SDL2 code for capturing multiple keypresses in one go, based on http://www.programmersranch.com/2014/02/sdl2-keyboard-and-mouse-movement-events.html

spaceShip_8dir.cpp

#include <SDL.h>
#include <iostream>
using namespace std;
int main(int argc, char ** argv)
{

    bool quit = false;
    SDL_Event event;
    int x = 288;
    int y = 208;

    // init SDL

    SDL_Init(SDL_INIT_VIDEO);
    SDL_Window * window = SDL_CreateWindow("SDL2 Keyboard/Mouse events",
                                           SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0);
    SDL_Renderer * renderer = SDL_CreateRenderer(window, -1, 0);

    SDL_Surface * image = SDL_LoadBMP("spaceship.bmp");
    SDL_Texture * texture = SDL_CreateTextureFromSurface(renderer,
                            image);
    SDL_FreeSurface(image);

    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);

    
    while (!quit)
    {
        SDL_Delay(20);
        SDL_PollEvent(&event);
        switch (event.type)
        {
        case SDL_QUIT:
            quit = true;
            break;
        }
        /*Multiple Key Capture Begins*/
        const Uint8 *state = SDL_GetKeyboardState(NULL);

        /*Verbose for no particular reason*/
        bool up = state[SDL_SCANCODE_UP],
             left = state[SDL_SCANCODE_LEFT],
             right = state[SDL_SCANCODE_RIGHT],
             down = state[SDL_SCANCODE_DOWN];
        if(up) y--;
        if(down) y++;
        if(right) x++;
        if(left) x--;

        SDL_Rect dstrect = { x, y, 64, 64 };

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

    // cleanup SDL

    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();

    return 0;
}