GTK container

- In GTK container only one widget is added at a time

Code

```c
#include <gtk/gtk.h>

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

	gtk_init(&argc,&argv);
	GtkWidget *window;
	GtkWidget *button1;
	GtkWidget *button2;


	window=gtk_window_new(GTK_WINDOW_TOPLEVEL);

	gtk_window_set_default_size(GTK_WINDOW(window), 500, 500);

	button1= gtk_button_new_with_label("button1");
	button2= gtk_button_new_with_label("button2");

	gtk_container_add(GTK_CONTAINER(window), button1);
	gtk_container_remove(GTK_CONTAINER(window), button1);	
	gtk_container_add(GTK_CONTAINER(window), button2);

	g_signal_connect(GTK_WINDOW(window),"destroy",G_CALLBACK(gtk_main_quit),NULL);
	gtk_widget_show_all(window);
	gtk_main();
	return 0;
}
```