Code to make sure a single instance is running

singleinstance.cpp

@@ -0,0 +1,48 @@
+#include <QLockFile>
+#include <QProcessEnvironment>
+
+#include "singleinstance.h"
+
+/**
+ * @brief filename
+ * @param key
+ * @param scope
+ * @return a fully qualified filename
+ *
+ * Generates an appropriate filename for the lock
+ */
+static QString filename(QString key, scope_t scope) {
+
+    QProcessEnvironment env = QProcessEnvironment::systemEnvironment();
+    QString tmp = env.value("TEMP", "/tmp") + "/";
+    QString user = env.value("USER", "alfio");
+
+
+    QString r;
+    switch (scope) {
+        case SYSTEM:
+            r = tmp;
+            break;
+        case SESSION:
+            //TODO this will prevent trabucco to run in multiple sessions
+            r = env.value("XDG_RUNTIME_DIR", tmp + user) + "/";
+            break;
+    }
+    return r + key + ".lock";
+}
+
+/**
+ * @brief SingleInstance::unique
+ * @param key the unique name of the program
+ * @param scope wether it needs to be system-wide or session-wide
+ * @return true if this is the only instance
+ *
+ * Make sure that this instance is unique.
+ */
+bool SingleInstance::unique(QString key, scope_t scope) {
+    QLockFile* lock = new QLockFile(filename(key, scope));
+    bool r = lock->tryLock();
+    if (!r)
+        delete lock;
+    return r;
+}

singleinstance.h

@@ -0,0 +1,15 @@
+#ifndef SINGLEINSTANCE_H
+#define SINGLEINSTANCE_H
+
+typedef enum {
+    SYSTEM,
+    SESSION,
+} scope_t;
+
+class SingleInstance
+{
+public:
+    static bool unique(QString key, scope_t scope);
+};
+
+#endif // SINGLEINSTANCE_H

trabucco.pro

@@ -7,7 +7,8 @@ CONFIG += c++11
 LIBS        += -lX11
 
 SOURCES += main.cpp \
-    settings.cpp
+    settings.cpp \
+    singleinstance.cpp
 
 RESOURCES += qml.qrc
 
@@ -18,7 +19,8 @@ QML_IMPORT_PATH =
 include(deployment.pri)
 
 HEADERS += \
-    settings.h
+    settings.h \
+    singleinstance.h
 
 FORMS += \
     settings.ui