The following example demonstrates the use of both a fade effect and a path effect on the same actor, changing a rectangle's opacity while it is moved a long a straight line:
File: main.cc
#include <cluttermm.h> #include <vector> namespace { 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(const 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(); const int current_frame_num = timeline->get_current_frame(); const int n_frames = timeline->get_n_frames(); // Return a value that is simply proportional to the frame position: return Clutter::Alpha::MAX_ALPHA * current_frame_num / n_frames; } } // 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)); // 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(100 /*frames*/, 30 /*fps*/); timeline->set_loop(); timeline->start(); // Instead of our custom callback, we could use a standard callback. // For instance, Clutter::Alpha::sine_inc_func. const Glib::RefPtr<Clutter::EffectTemplate> effect = Clutter::EffectTemplate::create(timeline, &on_alpha); std::vector<Clutter::Knot> knots (2); knots[0].set_xy(10, 10); knots[1].set_xy(150, 150); // Move the actor along the path: effect->path(rect, knots); // Also change the actor's opacity while moving it along the path: // (You would probably want to use a different ClutterEffectTemplate, // so you could use a different alpha callback for this.) effect->fade(rect, 50); } // Start the main loop, so we can respond to events: Clutter::main(); return 0; }