private int QueryContinueDrag(int fEscapePressed, int grfKeyState) {
    if (topControl != null && topControl.isDisposed()) return COM.DRAGDROP_S_CANCEL;
    if (fEscapePressed != 0) {
      if (hwndDrag != 0) OS.ImageList_DragLeave(hwndDrag);
      return COM.DRAGDROP_S_CANCEL;
    }
    /*
     * Bug in Windows.  On some machines that do not have XBUTTONs,
     * the MK_XBUTTON1 and OS.MK_XBUTTON2 bits are sometimes set,
     * causing mouse capture to become stuck.  The fix is to test
     * for the extra buttons only when they exist.
     */
    int mask = OS.MK_LBUTTON | OS.MK_MBUTTON | OS.MK_RBUTTON;
    //	if (display.xMouse) mask |= OS.MK_XBUTTON1 | OS.MK_XBUTTON2;
    if ((grfKeyState & mask) == 0) {
      if (hwndDrag != 0) OS.ImageList_DragLeave(hwndDrag);
      return COM.DRAGDROP_S_DROP;
    }

    if (hwndDrag != 0) {
      POINT pt = new POINT();
      OS.GetCursorPos(pt);
      RECT rect = new RECT();
      OS.GetWindowRect(hwndDrag, rect);
      OS.ImageList_DragMove(pt.x - rect.left, pt.y - rect.top);
    }
    return COM.S_OK;
  }
 void update() {
   if (parent != null) {
     if (parent.isDisposed()) return;
     parent.getShell().update();
   } else {
     display.update();
   }
 }
  /**
   * Displays the Tracker rectangles for manipulation by the user. Returns when the user has either
   * finished manipulating the rectangles or has cancelled the Tracker.
   *
   * @return <code>true</code> if the user did not cancel the Tracker, <code>false</code> otherwise
   * @exception SWTException
   *     <ul>
   *       <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed
   *       <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
   *     </ul>
   */
  public boolean open() {
    checkWidget();
    int xDisplay = display.xDisplay;
    window = OS.XDefaultRootWindow(xDisplay);
    if (parent != null) {
      window = OS.XtWindow(parent.handle);
      if (window == 0) return false;
    }
    cancelled = false;
    tracking = true;
    update();
    drawRectangles(rectangles, stippled);
    int[] oldX = new int[1], oldY = new int[1];
    int[] unused = new int[1], mask = new int[1];
    OS.XQueryPointer(xDisplay, window, unused, unused, oldX, oldY, unused, unused, mask);

    /*
     * If exactly one of UP/DOWN is specified as a style then set the cursor
     * orientation accordingly (the same is done for LEFT/RIGHT styles below).
     */
    int vStyle = style & (SWT.UP | SWT.DOWN);
    if (vStyle == SWT.UP || vStyle == SWT.DOWN) {
      cursorOrientation |= vStyle;
    }
    int hStyle = style & (SWT.LEFT | SWT.RIGHT);
    if (hStyle == SWT.LEFT || hStyle == SWT.RIGHT) {
      cursorOrientation |= hStyle;
    }

    int mouseMasks = OS.Button1Mask | OS.Button2Mask | OS.Button3Mask;
    boolean mouseDown = (mask[0] & mouseMasks) != 0;
    if (!mouseDown) {
      Point cursorPos = null;
      if ((style & SWT.RESIZE) != 0) {
        cursorPos = adjustResizeCursor();
      } else {
        cursorPos = adjustMoveCursor();
      }
      if (cursorPos != null) {
        oldX[0] = cursorPos.x;
        oldY[0] = cursorPos.y;
      }
    }
    this.oldX = oldX[0];
    this.oldY = oldY[0];

    int ptrGrabResult =
        OS.XGrabPointer(
            xDisplay,
            window,
            0,
            OS.ButtonPressMask | OS.ButtonReleaseMask | OS.PointerMotionMask,
            OS.GrabModeAsync,
            OS.GrabModeAsync,
            OS.None,
            OS.None,
            OS.CurrentTime);
    int kbdGrabResult =
        OS.XGrabKeyboard(xDisplay, window, 0, OS.GrabModeAsync, OS.GrabModeAsync, OS.CurrentTime);

    /* Tracker behaves like a Dialog with its own OS event loop. */
    XAnyEvent anyEvent = new XAnyEvent();
    int xEvent = OS.XtMalloc(XEvent.sizeof);
    int dispatch = OS.XtMalloc(4);
    int xtContext = OS.XtDisplayToApplicationContext(xDisplay);
    while (tracking) {
      if (parent != null && parent.isDisposed()) break;
      OS.XtAppNextEvent(xtContext, xEvent);
      OS.memmove(anyEvent, xEvent, XAnyEvent.sizeof);
      int widget = OS.XtWindowToWidget(anyEvent.display, anyEvent.window);
      switch (anyEvent.type) {
        case OS.MotionNotify:
          XPointerMotion(widget, 0, xEvent, dispatch);
          break;
        case OS.ButtonRelease:
          XButtonRelease(widget, 0, xEvent, dispatch);
          break;
        case OS.KeyPress:
          XKeyPress(widget, 0, xEvent, dispatch);
          break;
        case OS.KeyRelease:
          XKeyRelease(widget, 0, xEvent, dispatch);
          break;
        case OS.ButtonPress:
        case OS.EnterNotify:
        case OS.LeaveNotify:
          /* Do not dispatch these */
          break;
        case OS.Expose:
          update();
          drawRectangles(rectangles, stippled);
          OS.XtDispatchEvent(xEvent);
          drawRectangles(rectangles, stippled);
          break;
        default:
          OS.XtDispatchEvent(xEvent);
      }
    }
    if (xEvent != 0) OS.XtFree(xEvent);
    if (dispatch != 0) OS.XtFree(dispatch);
    if (!isDisposed()) {
      update();
      drawRectangles(rectangles, stippled);
    }
    if (ptrGrabResult == OS.GrabSuccess) OS.XUngrabPointer(xDisplay, OS.CurrentTime);
    if (kbdGrabResult == OS.GrabSuccess) OS.XUngrabKeyboard(xDisplay, OS.CurrentTime);
    window = 0;
    return !cancelled;
  }