feat(input): Implement SDL3 input and window management by githubawn · Pull Request #2639 · TheSuperHackers/GeneralsGameCode

githubawn · 2026-04-20T14:56:39Z

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
Animated cursor support via .ani (RIFF) file loading.

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)	Precision Mode
RT (hold)	Force Attack (LCTRL)
LB	Select All (Q)
RB	Queue Orders (LSHIFT)
A	Left click
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: replicate to generals

greptile-apps · 2026-04-20T15:05:09Z

Greptile Summary

This PR introduces a complete SDL3-based input and windowing backend as a compile-time alternative to the legacy Win32/DirectInput path, selectable via the SAGE_USE_SDL3 CMake option (enabled by default for modern builds). The implementation centralises keyboard, mouse, and gamepad events through a unified ring-buffer manager and adds animated .ani/RIFF cursor loading via SDL3_image.

SDL3InputManager / SDL3Mouse / SDL3Keyboard — new input layer with coordinate scaling, directional cursor animation, and a hardcoded gamepad mapping that emits synthetic mouse and keyboard events.
SDL3GameEngine — new GameEngine subclass handling window creation, text-input routing (with custom UTF-8 decoder), minimised-window throttling, and all factory methods wired to the existing W3D/Miles subsystems.
WinMain.cpp — SDL3 window and splash-screen path added under SAGE_USE_SDL3 guards; vcpkg/FetchContent dependency management added via cmake/sdl3.cmake.

Confidence Score: 5/5

Safe to merge; all new code is behind the SAGE_USE_SDL3 compile flag and does not touch the legacy Win32/DirectInput path

The SDL3 backend is entirely additive and compile-flag gated. The ring-buffer event routing, coordinate scaling, and gamepad mapping are structurally sound. The issues found are style nits (NULL vs nullptr, single-line if body) and a type-punning pattern in the RIFF parser that is unlikely to produce incorrect results in practice but should be cleaned up before targeting Linux/Wine builds.

SDL3Cursor.cpp — strict-aliasing type-punning in RIFF tag comparisons; WinMain.cpp — minor style violations in the SDL3 init block

Important Files Changed

Filename	Overview
Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Input.cpp	New SDL3 mouse, keyboard, and input manager implementation; ring-buffer event routing, gamepad mapping, and coordinate scaling are all correctly structured
Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Cursor.cpp	New animated-cursor loader with RIFF/ACON parsing; three type-punning comparisons using `(Uint32)"tag"` are UB under strict aliasing — should use `memcmp`
Core/GameEngineDevice/Source/SDL3GameEngine.cpp	New SDL3 game engine with window management, text input routing, UTF-8 decoding, and factory methods; logic is sound and headless path correctly falls through to GameEngine::init()
GeneralsMD/Code/Main/WinMain.cpp	SDL3 window/splash screen init added under SAGE_USE_SDL3 guard; two `NULL` usages should be `nullptr` and one single-line `if` body violates project style
Core/GameEngineDevice/Include/SDL3Device/GameClient/SDL3Input.h	New header declaring SDL3Mouse, SDL3Keyboard, and SDL3InputManager; uses #pragma once and nullptr throughout; gamepad constants defined as constexpr
GeneralsMD/Code/GameEngineDevice/Include/W3DDevice/GameClient/W3DGameClient.h	Factory methods for keyboard/mouse now branch on SAGE_USE_SDL3 to return SDL3 or legacy Win32 devices; Win32Mouse extern correctly guarded
cmake/sdl3.cmake	vcpkg-first SDL3 discovery with FetchContent fallback; static build configured with required Windows system libs linked to SDL3-static

Sequence Diagram

sequenceDiagram
    participant WM as WinMain
    participant SGE as SDL3GameEngine
    participant SIM as SDL3InputManager
    participant SM as SDL3Mouse
    participant SK as SDL3Keyboard
    participant GE as GameEngine

    WM->>WM: SDL_Init + SDL_CreateWindow
    WM->>WM: Set TheSDL3Window
    WM->>SGE: CreateGameEngine()
    SGE->>SGE: init()
    SGE->>SIM: new SDL3InputManager(window)
    SIM->>SIM: openFirstGamepad()
    SGE->>GE: GameEngine::init()
    GE->>SM: createMouse() → SDL3Mouse(TheSDL3Window)
    GE->>SK: createKeyboard() → SDL3Keyboard()

    loop Per Frame
        SGE->>SGE: update()
        SGE->>SGE: pollSDL3Events()
        SGE->>SIM: update()
        SIM->>SIM: SDL_PollEvent loop
        SIM->>SIM: addMouseSDLEvent / addKeyboardSDLEvent
        SIM->>SIM: processGamepadInput()
        SIM-->>SIM: virtualPulseMouse / virtualPulseKey
        SGE->>GE: GameEngine::update()
        GE->>SM: getMouseEvent()
        SM->>SIM: getNextMouseEvent()
        SM->>SM: translateEvent() + scaleMouseCoordinates()
        GE->>SK: getKey()
        SK->>SIM: getNextKeyboardEvent()
    end

Prompt To Fix All With AI

Fix the following 5 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 5
GeneralsMD/Code/Main/WinMain.cpp:924
`NULL` is used as a null pointer literal in two places within the new SDL3 block. The codebase rule requires `nullptr` for all null pointer literals in C++ code.

```suggestion
			ApplicationHWnd = (HWND)SDL_GetPointerProperty(props, SDL_PROP_WINDOW_WIN32_HWND_POINTER, nullptr);
```

### Issue 2 of 5
GeneralsMD/Code/Main/WinMain.cpp:913
The `if` body sits on the same line as the condition. Per project style, the body should always be on a separate line to allow precise debugger breakpoint placement.

```suggestion
			if (!TheGlobalData->m_windowed)
				flags |= SDL_WINDOW_FULLSCREEN;
```

### Issue 3 of 5
Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Cursor.cpp:123-127
Casting a string-literal pointer to `Uint32*` and dereferencing it (`*(Uint32*)"anih"`) is undefined behaviour in C++ due to strict-aliasing rules. GCC/Clang with `-O2` can exploit this to produce wrong results when cross-compiled on Linux. Using `memcmp` (as already done for the outer RIFF/ACON check) is safe and equally readable. The same pattern appears for `"LIST"` and `"icon"` elsewhere in this function.

```suggestion
			if (memcmp(&id, "anih", 4) == 0 && sz >= 36)
			{
				memcpy(&rate, p + 28, 4);
			}
			else if (memcmp(&id, "LIST", 4) == 0 && sz >= 4 && memcmp(p, "fram", 4) == 0)
```

### Issue 4 of 5
Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Cursor.cpp:138
Same strict-aliasing UB as the sibling comparisons above — replace the type-punned dereference with `memcmp`.

```suggestion
					if (memcmp(&fid, "icon", 4) == 0)
```

### Issue 5 of 5
GeneralsMD/Code/Main/WinMain.cpp:940
The `NULL` passed as the source-rect argument to `SDL_BlitSurfaceScaled` should be `nullptr` — it is a pointer and the project rules require `nullptr` for all null pointer literals in C++ code.

_{Reviews (22): Last reviewed commit: "Merge remote-tracking branch 'upstream/m..." | Re-trigger Greptile}

stephanmeesters · 2026-04-20T18:13:28Z

+        OVERRIDE_FIND_PACKAGE
+    )
+
+    FetchContent_Declare(


Do you think we need SDL3_image? Looks like it's used to parse .ico for animated cursors? Maybe there is already code for that we can adapt

directinput lets windows directly handle the cursor rendering so new code and SDL3_image was needed

In that case consider putting AnimatedCursor in its own file.

SDL3_image seem overkill for handling animated cursors though as @stephanmeesters says, its just been used to decode the ico format, SDL itself already provides support for the animated cursors once the files are decoded and loaded.

Moved AnimatedCursor into its own file and switched to the SDL_CreateAnimatedCursor API.

Regarding the dependency: this is a conscious choice. While SDL core handles the animation logic, it doesn't decode ANI or ICO files. I’d rather offload that to SDL_image than maintain bespoke binary parsing. Using the library also makes it trivial for modders to use modern formats in the future.

I think this is the most maintainable path. Does that sound reasonable?

Regarding the dependency: this is a conscious choice. While SDL core handles the animation logic, it doesn't decode ANI or ICO files. I’d rather offload that to SDL_image than maintain bespoke binary parsing. Using the library also makes it trivial for modders to use modern formats in the future.

I think this is the most maintainable path. Does that sound reasonable?

Also @bobtista ’s #1785 could then use it for jpg and png encoding

stephanmeesters · 2026-04-20T18:17:14Z

+# Enable SDL3 by default for modern builds
+if(NOT IS_VS6_BUILD)
+    option(SAGE_USE_SDL3 "Enable SDL3 input/window backend" ON)
+    if(SAGE_USE_SDL3)


Maybe call it USE_SDL3

stephanmeesters · 2026-04-20T18:18:28Z

@@ -9,6 +9,16 @@ option(RTS_BUILD_OPTION_ASAN "Build code with Address Sanitizer." OFF)
 option(RTS_BUILD_OPTION_VC6_FULL_DEBUG "Build VC6 with full debug info." OFF)
 option(RTS_BUILD_OPTION_FFMPEG "Enable FFmpeg support" OFF)

+# Enable SDL3 by default for modern builds
+if(NOT IS_VS6_BUILD)
+    option(SAGE_USE_SDL3 "Enable SDL3 input/window backend" ON)


Options should be on top of the file and be something like RTS_BUILD_OPTION_SDL3

stephanmeesters · 2026-04-20T18:22:52Z

+
+namespace {
+
+Bool DecodeNextUtf8Codepoint(const char* text, size_t length, size_t& offset, UnsignedInt& outCodepoint)


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

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.

Consolidated all work from the test/sdl3-backport branch into a single atomic commit: - Centralized input management via SDL3InputManager. - Hardened Ani/RIFF cursor loading with robust bounds checking. - Native Gamepad support with analogue stick-to-mouse emulation and custom RTS mappings. - Modernized focus and capture handling for better stability during Alt-Tab. - Standardized and secured string operations throughout the SDL3 path.

Consolidated all work from the test/sdl3-backport branch into a single atomic commit: - Centralized input management via SDL3InputManager. - Hardened Ani/RIFF cursor loading with robust bounds checking. - Native Gamepad support with analogue stick-to-mouse emulation and custom RTS mappings. - Modernized focus and capture handling for better stability during Alt-Tab. - Standardized and secured string operations throughout the SDL3 path. - Updated credit attribution (fbraz3).

githubawn · 2026-04-21T21:23:05Z

+    }
+}
+
+AnimatedCursor* SDL3CursorManager::loadANI(const char* filepath)


libsdl-org/SDL_image#730
Ran into a bug in SDL_image. Ignore SDL3CursorManager::loadANI if you are reviewing this.

xezon

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

xezon · 2026-05-05T19:38:14Z

-            "git-tree": "3f05e04b9aededb96786a911a16193cdb711f0c9"
-        }
-    ]
+  "version": 1,


Indent changed in the json files.

xezon · 2026-05-05T19:39:31Z

 include(cmake/gamespy.cmake)
 include(cmake/lzhl.cmake)

+if(SAGE_USE_SDL3 AND NOT IS_VS6_BUILD)


Where does the SAGE_ prefix come from? We have not used that before for anything else.

xezon · 2026-05-05T19:42:03Z

+
+#if SAGE_USE_SDL3
+    #include <SDL3/SDL.h>
+    #include "SDL3GameEngine.h"


This SDL code is added to a file called WinMain (for Windows). Is this intentional?

This was intentional. The SDL3 input backend is designed with a future splitscreen skirmish feature in mind, supporting multiple simultaneous mice/keyboards so that 2–8 players can share a single machine rather than needing separate computers, either controlling the same or unique armies.

SDL3 input doesn't function without an SDL window, so creating the window here was the minimum viable approach to make the input backend functional. The Win32/DirectInput path doesn't lend itself to the multi-device model SDL3 enables, which is why SDL3 is the foundation for this direction.

xezon · 2026-05-05T19:46:07Z

+
+ParticleSystemManager* SDL3GameEngine::createParticleSystemManager(Bool dummy)
+{
+	(void)dummy;


Why not create dummy here?

xezon · 2026-05-05T19:48:02Z

+
+namespace {
+
+Bool DecodeNextUtf8Codepoint(const char* text, size_t length, size_t& offset, UnsignedInt& outCodepoint)


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.

xezon · 2026-05-12T18:07:44Z

+	  m_gamepad(nullptr),
+	  m_precisionMode(FALSE),
+	  m_lastUpdateTime(0),
+	  m_isQuitting(FALSE)


Or use false

xezon · 2026-05-12T18:08:01Z

+ */
+Bool SDL3InputManager::getNextMouseEvent(SDL_Event& outEvent)
+{
+	if (m_mouseEvents[m_mouseNextGet].type == SDL_EVENT_FIRST) return FALSE;


New line. Many times in this review.

xezon · 2026-05-12T18:09:09Z

+	handleGamepadButton(SDL_GAMEPAD_BUTTON_DPAD_RIGHT, m_state.buttonState[SDL_GAMEPAD_BUTTON_DPAD_RIGHT], SDL_GetGamepadButton(m_gamepad, SDL_GAMEPAD_BUTTON_DPAD_RIGHT), [&](bool d){ virtualPulseKey(SDL_SCANCODE_3, d); });
+	handleGamepadButton(SDL_GAMEPAD_BUTTON_DPAD_DOWN, m_state.buttonState[SDL_GAMEPAD_BUTTON_DPAD_DOWN], SDL_GetGamepadButton(m_gamepad, SDL_GAMEPAD_BUTTON_DPAD_DOWN), [&](bool d){ virtualPulseKey(SDL_SCANCODE_4, d); });
+	handleGamepadButton(SDL_GAMEPAD_BUTTON_LEFT_STICK, m_state.buttonState[SDL_GAMEPAD_BUTTON_LEFT_STICK], SDL_GetGamepadButton(m_gamepad, SDL_GAMEPAD_BUTTON_LEFT_STICK), [&](bool d){ if (d) TheMessageStream->appendMessage(GameMessage::MSG_META_SELECT_NEXT_IDLE_WORKER); });
+	handleGamepadButton(SDL_GAMEPAD_BUTTON_RIGHT_STICK, m_state.buttonState[SDL_GAMEPAD_BUTTON_RIGHT_STICK], SDL_GetGamepadButton(m_gamepad, SDL_GAMEPAD_BUTTON_RIGHT_STICK), [&](bool d){ if (d) TheMessageStream->appendMessage(GameMessage::MSG_META_VIEW_COMMAND_CENTER); });


These lines are awfully long.

xezon · 2026-05-12T18:19:41Z


+# Enable SDL3 by default for modern builds
+if(NOT IS_VS6_BUILD)
+    option(SAGE_USE_SDL3 "Enable SDL3 input/window backend" ON)


Please do not use SAGE_ keywords. We use RTS_

Maybe do RTS_SDL3_ENABLE. That is consistent style with RTS_CRASHDUMP_ENABLE

xezon · 2026-05-12T18:20:57Z


+# Enable SDL3 by default for modern builds
+if(NOT IS_VS6_BUILD)
+    option(SAGE_USE_SDL3 "Enable SDL3 input/window backend" ON)


Why is this default enabled on non VS6 builds but Windows builds? Will SDL3 perform better than Win API?

If we don't use DirectStorage and Raytracing the SDL3 boilerplate performs better than our current implementation even on Windows in trade for a slightly larger binary. Legacy version doesn't compile statistically against SDL3 and so VS6 changes are avoided.

xezon · 2026-05-12T22:32:25Z

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

githubawn · 2026-05-14T15:08:35Z

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

…ckport

…backport

githubawn force-pushed the feature/sdl3-input-backport branch from a785545 to 7cc0861 Compare April 20, 2026 15:00

greptile-apps Bot reviewed Apr 20, 2026

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Comment thread Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Input.cpp Outdated

greptile-apps Bot reviewed Apr 20, 2026

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Comment thread Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Input.cpp Outdated

greptile-apps Bot reviewed Apr 20, 2026

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Comment thread Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Input.cpp Outdated

greptile-apps Bot reviewed Apr 20, 2026

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Comment thread Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Input.cpp

OmniBlade reviewed Apr 20, 2026

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Comment thread cmake/sdl3.cmake Outdated

stephanmeesters reviewed Apr 20, 2026

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githubawn force-pushed the feature/sdl3-input-backport branch from e365605 to 627ef23 Compare April 20, 2026 18:24

githubawn changed the title ~~feat(input): Implement SDL3 input backend~~ feat(input): Implement SDL3 input and window management Apr 20, 2026

githubawn added 10 commits April 21, 2026 03:16

added build guards

e3b674b

greptile feedback

2499e0b

greptile feedback

f8fb43f

fixed build error

4ac91e0

greptile feedback

a0ac8f4

added vcpkg

d9d9ff0

vcpkg fix

d048867

changed dpad group numbers

534e694

githubawn force-pushed the feature/sdl3-input-backport branch from eb9908a to 534e694 Compare April 21, 2026 01:17

switch back to static linking

09fd4e6

greptile-apps Bot reviewed Apr 21, 2026

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Comment thread GeneralsMD/Code/Main/WinMain.cpp Outdated

githubawn added 3 commits April 21, 2026 17:40

move SDL3_image out SDL3input

9b0262c

properly fail on SDL_INIT failure

3a40b11

removed custom ICO decoder

4d82b81

greptile-apps Bot reviewed Apr 21, 2026

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Comment thread Core/GameEngineDevice/Source/SDL3Device/GameClient/SDL3Input.cpp Outdated

githubawn added 2 commits April 21, 2026 18:48

fixes SDL_WarpMouseInWindow mismatch

884218b

removed some dead declarations

b268cda

greptile-apps Bot reviewed Apr 21, 2026

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Comment thread Core/GameEngineDevice/Source/SDL3GameEngine.cpp Outdated

temporary re-added custom decoder

a7883e8

githubawn commented Apr 21, 2026

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dont early return for headless mode

038aea0

DevGeniusCode added this to the Linux support milestone Apr 29, 2026

xezon added Gen Relates to Generals ZH Relates to Zero Hour Platform Work towards platform support, such as Linux, MacOS Input labels May 12, 2026

xezon reviewed May 12, 2026

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githubawn added 3 commits May 14, 2026 18:10

applied clang to files new in this PR

390e2ee

Merge remote-tracking branch 'origin/main' into feature/sdl3-input-ba…

0ead8ea

…ckport

Merge remote-tracking branch 'upstream/main' into feature/sdl3-input-…

6f04138

…backport


		namespace {

		Bool DecodeNextUtf8Codepoint(const char* text, size_t length, size_t& offset, UnsignedInt& outCodepoint)

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Greptile Summary

Confidence Score: 5/5

Important Files Changed

Sequence Diagram

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xezon commented May 12, 2026

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