// gcc -lX11 -lXext xtest1.c -o xtest1

#include <X11/Xlib.h>

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

// Globals 
Display *g_display;
int      g_screen;

XColor createXColorFromRGB(short red, short green, short blue)
{
    XColor color;

    // m_color.red = red * 65535 / 255;
    color.red = (red * 0xFFFF) / 0xFF;
    color.green = (green * 0xFFFF) / 0xFF;
    color.blue = (blue * 0xFFFF) / 0xFF;
    color.flags = DoRed | DoGreen | DoBlue;

    if (!XAllocColor(g_display, DefaultColormap(g_display, g_screen), &color))
    {
        fprintf(stderr, "createXColorFromRGB: Cannot create color\n");
        exit(-1);      
    }
    return color;
}


void draw(Window w)
{
  GC gc;
  XGCValues gcv;
  XColor color;  
  int i;

  // XColor blue, blue_e;
  // XAllocNamedColor(dsp, DefaultColormap(dsp, screen), "blue", &blue, &blue_e);

  // gcv.foreground = BlackPixel(g_display, g_screen);  [ GCForeground ]
  gcv.line_width = 1;
  gcv.line_style = LineSolid;
  gc = XCreateGC(g_display, w,  GCLineWidth | GCLineStyle, &gcv);
  
  for (i = 1; i< 11; i++)
  {
    color = createXColorFromRGB(128+i*10, 64+i*10, 24+i*10);
    XSetForeground(g_display, gc, color.pixel);

    XFillRectangle(g_display, w, gc, i*10, i*10, i*10 + 150, 1*10+150);
    // XFillRectangle(g_display, w, gc, 50, 50, 150, 150);
  }
  XSync(g_display, False);
}


int main(int argc, char* argv[])
{
  Window win;			/* pointer to the newly created window.      */
  unsigned int display_width,
               display_height;	/* height and width of the X display.        */
  unsigned int width, height;	/* height and width for the new window.      */
  unsigned int win_x, win_y;	/* location of the window's top-left corner. */
  unsigned int win_border_width; /* width of window's border.                */

  Atom atoms[10];

  char *display_name = getenv("DISPLAY");  /* address of the X display.      */

  g_display = XOpenDisplay(display_name);

  if (g_display == NULL) 
  {
     fprintf(stderr, "%s: cannot connect to X server '%s'\n", argv[0], display_name);
     exit(1);
  }

  /* get the geometry of the default screen for our display. */
  g_screen = DefaultScreen(g_display);
  display_width = DisplayWidth(g_display, g_screen);
  display_height = DisplayHeight(g_display, g_screen);

  /* make the new window occupy 1/9 of the screen's size. */
  width = (display_width / 3);
  height = (display_height / 3);

  /* the window should be placed at the top-left corner of the screen. */
  win_x = 0;
  win_y = 0;

  /* the window's border shall be 2 pixels wide. */
  win_border_width = 2;

  win = XCreateSimpleWindow(g_display, RootWindow(g_display, g_screen),
                  win_x, win_y, width, height, win_border_width, BlackPixel(g_display, g_screen), WhitePixel(g_display,g_screen));


   // Window at the background test
   atoms[0] = XInternAtom (g_display, "_NET_WM_STATE_BELOW", False);
   atoms[1] = XInternAtom (g_display, "_NET_WM_STATE_DESKTOP", False);
   XChangeProperty (g_display, win, XInternAtom (g_display,"_NET_WM_STATE",False),XA_ATOM,32,PropModeReplace, (char *) &atoms, 2);


/*
   // Window transparency/opacity test
   double transparency = 0.4000; 
   unsigned int opacity = (uint)(0xffffffff * transparency);
   Atom atom_net_wm_window_opacity = XInternAtom(g_display, "_NET_WM_WINDOW_OPACITY", False);
   XChangeProperty(g_display, win, atom_net_wm_window_opacity, XA_CARDINAL, 32, PropModeReplace, (unsigned char *) &opacity, 1L);
*/

  // Ask these events 
  XSelectInput(g_display, win, ExposureMask | ButtonPressMask);

  /* make the window actually appear on the screen. */
  XMapWindow(g_display, win);

  /* flush all pending requests to the X server, and wait until */
  /* they are processed by the X server.                        */
  XSync(g_display, False);

  while(1) 
  {
      XEvent xe;
      XNextEvent(g_display, &xe);
      switch (xe.type) 
      {

           case Expose:
		draw(win);
                break;

            case ButtonPress: /* quit if a button is pressed */
                /* note that when using XShapeCombineMask(), i.e.
                 * trying to get a "transparent" background,
                 * no ButtonPress events are ever recognized
                 */
                printf("ButtonPress\n");
                exit(0);

            default:
                printf("Caught event %i\n", xe.type);
        }
    }

    XDestroyWindow(g_display, win);
    XCloseDisplay(g_display);

    return 0;
}