Qt: Implement hotkeys (+ configuration)

Source/Core/DolphinQt2/QtUtils/FocusEventFilter.cpp

@@ -0,0 +1,19 @@
+// Copyright 2017 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <QEvent>
+#include <QObject>
+
+#include "DolphinQt2/QtUtils/FocusEventFilter.h"
+
+bool FocusEventFilter::eventFilter(QObject* object, QEvent* event)
+{
+  if (event->type() == QEvent::FocusOut)
+    emit focusOutEvent();
+
+  if (event->type() == QEvent::FocusIn)
+    emit focusInEvent();
+
+  return false;
+}

Source/Core/DolphinQt2/QtUtils/FocusEventFilter.h

@@ -0,0 +1,18 @@
+// Copyright 2017 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <QObject>
+
+class FocusEventFilter : public QObject
+{
+  Q_OBJECT
+signals:
+  void focusInEvent();
+  void focusOutEvent();
+
+private:
+  bool eventFilter(QObject* object, QEvent* event) override;
+};