Windows Vista/XP Styles: Clean up some code

Remove public constructor of QWindowsXPStyle since it
cannot be instantiated via style factory since 5.0.
Remove overridden functions that merely call the base implementation.

Change-Id: I3b2998115c4ab65fabf3744874bc3a69a1f5e5b0
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/plugins/styles/windowsvista/qwindowsvistastyle.cpp

@@ -2285,22 +2285,6 @@ int QWindowsVistaStyle::pixelMetric(PixelMetric metric, const QStyleOption *opti
     return QWindowsXPStyle::pixelMetric(metric, option, widget);
 }
 
-/*!
- \internal
- */
-QPalette QWindowsVistaStyle::standardPalette() const
-{
-    return QWindowsXPStyle::standardPalette();
-}
-
-/*!
- \internal
- */
-void QWindowsVistaStyle::polish(QApplication *app)
-{
-    QWindowsXPStyle::polish(app);
-}
-
 /*!
  \internal
  */
@@ -2408,15 +2392,6 @@ void QWindowsVistaStyle::unpolish(QWidget *widget)
 #endif // QT_CONFIG(commandlinkbutton)
 }
 
-
-/*!
- \internal
- */
-void QWindowsVistaStyle::unpolish(QApplication *app)
-{
-    QWindowsXPStyle::unpolish(app);
-}
-
 /*!
  \internal
  */
@@ -2438,11 +2413,6 @@ QPixmap QWindowsVistaStyle::standardPixmap(StandardPixmap standardPixmap, const
     return QWindowsXPStyle::standardPixmap(standardPixmap, option, widget);
 }
 
-QWindowsVistaStylePrivate::QWindowsVistaStylePrivate() :
-    QWindowsXPStylePrivate()
-{
-}
-
 bool QWindowsVistaStylePrivate::transitionsEnabled() const
 {
     BOOL animEnabled = false;

src/plugins/styles/windowsvista/qwindowsvistastyle_p.h

@@ -94,9 +94,6 @@ public:
     void polish(QWidget *widget) override;
     void unpolish(QWidget *widget) override;
     void polish(QPalette &pal) override;
-    void polish(QApplication *app) override;
-    void unpolish(QApplication *app) override;
-    QPalette standardPalette() const override;
 
 private:
     Q_DISABLE_COPY_MOVE(QWindowsVistaStyle)

src/plugins/styles/windowsvista/qwindowsvistastyle_p_p.h

@@ -192,8 +192,6 @@ class QWindowsVistaStylePrivate :  public QWindowsXPStylePrivate
     Q_DECLARE_PUBLIC(QWindowsVistaStyle)
 
 public:
-    QWindowsVistaStylePrivate();
-
     static int fixedPixelMetric(QStyle::PixelMetric pm);
     static inline bool useVista();
     bool transitionsEnabled() const;

src/plugins/styles/windowsvista/qwindowsxpstyle.cpp

@@ -215,8 +215,9 @@ static HRGN qt_hrgn_from_qregion(const QRegion &region)
 }
 
 /* \internal
-    Checks if the theme engine can/should be used, or if we should
-    fall back to Windows style.
+    Checks if the theme engine can/should be used, or if we should fall back
+    to Windows style. For Windows 10, this will still return false for the
+    High Contrast themes.
 */
 bool QWindowsXPStylePrivate::useXP(bool update)
 {
@@ -1104,10 +1105,11 @@ bool QWindowsXPStylePrivate::drawBackgroundThruNativeBuffer(XPThemeData &themeDa
 */
 
 /*!
-    Constructs a QWindowsStyle
+    \internal
+
+    Constructs a QWindowsXPStyle object.
 */
-QWindowsXPStyle::QWindowsXPStyle()
-    : QWindowsStyle(*new QWindowsXPStylePrivate)
+QWindowsXPStyle::QWindowsXPStyle(QWindowsXPStylePrivate &dd) : QWindowsStyle(dd)
 {
 }
 
@@ -1116,20 +1118,6 @@ QWindowsXPStyle::QWindowsXPStyle()
 */
 QWindowsXPStyle::~QWindowsXPStyle() = default;
 
-/*! \reimp */
-void QWindowsXPStyle::unpolish(QApplication *app)
-{
-    QWindowsStyle::unpolish(app);
-}
-
-/*! \reimp */
-void QWindowsXPStyle::polish(QApplication *app)
-{
-    QWindowsStyle::polish(app);
-    if (!QWindowsXPStylePrivate::useXP())
-        return;
-}
-
 /*! \reimp */
 void QWindowsXPStyle::polish(QWidget *widget)
 {
@@ -3862,15 +3850,6 @@ QIcon QWindowsXPStyle::standardIcon(StandardPixmap standardIcon,
     return QWindowsStyle::standardIcon(standardIcon, option, widget);
 }
 
-/*!
-    \internal
-
-    Constructs a QWindowsXPStyle object.
-*/
-QWindowsXPStyle::QWindowsXPStyle(QWindowsXPStylePrivate &dd) : QWindowsStyle(dd)
-{
-}
-
 #ifndef QT_NO_DEBUG_STREAM
 QDebug operator<<(QDebug d, const XPThemeData &t)
 {

src/plugins/styles/windowsvista/qwindowsxpstyle_p.h

@@ -61,12 +61,8 @@ class QWindowsXPStyle : public QWindowsStyle
 {
     Q_OBJECT
 public:
-    QWindowsXPStyle();
-    QWindowsXPStyle(QWindowsXPStylePrivate &dd);
     ~QWindowsXPStyle() override;
 
-    void unpolish(QApplication*) override;
-    void polish(QApplication*) override;
     void polish(QWidget*) override;
     void polish(QPalette&) override;
     void unpolish(QWidget*) override;
@@ -95,6 +91,9 @@ public:
     QIcon standardIcon(StandardPixmap standardIcon, const QStyleOption *option = nullptr,
                        const QWidget *widget = nullptr) const override;
 
+protected:
+    QWindowsXPStyle(QWindowsXPStylePrivate &dd);
+
 private:
     Q_DISABLE_COPY_MOVE(QWindowsXPStyle)
     Q_DECLARE_PRIVATE(QWindowsXPStyle)