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From: zoo@aps1.spa.umn.edu (david d [zoo] zuhn)
Newsgroups: comp.windows.open-look,alt.toolkits.xview
Subject: XView with C++
Message-ID: <ZOO.90Dec16021713@grumpy.spa.umn.edu>
Date: 16 Dec 90 07:17:13 GMT
Sender: news@s1.msi.umn.edu
Distribution: all
Organization: Minnesota Automated Plate Scanner Lab
Lines: 103

I have gotten the XView header files to be compatible with g++ 1.37.2,
and now have a problem with a small program that I have written. 

My intention is to be able to keep a Frame inside of a class object,
and all of the callbacks for this object's controls will be methods of
the object.  My problem is that my quit callback (this is a hello
world type program to start with) will crash my program, with a bus
error deep in the notifier.  I don't have a -g XView, and don't have
the disk space to build one if I wanted to. 

This is probably a bug in my understanding of how and where C++
objects have their memory allocated and deallocated, but I can't
figure this out.

If someoneout there has an idea of how to do this, please let me know.

FWIW:  SunOS 4.1, XView 2.0 (with modified headers to allow ANSI C and
       C++ compilation), g++ 1.37.2a, libg++-1.37.2


david d [zoo] zuhn		Univ. of Minnesota Dept. of Astronomy
zoo@aps1.spa.umn.edu		      Automated Plate Scanner Project



------------------ The sample code --------------
#include <stddef.h>
#include <stream.h>


#include <xview/xview.h>
#include <xview/frame.h>
#include <xview/panel.h>
#include <xview/xv_xrect.h>


class Test
{
public:
  Test(int width, int height);
  ~Test();
  int quit (Panel_item item, Event *event);
  Frame frame;
  Panel panel;
};

Test::Test(int width, int height)
{
  frame = (Frame) xv_create (NULL, FRAME,
			     XV_WIDTH, width,
			     XV_HEIGHT, height,
			     NULL);

  panel = (Panel) xv_create (frame, PANEL,
			     PANEL_LAYOUT, PANEL_HORIZONTAL,
			     NULL);

  (void) xv_create (panel, PANEL_BUTTON,
		    PANEL_LABEL_STRING, "Quit",
		    PANEL_NOTIFY_PROC, quit,
		    NULL);

}

Test::~Test()
{
  if (frame)
    cout << "frame\n";
  else
    cout << "no frame\n";
}

int Test::quit (Panel_item item, Event *event)
{
  xv_destroy_safe (frame);
  return XV_OK;
}
  

int main (int argc, char *argv[])
{
  Test *test;

  xv_init (XV_INIT_ARGC_PTR_ARGV, &argc, argv, NULL);
  test = new Test (800, 400);

  xv_main_loop (test->frame);
  delete test;
  return 0;
}


---------------- The post mortem ------------------
#0  0x2fbc in xv_destroy_status ()
#1  0x5c58 in notify_destroy ()
#2  0x163f4 in ndis_default_prioritizer ()
#3  0x5954 in notify_client ()
#4  0x6078 in ndis_default_scheduler ()
#5  0x1bb88 in xv_scheduler_internal ()
#6  0x53bc in ndis_dispatch ()
#7  0x14538 in notify_start ()
#8  0xbd98 in xv_main_loop ()
#9  0x24d0 in main (argc=1, argv=0xf7fffc84) (xv.cc line 64)