I want to use expose-event to draw something then update or redraw. That's to say, there are a drawing area and a button in window. When clicking button, the drawing area will be redrawn accordingly. My problems are Following code worked but it only had a drawing area no button. If I add the button(cancel the comment for button), nothing is drawn. What's the reason? In the following code, if I changed gtk_container_add (GTK_CONTAINER (box), canvas); to gtk_box_pack_start(GTK_BOX(box), canvas, FALSE, FALSE, 0);, nothing is drawn. Usually we use gtk_box_pack_start to add something into box. Why doesn't it work this time? The function build_ACC_axis refreshed drawing area and prepared for new draw. I google it but I didn't know if it worked. Could you please comment on it? If the source file is test.c, then compilation is gcc -o test test.c `pkg-config --cflags --libs gtk+-2.0` The code is below: #include <gtk/gtk.h> #include <glib.h> static void draw (GdkDrawable *d, GdkGC *gc) { /* Draw with GDK */ gdk_draw_line (d, gc, 0, 0, 50, 50); gdk_draw_line (d, gc, 50, 50, 50, 150); gdk_draw_line (d, gc, 50, 150, 0, 200); gdk_draw_line (d, gc, 200, 0, 150, 50); gdk_draw_line (d, gc, 150, 50, 150, 150); gdk_draw_line (d, gc, 150, 150, 200, 200); gdk_draw_line (d, gc, 50, 50, 150, 50); gdk_draw_line (d, gc, 50, 150, 150, 150); } static gboolean expose_cb (GtkWidget *canvas, GdkEventExpose *event, gpointer user_data) { GdkGC *gc; gc = gdk_gc_new (canvas->window); draw (canvas->window, gc); g_object_unref (gc); return FALSE; } void build_ACC_axis (GtkWidget *button, GtkWidget *widget) { GdkRegion *region; GtkWidget *canvas = g_object_get_data(G_OBJECT(widget), "plat_GA_canvas"); region = gdk_drawable_get_visible_region(canvas->window); gdk_window_invalidate_region(canvas->window, region, TRUE); gtk_widget_queue_draw(canvas); /* gdk_window_process_updates(canvas->window, TRUE); */ gdk_region_destroy (region); } int main (int argc, char **argv) { GtkWidget *window; GtkWidget *canvas, *box, *button; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); g_signal_connect (G_OBJECT (window), "destroy", G_CALLBACK (gtk_main_quit), NULL); box = gtk_vbox_new(FALSE, 0); gtk_container_add (GTK_CONTAINER (window), box); canvas = gtk_drawing_area_new (); g_object_set_data(G_OBJECT(window), "plat_GA_canvas", canvas); /* gtk_box_pack_start(GTK_BOX(box), canvas, FALSE, FALSE, 0); */ gtk_container_add (GTK_CONTAINER (box), canvas); g_signal_connect (G_OBJECT (canvas), "expose-event", G_CALLBACK (expose_cb), NULL); /* button = gtk_button_new_with_label ("ok"); gtk_box_pack_start(GTK_BOX(box), button, FALSE, FALSE, 0); |+ gtk_container_add (GTK_CONTAINER (box), button); +| gtk_signal_connect(GTK_OBJECT(button), "clicked", GTK_SIGNAL_FUNC(build_ACC_axis), window); */ gtk_widget_show_all (window); gtk_main (); }