ImGui in OpenGL Games (Cocoa) (MacOS)

[aKalisch]

Hello guys.

I currently try to implement ImGui in CS:GO (MacOS).

Therefor I hooked SDL_GL_SwapWindow from the Game itself. So far so good. All works fine and the hook is executing.

void SDLHook::HookSwapWindow() {
    uintptr_t swapwindowFn = reinterpret_cast<uintptr_t>(dlsym(RTLD_NEXT, "SDL_GL_SwapWindow"));
    swapwindow_ptr = reinterpret_cast<uintptr_t*>(CPatternScanner::Instance()->GetAbsoluteAddress("libSDL2-2.0.0.dylib", swapwindowFn, 0xF, 0x4));

    swapwindow_original = *swapwindow_ptr;

    *swapwindow_ptr = reinterpret_cast<uintptr_t>(&SDLHook::SDLSwapWindow);
}

The code of the hooked method:

void SDLHook::SDLSwapWindow(SDL_Window* window) {
    static oSDL_GL_SwapWindowFn oSDL_GL_SwapWindow = reinterpret_cast<oSDL_GL_SwapWindowFn>(swapwindow_original);

    static SDL_GLContext original_context = SDL_GL_GetCurrentContext();

    static SDL_GLContext user_context = NULL;

    if (!user_context) {
        user_context = SDL_GL_CreateContext(window);

        SDL_GL_MakeCurrent(window, user_context);

        ImGui_ImplSdl_Init(window);
        
    } else {
        SDL_GL_MakeCurrent(window, user_context);
    }

    ImGui_ImplSdl_NewFrame(window);

    ImGui::SetNextWindowPos(ImVec2(10.f, 10.f));
    ImGui::SetNextWindowSize(ImVec2(320.f, 240.f));
    ImGui::Begin("Test Window");
    ImGui::Text("Just a simple text");
    ImGui::End();

    ImGui::Render();

    SDL_GL_MakeCurrent(window, original_context);

    oSDL_GL_SwapWindow(window);
}

There are no crashes and the game is running well.
But it's simply not drawing anything.

When I change the hooked method to:

void SDLHook::SDLSwapWindow(SDL_Window* window) {
    static oSDL_GL_SwapWindowFn oSDL_GL_SwapWindow = reinterpret_cast<oSDL_GL_SwapWindowFn>(swapwindow_original);

    static bool ImGuiInit = false;

    if (!ImGuiInit) {
        ImGuiInit = true;

        ImGui_ImplSdl_Init(window);
    }

    ImGui_ImplSdl_NewFrame(window);

    ImGui::SetNextWindowPos(ImVec2(10.f, 10.f));
    ImGui::SetNextWindowSize(ImVec2(320.f, 240.f));
    ImGui::Begin("Test Window");
    ImGui::Text("Just a simple text");
    ImGui::End();

    ImGui::Render();

    oSDL_GL_SwapWindow(window);
}

The "Test Window" is drawing. But the game freezes.

Does someone have a clue why this happens?

[raresica1234]

Maybe you are swapping the window before anything from CS:GO can render, therefore Windows sees the game as freezing because there is nothing drawing.

[aKalisch]

It's not windows... It's macOS ;-)

And no.. The Hook is the SwapWindow function. When ImGui Frame is executed I call the original funtction.

I think the problem is at the cocoa gl side.

[dwnste]

I'm kinda late, but I've found the workaround: https://github.com/dwnste/imgui_sdl_osx

[ocornut]

Sorry but #1586