Gracefully handling signals

Signed-off-by: Dušan Poizl <nou.spiro@gmail.com>

mainwindow.cpp

@@ -11,6 +11,11 @@
 #include <QDebug>
 #include <sys/ioctl.h>
 #include <linux/btrfs.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/socket.h>
+
+int MainWindow::socketPair[2] = {0, 0};
 
 MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent),
   loading(false),
@@ -50,6 +55,8 @@ MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent),
     m_database = new Database(this);
     if(!m_database->init())
         QMessageBox::critical(this, tr("Can't open DB"), tr("Can't open SQLITE database"));
+
+    setupSigterm();
 }
 
 MainWindow::~MainWindow()
@@ -87,6 +94,39 @@ void MainWindow::keyReleaseEvent(QKeyEvent *event)
     event->ignore();
 }
 
+void MainWindow::setupSigterm()
+{
+    struct sigaction signal;
+
+    signal.sa_handler = MainWindow::signalHandler;
+    sigemptyset(&signal.sa_mask);
+    signal.sa_flags = 0;
+    signal.sa_flags |= SA_RESTART;
+
+    sigaction(SIGHUP, &signal, 0);
+    sigaction(SIGTERM, &signal, 0);
+    sigaction(SIGINT, &signal, 0);
+
+    ::socketpair(AF_UNIX, SOCK_STREAM, 0, socketPair);
+    socketNotifier = new QSocketNotifier(socketPair[1], QSocketNotifier::Read, this);
+    connect(socketNotifier, SIGNAL(activated(int)), this, SLOT(socketNotify()));
+}
+
+void MainWindow::signalHandler(int)
+{
+    char a = 1;
+    ::write(socketPair[0], &a, sizeof(a));
+}
+
+void MainWindow::socketNotify()
+{
+    socketNotifier->setEnabled(false);
+    char tmp;
+    read(socketPair[1], &tmp, sizeof(tmp));
+    close();
+    socketNotifier->setEnabled(true);
+}
+
 void MainWindow::pixmapLoaded(QPixmap pix)
 {
     m_image->setImage(pix);

mainwindow.h

@@ -2,6 +2,7 @@
 #define MAINWINDOW_H
 
 #include <QMainWindow>
+#include <QSocketNotifier>
 #include "imageringlist.h"
 #include "imagescrollarea.h"
 #include "database.h"
@@ -14,13 +15,18 @@ class MainWindow : public QMainWindow
     Database *m_database;
     bool loading;
     int queued;
+    static int socketPair[2];
+    QSocketNotifier *socketNotifier;
 public:
     MainWindow(QWidget *parent = 0);
     ~MainWindow();
 protected:
     void keyPressEvent(QKeyEvent *event);
     void keyReleaseEvent(QKeyEvent *event);
+    void setupSigterm();
+    static void signalHandler(int);
 protected slots:
+    void socketNotify();
     void updateWindowTitle();
     void pixmapLoaded(QPixmap pix);
     void openFile();