Timeouts
You may be wondering how to make gtkmm do useful work while it's idling along (well, sleeping actually) in Gtk::Main::run(). Happily, you have several options. Using the following methods you can create a timeout method that will be called every few milliseconds.
sigc::connection Glib::SignalTimeout::connect(const sigc::slot<bool>& slot, unsigned int interval, int priority = Glib::PRIORITY_DEFAULT);
The first argument is a slot you wish to have called when the timeout occurs. The second argument is the number of milliseconds between calls to that method. You receive a sigc::connection object that can be used to deactivate the connection using its disconnect() method:
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; }
You can stop the timeout method by returning false from your signal handler. Therefore, if you want your method to be called repeatedly, it should return true.
Hier ein Beispiel für diese Technik:
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), // use Gtk::Stock wherever possible for buttons, etc. m_ButtonAddTimer(Gtk::Stock::ADD), m_ButtonDeleteTimer(Gtk::Stock::REMOVE), m_ButtonQuit(Gtk::Stock::QUIT), 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/main.h> int main (int argc, char *argv[]) { Gtk::Main app(argc, argv); TimerExample example; Gtk::Main::run(example); return 0; }