/* gcc touchgrab.c -lXi -Wall -std=c99 -o touchgrab */

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

int main(int argc, char **argv) {
  Display *dpy = XOpenDisplay(NULL);

  int opcode, event, error;
  if (!XQueryExtension(dpy, "XInputExtension", &opcode, &event, &error)) {
    printf("X Input extension not available.\n");
    return 1;
  }

  int major = 2, minor = 2;
  XIQueryVersion(dpy, &major, &minor);
  if (major * 1000 + minor < 2002) {
    printf("Server does not support XI 2.2\n");
    return 1;
  }

  if (argc != 3 || (strcmp(argv[2], "accept") && strcmp(argv[2], "reject"))) {
    printf("Usage: %s <device_number> accept|reject\n", argv[0]);
    return 1;
  }

  int dev = atoi(argv[1]);
  int mode = argv[2][0] == 'a' ? XIAcceptTouch : XIRejectTouch;

  static unsigned char touch_mask_data[4];
  static XIEventMask touch_mask;

  touch_mask.deviceid = dev;
  touch_mask.mask = touch_mask_data;
  touch_mask.mask_len = sizeof(touch_mask_data);
  memset(touch_mask.mask, 0, touch_mask.mask_len);
  XISetMask(touch_mask.mask, XI_TouchBegin);
  XISetMask(touch_mask.mask, XI_TouchUpdate);
  XISetMask(touch_mask.mask, XI_TouchEnd);

  XIGrabModifiers modifier = {0};
  modifier.modifiers = XIAnyModifier;

  Window win = XDefaultRootWindow(dpy);
  
  XIGrabButton(dpy, dev, 1, win, None, GrabModeAsync, GrabModeAsync, False, &touch_mask, 1, &modifier);
  if (XIGrabTouchBegin(dpy, dev, win, False, &touch_mask, 1, &modifier)) {
    printf("Grab failed\n");
    return 1;
  }
  XIGrabDevice(dpy, dev, win, CurrentTime, None, GrabModeAsync, GrabModeAsync, False, &touch_mask);

  while (1) {
    XEvent ev;
    XNextEvent(dpy, &ev);

    if (ev.xcookie.type == GenericEvent &&
        ev.xcookie.extension == opcode &&
        XGetEventData(dpy, &ev.xcookie)) {
      XIDeviceEvent *event = (XIDeviceEvent *)ev.xcookie.data;
      switch(event->evtype) {
        case XI_TouchBegin:
          printf("TouchBegin: %d -> %d\n", event->sourceid, event->deviceid);
          XIAllowTouchEvents(dpy, event->deviceid, event->detail, win, mode);
          break;
        case XI_TouchUpdate:
          printf("TouchUpdate: %d -> %d\n", event->sourceid, event->deviceid);
          break;
        case XI_TouchEnd:
          printf("TouchEnd: %d -> %d\n", event->sourceid, event->deviceid);
          break;
      }
    }

    XFreeEventData(dpy, &ev.xcookie);
  }

  return 0;
}