超时

你可能想知道如何使gtkmm在空闲的时候做一些有用的工作。幸运的是你有几种选择。你可以创建一个每几毫秒就调用的超时方法。

sigc::connection Glib::SignalTimeout::connect(const sigc::slot<bool()>& slot,
                                      unsigned int interval, int priority = Glib::PRIORITY_DEFAULT);

第一个参数是超时时你希望被调用的slot。第二个参数是调用该方法的时间间隔(多少毫秒)。你将收到一个sigc::connection对象,可以在该对象上调用disconnect()方法断开连接。

my_connection.disconnect();

破坏连接的另一种方法是通过你的信号处理函数的返回值。其类型必须是sigc::slot<bool()>。从定义可以看出信号处理函数必须返回一个bool类型的值。示例方法的定义可能如下所示:

bool MyCallback() { std::cout << "Hello World!\n" << std::endl; return true; }

你可以通过让你的信号处理函数返回false以停止此超时方法。因此,如果你还想重复调用此方法,则你需要让信号处理函数返回true

这是此技术的示例:

源代码

File: timerexample.h (For use with gtkmm 4)

#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: main.cc (For use with gtkmm 4)

#include "timerexample.h"
#include <gtkmm/application.h>

int main (int argc, char *argv[])
{
  auto app = Gtk::Application::create("org.gtkmm.example");

  return app->make_window_and_run<TimerExample>(argc, argv);
}

File: timerexample.cc (For use with gtkmm 4)

#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
{
  m_Box.set_margin(10);
  set_child(m_Box);
  m_Box.append(m_ButtonAddTimer);
  m_Box.append(m_ButtonDeleteTimer);
  m_Box.append(m_ButtonQuit);
  m_ButtonAddTimer.set_expand();
  m_ButtonDeleteTimer.set_expand();
  m_ButtonQuit.set_expand();

  // 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));
}

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()
  auto 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;
}