The following example demonstrates the use of a Clutter::BehaviourPath
with a simple custom alpha function. This simply moves the rectangle from the top-left to the
bottom-right of the canvas at constant speed:
File: main.cc
#include <cluttermm.h> namespace { static Glib::RefPtr<Clutter::Rectangle> rect; /* * This must return a value between 0 and Clutter::Alpha::MAX_ALPHA, where * 0 means the start of the path, and Clutter::Alpha::MAX_ALPHA is the end * of the path. * * This will be called as many times per seconds as specified in our call * to Clutter::Timeline::create(). * * See also, for instance Clutter::Alpha::sine_half_func for a useful * built-in callback. */ static guint32 on_alpha(Glib::RefPtr<Clutter::Alpha> alpha) { // Get the position in the timeline, so we can base our value upon it: const Glib::RefPtr<Clutter::Timeline> timeline = alpha->get_timeline(); // Return a value that is simply proportional to the frame position: return timeline->get_progress(); } } // anonymous namespace int main(int argc, char** argv) { Clutter::init(&argc, &argv); // Get the stage and set its size and color: const Glib::RefPtr<Clutter::Stage> stage = Clutter::Stage::get_default(); stage->set_size(200, 200); stage->set_color(Clutter::Color(0x00, 0x00, 0x00, 0xFF)); // black // Add a rectangle to the stage: rect = Clutter::Rectangle::create(Clutter::Color(0xFF, 0xFF, 0xFF, 0x99)); rect->set_size(40, 40); rect->set_position(10, 10); stage->add_actor(rect); rect->show(); // Show the stage: stage->show(); { const Glib::RefPtr<Clutter::Timeline> timeline = Clutter::Timeline::create(5000 /* milliseconds */); timeline->set_loop(true); timeline->start(); // Instead of our custom callback, we could use a standard callback. // For instance, Clutter::Alpha::sine_inc_func. const Glib::RefPtr<Clutter::Alpha> alpha = Clutter::Alpha::create(timeline, &on_alpha); std::vector<Clutter::Knot> knots (2); knots[0].set_xy(10, 10); knots[1].set_xy(150, 150); const Glib::RefPtr<Clutter::Behaviour> behaviour = Clutter::BehaviourPath::create_with_knots(alpha, knots); behaviour->apply(rect); } // Start the main loop, so we can respond to events: Clutter::main(); return 0; }