Do not rely on focusWindow() to get PMP main window

It's kind of unreliable. Even if not accounting for weird corner cases
like wanting to use PMP completely unfocused, it's entirely conceivable
that someone might unfocus the PMP window temporarily during playback
for whatever reasons. Then weird things will happen due to the
DisplayManager apparently not working.

src/display/DisplayComponent.cpp

@@ -24,6 +24,7 @@ DisplayComponent::DisplayComponent(QObject* parent) : ComponentBase(parent), m_i
   m_displayManager = NULL;
   m_lastVideoMode = -1;
   m_lastDisplay = -1;
+  m_applicationWindow = NULL;
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
@@ -223,7 +224,7 @@ bool DisplayComponent::restorePreviousVideoMode()
 //////////////////////////////////////////////////////////////////////////////////////////////////
 int DisplayComponent::getApplicationDisplay()
 {
-  QWindow* activeWindow = QGuiApplication::focusWindow();
+  QWindow* activeWindow = m_applicationWindow;
 
   int display = -1;
   if (activeWindow && m_displayManager)

src/display/DisplayComponent.h

@@ -21,6 +21,8 @@ public:
   inline DisplayManager* getDisplayManager() { return m_displayManager; }
   int getApplicationDisplay();
 
+  void setApplicationWindow(QWindow* window) { m_applicationWindow = window; }
+
   // Switch to the best video mode for the given video framerate. Return true only if the actual
   // mode was switched. If a good match was found, but the current video mode didn't have to be
   // changed, return false. Return false on failure too.
@@ -38,6 +40,7 @@ private:
   int m_lastVideoMode;
   int m_lastDisplay;
   QTimer m_initTimer;
+  QWindow* m_applicationWindow;
 
 public Q_SLOTS:
   void  monitorChange();

src/ui/KonvergoWindow.cpp

@@ -149,6 +149,7 @@ void KonvergoWindow::closingWindow()
 KonvergoWindow::~KonvergoWindow()
 {
   removeEventFilter(m_eventFilter);
+  DisplayComponent::Get().setApplicationWindow(0);
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
@@ -204,6 +205,7 @@ QRect KonvergoWindow::loadGeometryRect()
 void KonvergoWindow::enableVideoWindow()
 {
   PlayerComponent::Get().setWindow(this);
+  DisplayComponent::Get().setApplicationWindow(this);
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////