testSDL.cpp

#include <iostream>
#include <SDL2/SDL.h>

int main(int argc, char ** argv)
{
    bool leftMouseButtonDown = false;
    bool quit = false;
    SDL_Event event;

    SDL_Init(SDL_INIT_VIDEO);

    SDL_Window * window = SDL_CreateWindow("SDL2 Pixel Drawing",
        SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0);

    SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, 0);
    SDL_Texture * texture = SDL_CreateTexture(renderer,
        SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_STATIC, 640, 480);
    Uint32 * pixels = new Uint32[640 * 480];
    memset(pixels, 255, 640 * 480 * sizeof(Uint32));

    while (!quit)
    {
        SDL_UpdateTexture(texture, NULL, pixels, 640 * sizeof(Uint32));
        SDL_WaitEvent(&event);

        switch (event.type)
        {
        case SDL_MOUSEBUTTONUP:
            if (event.button.button == SDL_BUTTON_LEFT)
                leftMouseButtonDown = false;
            break;
        case SDL_MOUSEBUTTONDOWN:
            if (event.button.button == SDL_BUTTON_LEFT)
                leftMouseButtonDown = true;
        case SDL_MOUSEMOTION:
            if (leftMouseButtonDown)
            {
                int mouseX = event.motion.x;
                int mouseY = event.motion.y;
                pixels[mouseY * 640 + mouseX] = 0;
            }
            break;
        case SDL_QUIT:
            quit = true;
            break;
        }

        SDL_RenderClear(renderer);
        SDL_RenderCopy(renderer, texture, NULL, NULL);
        SDL_RenderPresent(renderer);
    }

    delete[] pixels;
    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}