#include<gnome.h>#include"bg.h"int show_bg(GtkWidget * canvas){  GnomeCanvasGroup *group;  group=gnome_canvas_root(GNOME_CANVAS(canvas));   gnome_canvas_item_new(group,                        gnome_canvas_rect_get_type(),/*背景*/			"x1",0.0,			"x2",800.0,			"y1",0.0,                        "y2",600.0,		       	"fill_color","black",		       	"outline_color","blue",		       	"width_units",1.0,			NULL);  return 0;}