Fix short UI hang when manually stopping the stream after losing connection with the host

app/gui/StreamSegue.qml

@@ -103,7 +103,10 @@ Item {
                 streamSegueErrorDialog.open()
             }
         }
+    }
 
+    function sessionReadyForDeletion()
+    {
         // Garbage collect the Session object since it's pretty heavyweight
         // and keeps other libraries (like SDL_TTF) around until it is deleted.
         session = null
@@ -130,6 +133,7 @@ Item {
         session.displayLaunchWarning.connect(displayLaunchWarning)
         session.quitStarting.connect(quitStarting)
         session.sessionFinished.connect(sessionFinished)
+        session.readyForDeletion.connect(sessionReadyForDeletion)
 
         // Kick off the stream
         spinnerTimer.start()

app/streaming/session.cpp

@@ -464,16 +464,6 @@ Session::Session(NvComputer* computer, NvApp& app, StreamingPreferences *prefere
     SDL_AtomicSet(&m_NeedsIdr, 0);
 }
 
-// NB: This may not get destroyed for a long time! Don't put any vital cleanup here.
-// Use Session::exec() or DeferredSessionCleanupTask instead.
-Session::~Session()
-{
-    // Acquire session semaphore to ensure all cleanup is done before the destructor returns
-    // and the object is deallocated.
-    s_ActiveSessionSemaphore.acquire();
-    s_ActiveSessionSemaphore.release();
-}
-
 bool Session::initialize()
 {
     if (SDL_InitSubSystem(SDL_INIT_VIDEO) != 0) {
@@ -856,6 +846,9 @@ private:
         // Allow another session to start now that we're cleaned up
         Session::s_ActiveSession = nullptr;
         Session::s_ActiveSessionSemaphore.release();
+
+        // Notify that the session is ready to be cleaned up
+        emit m_Session->readyForDeletion();
     }
 
     void run() override
@@ -1316,6 +1309,7 @@ void Session::execInternal()
     // called on the main thread.
     if (!initialize()) {
         emit sessionFinished(0);
+        emit readyForDeletion();
         return;
     }
 

app/streaming/session.h

@@ -22,7 +22,9 @@ class Session : public QObject
 public:
     explicit Session(NvComputer* computer, NvApp& app, StreamingPreferences *preferences = nullptr);
 
-    virtual ~Session();
+    // NB: This may not get destroyed for a long time! Don't put any cleanup here.
+    // Use Session::exec() or DeferredSessionCleanupTask instead.
+    virtual ~Session() {};
 
     Q_INVOKABLE void exec(int displayOriginX, int displayOriginY);
 
@@ -60,6 +62,9 @@ signals:
 
     void sessionFinished(int portTestResult);
 
+    // Emitted after sessionFinished() when the session is ready to be destroyed
+    void readyForDeletion();
+
 private:
     void execInternal();
 

app/streaming/video/overlaymanager.cpp

@@ -15,7 +15,11 @@ OverlayManager::OverlayManager() :
     m_Overlays[OverlayType::OverlayStatusUpdate].color = {0xCC, 0x00, 0x00, 0xFF};
     m_Overlays[OverlayType::OverlayStatusUpdate].fontSize = 36;
 
-    SDL_assert(TTF_WasInit() == 0);
+    // While TTF will usually not be initialized here, it is valid for that not to
+    // be the case, since Session destruction is deferred and could overlap with
+    // the lifetime of a new Session object.
+    //SDL_assert(TTF_WasInit() == 0);
+
     if (TTF_Init() != 0) {
         SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
                     "TTF_Init() failed: %s",
@@ -36,7 +40,12 @@ OverlayManager::~OverlayManager()
     }
 
     TTF_Quit();
-    SDL_assert(TTF_WasInit() == 0);
+
+    // For similar reasons to the comment in the constructor, this will usually,
+    // but not always, deinitialize TTF. In the cases where Session objects overlap
+    // in lifetime, there may be an additional reference on TTF for the new Session
+    // that means it will not be cleaned up here.
+    //SDL_assert(TTF_WasInit() == 0);
 }
 
 bool OverlayManager::isOverlayEnabled(OverlayType type)