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/* Basic code to enable LADISH level 1 support to an event driven Qt (3/4)
* application
* (c) 2010 Guido Scholz, License: GNU GPL v2
*/
/* (1) */
/* Add this declaration to the header file of your MainWindow class:*/
private:
static int sigpipe[2];
static void handleSignal(int);
bool installSignalHandlers();
private slots:
void signalAction(int);
/* (2) */
/* Add this code to the cpp file of your MainWindow class:*/
#include <cerrno> // for errno
#include <csignal> // for sigaction()
#include <cstring> // for strerror()
#include <unistd.h> // for pipe()
#include <QSocketNotifier>
int MainWindow::sigpipe[2];
MainWindow::MainWindow(...)
{
/* ... */
/*add this lines to the constuctor of your MainWindow class: */
if (!installSignalHandlers())
qWarning("%s", "Signal handlers not installed!");
/* ... */
}
/* Handler for system signals (SIGUSR1, SIGINT...)
* Write a message to the pipe and leave as soon as possible
*/
void MainWindow::handleSignal(int sig)
{
if (write(sigpipe[1], &sig, sizeof(sig)) == -1) {
qWarning("write() failed: %s", std::strerror(errno));
}
}
/* Install signal handlers (may be more than one; called from the
* constructor of your MainWindow class*/
bool MainWindow::installSignalHandlers()
{
/*install pipe to forward received system signals*/
if (pipe(sigpipe) < 0) {
qWarning("pipe() failed: %s", std::strerror(errno));
return false;
}
/*install notifier to handle pipe messages*/
QSocketNotifier* signalNotifier = new QSocketNotifier(sigpipe[0],
QSocketNotifier::Read, this);
connect(signalNotifier, SIGNAL(activated(int)),
this, SLOT(signalAction(int)));
/*install signal handlers*/
struct sigaction action;
memset(&action, 0, sizeof(action));
action.sa_handler = handleSignal;
if (sigaction(SIGUSR1, &action, NULL) == -1) {
qWarning("sigaction() failed: %s", std::strerror(errno));
return false;
}
/* optional: register more signals to handle:
if (sigaction(SIGINT, &action, NULL) == -1) {
qWarning("sigaction() failed: %s", std::strerror(errno));
return false;
}
*/
return true;
}
/* Slot to give response to the incoming pipe message;
e.g.: save current file */
void MainWindow::signalAction(int fd)
{
int message;
if (read(fd, &message, sizeof(message)) == -1) {
qWarning("read() failed: %s", std::strerror(errno));
return;
}
switch (message) {
case SIGUSR1:
saveFile();
break;
/* optional: handle more signals:
case SIGINT:
//do something usefull like ...
close();
break;
*/
default:
qWarning("Unexpected signal received: %d", message);
break;
}
}
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