Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!ucsd!sdcsvax!ucsdhub!esosun!seismo!uunet!salt.uucp!dan
From: dan@salt.uucp (Dan Williams)
Newsgroups: comp.windows.x
Subject: Question on Callbacks
Summary: Why do I get a Segmentation Violation on this code?
Keywords: Expose, Callbacks, long, shar source code
Message-ID: <332@salt.UUCP>
Date: 9 Mar 89 17:33:22 GMT
References: <634@uvicctr.UUCP>
Reply-To: dan@salt.UUCP (Dan Williams)
Organization: MDCCIS, Englewood, CO
Lines: 538


	I am working in X11r3 on a sun and I am building a widget subclass
of an athena box widget.  I added a callback list for button press events
and that worked so well that I wanted to add another call back that would
do the client procedures for redrawing my graphics and be initiated from
the expose procedure in the widget.  I copied what I did for the button
press callback list and attempted to add the second callback.  The widget
subclass gave me no errors but when I attempt to do an XtPopup of  my root
I get the infamous "Segmentation fault" error and everything bombs out.
	What am I doing wrong ? 
	The following is a shar file containing a tstmain.c and 3 diff
files that give the difference of my widget BaarsBox from the Template
widget code under X11/lib/Xaw/ Template.c Template.h and TemplateP.h
and a Makefile for the set.  Run patch and compile the set to see it "run"
then produce educated analysis on where I fouled up.

_______________________________________________________________

#The following is a shar file delete all above this line before running
#through sh
echo x - tstmain.c
sed 's/^X//' >tstmain.c <<'*-*-END-of-tstmain.c-*-*'
X/* SCCS ID %W%    %G% */
X#include <stdio.h>
X#include <X11/Cardinals.h>
X#include <X11/Xlib.h>
X#include <X11/Intrinsic.h>
X#include <X11/Shell.h>
X#include <X11/StringDefs.h>
X#include "BaarsBox.h"
X#include <X11/Shell.h>
X
XWidget root_widget;            /* global toplevel shell. */
Xstatic int next_window_num = 1; /* private variable to set the window num */
X
Xvoid my_button3_hit (w,widget_winid,eventptr)
X     Widget  w;
X     caddr_t widget_winid;	/* passes parent of window */
X     caddr_t eventptr;		/* unused */
X{
X     fprintf (stderr,"got a button 3 hit\n");      
X     return;
X}
X
Xvoid expose_graphics (w,windata,call_data)
X     Widget  w;
X     caddr_t windata;	        /* passes data with window */
X     caddr_t call_data;		/* unused */
X{    
X     printf ("doing expose_graphics routine\n");
X     return;  
X}
X
Xint  make_window (toplevel,xloc,yloc,xsiz,ysiz)
X     Widget   toplevel;
X     long xloc,yloc,xsiz,ysiz;     
X{
X     Dimension          win_height,win_width;
X     int                i;
X     Widget             pop_shell,viewpane;
X     XtCallbackRec      callbacks [2];
X     XtCallbackRec      morecallbacks [2];
X     Arg                carg[10];
X     char               widget_name[20];
X     XtCallbackStatus   stat;
X     int                win_data;
X    
X     win_data = next_window_num++; /* setup window data */
X     i = 0;
X     XtSetArg( carg[i], XtNx,(Position)xloc ) ; i++;
X     XtSetArg( carg[i], XtNy,(Position)yloc ) ; i++;
X     sprintf(widget_name,"popshell%d\0",win_data);
X     pop_shell = XtCreatePopupShell(widget_name,applicationShellWidgetClass,
X                              toplevel, carg, i);
X     i = 0;
X     win_height = (Dimension) (ysiz);
X     win_width = (Dimension) (xsiz);
X     XtSetArg(carg[i],XtNheight, win_height ); i++;
X     XtSetArg(carg[i],XtNwidth, win_width ); i++;
X     viewpane =
X	  XtCreateWidget("VIEWPANE",baarsBoxWidgetClass,pop_shell,carg,i);
X     XtManageChild(viewpane);
X     /* add a call back for button 3 hits */
X     XtAddCallback(viewpane,XtNbaarsBoxCallback,(XtCallbackProc)my_button3_hit,
X		   (caddr_t)win_data);
X
X/* if this next call is commented out then this program runs */
X
X     XtAddCallback(viewpane,XtNboxExposeCallback,
X		   (XtCallbackProc)expose_graphics,(caddr_t)win_data); /*  */
X
X     stat = XtHasCallbacks(viewpane,XtNboxExposeCallback);
X     switch (stat) {
X	  case XtCallbackNoList :
X	       fprintf (stderr,"Nolist"); 
X	       break;
X	  case XtCallbackHasSome :
X	       fprintf (stderr,"HasSome\n"); 
X	       break;
X	  case XtCallbackHasNone :
X	       fprintf (stderr,"HasNone\n"); 
X	       break;
X     }
X        /* Now pop up the widget */
X
X/* here is where the error manifests itself */
X
X     XtPopup(pop_shell,XtGrabNone);
X     return(win_data);
X}
X
X  XrmOptionDescRec options[] = {
X     {"-label","*button.label",XrmoptionSepArg,NULL}
X  };
X
Xmain (argc, argv)
X     int argc;
X     char *argv [];
X{
X     
X  root_widget = XtInitialize("main","DEMO",options,XtNumber(options),
X			     &argc,argv);
X
X  make_window(root_widget, (long)300, (long)300,
X	       (long)500, (long)500);
X
X  XtMainLoop();
X}
*-*-END-of-tstmain.c-*-*
echo x - diff.c2
sed 's/^X//' >diff.c2 <<'*-*-END-of-diff.c2-*-*'
X2c2,3
X< /* $XConsortium: BaarsBox.c,v 1.2 88/10/25 17:40:25 swick Exp $ */
X---
X> 
X> /* $XConsortium: Template.c,v 1.2 88/10/25 17:40:25 swick Exp $ */
X5,6d5
X< 
X< #include <stdio.h>
X9,10c8
X< #include <X11/XawMisc.h>
X< #include "BaarsBoxP.h"
X---
X> #include "TemplateP.h"
X12,21d9
X< /* #DEFINES */
X< #define offset(field) XtOffset(BaarsBoxWidget, BaarsBox.field)
X< 
X< /* TYPEDEFS */
X< 
X< struct EventData {
X< 	XEvent *oldEvent;
X< 	int count;
X< };
X< 
X22a11
X> #define offset(field) XtOffset(TemplateWidget, template.field)
X24,28c13,14
X<     { XtNbaarsBoxCallback, XtCCallback, XtRCallback, sizeof(caddr_t),
X< 	  offset(baarsbox_callback), XtRCallback, NULL },
X<     { XtNboxExposeCallback, XtCCallback, XtRCallback, sizeof(caddr_t),
X< 	  offset(boxexpose_callback), XtRCallback, NULL },
X< };
X---
X>     { XtNtemplateResource, XtCTemplateResource, XtRTemplateResource, sizeof(char*),
X> 	  offset(resource), XtRString, "default" },
X29a16
X> };
X31,32c18
X<  /* superclass definition */
X< #define superclass   (&boxClassRec)
X---
X> static void TemplateAction(/* Widget, XEvent*, String*, Cardinal* */);
X34,44d19
X< 
X< /* GLOBALS */
X< 
X< 
X< /* EXTERNS */
X< extern void GotButton3Hit(/* Widget, XEvent*, String*, Cardinal* */);
X< 
X< static void Initialize();
X< static void Realize();
X< static void Expose_proc();
X< static void ExtractPosition();
X47,48c22,23
X<   /* {name,              procedure}, */
X<   {"GotButton3Hit",	GotButton3Hit},
X---
X>   /* {name, procedure}, */
X>     {"template",	TemplateAction},
X50,52d24
X< static char defaultTranslations[] =
X<    /*   event,       procedure   */
X<    "<Btn3Down>:   GotButton3Hit()";
X53a26,28
X> static char translations[] =
X> "<Key>:		template()	\n\
X> ";
X55,60c30,34
X< BaarsBoxClassRec baarsBoxClassRec = {
X<       /* core fields */
X<   {
X<     /* superclass		*/	(WidgetClass) &boxClassRec,
X<     /* class_name		*/	"BaarsBox",
X<     /* widget_size		*/	sizeof(BaarsBoxRec),
X---
X> TemplateClassRec templateClassRec = {
X>   { /* core fields */
X>     /* superclass		*/	(WidgetClass) &widgetClassRec,
X>     /* class_name		*/	"Template",
X>     /* widget_size		*/	sizeof(TemplateRec),
X64c38
X<     /* initialize		*/	Initialize,
X---
X>     /* initialize		*/	NULL,
X66c40
X<     /* realize function		*/	Realize,
X---
X>     /* realize			*/	XtInheritRealize,
X78c52
X<     /* expose			*/	Expose_proc,
X---
X>     /* expose			*/	NULL,
X86c60
X<     /* tm_table			*/	defaultTranslations,
X---
X>     /* tm_table			*/	translations,
X90,99d63
X<   },{
X< /* composite_class fields */
X<     /* geometry_manager   */    XtInheritGeometryManager,
X<     /* change_managed     */    XtInheritChangeManaged,
X<     /* insert_child       */    XtInheritInsertChild,
X<     /* delete_child       */    XtInheritDeleteChild,
X<     /* extension          */    NULL
X<   },{
X< /* Box class fields */
X<     /* empty              */    0,
X101,104c65,66
X< 
X< 	  /* BaarsBox fields */
X<   {
X<     /* empty		*/	0,
X---
X>   { /* template fields */
X>     /* empty			*/	0
X108,224c70
X< WidgetClass baarsBoxWidgetClass = (WidgetClass)&baarsBoxClassRec;
X< 
X< /* FUNCTIONS */
X< 
X< 
X< static void Initialize(request,new)
X<      Widget request, new;
X< {
X<      BaarsBoxWidget newbbw = (BaarsBoxWidget)new;
X<      BaarsBoxWidget rw = (BaarsBoxWidget)request;
X<      XtCallbackStatus stat;
X<      
X<      fprintf (stderr,"In the Initialize\n"); 
X< 
X< 
X< }
X< 
X< static void Realize(widget, value_mask, attributes)
X<     Widget widget;/* ARGSUSED */
X<     XtValueMask *value_mask;
X<     XSetWindowAttributes *attributes;
X< {
X<     *value_mask |= CWBitGravity;
X<     attributes->bit_gravity = NorthWestGravity;
X<     XtCreateWindow(widget, (unsigned int)CopyFromParent, 
X< 		   (Visual *)CopyFromParent, *value_mask, attributes);
X<         XSelectInput(XtDisplay(widget),XtWindow(widget), ButtonPressMask |
X< 		  ButtonReleaseMask | ButtonMotionMask |
X< 		  PointerMotionHintMask | ExposureMask);
X< } 
X< 
X< static void Expose_proc(widget,event,region)
X<      Widget widget;
X<      XEvent event;
X<      Region region;
X< {
X<      fprintf (stderr,"Got an Expose call\n"); 
X<      
X<      XtCallCallbacks(widget,XtNboxExposeCallback,(caddr_t)0);
X< 				/*  */
X< }
X< 
X< static Boolean CompareEvents( oldEvent, newEvent )
X<     XEvent *oldEvent, *newEvent;
X< {
X< #define Check(field) if (newEvent->field != oldEvent->field) return False;
X< 
X<     Check(xany.display);
X<     Check(xany.type);
X<     Check(xany.window);
X< 
X<     switch( newEvent->type ) {
X<       case MotionNotify:
X< 		Check(xmotion.state); break;
X<       case ButtonPress:
X<       case ButtonRelease:
X< 		Check(xbutton.state);
X< 		Check(xbutton.button); break;
X<       case KeyPress:
X<       case KeyRelease:
X< 		Check(xkey.state);
X< 		Check(xkey.keycode); break;
X<       case EnterNotify:
X<       case LeaveNotify:
X< 		Check(xcrossing.mode);
X< 		Check(xcrossing.detail);
X< 		Check(xcrossing.state); break;
X<     }
X< #undef Check
X< 
X<     return True;
X< }
X< 
X< static Boolean PeekNotifyEvent( dpy, event, args )
X<     Display *dpy;
X<     XEvent *event;
X<     char *args;
X< {
X<     struct EventData *eventData = (struct EventData*)args;
X< 
X<     return ((++eventData->count == QLength(dpy)) /* since PeekIf blocks */
X< 	    || CompareEvents(event, eventData->oldEvent));
X< }
X< 
X< static Boolean LookAhead( w, event )
X<     Widget w;
X<     XEvent *event;
X< {
X<     XEvent newEvent;
X<     struct EventData eventData;
X< 
X<     if (QLength(XtDisplay(w)) == 0) return False;
X< 
X<     eventData.count = 0;
X<     eventData.oldEvent = event;
X< 
X<     XPeekIfEvent(XtDisplay(w), &newEvent, PeekNotifyEvent, (char*)&eventData);
X< 
X<     if (CompareEvents(event, &newEvent))
X< 	return True;
X<     else
X< 	return False;
X< }
X< 
X< void GotButton3Hit (gw, event, params, num_params )
X<    Widget gw;
X<    XEvent *event;
X<    String *params;		/* unused */
X<    Cardinal *num_params;	/* unused */
X< {
X<     BaarsBoxWidget w = (BaarsBoxWidget) gw;
X<     Position x, y;
X< 
X<     if (LookAhead(gw, event)) return;
X<     XtCallCallbacks(w, XtNbaarsBoxCallback, (caddr_t)event);
X< 
X< }
X---
X> WidgetClass templateWidgetClass = (WidgetClass)&templateClassRec;
*-*-END-of-diff.c2-*-*
echo x - diff.h2
sed 's/^X//' >diff.h2 <<'*-*-END-of-diff.h2-*-*'
X1,2d0
X< /* SCCS ID "@(#)BaarsBox.h     1.1        11/17/88" */
X< 
X5c3
X< /* $XConsortium: BaarsBox.h,v 1.2 88/10/25 17:22:09 swick Exp $ */
X---
X> /* $XConsortium: Template.h,v 1.2 88/10/25 17:22:09 swick Exp $ */
X8,9c6,7
X< #ifndef BaarsBox_h
X< #define BaarsBox_h
X---
X> #ifndef _Template_h
X> #define _Template_h
X11,12d8
X< #include <X11/Box.h>
X< 
X15c11
X<  * BaarsBox widget
X---
X>  * Template widget
X26,27d21
X<  baarsBoxCallback    Callback		Pointer		NULL
X<  boxExposeCallback   Callback		Pointer		NULL
X40,41c34
X< #define XtNbaarsBoxCallback		"baarsBoxCallback"
X< #define XtCBaarsBoxCallback		"BaarsBoxCallback"
X---
X> #define XtNtemplateResource		"templateResource"
X43,44c36
X< #define XtNboxExposeCallback		"boxExoseCallback"
X< #define XtCBoxExposeCallback		"BoxExposeCallback"
X---
X> #define XtCTemplateResource		"TemplateResource"
X46c38
X< /* declare specific BaarsBoxWidget class and instance datatypes */
X---
X> /* declare specific TemplateWidget class and instance datatypes */
X48,49c40,41
X< typedef struct _BaarsBoxClassRec*	BaarsBoxWidgetClass;
X< typedef struct _BaarsBoxRec*		BaarsBoxWidget;
X---
X> typedef struct _TemplateClassRec*	TemplateWidgetClass;
X> typedef struct _TemplateRec*		TemplateWidget;
X53c45
X< extern WidgetClass baarsBoxWidgetClass;
X---
X> extern WidgetClass templateWidgetClass;
X55c47
X< #endif  BaarsBox_h
X---
X> #endif  _Template_h
*-*-END-of-diff.h2-*-*
echo x - diffP.h2
sed 's/^X//' >diffP.h2 <<'*-*-END-of-diffP.h2-*-*'
X1,2d0
X< /* SCCS ID "@(#)BaarsBoxP.h     1.1        11/17/88" */
X< 
X5c3
X< /* $XConsortium: BaarsBoxP.h,v 1.2 88/10/25 17:37:59 swick Exp $ */
X---
X> /* $XConsortium: TemplateP.h,v 1.2 88/10/25 17:37:59 swick Exp $ */
X8,9c6,7
X< #ifndef BaarsBoxP_h
X< #define BaarsBoxP_h
X---
X> #ifndef _TemplateP_h
X> #define _TemplateP_h
X11,12c9
X< #include "BaarsBox.h"
X< 
X---
X> #include "Template.h"
X14c11
X< #include <X11/BoxP.h>	
X---
X> #include <X11/CoreP.h>
X17d13
X< 				/* no unique types */
X19,22c15
X< typedef struct
X< {
X<   int make_compiler_happy;
X< } BaarsBoxClassPart;
X---
X> #define XtRTemplateResource		"TemplateResource"
X24,30c17,19
X< typedef struct _BaarsBoxClassRec
X< {
X<   CoreClassPart	      core_class;
X<   CompositeClassPart  composite_class;
X<   BoxClassPart        box_class;
X<   BaarsBoxClassPart   baarsbox_class;
X< } BaarsBoxClassRec;
X---
X> typedef struct {
X>     int empty;
X> } TemplateClassPart;
X32c21,24
X< extern BaarsBoxClassRec baarsBoxClassRec;
X---
X> typedef struct _TemplateClassRec {
X>     CoreClassPart	core_class;
X>     TemplateClassPart	template_class;
X> } TemplateClassRec;
X34,40c26
X< typedef struct
X< {
X<   /* resources */
X<   XtCallbackList baarsbox_callback;
X<   XtCallbackList boxexpose_callback;
X<   /* private state */
X< } BaarsBoxPart;
X---
X> extern TemplateClassRec templateClassRec;
X42,46c28,32
X< typedef struct _BaarsBoxRec
X< {
X<   CorePart	core;
X<   BaarsBoxPart	BaarsBox;
X< } BaarsBoxRec;
X---
X> typedef struct {
X>     /* resources */
X>     char* resource;
X>     /* private state */
X> } TemplatePart;
X48c34,39
X< #endif  BaarsBoxP_h
X---
X> typedef struct _TemplateRec {
X>     CorePart		core;
X>     TemplatePart	template;
X> } TemplateRec;
X> 
X> #endif  _TemplateP_h
*-*-END-of-diffP.h2-*-*
echo x - Makefile
sed 's/^X//' >Makefile <<'*-*-END-of-Makefile-*-*'
X# Dan's personal makefile for his test and development area 
X#
XCC = /bin/cc
XINC_DIR = /usr/xbaars/include
XTEST_INC_DIR = /u1/dan/X/VIEW
XLIBS = -lXaw -lXmu -lXt -lX11 -lm
XEWO_DIR = /usr/xbaars/src/ewo/
XMENU_DIR = /usr/xbaars/src/xmenu/
XCFLAGS = -g
XCC = cc
XLIBS = -lXaw -lXmu -lXt -lX11 -lm
X
X
X#############################################################################
Xall	:	tst
X
Xtst	:  tstmain.o BaarsBox.o 
X	$(CC) tstmain.o BaarsBox.o -o tst $(CFLAGS) $(LIBS)
X
Xclean	:
X	rm -f *.o core tst 
X
Xtstmain.o : tstmain.c
X	$(CC) -c $(CFLAGS) $*.c 
X
XBaarsBox.o : BaarsBox.c BaarsBox.h BaarsBoxP.h
X	$(CC) -c $(CFLAGS) $*.c 
X
*-*-END-of-Makefile-*-*
exit