Λήξεις χρόνου
Μπορεί να αναρωτιέστε πώς γίνεται η gtkmm να κάνει χρήσιμη εργασία, ενώ είναι αδρανής. Ευτυχώς, έχετε πολλές επιλογές. Χρησιμοποιώντας τις ακόλουθες μεθόδους μπορείτε να δημιουργήσετε μια μέθοδο ορίου χρόνου που θα καλείται κάθε λίγα χιλιοστά του δευτερολέπτου.
sigc::connection Glib::SignalTimeout::connect(const sigc::slot<bool>& slot, unsigned int interval, int priority = Glib::PRIORITY_DEFAULT);
Το πρώτο όρισμα είναι μια slot που θέλετε να κληθεί όταν συμβαίνει λήξη χρόνου. Το δεύτερο όρισμα είναι ένας αριθμός χιλιοστών του δευτερολέπτου μεταξύ κλήσεων σε αυτήν τη μέθοδο. Δέχεστε ένα αντικείμενο sigc::connection που μπορεί να χρησιμοποιηθεί για απενεργοποίηση της σύνδεσης χρησιμοποιώντας τη μέθοδό του disconnect():
my_connection.disconnect();
Another way of destroying the connection is your signal handler. It has to be of the type sigc::slot<bool>. As you see from the definition your signal handler has to return a value of the type bool. A definition of a sample method might look like this:
bool MyCallback() { std::cout << "Hello World!\n" << std::endl; return true; }
Μπορείτε να σταματήσετε τη μέθοδο λήξης χρόνου επιστρέφοντας false από τον χειριστή σήματός σας. Συνεπώς, αν θέλετε η μέθοδός σας να καλείται επανειλημμένα, θα πρέπει να επιστρέψετε true.
Ιδού ένα παράδειγμα αυτής της τεχνικής:
File: timerexample.h (For use with gtkmm 3, not gtkmm 2)
#ifndef GTKMM_EXAMPLE_TIMEREXAMPLE_H #define GTKMM_EXAMPLE_TIMEREXAMPLE_H #include <gtkmm.h> #include <iostream> #include <map> class TimerExample : public Gtk::Window { public: TimerExample(); protected: // signal handlers void on_button_add_timer(); void on_button_delete_timer(); void on_button_quit(); // This is the callback function the timeout will call bool on_timeout(int timer_number); // Member data: Gtk::Box m_Box; Gtk::Button m_ButtonAddTimer, m_ButtonDeleteTimer, m_ButtonQuit; // Keep track of the timers being added: int m_timer_number; // These two constants are initialized in the constructor's member initializer: const int count_value; const int timeout_value; // STL map for storing our connections std::map<int, sigc::connection> m_timers; // STL map for storing our timer values. // Each timer counts back from COUNT_VALUE to 0 and is removed when it reaches 0 std::map<int, int> m_counters; }; #endif // GTKMM_EXAMPLE_TIMEREXAMPLE_H
File: timerexample.cc (For use with gtkmm 3, not gtkmm 2)
#include "timerexample.h" TimerExample::TimerExample() : m_Box(Gtk::ORIENTATION_HORIZONTAL, 10), m_ButtonAddTimer("_Add", true), m_ButtonDeleteTimer("_Remove", true), m_ButtonQuit("_Quit", true), m_timer_number(0), // start numbering the timers at 0 count_value(5), // each timer will count down 5 times before disconnecting timeout_value(1500) // 1500 ms = 1.5 seconds { set_border_width(10); add(m_Box); m_Box.pack_start(m_ButtonAddTimer); m_Box.pack_start(m_ButtonDeleteTimer); m_Box.pack_start(m_ButtonQuit); // Connect the three buttons: m_ButtonQuit.signal_clicked().connect(sigc::mem_fun(*this, &TimerExample::on_button_quit)); m_ButtonAddTimer.signal_clicked().connect(sigc::mem_fun(*this, &TimerExample::on_button_add_timer)); m_ButtonDeleteTimer.signal_clicked().connect(sigc::mem_fun(*this, &TimerExample::on_button_delete_timer)); show_all_children(); } void TimerExample::on_button_quit() { hide(); } void TimerExample::on_button_add_timer() { // Creation of a new object prevents long lines and shows us a little // how slots work. We have 0 parameters and bool as a return value // after calling sigc::bind. sigc::slot<bool> my_slot = sigc::bind(sigc::mem_fun(*this, &TimerExample::on_timeout), m_timer_number); // This is where we connect the slot to the Glib::signal_timeout() sigc::connection conn = Glib::signal_timeout().connect(my_slot, timeout_value); // Remember the connection: m_timers[m_timer_number] = conn; // Initialize timer count: m_counters[m_timer_number] = count_value + 1; // Print some info to the console for the user: std::cout << "added timeout " << m_timer_number++ << std::endl; } void TimerExample::on_button_delete_timer() { // any timers? if(m_timers.empty()) { // no timers left std::cout << "Sorry, there are no timers left." << std::endl; } else { // get the number of the first timer int timer_number = m_timers.begin()->first; // Give some info to the user: std::cout << "manually disconnecting timer " << timer_number << std::endl; // Remove the entry in the counter values m_counters.erase(timer_number); // Diconnect the signal handler: m_timers[timer_number].disconnect(); // Forget the connection: m_timers.erase(timer_number); } } bool TimerExample::on_timeout(int timer_number) { // Print the timer: std::cout << "This is timer " << timer_number; // decrement and check counter value if (--m_counters[timer_number] == 0) { std::cout << " being disconnected" << std::endl; // delete the counter entry in the STL MAP m_counters.erase(timer_number); // delete the connection entry in the STL MAP m_timers.erase(timer_number); // Note that we do not have to explicitly call disconnect() on the // connection since Gtk::Main does this for us when we return false. return false; } // Print the timer value std::cout << " - " << m_counters[timer_number] << "/" << count_value << std::endl; // Keep going (do not disconnect yet): return true; }
File: main.cc (For use with gtkmm 3, not gtkmm 2)
#include "timerexample.h" #include <gtkmm/application.h> int main (int argc, char *argv[]) { Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example"); TimerExample example; return app->run(example); }