Use our ShutdownEventListener utility in Interface, and absorb quit

signal when we handle it.

interface/src/Application.cpp

@@ -91,6 +91,7 @@
 #include <ScriptCache.h>
 #include <SoundCache.h>
 #include <ScriptEngines.h>
+#include <ShutdownEventListener.h>
 #include <Tooltip.h>
 #include <udt/PacketHeaders.h>
 #include <UserActivityLogger.h>
@@ -717,6 +718,12 @@ Application::Application(int& argc, char** argv, QElapsedTimer& startupTimer) :
 
     connect(addressManager.data(), &AddressManager::hostChanged, this, &Application::updateWindowTitle);
     connect(this, &QCoreApplication::aboutToQuit, addressManager.data(), &AddressManager::storeCurrentAddress);
+    // setup a shutdown event listener to handle SIGTERM or WM_CLOSE for us
+#ifdef _WIN32
+    installNativeEventFilter(&ShutdownEventListener::getInstance());
+#else
+    ShutdownEventListener::getInstance();
+#endif
 
     // Save avatar location immediately after a teleport.
     connect(getMyAvatar(), &MyAvatar::positionGoneTo,

libraries/shared/src/ShutdownEventListener.cpp

@@ -47,6 +47,7 @@ bool ShutdownEventListener::nativeEventFilter(const QByteArray &eventType, void*
         if (message->message == WM_CLOSE) {
             // tell our registered application to quit
             QMetaObject::invokeMethod(qApp, "quit");
+            return true; // Don't zombify the application by OS-exitting. Let the application quit in the normal quit-signal way.
         }
     }
 #endif