[cairo] global clip for a cairo context

[Lawrence D'Oliveiro]

On Sun, 3 Jan 2016 16:17:04 +1030, Adrian Johnson wrote:

> Assuming a rectangular clip you could use something like:
> 
> clipped_surf = cairo_surface_create_for_rectangle (cairo_get_target
> (cr), x, y, w, h);
> clipped_cr = cairo_create (clipped_surf);

Presumably that is intersected with the current clip on the parent
surface...