Defer launch warnings until after launch validation

We need to destroy the SDL window before we can be sure that Qt
can draw to the screen if we used KMSDRM.

app/streaming/session.cpp

@@ -902,11 +902,10 @@ bool Session::initialize()
         return false;
     }
 
-    return true;
-}
-
-void Session::emitLaunchWarning(QString text)
-{
+    // Display launch warnings in Qt only after destroying SDL's window.
+    // This avoids conflicts between the windows on display subsystems
+    // such as KMSDRM that only support a single window.
+    for (const auto &text : m_LaunchWarnings) {
         // Emit the warning to the UI
         emit displayLaunchWarning(text);
 
@@ -923,6 +922,15 @@ void Session::emitLaunchWarning(QString text)
                 QCoreApplication::sendPostedEvents();
             }
         }
+    }
+
+    return true;
+}
+
+void Session::emitLaunchWarning(QString text)
+{
+    // Queue this launch warning to be displayed after validation
+    m_LaunchWarnings.append(text);
 }
 
 bool Session::validateLaunch(SDL_Window* testWindow)

app/streaming/session.h

@@ -260,6 +260,7 @@ private:
     SdlInputHandler* m_InputHandler;
     int m_MouseEmulationRefCount;
     int m_FlushingWindowEventsRef;
+    QList<QString> m_LaunchWarnings;
 
     bool m_AsyncConnectionSuccess;
     int m_PortTestResults;