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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter17.Timeouts, I/O and Idle Functions </title><meta name="generator" content="DocBook XSL Stylesheets V1.64.1"><link rel="home" href="index.html" title="Programming with gtkmm2"><link rel="up" href="index.html" title="Programming with gtkmm2"><link rel="previous" href="ch16s04.html" title="Examples"><link rel="next" href="ch17s02.html" title="Monitoring I/O"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter17.Timeouts, I/O and Idle Functions </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch16s04.html">Prev</a></td><th width="60%" align="center"></th><td width="20%" align="right"><a accesskey="n" href="ch17s02.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="sec-timeouts"></a>Chapter17.Timeouts, I/O and Idle Functions </h2></div></div><div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="ch17.html#id2518043">Timeouts</a></span></dt><dt><span class="sect1"><a href="ch17s02.html">Monitoring I/O</a></span></dt><dt><span class="sect1"><a href="ch17s03.html">Idle Functions</a></span></dt></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2518043"></a>Timeouts</h2></div></div><div></div></div><p>
You may be wondering how to make gtkmm do useful work while it's
idling along (well, sleeping actually) in <tt class="literal">Gtk::Main::run()</tt>. Happily,
you have several options. Using the following methods you can create
a timeout method that will be called every few milliseconds.
</p><p>
</p><pre class="programlisting">
SigC::Connection Glib::SignalTimeout::connect(const SigC::Slot0<bool>& slot, unsigned int interval, int priority = Glib::PRIORITY_DEFAULT);
</pre><p>
</p><p>
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 <tt class="literal">SigC::Connection</tt> object that can be
used to deactivate the connection.
</p><p>
</p><pre class="programlisting">
MyConnection.disconnect();
</pre><p>
</p><p>
to destroy the connection. Another way of destroying the Connection
is your signal handler. It has to be of the type
<tt class="literal">SigC::Slot0<bool></tt>. As you see from the definition your
signal handler has to return a value of the type <tt class="literal">bool</tt>. A
definition of a sample method might look like this:
</p><p>
</p><pre class="programlisting">
bool MyCallback() { std::cout << "Hello World!\n"; return true; }
</pre><p>
</p><p>
You can stop the timeout method by returning <tt class="literal">false</tt> from
your signal handler. Therefore, if you want your
method to be called repeatedly, it should return <tt class="literal">true</tt>.
</p><p>
Here's an example of this technique:
</p><p><a href="../../../examples/book/timeout/" target="_top">Source Code</a></p><p>File: timerexample.h
</p><pre class="programlisting">
#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();
// This is the callback function the timeout will call
bool on_timeout(int timer_number);
// Member data:
Gtk::HBox 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
</pre><p>
</p><p>File: main.cc
</p><pre class="programlisting">
#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;
}
</pre><p>
</p><p>File: timerexample.cc
</p><pre class="programlisting">
#include "timerexample.h"
TimerExample::TimerExample() :
m_Box(true, 10),
m_ButtonAddTimer(Gtk::Stock::ADD), // use Gtk::Stock wherever possible for buttons, etc.
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::slot(*this, &Gtk::Widget::hide));
m_ButtonAddTimer.signal_clicked().connect(SigC::slot(*this,&TimerExample::on_button_add_timer));
m_ButtonDeleteTimer.signal_clicked().connect(SigC::slot(*this,&TimerExample::on_button_delete_timer));
show_all_children();
}
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::Slot0<bool> my_slot = SigC::bind(SigC::slot(*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;
}
</pre><p>
</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch16s04.html">Prev</a></td><td width="20%" align="center"><a accesskey="u" href="index.html">Up</a></td><td width="40%" align="right"><a accesskey="n" href="ch17s02.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Examples</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">Monitoring I/O</td></tr></table></div></body></html>
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