Patch reworked for Qt 5.5.
Sent upstream: https://codereview.qt-project.org/#/c/144744/

commit d5120908c74133d9fd249b920cff0dc76313f43f
Author: Raphael Kubo da Costa <rakuco@FreeBSD.org>
Date:   Mon Dec 28 00:46:31 2015 +0100

    Stop using enum references that require C++11.

    Use Qt::Foo instead of Qt::Enum::Foo, which is a C++11 extension. When
    building with clang without -std=c++11, this results in warnings. With
    older GCC versions, the code simply does not build.

    This is similar to commit deffdaf9 ("GraphicsHelper: fix switch").

    Change-Id: I28389b90bafb3df87187742ef55267ce2df1ba1a
    Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

--- src/input/q3dmouseevent.cpp
+++ src/input/q3dmouseevent.cpp
@@ -114,16 +114,16 @@ Q3DMouseEvent::~Q3DMouseEvent()
 Q3DMouseEvent::Buttons Q3DMouseEvent::button() const
 {
     switch (m_event.button()) {
-    case Qt::MouseButton::LeftButton:
-        return Q3DMouseEvent::Buttons::LeftButton;
-    case Qt::MouseButton::RightButton:
-        return Q3DMouseEvent::Buttons::RightButton;
-    case Qt::MouseButton::MiddleButton:
-        return Q3DMouseEvent::Buttons::MiddleButton;
-    case Qt::MouseButton::BackButton:
-        return Q3DMouseEvent::Buttons::BackButton;
+    case Qt::LeftButton:
+        return Q3DMouseEvent::LeftButton;
+    case Qt::RightButton:
+        return Q3DMouseEvent::RightButton;
+    case Qt::MiddleButton:
+        return Q3DMouseEvent::MiddleButton;
+    case Qt::BackButton:
+        return Q3DMouseEvent::BackButton;
     default:
-        return Q3DMouseEvent::Buttons::NoButton;
+        return Q3DMouseEvent::NoButton;
     }
 }
 
@@ -143,17 +143,17 @@ Q3DMouseEvent::Modifiers Q3DMouseEvent::modifier() const
 {
     switch (m_event.modifiers()) {
     case Qt::ShiftModifier:
-        return Q3DMouseEvent::Modifiers::ShiftModifier;
+        return Q3DMouseEvent::ShiftModifier;
     case Qt::ControlModifier:
-        return Q3DMouseEvent::Modifiers::ControlModifier;
+        return Q3DMouseEvent::ControlModifier;
     case Qt::AltModifier:
-        return Q3DMouseEvent::Modifiers::AltModifier;
+        return Q3DMouseEvent::AltModifier;
     case Qt::MetaModifier:
-        return Q3DMouseEvent::Modifiers::MetaModifier;
+        return Q3DMouseEvent::MetaModifier;
     case Qt::KeypadModifier:
-        return Q3DMouseEvent::Modifiers::KeypadModifier;
+        return Q3DMouseEvent::KeypadModifier;
     default:
-        return Q3DMouseEvent::Modifiers::NoModifier;
+        return Q3DMouseEvent::NoModifier;
     }
 }
 
@@ -242,17 +242,17 @@ Q3DWheelEvent::Modifiers Q3DWheelEvent::modifier() const
 {
     switch (m_event.modifiers()) {
     case Qt::ShiftModifier:
-        return Q3DWheelEvent::Modifiers::ShiftModifier;
+        return Q3DWheelEvent::ShiftModifier;
     case Qt::ControlModifier:
-        return Q3DWheelEvent::Modifiers::ControlModifier;
+        return Q3DWheelEvent::ControlModifier;
     case Qt::AltModifier:
-        return Q3DWheelEvent::Modifiers::AltModifier;
+        return Q3DWheelEvent::AltModifier;
     case Qt::MetaModifier:
-        return Q3DWheelEvent::Modifiers::MetaModifier;
+        return Q3DWheelEvent::MetaModifier;
     case Qt::KeypadModifier:
-        return Q3DWheelEvent::Modifiers::KeypadModifier;
+        return Q3DWheelEvent::KeypadModifier;
     default:
-        return Q3DWheelEvent::Modifiers::NoModifier;
+        return Q3DWheelEvent::NoModifier;
     }
 }
 
--- src/input/q3dmouseevent.h
+++ src/input/q3dmouseevent.h
@@ -59,11 +59,11 @@ class QT3DINPUTSHARED_EXPORT QMouseEvent : public QObject
 
 public:
     enum Buttons {
-        LeftButton = Qt::MouseButton::LeftButton,
-        RightButton = Qt::MouseButton::RightButton,
-        MiddleButton = Qt::MouseButton::MiddleButton,
-        BackButton = Qt::MouseButton::BackButton,
-        NoButton = Qt::MouseButton::NoButton
+        LeftButton = Qt::LeftButton,
+        RightButton = Qt::RightButton,
+        MiddleButton = Qt::MiddleButton,
+        BackButton = Qt::BackButton,
+        NoButton = Qt::NoButton
     };
     Q_ENUM(Buttons)
 
@@ -109,11 +109,11 @@ class QT3DINPUTSHARED_EXPORT QWheelEvent : public QObject
 
 public:
     enum Buttons {
-        LeftButton = Qt::MouseButton::LeftButton,
-        RightButton = Qt::MouseButton::RightButton,
-        MiddleButton = Qt::MouseButton::MiddleButton,
-        BackButton = Qt::MouseButton::BackButton,
-        NoButton = Qt::MouseButton::NoButton
+        LeftButton = Qt::LeftButton,
+        RightButton = Qt::RightButton,
+        MiddleButton = Qt::MiddleButton,
+        BackButton = Qt::BackButton,
+        NoButton = Qt::NoButton
     };
     Q_ENUM(Buttons)
 
--- src/quick3d/quick3d/items/quick3dentityloader.cpp
+++ src/quick3d/quick3d/items/quick3dentityloader.cpp
@@ -64,7 +64,7 @@ protected:
         Quick3DEntityLoaderPrivate *priv = Quick3DEntityLoaderPrivate::get(m_loader);
 
         switch (status) {
-        case Status::Ready: {
+        case Ready: {
             Q_ASSERT(priv->m_entity == Q_NULLPTR);
             priv->m_entity = qobject_cast<QEntity *>(object());
             Q_ASSERT(priv->m_entity != Q_NULLPTR);
@@ -73,7 +73,7 @@ protected:
             break;
         }
 
-        case Status::Error: {
+        case Error: {
             QQmlEnginePrivate::warning(qmlEngine(m_loader), errors());
             priv->clear();
             emit m_loader->entityChanged();