Add and locate widgets in Gtk::DrawingArea - gtkmm

Question

Greetings to all, I would like to know whether there is a way to add and locate a Gtk::Widget in Gtk::DrawingArea. My purpose of doing that is to show some detailed information on the graphics in the drawing area when the graphics is clicked. The detailed information can be rich-formatted.
I understood that Gtk::DrawingArea does not have the function like add(Widget). So I wonder if a work-around is available.
Thanks in advance & best regards.
CHEN Kai

Answer 1

Not sure how helpful it is, but I found this by searching:
Old Nabble - Gtk+ - Python - overlaying gtk widget over a gtk.drawing area
seems there is a gtk.Fixed()->put() function, but I cannot tell if it should run in a drawing loop or not.. (edit: see also GTK v1.2 Tutorial: Container Widgets)
Cheers!

Answer 2

Yep it's possible. Here you are. Enjoy the code in C:
#include <gtk/gtk.h>
#include <math.h>
GtkWidget *window;
GtkWidget *layout;
GtkWidget *canvas;
GtkWidget *image;
GtkWidget *eventbox;
static gboolean on_window_draw (GtkWidget *da, GdkEventExpose *event, gpointer data)
{
GdkWindow *window;
GdkDrawingContext *drawingContext;
cairo_region_t *cairoRegion;
cairo_t *cr;
cairoRegion = cairo_region_create();
window = gtk_layout_get_bin_window(GTK_LAYOUT(layout));
drawingContext = gdk_window_begin_draw_frame(window, cairoRegion);
cr = gdk_drawing_context_get_cairo_context(drawingContext);
cairo_set_line_width(cr, 9);
cairo_set_source_rgb(cr, 0.69, 0.19, 0);
cairo_translate(cr, 300/2, 200/2);
cairo_arc(cr, 0, 0, 50, 0, 2 * M_PI);
cairo_stroke_preserve(cr);
cairo_set_source_rgb(cr, 0.3, 0.4, 0.6);
cairo_fill(cr);
gdk_window_end_draw_frame(window, drawingContext);
cairo_region_destroy(cairoRegion);
return FALSE;
}
int main ( int argc, char **argv)
{
GtkWidget *button;
gtk_init (&argc , &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_widget_set_size_request (window, 300, 200);
g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit) , NULL);
canvas = gtk_drawing_area_new ();
layout = gtk_layout_new(NULL,NULL);
gtk_container_add (GTK_CONTAINER (layout), canvas);
gtk_container_add (GTK_CONTAINER (window), layout);
button = gtk_button_new_with_label("I feel alone...");
gtk_container_add(GTK_CONTAINER(layout), button);
gtk_layout_move(GTK_LAYOUT(layout), button, 90, 50);
g_signal_connect (canvas, "draw", (GCallback) on_window_draw, NULL);
gtk_widget_show_all (window);
gtk_main ();
return 0;
}