positions of vertices

Good day to you. I'm trying to create pop-up windows in graph-tool
graph. Using your advises I add a function, which making callback from
the graph and give coordinates of my mouse pointer. But graph-vertices
coordinates are not simular with gdk-window coordinates. In example: I
placed some vertices, but a vertex with (0,0) coordinates not in left-up
angle of the window. How I can get coordinates of vertices in gdk style?
My pointer's coordinates of (0,0) are in left-up side of the window.