-->>GC: KeyboardIO
    GC->>MS: getMouseEvent() [mouse poll]
    MS->>IM: getNextMouseEvent()
    IM-->>MS: SDL_MouseEvent
    MS->>MS: translateEvent then scaleMouseCoordinates
    MS-->>GC: MouseIO (scaled coords)

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_{Reviews (37): Last reviewed commit: "greptile feedback" | Re-trigger Greptile}

[stephanmeesters]

Do we need this, maybe better placed in UnicodeString? Or some other helper if it's generic stuff

[githubawn]

Good point.

I looked at #2045 and #2528 which are working on UTF-8 infrastructure.
If one of those lands first, forwardTextInputEvent could use the bulk Utf8_To_Utf16Le conversion and iterate the resulting wchar_t string directly, making this function unnecessary.

Happy to refactor once there's a clear winner between those two. For now it's self-contained here.

[xezon]

This needs polishing. Not yet reviewed extensively until the obvious style issues are fixed.

[xezon]

This function looks out of place. Bobtista was also working on Utf8 decoding in another change. It would be good to have this as a utility somewhere accessible engine wide, and not specific to this file.

[githubawn]

Once #2528 lands I will migrate this.

[xezon]

Perhaps also check Fighter19's fork for SDL related implementations. As far as I am aware he has it all done.

[githubawn]

I have looked at all existing forks and attributed where possible.

[bobtista]

How about changing display-mode? eg getDisplayModeCount() / getDisplayModeDescription() using SDL_GetFullscreenDisplayModes + desktop mode + resolution filtering. EDIT: Also account for mouse position which can sometimes not match clicks to cursor position.

[bobtista]

Is it better to use SDL3InputManager (+ SDL3CursorManager) or to split out SDL3Keyboard + SDL3Mouse that subclass the engine's existing Keyboard/Mouse base classes?

[xezon]

Will we have a SDL3Main or not?

[githubawn]

I've started cleaning up the style and structural issues in the latest commits.

Regarding SDL3Main: The main benefit of the current approach is that we keep the game's native Win32 WinMain entry point and startup sequence intact.

To get rid of the #ifdef blocks in WinMain while minimizing duplication, I can move the window initialization out into SDL3Window.

Regarding splitting out subclasses: I don't think splitting the input handling into isolated SDL3Keyboard and SDL3Mouse subclasses is the right way. It runs contrary to how SDL3 tries to be a unified way; it relies on a single event pump where all keyboard, mouse, and gamepad signals flow together.

[xezon]

I don't think splitting the input handling into isolated SDL3Keyboard and SDL3Mouse subclasses is the right way.

But this is how you currently have set this up. What is the plan here?

[bobtista]

There's a lot of SDL stuff in my stack that you could use here, and I'd extract this into a separate SDL3Gamepad translator vs adopt its central input manager. See if Gippity can take a stab at taking the best of both

[bobtista]

It's improved a lot. I left more comments - also, there are thousands of lines changed in MainMenuUtils.cpp, CHATAPI.cpp, and both OptionsMenu.cpp that are just line ending stuff, could remove that and let a formatting pass deal with it later. My stack has working implementations of several of the inline items (close → MSG_META_DEMO_INSTANT_QUIT routing, focus → setIsActive + keyboard reset, Return → GWM_IME_CHAR commit, cursor position sync, deferred resize) if you want to lift from them.