void draw_grabbing_point_on_canvas(CanvasCairo *canvas, scalar_t scaling,
scalar_t xg, scalar_t yg,
scalar_t r, scalar_t g, scalar_t b) {
void draw_grabbing_point_on_canvas(CanvasCairo *canvas, scalar_t scaling,
scalar_t xg, scalar_t yg,
scalar_t r, scalar_t g, scalar_t b) {