example-apps/level1-qt.cpp

   1 /* Basic code to enable LADISH level 1 support to an event driven Qt (3/4)
   2  * application
   3  * (c) 2010 Guido Scholz, License: GNU GPL v2
   4  */
   5
   6
   7 /* (1) */
   8 /* Add this declaration to the header file of your MainWindow class:*/
   9
  10 private:
  11     static int sigpipe[2];
  12
  13     static void handleSignal(int);
  14     bool installSignalHandlers();
  15
  16 private slots:
  17     void signalAction(int);
  18
  19
  20
  21 /* (2) */
  22 /* Add this code to the cpp file of your MainWindow class:*/
  23
  24 #include <cerrno>   // for errno
  25 #include <csignal>  // for sigaction()
  26 #include <cstring>  // for strerror()
  27 #include <unistd.h> // for pipe()
  28 #include <QSocketNotifier>
  29
  30
  31 int MainWindow::sigpipe[2];
  32
  33
  34 MainWindow::MainWindow(...)
  35 {
  36     /* ... */
  37     /*add this lines to the constuctor of your MainWindow class: */
  38     if (!installSignalHandlers())
  39         qWarning("%s", "Signal handlers not installed!");
  40     /* ... */
  41 }
  42
  43
  44
  45 /* Handler for system signals (SIGUSR1, SIGINT...)
  46  * Write a message to the pipe and leave as soon as possible
  47  */
  48 void MainWindow::handleSignal(int sig)
  49 {
  50     if (write(sigpipe[1], &sig, sizeof(sig)) == -1) {
  51         qWarning("write() failed: %s", std::strerror(errno));
  52     }
  53 }
  54
  55 /* Install signal handlers (may be more than one; called from the
  56  * constructor of your MainWindow class*/
  57 bool MainWindow::installSignalHandlers()
  58 {
  59     /*install pipe to forward received system signals*/
  60     if (pipe(sigpipe) < 0) {
  61         qWarning("pipe() failed: %s", std::strerror(errno));
  62         return false;
  63     }
  64
  65     /*install notifier to handle pipe messages*/
  66     QSocketNotifier* signalNotifier = new QSocketNotifier(sigpipe[0],
  67             QSocketNotifier::Read, this);
  68     connect(signalNotifier, SIGNAL(activated(int)),
  69             this, SLOT(signalAction(int)));
  70
  71     /*install signal handlers*/
  72     struct sigaction action;
  73     memset(&action, 0, sizeof(action));
  74     action.sa_handler = handleSignal;
  75
  76     if (sigaction(SIGUSR1, &action, NULL) == -1) {
  77         qWarning("sigaction() failed: %s", std::strerror(errno));
  78         return false;
  79     }
  80
  81     /* optional: register more signals to handle:
  82     if (sigaction(SIGINT, &action, NULL) == -1) {
  83         qWarning("sigaction() failed: %s", std::strerror(errno));
  84         return false;
  85     }
  86      */
  87
  88     return true;
  89 }
  90
  91 /* Slot to give response to the incoming pipe message;
  92    e.g.: save current file */
  93 void MainWindow::signalAction(int fd)
  94 {
  95     int message;
  96
  97     if (read(fd, &message, sizeof(message)) == -1) {
  98         qWarning("read() failed: %s", std::strerror(errno));
  99         return;
 100     }
 101
 102     switch (message) {
 103         case SIGUSR1:
 104             saveFile();
 105             break;
 106     /* optional: handle more signals:
 107         case SIGINT:
 108             //do something usefull like ...
 109             close();
 110             break;
 111      */
 112         default:
 113             qWarning("Unexpected signal received: %d", message);
 114             break;
 115     }
 116 }
 117