Custom resizable Gtk.Image

namespace My {
    public class Image : Gtk.DrawingArea {
        construct {
            draw.connect (context => {
                int width = get_allocated_width();
                int height = get_allocated_height();
                uint8[] buffer;
                var res = pixbuf.scale_simple (width, width * pixbuf.height / pixbuf.width, Gdk.InterpType.BILINEAR);
                if (height < res.height)
                    res = pixbuf.scale_simple (height * res.width / res.height, height, Gdk.InterpType.BILINEAR);
                res.save_to_buffer (out buffer, "png");
                var stream = new MemoryInputStream.from_data (buffer);
                var surface = new Cairo.ImageSurface.from_png_stream (data => {
                    stream.read (data);
                    return Cairo.Status.SUCCESS;
                });
                context.set_source_surface (surface, (width - res.width) / 2, (height - res.height) / 2);
                context.paint();
            });
            notify["location"].connect (() => {
                pixbuf = new Gdk.Pixbuf.from_stream (File.new_for_path (location).read());
            });
        }

        public Gdk.Pixbuf pixbuf { get; set; }
        public string location { get; set; }
    }
}

// compile with : valac sample.vala --pkg gtk+-3.0