Conference bulova::decw_jan-89_to_nov-90

3364.0. "Access violation using XtWindowToWidget" by DRIVEN::SANFORD () Wed Sep 19 1990 18:53

In the example below I am attempting to use a high level MESSAGE BOX 
widget from within an application written using XLIB calls.  Using the 
"XtWindowToWidget" I had hoped to create a widget instance so that I
could call "DwtMessageBox".  All I get is an access violation.

Below is a simple application showing the problem.  This was built under
VMS V5.3 with DECW$XLIBSHR (ident DECW X21-IFT) and DECW$DWTLIBSHR 
(ident DECWINDOWS V5.3).

I've tried almost everything, now I'm at the mercy of a response.

Thanks, -drew sanford


#include <DECW$INCLUDE:XLIB.H>
#include <DECW$INCLUDE:XUTIL.H>
#include <DECW$INCLUDE:XATOM.H>
#include <DECW$INCLUDE:INTRINSIC.H>
#include <decw$include:DwtAppl.h>

main ()
MAIN_PROGRAM
{
  static Widget widget, mwidget;
  static Display *display;
  static Window window;
  static XEvent event;
  static int screen;
  static DwtCompString label;

  display = XOpenDisplay("");

  screen = DefaultScreen(display);

  window  = XCreateSimpleWindow(display,
    RootWindow(display, screen), 100, 50, 200, 150, 4,
    BlackPixel(display, screen), 
    WhitePixel(display, screen) );

  XSelectInput(display, window, ExposureMask);
  XMapRaised(display, window);
  XNextEvent(display, &event);

  widget  = XtWindowToWidget(display, window);
  label   = DwtLatin1String("Sample Message");
  mwidget = DwtMessageBox (widget, "Message", 1, NULL, 
	     NULL, DwtModal, label, NULL, NULL, NULL);
}


%SYSTEM-F-ACCVIO, access violation, reason mask=00, virtual address=00000000, 
    PC=0007851C, PSL=03C00004
%TRACE-F-TRACEBACK, symbolic stack dump follows
module name     routine name                     line       rel PC    abs PC

                                                           0007851C  0007851C
TEST            main                            10869      000000E9  000004E9

> In the example below I am attempting to use a high level MESSAGE BOX 
> widget from within an application written using XLIB calls.  Using the 
> "XtWindowToWidget" I had hoped to create a widget instance so that I
> could call "DwtMessageBox".  All I get is an access violation.


XtWindowToWidget returns a widget id for a given window.
If this window is a widget's window, you get the widget id.
Else you get NULL.

XtWindowToWidget doesn't not create a widget instance.
Giving a null widget parent to the message box results in accvio.

Hope this helps

Jean-Marc.

    The Intrinsic documentation for "Window To Widget" describes the
    function to translate a window and display pointer into a widget
    instance.  I would assume they are referring to a low level Xlib
    display/window.
    
    The arguments (widget = XtWindowToWidget(display,window)):
    
    	display - The display on which the window is defined.
    	window  - The window for which you want the widget.
    
    Can I assume you CAN NOT mix Xlib with XUI calls?  Seems unheard of 
    since they should only be different layers of protcol.
    
    Confused... -drew

 
.1 is correct; XtWindowToWidget does NOT create a widget instance.  There is no way
to create a widget given a window.  You create a widget which creates its own window.
The purpose of XtWindowToWidget is, given a window, tell me which widget it belongs to.
   
>    Can I assume you CAN NOT mix Xlib with XUI calls?  Seems unheard of 
>    since they should only be different layers of protcol.
 
Yes, you can, once you understand what they do and the limitations.

Leo

Actually, Steve Klein built a pseudo-widget that would create widget structures
for an already existing window.  I think it is in the VToolkit which can be
found in ELKTRA::DW_EXAMPLES.  I am not sure that this will do what you want
but you might want to give it a try.

Dick