Make event handling of `syncthingctl wait-for-idle` more efficient

Don't go though the list of dirs/devs for every dir/dev change event. Just
go though the list once after receiving new events. This makes also the
code a little bit easier to follow.

cli/application.cpp

@@ -943,46 +943,45 @@ void Application::waitForIdle(const ArgumentOccurrence &)
 {
     m_preventDisconnect = true;
 
-    // setup timer
-    QTimer idleTime;
+    // setup timer for handling minimum idle duration
+    auto idleTime = QTimer();
     idleTime.setSingleShot(true);
     idleTime.setInterval(m_idleDuration);
 
-    // define variable which is set to true if handleTimeout to indicate the idle state has persisted long enough
-    bool isLongEnoughIdle = false;
-
-    // define handler for timer timeout
-    function<void(void)> handleTimeout([this, &isLongEnoughIdle] {
+    // define event handlers
+    auto isLongEnoughIdle = false, dirsOrDevsChanged = true, newDirsOrDevs = true;
+    const auto handleStatusChange = [&dirsOrDevsChanged] { dirsOrDevsChanged = true; };
+    const auto handleNewDirsOrDevs = [&newDirsOrDevs] { newDirsOrDevs = true; };
+    const auto handleAllEventsProcessed = [this, &newDirsOrDevs, &dirsOrDevsChanged, &idleTime] {
+        if (newDirsOrDevs) {
+            findRelevantDirsAndDevs(OperationType::WaitForIdle);
+        }
+        if (newDirsOrDevs || dirsOrDevsChanged) {
+            if (!checkWhetherIdle()) {
+                idleTime.stop();
+                return;
+            }
+            if (!idleTime.isActive()) {
+                idleTime.start();
+            }
+        }
+        newDirsOrDevs = dirsOrDevsChanged = false;
+    };
+    const auto handleIdleTimer = [this, &isLongEnoughIdle] {
         if (checkWhetherIdle()) {
             isLongEnoughIdle = true;
         }
-    });
-
-    // define handler for dirStatusChanged/devStatusChanged
-    function<void(void)> handleStatusChange([this, &idleTime] {
-        if (!checkWhetherIdle()) {
-            idleTime.stop();
-            return;
-        }
-        if (!idleTime.isActive()) {
-            idleTime.start();
-        }
-    });
-
-    // define handler for newDirs/newDevices to call findRelevantDirsAndDevs() in that case
-    function<void(void)> handleNewDirsOrDevs([this, &handleStatusChange] {
-        findRelevantDirsAndDevs(OperationType::WaitForIdle);
-        handleStatusChange();
-    });
+    };
 
     // invoke handler manually because Syncthing could already be idling
-    handleNewDirsOrDevs();
+    handleAllEventsProcessed();
 
     waitForSignals(&noop, m_idleTimeout, signalInfo(&m_connection, &SyncthingConnection::dirStatusChanged, handleStatusChange, &isLongEnoughIdle),
         signalInfo(&m_connection, &SyncthingConnection::devStatusChanged, handleStatusChange, &isLongEnoughIdle),
         signalInfo(&m_connection, &SyncthingConnection::newDirs, handleNewDirsOrDevs, &isLongEnoughIdle),
         signalInfo(&m_connection, &SyncthingConnection::newDevices, handleNewDirsOrDevs, &isLongEnoughIdle),
-        signalInfo(&idleTime, &QTimer::timeout, handleTimeout, &isLongEnoughIdle));
+        signalInfo(&m_connection, &SyncthingConnection::allEventsProcessed, handleAllEventsProcessed, &isLongEnoughIdle),
+        signalInfo(&idleTime, &QTimer::timeout, handleIdleTimer, &isLongEnoughIdle));
 
     if (!isLongEnoughIdle) {
         cerr << Phrases::Warning << "Exiting after timeout" << Phrases::End << flush;

syncthingconnector/syncthingconnection.cpp

@@ -1113,6 +1113,16 @@ void SyncthingConnection::recalculateStatus()
  * \remarks New events are automatically polled when connected.
  */
 
+/*!
+ * \fn SyncthingConnection::allEventsProcesses()
+ * \brief Indicates all new events have been processed.
+ * \remarks
+ * This event is emitted after newEvents() and dirStatusChanged(), devStatusChanged() and other specific events.
+ * If you would go through the list of all directories on every dirStatusChanged() event using instead might
+ * be a more efficient alternative allEventsProcesses(). Just set a flag on dirStatusChanged() and go though the
+ * list of directories only once on the allEventsProcesses() event when the flag has been set.
+ */
+
 /*!
  * \fn SyncthingConnection::dirStatusChanged()
  * \brief Indicates the status of the specified \a dir changed.

syncthingconnector/syncthingconnection.h

@@ -233,6 +233,7 @@ Q_SIGNALS:
     void newDevices(const std::vector<SyncthingDev> &devs);
     void newConfigApplied();
     void newEvents(const QJsonArray &events);
+    void allEventsProcessed();
     void dirStatusChanged(const Data::SyncthingDir &dir, int index);
     void devStatusChanged(const Data::SyncthingDev &dev, int index);
     void fileChanged(const Data::SyncthingDir &dir, int index, const Data::SyncthingFileChange &fileChange);

syncthingconnector/syncthingconnection_requests.cpp

@@ -1737,7 +1737,9 @@ void SyncthingConnection::readEvents()
         m_hasEvents = true;
         const auto replyArray = replyDoc.array();
         emit newEvents(replyArray);
-        if (!readEventsFromJsonArray(replyArray, m_lastEventId)) {
+        const auto res = readEventsFromJsonArray(replyArray, m_lastEventId);
+        emit allEventsProcessed();
+        if (!res) {
             return;
         }