Refresh the filling in the cCairoContext.
Dim CC As cCairoContext
'unlike in GDI, where we would "Select" a Bitmap into a hDC first...
'with Cairo we can create such a CC "anytime" from any Surface
'in a non-expensive Operation (this does not need larger CPU-cycles)
Set CC = Srf.CreateContext
'the following two lines ensure a complete Surface-Fill