Basic code to enable LADISH level 1 support to an event driven Qt (3/4) application.

example-apps/level1-qt.cpp

@@ -0,0 +1,117 @@
+/* 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;
+    }
+}
+