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;
}