Path: utzoo!attcan!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hplabsz!mayer
From: mayer@hplabsz.HPL.HP.COM (Niels Mayer)
Newsgroups: comp.windows.x,hp.windows.motif
Subject: Re: Need help in interactive selection of a motif widget/gadget
Message-ID: <4228@hplabsz.HPL.HP.COM>
Date: 27 Oct 89 08:53:13 GMT
References: <4219@hplabsz.HPL.HP.COM>
Reply-To: mayer@hplabs.hp.com (Niels Mayer)
Organization: Hewlett-Packard Labs, Software Technology Lab, Palo Alto, CA.
Lines: 92
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In article <4219@hplabsz.HPL.HP.COM> mayer@hplabs.hp.com (Niels Mayer) writes:
>I have added a primitive to my WINTERP application (a Motif application
>prototyping/develpment/delivery environment) which will allow users click
>on a widget to get back the WIDGET-OBJECT corresponding to the widget.
> ... [description of bug deleted] ...
>Am I doing something wrong? Is this a Motif or Xtoolkit bug?  Do I have to
>add yet another special kludge for a gadget-inside-a-manager-
>-inside-a-scrolled-window? Inquiring minds want to know.

Please ignore my previous request. When I wrote my GET_MOUSED_WIDGET
routine, I misunderstood how XTranslateCoordinates() worked. After
rereading the manpage, I was able to find the (trivial) bug in my code.
Clearly a case of earthquake-induced braindamage on my part.

Here's the working version of GET_MOUSED_WIDGET. You may find it useful...

/******************************************************************************
 * (GET_MOUSED_WIDGET)
 * evaluating this function will change the cursor to a crossbar, indicating
 * that the user is to 'click' the mouse to designate an object on the screen.
 * If the user clicks on a visual item within WINTERP, this fucntion will
 * return the WIDGETOBJ associated with the visual item. 
 ******************************************************************************/
LVAL Wut_UserClick_To_WidgetObj()
{
  extern Display* display;	/* global in winterp.c */
  extern LVAL     Wcls_WidgetID_To_WidgetObj();	/* from w_classes.c */
  extern XmGadget _XmInputInGadget(); /* in Xm/GadetUtils.c extern'd in XmP.h */
  Cursor	  cursor = XCreateFontCursor(display, XC_crosshair);
  Window          root = DefaultRootWindow(display);
  Window          parent_win, cur_win, child_win;
  int             win_x, win_y;
  Widget          widget_id, gadget_id;
  XEvent	  event;
  Bool            xtc_ok;
  
  xllastarg();

  if (GrabSuccess != XGrabPointer(display, root, 0, ButtonPressMask, GrabModeAsync,
				  GrabModeAsync, None, cursor, CurrentTime))
    xlfail("GET_MOUSED_WIDGET -- couldn't grab pointer (XGrabPointer() failed).");
  
  XWindowEvent(display, root, ButtonPressMask, &event);
  XUngrabPointer(display, CurrentTime);
  XFlush(display);

  if (event.type != ButtonPress) /* sanity check: ensure valid access to event.xbutton variant */
    xlfail("Bug in GET_MOUSED_WIDGET -- expected a button event.");
  if (!event.xbutton.subwindow)
    xlfail("GET_MOUSED_WIDGET aborted -- you clicked on the root window.");

  parent_win = event.xbutton.window; /* ASSERT event.xbutton.window == root, due to using XWindowEvent(root) */
  win_x      = event.xbutton.x;
  win_y      = event.xbutton.y;
  cur_win    = event.xbutton.subwindow;
  while ((xtc_ok = XTranslateCoordinates(display,
					 parent_win, cur_win,
					 win_x, win_y, /* give the x,y coords of event in parent_w */
					 &win_x, &win_y, /* return the x,y coords relative to cur_win */
					 &child_win)) /* returns child window of cur_win if that contains coords, else nil */
	 && child_win) {
#ifdef DEBUG_WINTERP_1
    fprintf(stderr, "parent_win=%lx, cur_win=%lx, child_win=%lx\n", parent_win, cur_win, child_win);
#endif
    parent_win = cur_win;
    cur_win    = child_win;
  }

#ifdef DEBUG_WINTERP_1
  fprintf(stderr, "	Smallest window containing userclick is %lx\n", cur_win);
#endif

  if (!xtc_ok)
    xlerror("Bug in GET_MOUSED_WIDGET -- XTranslateCoordinates() failed.");

  if (!(widget_id = XtWindowToWidget(display, cur_win)))
    xlfail("GET_MOUSED_WIDGET -- Couldn't find widget associated with window.\n	(Is the selected widget/window inside a different application?).\n");

  /* if the widget is a composite it may be managing a gadget -- attempt to retrieve it by looking up x,y coords in manager */
  if (XtIsComposite(widget_id) &&
      (gadget_id = (Widget) _XmInputInGadget(widget_id, win_x, win_y)))
    return (Wcls_WidgetID_To_WidgetObj(gadget_id)); /* then return the WIDGETOBJ assoc'd with gadget */
  else
    return (Wcls_WidgetID_To_WidgetObj(widget_id)); /* otherwise, we return the WIDGETOBJ assoc'd with smallest window */
}

-------------------------------------------------------------------------------
	    Niels Mayer -- hplabs!mayer -- mayer@hplabs.hp.com
		  Human-Computer Interaction Department
		       Hewlett-Packard Laboratories
			      Palo Alto, CA.
				   *