#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>
#include <unistd.h>

int  WINDOW_WIDTH = 600;
int  WINDOW_HEIGHT = 300;

void quit(Display *display, Window win, GC gc) {
  // Clean up and close the window
  XFreeGC(display, gc);
  XUnmapWindow(display, win);
  XDestroyWindow(display, win);
  XCloseDisplay(display);
  exit(0);
}

void redraw(Display *display, Window win, GC gc) {
  XSetForeground(display, gc, 0xFFFFFF);
  XFillRectangle(display, win, gc, 0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
  XFlush(display);
}

int main() {
  Display         *display;
  Window           win;
  GC               gc;
  XEvent           event;
  int              key, button;
  Window           window_returned;
  int              x, y, screenX, screenY, width, height, borderWidth, depth;
  unsigned int     mask_return;
  XConfigureEvent  cEvent;

  
  // Opens connection to X server
  display = XOpenDisplay(NULL);

  // Create a simple window, set the title and get the graphics context then
  // make is visible and get ready to draw
  win = XCreateSimpleWindow(display,  RootWindow(display, 0), 0, 0,
			    WINDOW_WIDTH, WINDOW_HEIGHT, 0, 0x000000, 0xFFFFFF);

  // Indicate which events we want to handle
  XSelectInput(display, win,
	       KeyPressMask |             // When key is pressed on keyboard
	       KeyReleaseMask |           // When key is released on keyboard
	       ButtonPressMask |          // When Mouse Button is Pressed
	       ButtonReleaseMask |        // When Mouse Button is Released
	       EnterWindowMask |          // When Mouse Enters Window
	       LeaveWindowMask |          // When mouse Leaves Window
	       PointerMotionMask |        // When mouse is moved within window
	       ExposureMask |		  // When the window is exposed
	       StructureNotifyMask        // When there is a change in window structure 
	       );      

  // Create the window and display it
  XStoreName(display, win, "Event Handler");
  gc = XCreateGC(display, win, 0, NULL);
  XMapWindow(display, win);
  XFlush(display);
  usleep(20000);  // sleep for 20 milliseconds.

  // Indicate that we'd like to be able to gracefully handle window closing
  Atom WM_DELETE_WINDOW = XInternAtom(display, "WM_DELETE_WINDOW", False); 
  XSetWMProtocols(display, win, &WM_DELETE_WINDOW, 1);
  
  // Go into infinite loop handling X11 events
  while(1) {
    XNextEvent(display, &event);
    switch(event.type) {
    case EnterNotify:
      printf("Mouse entered window\n"); break;
    case LeaveNotify:
      printf("Mouse left window\n"); break;
    case Expose:
      printf("Window has been exposed\n");
      redraw(display, win, gc);
      break;
    case KeyPress:
      key = event.xkey.keycode;
      printf("Key has been pressed with keycode: %d\n", key);
      if (key == 0x09) // Check for ESC key, then quit
	quit(display, win, gc);
      break;
    case KeyRelease:
      key = event.xkey.keycode;
      printf("Key has been released with keycode: %d\n", key); break;
    case ButtonPress:
      button = event.xbutton.button;
      XQueryPointer(display, win, &window_returned,
                &window_returned, &screenX, &screenY, &x, &y,
                &mask_return);
      printf("Button %d has been pressed at location (%d, %d)\n", button, x, y); break;
    case ButtonRelease:
      button = event.xbutton.button;
      printf("Button %d has been released\n", button); break;
    case MotionNotify:
      XQueryPointer(display, win, &window_returned,
                &window_returned, &screenX, &screenY, &x, &y,
                &mask_return);
      printf("Mouse moved to window position (%d, %d) and screen position (%d, %d)\n", x, y, screenX, screenY);
      break;
    case ConfigureNotify:
      cEvent = event.xconfigure;
      // Need to check for window resizing, since this type of event can be generated for other reasons too
      if ((cEvent.width != WINDOW_WIDTH) || (cEvent.height != WINDOW_HEIGHT)) {
	WINDOW_WIDTH = cEvent.width;
	WINDOW_HEIGHT = cEvent.height;
	printf("Window resized to be %d X %d\n", WINDOW_WIDTH, WINDOW_HEIGHT);
	redraw(display, win, gc);
      }
      break;
    case ClientMessage:
      printf("Window closed\n");
      // We really should check here for other client message types, 
      // but since the only protocol registered above is WM_DELETE_WINDOW,
      // it is safe to assume that we want the window closing event.
      quit(display, win, gc);
    default:
      printf("Unknown Event\n");
    }
  }
}