Re: seg fault while moving a event box

[abhi <abhi_don_linux yahoo com>]

Sorry folks,
  the declaration of the move callback has to be 

 static void move( GtkWidget *widget,
                  GdkEventButton *event,
                         GtkWidget *layout )

I was missing the event parameter and that probably
caused the casting errors.

Thanks for reading,
Regards,
Abhijeet 


--- abhi <abhi_don_linux yahoo com> wrote:

> Hello List,
> 
>   This is my first GTK app and I want to move the
> image when the user clicks on it. I created an
> eventbox  and placed it on a GtkLayout. I catch the
> mouse_pressed event but when I move the event_bx I
> get
> a segfault. I dont have the symbols from the
> libraries
> but gdb tells me this
> 
> 
> Breakpoint 1, move (widget=0x94a10e8,
> layout=0x94aef68) at g2.c:14
> 14        g_print("button_press_event_received\n");
> (gdb) step
> button_press_event_received
> 15        x = (x + 30) % 300;
> (gdb) step
> 16        y = (y + 50) % 300;
> (gdb) step
> 18        gtk_layout_get_size ( GTK_LAYOUT (layout)
> ,
> &width, &height);
> (gdb) print width
> $1 = -1073765136
> (gdb) print height
> $2 = 155848184
> (gdb) step
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x0017015c in g_type_check_instance_cast () from
> /usr/lib/libgobject-2.0.so.0
> (gdb) Quit
>  
> 
> The source code is as follows
> #include <gtk/gtk.h>
> #include <stdlib.h>
> gint x = 50;
> gint y = 50;
> GtkWidget *image = NULL;
> /* This callback function moves the button to a new
> position
>  * in the layout container. */
> static void move( GtkWidget *widget,
>                          GtkWidget *layout )
> {
>   gint width,height;
>   g_print("button_press_event_received\n");
>   x = (x + 30) % 300;
>   y = (y + 50) % 300;
>   gtk_layout_get_size ( GTK_LAYOUT (layout) ,
> &width,
> &height);
>   gtk_layout_move ( GTK_LAYOUT(layout), widget , x,
> y); 
> }
> void usage()
> {
>    g_print(" incorrect usage need a image
> parameter\n");
>    exit( EXIT_FAILURE );
> }
> int main( int   argc,
>           char *argv[] )
> {
>   /* GtkWidget is the storage type for widgets */
>   GtkWidget *window;
>   GtkWidget *layout;
>   GtkWidget *event_box;
>   GtkWidget *button;
>   GdkPixbuf *pixbuf;
>   gint i;
> 
>   if (argc < 2)  usage();
> 
>   /* Initialise GTK */
>   gtk_init (&argc, &argv);
>     
>   /* Create a new window */
>   window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
>   gtk_window_set_title (GTK_WINDOW (window), "Layout
> Container");
> 
>   /* Here we connect the "destroy" event to a signal
> handler */ 
>   g_signal_connect (G_OBJECT (window), "destroy",
> 		    G_CALLBACK (gtk_main_quit), NULL);
>  
>   /* Sets the border width of the window. */
>   gtk_container_set_border_width (GTK_CONTAINER
> (window), 10);
> 
>   /* Create a Layout Container */
>   layout = gtk_layout_new ( NULL, NULL);
>   gtk_container_add (GTK_CONTAINER (window),
> layout);
>   gtk_widget_show (layout);
>  
>   /* Create an image widget form the pixbuf */
>   pixbuf = gdk_pixbuf_new_from_file(argv[1],NULL);
>   image = gtk_image_new_from_pixbuf (pixbuf);
> 
>   /* Create an event box and add image widget*/
>   event_box = gtk_event_box_new ();
>   gtk_container_add (GTK_CONTAINER (event_box),
> image);
>   gtk_widget_show (image);
>    
>   /*put the event box somewhere on the layout */
>   gtk_layout_put (GTK_LAYOUT (layout), event_box, 50
> ,
> 50 );
>   gtk_widget_show (event_box);
> 
>   /* And bind an action to it */
>   gtk_widget_set_events (event_box,
> GDK_BUTTON_PRESS_MASK);
>   g_signal_connect (G_OBJECT (event_box),
> "button_press_event",
> 	              G_CALLBACK (move), layout);
>   gtk_widget_realize (event_box);
> 
>   /* Display the window */
>   gtk_widget_show (window);
>     
>   /* Enter the event loop */
>   gtk_main ();
>     
>   return 0;
> }
> /*
> gcc g2.c -o g2 `pkg-config --cflags --libs gtk+-2.0`
> */
> 
> 
> Any help educating me towards the cause of segfault
> will be appreciated.
> 
> TIA,
> Abhijeet 
> 
> 
>      
>
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