Postpone FSEvent stream updates to avoid churn when adding large numbers of directories.

src/core/macfslistener.h

@@ -22,6 +22,7 @@
 
 #include <QObject>
 #include <QSet>
+#include <QTimer>
 
 #include "filesystemwatcherinterface.h"
 
@@ -38,9 +39,12 @@ class MacFSListener : public FileSystemWatcherInterface {
  signals:
   void PathChanged(const QString& path);
 
- private:
+ private slots:
   void UpdateStream();
 
+ private:
+  void UpdateStreamAsync();
+
   static void EventStreamCallback(
       ConstFSEventStreamRef stream,
       void* user_data,
@@ -53,6 +57,7 @@ class MacFSListener : public FileSystemWatcherInterface {
   FSEventStreamRef stream_;
 
   QSet<QString> paths_;
+  QTimer update_timer_;
 };
 
 #endif

src/core/macfslistener.mm

@@ -28,6 +28,9 @@ MacFSListener::MacFSListener(QObject* parent)
     : FileSystemWatcherInterface(parent),
       run_loop_(NULL),
       stream_(NULL) {
+  update_timer_.setSingleShot(true);
+  update_timer_.setInterval(2000);
+  connect(&update_timer_, SIGNAL(timeout()), SLOT(UpdateStream()));
 }
 
 void MacFSListener::Init() {
@@ -56,18 +59,22 @@ void MacFSListener::EventStreamCallback(
 void MacFSListener::AddPath(const QString& path) {
   Q_ASSERT(run_loop_);
   paths_.insert(path);
-  UpdateStream();
+  UpdateStreamAsync();
 }
 
 void MacFSListener::RemovePath(const QString& path) {
   Q_ASSERT(run_loop_);
   paths_.remove(path);
-  UpdateStream();
+  UpdateStreamAsync();
 }
 
 void MacFSListener::Clear() {
   paths_.clear();
-  UpdateStream();
+  UpdateStreamAsync();
+}
+
+void MacFSListener::UpdateStreamAsync() {
+  update_timer_.start();
 }
 
 void MacFSListener::UpdateStream() {