support lock/unlock in layout

--identify if a layout is locked and
support lock/unlock for that layout

app/layout.cpp

@@ -220,6 +220,35 @@ void Layout::setShowInMenu(bool show)
     emit showInMenuChanged();
 }
 
+bool Layout::isWritable() const
+{
+    QFileInfo layoutFileInfo(m_layoutFile);
+
+    if (layoutFileInfo.exists() && !layoutFileInfo.isWritable()) {
+        return false;
+    } else {
+        return true;
+    }
+}
+
+void Layout::lock()
+{
+    QFileInfo layoutFileInfo(m_layoutFile);
+
+    if (layoutFileInfo.exists() && layoutFileInfo.isWritable()) {
+        QFile(m_layoutFile).setPermissions(QFileDevice::ReadUser | QFileDevice::ReadGroup | QFileDevice::ReadOther);
+    }
+}
+
+void Layout::unlock()
+{
+    QFileInfo layoutFileInfo(m_layoutFile);
+
+    if (layoutFileInfo.exists() && !layoutFileInfo.isWritable()) {
+        QFile(m_layoutFile).setPermissions(QFileDevice::ReadUser | QFileDevice::WriteUser | QFileDevice::ReadGroup | QFileDevice::ReadOther);
+    }
+}
+
 QString Layout::background() const
 {
     return m_background;

app/layout.h

@@ -77,6 +77,8 @@ public:
     //!it is original layout compared to pseudo-layouts that are combinations of multiple-original layouts
     bool isOriginalLayout() const;
 
+    bool isWritable() const;
+
     int version() const;
     void setVersion(int ver);
 
@@ -132,6 +134,11 @@ public:
     QList<Plasma::Types::Location> freeEdges(QScreen *screen) const;
     QList<Plasma::Types::Location> freeEdges(int screen) const;
 
+    //! make it only read-only
+    void lock();
+    //! make it writable which it should be the default
+    void unlock();
+
     int noDocksWithTasks() const;
     int docksCount() const;
     int docksCount(int screen) const;