Question

How to create a window and renderer with smooth fading between colors using SDL3 in Win32 C++

Answer 1

#include <SDL3/SDL.h>

#if _WIN32 // PLATFORM_WINDOWS 

#define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers
#include <windows.h>

int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
    _In_opt_ HINSTANCE hPrevInstance,
    _In_ LPWSTR lpCmdLine,
    _In_ int nCmdShow) {
  
    if (!SDL_Init(SDL_INIT_VIDEO)) {
        //SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't initialize SDL: %s", SDL_GetError());
        MessageBoxA(0, SDL_GetError(), "Couldn't initialize SDL", MB_OK);
        return 3;
    }

    SDL_Window* window;
    SDL_Renderer* renderer;
    if (!SDL_CreateWindowAndRenderer("SDL3 Create Window and Renderer with smooth fading between colors", 640, 480, SDL_WINDOW_RESIZABLE, &window, &renderer)) {
        //SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create window and renderer: %s", SDL_GetError());
        MessageBoxA(0, SDL_GetError(), "Couldn't create window and renderer", MB_OK);
        return 3;
    }

    SDL_Event event;

    while (1) {
        SDL_PollEvent(&event);
        if (event.type == SDL_EVENT_QUIT) {
            break;
        }
        
        // convert from milliseconds to seconds
        const double now = ((double)SDL_GetTicks()) / 1000.0;  
        
        // The sine wave makes it fade between colors smoothly
        const float red = (float)(0.5 + 0.5 * SDL_sin(now));
        const float green = (float)(0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 2 / 3));
        const float blue = (float)(0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 4 / 3));

        SDL_SetRenderDrawColorFloat(renderer, red, green, blue, SDL_ALPHA_OPAQUE_FLOAT); 

        SDL_RenderClear(renderer);
        SDL_RenderPresent(renderer);
    }

    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);

    SDL_Quit();

    return 0;
}

#endif

 

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