Seek help on displaying svg file content onto screen using Rsvg and Cairo/Gtk

In a custom draw function, I have this snippet:
when the draw function is called, I can see the
println messages printed on the REPL.
But the Gtk window did not show the image from the svg file.

{ I also tried to comment out lines marked by # ?
Still no image. }

What do I need to change in the code ?


ctx = Gtk.getgc(widget)

r = Rsvg.handle_new_from_file("/Users/hpwei/julia/pieces/merida/w_q.svg")
d = Rsvg.handle_get_dimensions®
cs = Cairo.CairoImageSurface(d.width,d.height,Cairo.FORMAT_ARGB32);
c = Cairo.CairoContext(cs); # ?
Rsvg.handle_render_cairo(c,r). # ?

println("svg width ", d.width).          # this is ok
println("svg height ", d.height)

set_source_surface(ctx, cs, 0, 0) 
paint(ctx).    # ?