GTK！ GTK！

qiqixiao

   创建了一个窗口，用set_title设置了标题为：“HELLO！”，然后添加了一个按钮，请问当点击按钮后，如何改变此窗体的title？（比如title改为“HI！”）
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>;       我水平不高，没能实现，请看我的代码，麻烦高手帮我修改一下！

#include <gtk/gtk.h>;

GtkWidget *window;

void set_title ( GtkWidget *widget, GdkEvent *event, gpointer data )
{
  
/* window = gtk_window_new (GTK_WINDOW_TOPLEVEL);*/

  gtk_window_set_title (GTK_WINDOW (window), "HI!";

/* window = gtk_window_new (GTK_WINDOW_TOPLEVEL);*/

  gtk_widget_show (window);
}

gint delete_event (GtkWidget *widget, GdkEvent *event, gpointer data)
{
  return FALSE;

}       

void destroy(GtkWidget *widget, gpointer data)
{
gtk_main_quit ();
}


int main( int argc, char *argv[] )
{
  /* GtkWidget *window;*/
   GtkWidget *button;
   GtkWidget *box1;
   
   gtk_init(&argc, &argv);

   /*建立窗体*/
   window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
   gtk_window_set_title (GTK_WINDOW (window), "Hello!";
   g_signal_connect (G_OBJECT (window), "delete_event", G_CALLBACK (delete_event), NULL);
   g_signal_connect (G_OBJECT (window), "destroy",G_CALLBACK (destroy), NULL);
   gtk_widget_set_size_request (window, 300, 100);

   /*建立组装盒*/
   box1 = gtk_vbox_new (TRUE, 0);
   gtk_container_add (GTK_CONTAINER (window), box1);

   /*建立“Input”按纽*/
   button = gtk_button_new_with_label ("Input";
   /* g_signal_connect (G_OBJECT (button), "clicked", G_CALLBACK (callback), "Input";*/
   gtk_box_pack_start (GTK_BOX(box1), button, TRUE, TRUE, 0);
   gtk_widget_show (button);

   /*建立“ChangeTitle”按钮*/
   button = gtk_button_new_with_label ("ChangeTitle";
   g_signal_connect (G_OBJECT (button), "clicked", G_CALLBACK (gtk_window_set_title), "ChangeTitle";
   gtk_box_pack_start (GTK_BOX(box1), button, TRUE, TRUE, 0);
   gtk_widget_show (button);
   /*建立“Quit”按钮*/
   button = gtk_button_new_with_label ("Quit";
   g_signal_connect_swapped (G_OBJECT (button), "clicked",   G_CALLBACK (gtk_widget_destroy), window);
   gtk_box_pack_start (GTK_BOX(box1), button, TRUE, TRUE, 0);
   gtk_widget_show (button);

   gtk_widget_show (box1);
   gtk_widget_show (window);
   gtk_main();
   return 0;

}       

请教：
       代码虽然编译通过，但是“ChangTitle”的功能没实现，并且每点击一次“ChangeTitle”，终端就输出一条信息 ，如下：

       GTK-CRITICAL**：file gtkwindow.c: line 953 (gtk_window_set_title) : assertion `GTK_IS_WINDOW (window)` failed