+ startMonitoring();
+ monitor_->checkModifiedAsync();
+}
+
+
+signals2::connection RenderMonitoredPreview::connect(slot const & slot)
+{
+ return changed_.connect(slot);
+}
+
+
+bool RenderMonitoredPreview::monitoring() const
+{
+ return (bool) monitor_;
+}
+
+
+void RenderMonitoredPreview::startMonitoring() const
+{
+ if (!monitoring()) {
+ monitor_ = FileSystemWatcher::activeMonitor(filename_);
+ monitor_->connect([this](bool /* exists */){ changed_(); });
+ }