cairo/canvas.go
func (v *Context) SetSourceRGB(red, green, blue float64) {
	C.cairo_set_source_rgb(v.native(), C.double(red), C.double(green),
		C.double(blue))
}
func (v *Context) SetSourceRGB(red, green, blue float64) {
	C.cairo_set_source_rgb(v.native(), C.double(red), C.double(green),
		C.double(blue))
}
// SetSourceRGB is a wrapper around cairo_set_source_rgb().