从Goocanvas::Points获取坐标

Question

我正在尝试从goocanvasmm中的Goocanvas::Points的实例中获取坐标。我有这个：

double x = 0, y = 0;
int i;
Goocanvas::Points points;
Glib::RefPtr<Goocanvas::Item> root = canvaswidget.get_root_item();
Glib::RefPtr<Goocanvas::Polyline> line = Goocanvas::Polyline::create(100, 100, 110, 120);
root->add_child(line);
points = line->property_points().get_value();
for (i = 0; i < 2; i++){
    points.get_coordinate(i, &x, &y);
    printf("%f03, %f03", x, y);
}

这应该行得通。但当我尝试编译时，它会输出以下内容：

main.cpp: In function ‘int main(int, char**)’:
main.cpp:21: error: no matching function for call to ‘Goocanvas::Points::get_coordinate(int&, double*, double*)’
/usr/include/goocanvasmm-0.1/goocanvasmm/points.h:82: note: candidates are: void Goocanvas::Points::get_coordinate(int, double&, double&) const
make: *** [all] Error 1

Answer 1

你试过这个吗？

points.get_coordinate(i, x, y);