Cairo and Gdk.Window with Gtk.DrawingArea using python gobject-introspection and gtk3

Question

I am trying to follow the Gtk+ v3 tutorial found in the reference documentation. Specifically the first Drawing example using cairo to handle the drawing onto a Gtk.DrawingArea.

https://developer.gnome.org/gtk3/stable/ch01s03.html

For reference, I am using these resources:

https://python-gtk-3-tutorial.readthedocs.org/en/latest/

http://lazka.github.io/pgi-docs/

Please take a look at my (partial) translation of the ch01s03 program into python. The main problem I have is with configure_event_cb() where the program should create a cairo.Surface object connected to a Gdk.Window. I do not know how to get at this Gdk.Window or even where to look in the reference documentation.

from gi.repository import Gtk, Gdk, cairo

surface = None

def clear_surface():
    global surface
    surface = cairo.Surface()
    surface.set_source_rgb(1,1,1)
    surface.paint()

def configure_event_cb(wid,evt):
    global surface

    if surface is not None:
        surface.destroy()
        surface = None

    '''
    Here, I am trying to implement the following C code:

    surface = gdk_window_create_similar_surface(
                gtk_widget_get_window(widget),
                CAIRO_CONTENT_COLOR,
                gtk_widget_get_allocated_width(widget),
                gtk_widget_get_allocated_height(widget) );
    '''

    clear_surface()
    return True

def close_window(wid):
    global surface
    if surface is not None:
        surface.destroy()
    Gtk.main_quit()

if __name__ == '__main__':
    win = Gtk.Window(Gtk.WindowType.TOPLEVEL)
    win.set_title('Drawing Area')
    win.connect('destroy',close_window)
    win.set_border_width(8)

    frame = Gtk.Frame()
    frame.set_shadow_type(Gtk.ShadowType.IN)
    win.add(frame)

    da = Gtk.DrawingArea()
    da.set_size_request(100,100)
    frame.add(da)

    da.connect('configure-event',configure_event_cb)

    win.show_all()
    Gtk.main()

Answer 1

I have understood that the DrawingArea use the draw event now instead of the configure-event here is a simple code that works:

from gi.repository import Gtk

def draw_cb(widget, cr):
  cr.set_source_rgba(0,0,0,0.5)
  cr.rectangle(50,75,100,100)
  cr.fill()
  return False

win = Gtk.Window()

win.set_title("test")
win.set_default_size(800,600)
win.connect('delete-event', Gtk.main_quit)
da=Gtk.DrawingArea()
da.connect('draw', draw_cb)
win.add(da)
win.show_all()
Gtk.main()

But instead if you really want to create a cairo context in the callback of the expose-event, just use this to get the gtk.gdk.window:

myGdkWindow = mywin.get_window()
cr = myGdkWindow.cairo_create()