/*
gcc -Wall `pkg-config --libs --cflags x11 xi` focusout.c -o focusout
*/

#include <X11/Xlib.h>
#include <X11/extensions/XInput2.h>
#include <stdio.h>

static const char *notify_modes[] = {
  "Normal",
  "Grab",
  "Ungrab",
  "Grabbed"
};

static const char *notify_details[] = {
  "Ancestor",
  "Virtual",
  "Inferior",
  "Nonlinear",
  "NonlinearVirtual",
  "Pointer",
  "PointerRoot",
  "DetailNone"
};

int
main (void)
{
  Display *display;
  Window toplevel, mid, focus;
  XEvent event;
  XIEnterEvent *ev;
  int opcode, firstevent, firsterror;
  unsigned char mask[XIMaskLen (XI_LASTEVENT)];
  XIEventMask event_mask;

  display = XOpenDisplay (NULL);
  
  if (XQueryExtension (display, "XInputExtension",
                       &opcode, &firstevent, &firsterror))
    {
      int major, minor;

      major = 2;
      minor = 0;

      if (XIQueryVersion (display, &major, &minor) == BadRequest)
        return 1;
    }
  else
    return 1;

  toplevel = XCreateSimpleWindow (display, DefaultRootWindow (display),
                                  10, 10, 10, 10, 0,
                                  0, 0);
  mid = XCreateSimpleWindow (display, toplevel,
                             0, 0, 10, 10, 0,
                             0, 0);
  focus = XCreateSimpleWindow (display, mid,
                               -1, -1, 1, 1, 0,
                               0, 0);

  XISetMask (mask, XI_KeyPress);
  XISetMask (mask, XI_KeyRelease);
  XISetMask (mask, XI_FocusIn);
  XISetMask (mask, XI_FocusOut);

  event_mask.deviceid = XIAllMasterDevices;
  event_mask.mask = mask;
  event_mask.mask_len = sizeof (mask);

  XISelectEvents (display, toplevel, &event_mask, 1);
  XISelectEvents (display, mid, &event_mask, 1);
  XISelectEvents (display, focus, &event_mask, 1);
  XSelectInput (display, toplevel, StructureNotifyMask | PropertyChangeMask | FocusChangeMask);
  XSelectInput (display, mid, KeyPressMask | KeyReleaseMask | FocusChangeMask);
  XSelectInput (display, focus, KeyPressMask | KeyReleaseMask | FocusChangeMask);

  XMapWindow (display, focus);
  XMapWindow (display, mid);
  XMapWindow (display, toplevel);

  while (XNextEvent (display, &event) == 0)
    {
      switch (event.type)
      {
        case FocusIn:
          XSetInputFocus (display, focus, RevertToParent, CurrentTime);
        case FocusOut:
          printf ("    %s %s %7s %s\n",
                  event.type == FocusIn ? "IN " : "OUT",
                  event.xany.window == toplevel ? " top "
                    : event.xany.window == mid ? " mid "
                    : event.xany.window == focus ? "focus" : " ??? ",
                  notify_modes[event.xfocus.mode],
                  notify_details[event.xfocus.detail]);
          break;
        case GenericEvent:
          XGetEventData (display, &event.xcookie);
          ev = (XIEnterEvent *) event.xcookie.data;
          switch (ev->evtype)
          {
            case XI_FocusIn:
              XSetInputFocus (display, focus, RevertToParent, CurrentTime);
            case XI_FocusOut:
              printf ("XI2 %s %s %7s %s\n",
                  ev->evtype == XI_FocusIn ? "IN " : "OUT",
                  ev->event == toplevel ? " top "
                    : ev->event == mid ? " mid "
                    : ev->event == focus ? "focus" : " ??? ",
                  notify_modes[ev->mode],
                  notify_details[ev->detail]);
              break;
            default:
              break;
          }
          XFreeEventData (display, &event.xcookie);
          break;
        default:
          break;
      }
    }

  return 0;
}