1.cpp

    SDL_RenderCopy(rend, tex, NULL, &pos);

2.cpp

void ApplySurface(int x, int y, SDL_Texture *tex, SDL_Renderer *rend, SDL_Rect *clip = NULL){
    SDL_Rect pos;
    pos.x = x;
    pos.y = y;
    //Detect if we should use clip width settings or texture width
    if (clip != NULL){
        pos.w = clip->w;
	pos.h = clip->h;
    }
    else {
        SDL_QueryTexture(tex, NULL, NULL, &pos.w, &pos.h);
    }
    SDL_RenderCopy(rend, tex, clip, &pos);
}

3.cpp

    //iW and iH are the desired clip width and height
    int iW = 100, iH = 100;
    SDL_Rect clips[4];
    //We use a for loop this time to setup our clips
    int column = 0;
    for (int i = 0; i < 4; ++i){
        if (i != 0 && i % 2 == 0)
            ++column;

        clips[i].x = column * iW;
        clips[i].y = i % 2 * iH;
        clips[i].w = iW;
        clips[i].h = iH;
    }

4.cpp

    //Specify a default clip to start with
    int useClip = 0;

5.cpp

    //If user presses any key
    if (e.type == SDL_KEYDOWN){
        switch (e.key.keysym.sym){
	    case SDLK_1:
	        useClip = 0;
		break;
	    case SDLK_2:
	        useClip = 1;
		break;
	    case SDLK_3:
	        useClip = 2;
		break;
            case SDLK_4:
	        useClip = 3;
		break;
            //For quitting, escape key
	    case SDLK_ESCAPE:
	        quit = true;
		break;
            default:
	        break;
	}
    }

6.cpp

    ApplySurface(x, y, image, renderer, &clips[useClip]);