Now we can open up a window and draw simple shapes on it, it would be a good idea to be able to interact with it. Things like clicking the close button would be nice, until its coded for, a program will keep right on running and might even ignore CTRL-C in the terminal too if you are unlucky enough to have an infinite loop.

SDL_Event event;
bool running=true;

while(running) {                                 // read the event queue
	
  if( SDL_PollEvent( &event ) != 0 ) {           // if there is an event
    if(event.type==SDL_QUIT) { running=false; }  // if its a quit event
  }

}

This structure can be extended to handle other events, like the mouse moving over the window, clicking buttons, and also keypresses. It is however slightly confusing.

while(running) {
	
  if( SDL_PollEvent( &event ) != 0 ) {

    if (event.type==SDL_KEYDOWN) {
    if (event.key.keysym.sym==SDLK_LSHIFT) { ; }
    }

    if (event.type==SDL_KEYUP) {
      if (event.key.keysym.sym==SDLK_LSHIFT) { ; } // watch out for these
    }

    if (event.type == SDL_MOUSEMOTION) {
      mx=event.button.x;                           // button is the name of
      my=event.button.y;                           // the event structure
    }

    if (event.type == SDL_MOUSEBUTTONDOWN) {
      btn = event.button.button;                   // also containing the
      if (btn==1) { ; }                            // actual button data
      if (btn==3) { ; }
    }

    if (event.type == SDL_MOUSEBUTTONUP) {
      btn = event.button.button;
      if (btn==1) { ; }
      if (btn==3) { ; }
    }
      
}

 There is an extensive list of event codes in the documentation which there is little point duplicating here.