QtWidgets: Use Q_NULLPTR instead of 0 in all public headers

This is in preparation of adding -Wzero-as-null-pointer-constant (or similar)
to the headers check.

Task-number: QTBUG-45291
Change-Id: Ie67d235151ca8d4ef5e721c9cf4a6fd32bd167a0
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

98 files changed, 298 insertions, 298 deletions

diff --git a/src/widgets/accessible/itemviews.h b/src/widgets/accessible/itemviews.h
index c1bd70a390..33757f168a 100644
--- a/src/widgets/accessible/itemviews.h
+++ b/src/widgets/accessible/itemviews.h
@@ -161,13 +161,13 @@ public:
     QAccessibleTableCell(QAbstractItemView *view, const QModelIndex &m_index, QAccessible::Role role);
 
     void *interface_cast(QAccessible::InterfaceType t) Q_DECL_OVERRIDE;
-    QObject *object() const Q_DECL_OVERRIDE { return 0; }
+    QObject *object() const Q_DECL_OVERRIDE { return Q_NULLPTR; }
     QAccessible::Role role() const Q_DECL_OVERRIDE;
     QAccessible::State state() const Q_DECL_OVERRIDE;
     QRect rect() const Q_DECL_OVERRIDE;
     bool isValid() const Q_DECL_OVERRIDE;
 
-    QAccessibleInterface *childAt(int, int) const Q_DECL_OVERRIDE { return 0; }
+    QAccessibleInterface *childAt(int, int) const Q_DECL_OVERRIDE { return Q_NULLPTR; }
     int childCount() const Q_DECL_OVERRIDE { return 0; }
     int indexOfChild(const QAccessibleInterface *) const Q_DECL_OVERRIDE { return -1; }
 
@@ -213,13 +213,13 @@ public:
     // For header cells, pass the header view in addition
     QAccessibleTableHeaderCell(QAbstractItemView *view, int index, Qt::Orientation orientation);
 
-    QObject *object() const Q_DECL_OVERRIDE { return 0; }
+    QObject *object() const Q_DECL_OVERRIDE { return Q_NULLPTR; }
     QAccessible::Role role() const Q_DECL_OVERRIDE;
     QAccessible::State state() const Q_DECL_OVERRIDE;
     QRect rect() const Q_DECL_OVERRIDE;
     bool isValid() const Q_DECL_OVERRIDE;
 
-    QAccessibleInterface *childAt(int, int) const Q_DECL_OVERRIDE { return 0; }
+    QAccessibleInterface *childAt(int, int) const Q_DECL_OVERRIDE { return Q_NULLPTR; }
     int childCount() const Q_DECL_OVERRIDE { return 0; }
     int indexOfChild(const QAccessibleInterface *) const Q_DECL_OVERRIDE { return -1; }
 
@@ -250,13 +250,13 @@ public:
         :view(view_)
     {}
 
-    QObject *object() const Q_DECL_OVERRIDE { return 0; }
+    QObject *object() const Q_DECL_OVERRIDE { return Q_NULLPTR; }
     QAccessible::Role role() const Q_DECL_OVERRIDE { return QAccessible::Pane; }
     QAccessible::State state() const Q_DECL_OVERRIDE { return QAccessible::State(); }
     QRect rect() const Q_DECL_OVERRIDE { return QRect(); }
     bool isValid() const Q_DECL_OVERRIDE { return true; }
 
-    QAccessibleInterface *childAt(int, int) const Q_DECL_OVERRIDE { return 0; }
+    QAccessibleInterface *childAt(int, int) const Q_DECL_OVERRIDE { return Q_NULLPTR; }
     int childCount() const Q_DECL_OVERRIDE { return 0; }
     int indexOfChild(const QAccessibleInterface *) const Q_DECL_OVERRIDE { return -1; }
 
@@ -267,7 +267,7 @@ public:
         return QAccessible::queryAccessibleInterface(view);
     }
     QAccessibleInterface *child(int) const Q_DECL_OVERRIDE {
-        return 0;
+        return Q_NULLPTR;
     }
 
 private:
diff --git a/src/widgets/dialogs/qcolordialog.h b/src/widgets/dialogs/qcolordialog.h
index 43c7716ef6..fdb5bf55f0 100644
--- a/src/widgets/dialogs/qcolordialog.h
+++ b/src/widgets/dialogs/qcolordialog.h
@@ -61,8 +61,8 @@ public:
 
     Q_DECLARE_FLAGS(ColorDialogOptions, ColorDialogOption)
 
-    explicit QColorDialog(QWidget *parent = 0);
-    explicit QColorDialog(const QColor &initial, QWidget *parent = 0);
+    explicit QColorDialog(QWidget *parent = Q_NULLPTR);
+    explicit QColorDialog(const QColor &initial, QWidget *parent = Q_NULLPTR);
     ~QColorDialog();
 
     void setCurrentColor(const QColor &color);
@@ -81,12 +81,12 @@ public:
     void setVisible(bool visible) Q_DECL_OVERRIDE;
 
     static QColor getColor(const QColor &initial = Qt::white,
-                           QWidget *parent = 0,
+                           QWidget *parent = Q_NULLPTR,
                            const QString &title = QString(),
                            ColorDialogOptions options = 0);
 
     // obsolete
-    static QRgb getRgba(QRgb rgba = 0xffffffff, bool *ok = 0, QWidget *parent = 0);
+    static QRgb getRgba(QRgb rgba = 0xffffffff, bool *ok = Q_NULLPTR, QWidget *parent = Q_NULLPTR);
 
     static int customCount();
     static QColor customColor(int index);
diff --git a/src/widgets/dialogs/qerrormessage.h b/src/widgets/dialogs/qerrormessage.h
index 55d0b389b1..1d69515dfb 100644
--- a/src/widgets/dialogs/qerrormessage.h
+++ b/src/widgets/dialogs/qerrormessage.h
@@ -48,7 +48,7 @@ class Q_WIDGETS_EXPORT QErrorMessage: public QDialog
     Q_OBJECT
     Q_DECLARE_PRIVATE(QErrorMessage)
 public:
-    explicit QErrorMessage(QWidget* parent = 0);
+    explicit QErrorMessage(QWidget* parent = Q_NULLPTR);
     ~QErrorMessage();
 
     static QErrorMessage * qtHandler();
diff --git a/src/widgets/dialogs/qfiledialog.h b/src/widgets/dialogs/qfiledialog.h
index 95209bceb5..6bbeb3817a 100644
--- a/src/widgets/dialogs/qfiledialog.h
+++ b/src/widgets/dialogs/qfiledialog.h
@@ -91,7 +91,7 @@ public:
     Q_DECLARE_FLAGS(Options, Option)
 
     QFileDialog(QWidget *parent, Qt::WindowFlags f);
-    explicit QFileDialog(QWidget *parent = 0,
+    explicit QFileDialog(QWidget *parent = Q_NULLPTR,
                          const QString &caption = QString(),
                          const QString &directory = QString(),
                          const QString &filter = QString());
@@ -196,59 +196,59 @@ Q_SIGNALS:
 
 public:
 
-    static QString getOpenFileName(QWidget *parent = 0,
+    static QString getOpenFileName(QWidget *parent = Q_NULLPTR,
                                    const QString &caption = QString(),
                                    const QString &dir = QString(),
                                    const QString &filter = QString(),
-                                   QString *selectedFilter = 0,
+                                   QString *selectedFilter = Q_NULLPTR,
                                    Options options = 0);
 
-    static QUrl getOpenFileUrl(QWidget *parent = 0,
+    static QUrl getOpenFileUrl(QWidget *parent = Q_NULLPTR,
                                const QString &caption = QString(),
                                const QUrl &dir = QUrl(),
                                const QString &filter = QString(),
-                               QString *selectedFilter = 0,
+                               QString *selectedFilter = Q_NULLPTR,
                                Options options = 0,
                                const QStringList &supportedSchemes = QStringList());
 
-    static QString getSaveFileName(QWidget *parent = 0,
+    static QString getSaveFileName(QWidget *parent = Q_NULLPTR,
                                    const QString &caption = QString(),
                                    const QString &dir = QString(),
                                    const QString &filter = QString(),
-                                   QString *selectedFilter = 0,
+                                   QString *selectedFilter = Q_NULLPTR,
                                    Options options = 0);
 
-    static QUrl getSaveFileUrl(QWidget *parent = 0,
+    static QUrl getSaveFileUrl(QWidget *parent = Q_NULLPTR,
                                const QString &caption = QString(),
                                const QUrl &dir = QUrl(),
                                const QString &filter = QString(),
-                               QString *selectedFilter = 0,
+                               QString *selectedFilter = Q_NULLPTR,
                                Options options = 0,
                                const QStringList &supportedSchemes = QStringList());
 
-    static QString getExistingDirectory(QWidget *parent = 0,
+    static QString getExistingDirectory(QWidget *parent = Q_NULLPTR,
                                         const QString &caption = QString(),
                                         const QString &dir = QString(),
                                         Options options = ShowDirsOnly);
 
-    static QUrl getExistingDirectoryUrl(QWidget *parent = 0,
+    static QUrl getExistingDirectoryUrl(QWidget *parent = Q_NULLPTR,
                                         const QString &caption = QString(),
                                         const QUrl &dir = QUrl(),
                                         Options options = ShowDirsOnly,
                                         const QStringList &supportedSchemes = QStringList());
 
-    static QStringList getOpenFileNames(QWidget *parent = 0,
+    static QStringList getOpenFileNames(QWidget *parent = Q_NULLPTR,
                                         const QString &caption = QString(),
                                         const QString &dir = QString(),
                                         const QString &filter = QString(),
-                                        QString *selectedFilter = 0,
+                                        QString *selectedFilter = Q_NULLPTR,
                                         Options options = 0);
 
-    static QList<QUrl> getOpenFileUrls(QWidget *parent = 0,
+    static QList<QUrl> getOpenFileUrls(QWidget *parent = Q_NULLPTR,
                                        const QString &caption = QString(),
                                        const QUrl &dir = QUrl(),
                                        const QString &filter = QString(),
-                                       QString *selectedFilter = 0,
+                                       QString *selectedFilter = Q_NULLPTR,
                                        Options options = 0,
                                        const QStringList &supportedSchemes = QStringList());
 
diff --git a/src/widgets/dialogs/qfilesystemmodel.h b/src/widgets/dialogs/qfilesystemmodel.h
index 7c98a102f3..f749c97bcb 100644
--- a/src/widgets/dialogs/qfilesystemmodel.h
+++ b/src/widgets/dialogs/qfilesystemmodel.h
@@ -69,7 +69,7 @@ public:
         FilePermissions = Qt::UserRole + 3
     };
 
-    explicit QFileSystemModel(QObject *parent = 0);
+    explicit QFileSystemModel(QObject *parent = Q_NULLPTR);
     ~QFileSystemModel();
 
     QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
@@ -136,7 +136,7 @@ public:
     bool remove(const QModelIndex &index);
 
 protected:
-    QFileSystemModel(QFileSystemModelPrivate &, QObject *parent = 0);
+    QFileSystemModel(QFileSystemModelPrivate &, QObject *parent = Q_NULLPTR);
     void timerEvent(QTimerEvent *event) Q_DECL_OVERRIDE;
     bool event(QEvent *event) Q_DECL_OVERRIDE;
 
diff --git a/src/widgets/dialogs/qfontdialog.h b/src/widgets/dialogs/qfontdialog.h
index 8ca9bf14dd..b61137e4d0 100644
--- a/src/widgets/dialogs/qfontdialog.h
+++ b/src/widgets/dialogs/qfontdialog.h
@@ -65,8 +65,8 @@ public:
 
     Q_DECLARE_FLAGS(FontDialogOptions, FontDialogOption)
 
-    explicit QFontDialog(QWidget *parent = 0);
-    explicit QFontDialog(const QFont &initial, QWidget *parent = 0);
+    explicit QFontDialog(QWidget *parent = Q_NULLPTR);
+    explicit QFontDialog(const QFont &initial, QWidget *parent = Q_NULLPTR);
     ~QFontDialog();
 
     void setCurrentFont(const QFont &font);
@@ -84,8 +84,8 @@ public:
 
     void setVisible(bool visible) Q_DECL_OVERRIDE;
 
-    static QFont getFont(bool *ok, QWidget *parent = 0);
-    static QFont getFont(bool *ok, const QFont &initial, QWidget *parent = 0, const QString &title = QString(),
+    static QFont getFont(bool *ok, QWidget *parent = Q_NULLPTR);
+    static QFont getFont(bool *ok, const QFont &initial, QWidget *parent = Q_NULLPTR, const QString &title = QString(),
                          FontDialogOptions options = 0);
 
 Q_SIGNALS:
diff --git a/src/widgets/dialogs/qmessagebox.h b/src/widgets/dialogs/qmessagebox.h
index 464bf734dc..b108354466 100644
--- a/src/widgets/dialogs/qmessagebox.h
+++ b/src/widgets/dialogs/qmessagebox.h
@@ -125,9 +125,9 @@ public:
 
     Q_DECLARE_FLAGS(StandardButtons, StandardButton)
 
-    explicit QMessageBox(QWidget *parent = 0);
+    explicit QMessageBox(QWidget *parent = Q_NULLPTR);
     QMessageBox(Icon icon, const QString &title, const QString &text,
-                StandardButtons buttons = NoButton, QWidget *parent = 0,
+                StandardButtons buttons = NoButton, QWidget *parent = Q_NULLPTR,
                 Qt::WindowFlags flags = Qt::Dialog | Qt::MSWindowsFixedSizeDialogHint);
     ~QMessageBox();
 
@@ -198,7 +198,7 @@ public:
 
     QMessageBox(const QString &title, const QString &text, Icon icon,
                   int button0, int button1, int button2,
-                  QWidget *parent = 0,
+                  QWidget *parent = Q_NULLPTR,
                   Qt::WindowFlags f = Qt::Dialog | Qt::MSWindowsFixedSizeDialogHint);
 
     static int information(QWidget *parent, const QString &title,
diff --git a/src/widgets/dialogs/qwizard.h b/src/widgets/dialogs/qwizard.h
index e456f678ac..9193f0b659 100644
--- a/src/widgets/dialogs/qwizard.h
+++ b/src/widgets/dialogs/qwizard.h
@@ -209,7 +209,7 @@ class Q_WIDGETS_EXPORT QWizardPage : public QWidget
     Q_PROPERTY(QString subTitle READ subTitle WRITE setSubTitle)
 
 public:
-    explicit QWizardPage(QWidget *parent = 0);
+    explicit QWizardPage(QWidget *parent = Q_NULLPTR);
     ~QWizardPage();
 
     void setTitle(const QString &title);
@@ -237,8 +237,8 @@ Q_SIGNALS:
 protected:
     void setField(const QString &name, const QVariant &value);
     QVariant field(const QString &name) const;
-    void registerField(const QString &name, QWidget *widget, const char *property = 0,
-                       const char *changedSignal = 0);
+    void registerField(const QString &name, QWidget *widget, const char *property = Q_NULLPTR,
+                       const char *changedSignal = Q_NULLPTR);
     QWizard *wizard() const;
 
 private:
diff --git a/src/widgets/effects/qgraphicseffect.h b/src/widgets/effects/qgraphicseffect.h
index 678ece3dd2..c43b607d39 100644
--- a/src/widgets/effects/qgraphicseffect.h
+++ b/src/widgets/effects/qgraphicseffect.h
@@ -72,7 +72,7 @@ public:
         PadToEffectiveBoundingRect
     };
 
-    QGraphicsEffect(QObject *parent = 0);
+    QGraphicsEffect(QObject *parent = Q_NULLPTR);
     virtual ~QGraphicsEffect();
 
     virtual QRectF boundingRectFor(const QRectF &sourceRect) const;
@@ -88,7 +88,7 @@ Q_SIGNALS:
     void enabledChanged(bool enabled);
 
 protected:
-    QGraphicsEffect(QGraphicsEffectPrivate &d, QObject *parent = 0);
+    QGraphicsEffect(QGraphicsEffectPrivate &d, QObject *parent = Q_NULLPTR);
     virtual void draw(QPainter *painter) = 0;
     virtual void sourceChanged(ChangeFlags flags);
     void updateBoundingRect();
@@ -97,7 +97,7 @@ protected:
     QRectF sourceBoundingRect(Qt::CoordinateSystem system = Qt::LogicalCoordinates) const;
     void drawSource(QPainter *painter);
     QPixmap sourcePixmap(Qt::CoordinateSystem system = Qt::LogicalCoordinates,
-                         QPoint *offset = 0,
+                         QPoint *offset = Q_NULLPTR,
                          PixmapPadMode mode = PadToEffectiveBoundingRect) const;
 
 private:
@@ -122,7 +122,7 @@ class Q_WIDGETS_EXPORT QGraphicsColorizeEffect: public QGraphicsEffect
     Q_PROPERTY(QColor color READ color WRITE setColor NOTIFY colorChanged)
     Q_PROPERTY(qreal strength READ strength WRITE setStrength NOTIFY strengthChanged)
 public:
-    QGraphicsColorizeEffect(QObject *parent = 0);
+    QGraphicsColorizeEffect(QObject *parent = Q_NULLPTR);
     ~QGraphicsColorizeEffect();
 
     QColor color() const;
@@ -159,7 +159,7 @@ public:
     };
     Q_DECLARE_FLAGS(BlurHints, BlurHint)
 
-    QGraphicsBlurEffect(QObject *parent = 0);
+    QGraphicsBlurEffect(QObject *parent = Q_NULLPTR);
     ~QGraphicsBlurEffect();
 
     QRectF boundingRectFor(const QRectF &rect) const Q_DECL_OVERRIDE;
@@ -194,7 +194,7 @@ class Q_WIDGETS_EXPORT QGraphicsDropShadowEffect: public QGraphicsEffect
     Q_PROPERTY(qreal blurRadius READ blurRadius WRITE setBlurRadius NOTIFY blurRadiusChanged)
     Q_PROPERTY(QColor color READ color WRITE setColor NOTIFY colorChanged)
 public:
-    QGraphicsDropShadowEffect(QObject *parent = 0);
+    QGraphicsDropShadowEffect(QObject *parent = Q_NULLPTR);
     ~QGraphicsDropShadowEffect();
 
     QRectF boundingRectFor(const QRectF &rect) const Q_DECL_OVERRIDE;
@@ -247,7 +247,7 @@ class Q_WIDGETS_EXPORT QGraphicsOpacityEffect: public QGraphicsEffect
     Q_PROPERTY(qreal opacity READ opacity WRITE setOpacity NOTIFY opacityChanged)
     Q_PROPERTY(QBrush opacityMask READ opacityMask WRITE setOpacityMask NOTIFY opacityMaskChanged)
 public:
-    QGraphicsOpacityEffect(QObject *parent = 0);
+    QGraphicsOpacityEffect(QObject *parent = Q_NULLPTR);
     ~QGraphicsOpacityEffect();
 
     qreal opacity() const;
diff --git a/src/widgets/graphicsview/qgraphicsanchorlayout.h b/src/widgets/graphicsview/qgraphicsanchorlayout.h
index 90406fe71f..2fdfe75be9 100644
--- a/src/widgets/graphicsview/qgraphicsanchorlayout.h
+++ b/src/widgets/graphicsview/qgraphicsanchorlayout.h
@@ -71,7 +71,7 @@ private:
 class Q_WIDGETS_EXPORT QGraphicsAnchorLayout : public QGraphicsLayout
 {
 public:
-    QGraphicsAnchorLayout(QGraphicsLayoutItem *parent = 0);
+    QGraphicsAnchorLayout(QGraphicsLayoutItem *parent = Q_NULLPTR);
     virtual ~QGraphicsAnchorLayout();
 
     QGraphicsAnchor *addAnchor(QGraphicsLayoutItem *firstItem, Qt::AnchorPoint firstEdge,
diff --git a/src/widgets/graphicsview/qgraphicsgridlayout.h b/src/widgets/graphicsview/qgraphicsgridlayout.h
index 90cc316025..5a4b6164d0 100644
--- a/src/widgets/graphicsview/qgraphicsgridlayout.h
+++ b/src/widgets/graphicsview/qgraphicsgridlayout.h
@@ -47,7 +47,7 @@ class QGraphicsGridLayoutPrivate;
 class Q_WIDGETS_EXPORT QGraphicsGridLayout : public QGraphicsLayout
 {
 public:
-    QGraphicsGridLayout(QGraphicsLayoutItem *parent = 0);
+    QGraphicsGridLayout(QGraphicsLayoutItem *parent = Q_NULLPTR);
     virtual ~QGraphicsGridLayout();
 
     void addItem(QGraphicsLayoutItem *item, int row, int column, int rowSpan, int columnSpan,
diff --git a/src/widgets/graphicsview/qgraphicsitem.h b/src/widgets/graphicsview/qgraphicsitem.h
index d3540beb77..b2f8fcbe74 100644
--- a/src/widgets/graphicsview/qgraphicsitem.h
+++ b/src/widgets/graphicsview/qgraphicsitem.h
@@ -153,7 +153,7 @@ public:
         SceneModal
     };
 
-    explicit QGraphicsItem(QGraphicsItem *parent = 0);
+    explicit QGraphicsItem(QGraphicsItem *parent = Q_NULLPTR);
     virtual ~QGraphicsItem();
 
     QGraphicsScene *scene() const;
@@ -189,7 +189,7 @@ public:
 
     PanelModality panelModality() const;
     void setPanelModality(PanelModality panelModality);
-    bool isBlockedByModalPanel(QGraphicsItem **blockingPanel = 0) const;
+    bool isBlockedByModalPanel(QGraphicsItem **blockingPanel = Q_NULLPTR) const;
 
 #ifndef QT_NO_TOOLTIP
     QString toolTip() const;
@@ -285,7 +285,7 @@ public:
     QTransform transform() const;
     QTransform sceneTransform() const;
     QTransform deviceTransform(const QTransform &viewportTransform) const;
-    QTransform itemTransform(const QGraphicsItem *other, bool *ok = 0) const;
+    QTransform itemTransform(const QGraphicsItem *other, bool *ok = Q_NULLPTR) const;
     void setTransform(const QTransform &matrix, bool combine = false);
     void resetTransform();
 #if QT_DEPRECATED_SINCE(5, 0)
@@ -336,7 +336,7 @@ public:
     void setBoundingRegionGranularity(qreal granularity);
 
     // Drawing
-    virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0) = 0;
+    virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR) = 0;
     void update(const QRectF &rect = QRectF());
     inline void update(qreal x, qreal y, qreal width, qreal height);
     void scroll(qreal dx, qreal dy, const QRectF &rect = QRectF());
@@ -553,7 +553,7 @@ class Q_WIDGETS_EXPORT QGraphicsObject : public QObject, public QGraphicsItem
     Q_CLASSINFO("DefaultProperty", "children")
     Q_INTERFACES(QGraphicsItem)
 public:
-    explicit QGraphicsObject(QGraphicsItem *parent = 0);
+    explicit QGraphicsObject(QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsObject();
 
     using QObject::children;
@@ -595,7 +595,7 @@ class QAbstractGraphicsShapeItemPrivate;
 class Q_WIDGETS_EXPORT QAbstractGraphicsShapeItem : public QGraphicsItem
 {
 public:
-    explicit QAbstractGraphicsShapeItem(QGraphicsItem *parent = 0);
+    explicit QAbstractGraphicsShapeItem(QGraphicsItem *parent = Q_NULLPTR);
     ~QAbstractGraphicsShapeItem();
 
     QPen pen() const;
@@ -620,8 +620,8 @@ class QGraphicsPathItemPrivate;
 class Q_WIDGETS_EXPORT QGraphicsPathItem : public QAbstractGraphicsShapeItem
 {
 public:
-    explicit QGraphicsPathItem(QGraphicsItem *parent = 0);
-    explicit QGraphicsPathItem(const QPainterPath &path, QGraphicsItem *parent = 0);
+    explicit QGraphicsPathItem(QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsPathItem(const QPainterPath &path, QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsPathItem();
 
     QPainterPath path() const;
@@ -631,7 +631,7 @@ public:
     QPainterPath shape() const Q_DECL_OVERRIDE;
     bool contains(const QPointF &point) const Q_DECL_OVERRIDE;
 
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0) Q_DECL_OVERRIDE;
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR) Q_DECL_OVERRIDE;
 
     bool isObscuredBy(const QGraphicsItem *item) const Q_DECL_OVERRIDE;
     QPainterPath opaqueArea() const Q_DECL_OVERRIDE;
@@ -653,9 +653,9 @@ class QGraphicsRectItemPrivate;
 class Q_WIDGETS_EXPORT QGraphicsRectItem : public QAbstractGraphicsShapeItem
 {
 public:
-    explicit QGraphicsRectItem(QGraphicsItem *parent = 0);
-    explicit QGraphicsRectItem(const QRectF &rect, QGraphicsItem *parent = 0);
-    explicit QGraphicsRectItem(qreal x, qreal y, qreal w, qreal h, QGraphicsItem *parent = 0);
+    explicit QGraphicsRectItem(QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsRectItem(const QRectF &rect, QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsRectItem(qreal x, qreal y, qreal w, qreal h, QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsRectItem();
 
     QRectF rect() const;
@@ -666,7 +666,7 @@ public:
     QPainterPath shape() const Q_DECL_OVERRIDE;
     bool contains(const QPointF &point) const Q_DECL_OVERRIDE;
 
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0) Q_DECL_OVERRIDE;
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR) Q_DECL_OVERRIDE;
 
     bool isObscuredBy(const QGraphicsItem *item) const Q_DECL_OVERRIDE;
     QPainterPath opaqueArea() const Q_DECL_OVERRIDE;
@@ -691,9 +691,9 @@ class QGraphicsEllipseItemPrivate;
 class Q_WIDGETS_EXPORT QGraphicsEllipseItem : public QAbstractGraphicsShapeItem
 {
 public:
-    explicit QGraphicsEllipseItem(QGraphicsItem *parent = 0);
-    explicit QGraphicsEllipseItem(const QRectF &rect, QGraphicsItem *parent = 0);
-    explicit QGraphicsEllipseItem(qreal x, qreal y, qreal w, qreal h, QGraphicsItem *parent = 0);
+    explicit QGraphicsEllipseItem(QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsEllipseItem(const QRectF &rect, QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsEllipseItem(qreal x, qreal y, qreal w, qreal h, QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsEllipseItem();
 
     QRectF rect() const;
@@ -710,7 +710,7 @@ public:
     QPainterPath shape() const Q_DECL_OVERRIDE;
     bool contains(const QPointF &point) const Q_DECL_OVERRIDE;
 
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0) Q_DECL_OVERRIDE;
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR) Q_DECL_OVERRIDE;
 
     bool isObscuredBy(const QGraphicsItem *item) const Q_DECL_OVERRIDE;
     QPainterPath opaqueArea() const Q_DECL_OVERRIDE;
@@ -735,9 +735,9 @@ class QGraphicsPolygonItemPrivate;
 class Q_WIDGETS_EXPORT QGraphicsPolygonItem : public QAbstractGraphicsShapeItem
 {
 public:
-    explicit QGraphicsPolygonItem(QGraphicsItem *parent = 0);
+    explicit QGraphicsPolygonItem(QGraphicsItem *parent = Q_NULLPTR);
     explicit QGraphicsPolygonItem(const QPolygonF &polygon,
-                                  QGraphicsItem *parent = 0);
+                                  QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsPolygonItem();
 
     QPolygonF polygon() const;
@@ -750,7 +750,7 @@ public:
     QPainterPath shape() const Q_DECL_OVERRIDE;
     bool contains(const QPointF &point) const Q_DECL_OVERRIDE;
 
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0) Q_DECL_OVERRIDE;
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR) Q_DECL_OVERRIDE;
 
     bool isObscuredBy(const QGraphicsItem *item) const Q_DECL_OVERRIDE;
     QPainterPath opaqueArea() const Q_DECL_OVERRIDE;
@@ -772,9 +772,9 @@ class QGraphicsLineItemPrivate;
 class Q_WIDGETS_EXPORT QGraphicsLineItem : public QGraphicsItem
 {
 public:
-    explicit QGraphicsLineItem(QGraphicsItem *parent = 0);
-    explicit QGraphicsLineItem(const QLineF &line, QGraphicsItem *parent = 0);
-    explicit QGraphicsLineItem(qreal x1, qreal y1, qreal x2, qreal y2, QGraphicsItem *parent = 0);
+    explicit QGraphicsLineItem(QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsLineItem(const QLineF &line, QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsLineItem(qreal x1, qreal y1, qreal x2, qreal y2, QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsLineItem();
 
     QPen pen() const;
@@ -789,7 +789,7 @@ public:
     QPainterPath shape() const Q_DECL_OVERRIDE;
     bool contains(const QPointF &point) const Q_DECL_OVERRIDE;
 
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0) Q_DECL_OVERRIDE;
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR) Q_DECL_OVERRIDE;
 
     bool isObscuredBy(const QGraphicsItem *item) const Q_DECL_OVERRIDE;
     QPainterPath opaqueArea() const Q_DECL_OVERRIDE;
@@ -817,8 +817,8 @@ public:
         HeuristicMaskShape
     };
 
-    explicit QGraphicsPixmapItem(QGraphicsItem *parent = 0);
-    explicit QGraphicsPixmapItem(const QPixmap &pixmap, QGraphicsItem *parent = 0);
+    explicit QGraphicsPixmapItem(QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsPixmapItem(const QPixmap &pixmap, QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsPixmapItem();
 
     QPixmap pixmap() const;
@@ -869,8 +869,8 @@ class Q_WIDGETS_EXPORT QGraphicsTextItem : public QGraphicsObject
     QDOC_PROPERTY(QTextCursor textCursor READ textCursor WRITE setTextCursor)
 
 public:
-    explicit QGraphicsTextItem(QGraphicsItem *parent = 0);
-    explicit QGraphicsTextItem(const QString &text, QGraphicsItem *parent = 0);
+    explicit QGraphicsTextItem(QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsTextItem(const QString &text, QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsTextItem();
 
     QString toHtml() const;
@@ -960,8 +960,8 @@ class QGraphicsSimpleTextItemPrivate;
 class Q_WIDGETS_EXPORT QGraphicsSimpleTextItem : public QAbstractGraphicsShapeItem
 {
 public:
-    explicit QGraphicsSimpleTextItem(QGraphicsItem *parent = 0);
-    explicit QGraphicsSimpleTextItem(const QString &text, QGraphicsItem *parent = 0);
+    explicit QGraphicsSimpleTextItem(QGraphicsItem *parent = Q_NULLPTR);
+    explicit QGraphicsSimpleTextItem(const QString &text, QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsSimpleTextItem();
 
     void setText(const QString &text);
@@ -996,14 +996,14 @@ class QGraphicsItemGroupPrivate;
 class Q_WIDGETS_EXPORT QGraphicsItemGroup : public QGraphicsItem
 {
 public:
-    explicit QGraphicsItemGroup(QGraphicsItem *parent = 0);
+    explicit QGraphicsItemGroup(QGraphicsItem *parent = Q_NULLPTR);
     ~QGraphicsItemGroup();
 
     void addToGroup(QGraphicsItem *item);
     void removeFromGroup(QGraphicsItem *item);
 
     QRectF boundingRect() const Q_DECL_OVERRIDE;
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0) Q_DECL_OVERRIDE;
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR) Q_DECL_OVERRIDE;
 
     bool isObscuredBy(const QGraphicsItem *item) const Q_DECL_OVERRIDE;
     QPainterPath opaqueArea() const Q_DECL_OVERRIDE;
diff --git a/src/widgets/graphicsview/qgraphicsitemanimation.h b/src/widgets/graphicsview/qgraphicsitemanimation.h
index 02a20f3f01..a54ba3a9e9 100644
--- a/src/widgets/graphicsview/qgraphicsitemanimation.h
+++ b/src/widgets/graphicsview/qgraphicsitemanimation.h
@@ -52,7 +52,7 @@ class Q_WIDGETS_EXPORT QGraphicsItemAnimation : public QObject
 {
     Q_OBJECT
 public:
-    QGraphicsItemAnimation(QObject *parent = 0);
+    QGraphicsItemAnimation(QObject *parent = Q_NULLPTR);
     virtual ~QGraphicsItemAnimation();
 
     QGraphicsItem *item() const;
diff --git a/src/widgets/graphicsview/qgraphicslayout.h b/src/widgets/graphicsview/qgraphicslayout.h
index ebd90735f1..84a8d97943 100644
--- a/src/widgets/graphicsview/qgraphicslayout.h
+++ b/src/widgets/graphicsview/qgraphicslayout.h
@@ -48,7 +48,7 @@ class QGraphicsWidget;
 class Q_WIDGETS_EXPORT QGraphicsLayout : public QGraphicsLayoutItem
 {
 public:
-    QGraphicsLayout(QGraphicsLayoutItem *parent = 0);
+    QGraphicsLayout(QGraphicsLayoutItem *parent = Q_NULLPTR);
     ~QGraphicsLayout();
 
     void setContentsMargins(qreal left, qreal top, qreal right, qreal bottom);
diff --git a/src/widgets/graphicsview/qgraphicslayoutitem.h b/src/widgets/graphicsview/qgraphicslayoutitem.h
index 85b6d901f2..1608d79836 100644
--- a/src/widgets/graphicsview/qgraphicslayoutitem.h
+++ b/src/widgets/graphicsview/qgraphicslayoutitem.h
@@ -48,7 +48,7 @@ class QGraphicsItem;
 class Q_WIDGETS_EXPORT QGraphicsLayoutItem
 {
 public:
-    QGraphicsLayoutItem(QGraphicsLayoutItem *parent = 0, bool isLayout = false);
+    QGraphicsLayoutItem(QGraphicsLayoutItem *parent = Q_NULLPTR, bool isLayout = false);
     virtual ~QGraphicsLayoutItem();
 
     void setSizePolicy(const QSizePolicy &policy);
diff --git a/src/widgets/graphicsview/qgraphicslinearlayout.h b/src/widgets/graphicsview/qgraphicslinearlayout.h
index 997bff7da1..3232da22ca 100644
--- a/src/widgets/graphicsview/qgraphicslinearlayout.h
+++ b/src/widgets/graphicsview/qgraphicslinearlayout.h
@@ -47,8 +47,8 @@ class QGraphicsLinearLayoutPrivate;
 class Q_WIDGETS_EXPORT QGraphicsLinearLayout : public QGraphicsLayout
 {
 public:
-    QGraphicsLinearLayout(QGraphicsLayoutItem *parent = 0);
-    QGraphicsLinearLayout(Qt::Orientation orientation, QGraphicsLayoutItem *parent = 0);
+    QGraphicsLinearLayout(QGraphicsLayoutItem *parent = Q_NULLPTR);
+    QGraphicsLinearLayout(Qt::Orientation orientation, QGraphicsLayoutItem *parent = Q_NULLPTR);
     virtual ~QGraphicsLinearLayout();
 
     void setOrientation(Qt::Orientation orientation);
diff --git a/src/widgets/graphicsview/qgraphicsscene.h b/src/widgets/graphicsview/qgraphicsscene.h
index 6f2389d83e..c93db20716 100644
--- a/src/widgets/graphicsview/qgraphicsscene.h
+++ b/src/widgets/graphicsview/qgraphicsscene.h
@@ -115,9 +115,9 @@ public:
     };
     Q_DECLARE_FLAGS(SceneLayers, SceneLayer)
 
-    QGraphicsScene(QObject *parent = 0);
-    QGraphicsScene(const QRectF &sceneRect, QObject *parent = 0);
-    QGraphicsScene(qreal x, qreal y, qreal width, qreal height, QObject *parent = 0);
+    QGraphicsScene(QObject *parent = Q_NULLPTR);
+    QGraphicsScene(const QRectF &sceneRect, QObject *parent = Q_NULLPTR);
+    QGraphicsScene(qreal x, qreal y, qreal width, qreal height, QObject *parent = Q_NULLPTR);
     virtual ~QGraphicsScene();
 
     QRectF sceneRect() const;
@@ -279,7 +279,7 @@ protected:
     virtual void drawItems(QPainter *painter, int numItems,
                            QGraphicsItem *items[],
                            const QStyleOptionGraphicsItem options[],
-                           QWidget *widget = 0);
+                           QWidget *widget = Q_NULLPTR);
 
 protected Q_SLOTS:
     // ### Qt 6: make unconditional
diff --git a/src/widgets/graphicsview/qgraphicstransform.h b/src/widgets/graphicsview/qgraphicstransform.h
index 4a7a3d0c0b..6fa76683f2 100644
--- a/src/widgets/graphicsview/qgraphicstransform.h
+++ b/src/widgets/graphicsview/qgraphicstransform.h
@@ -50,7 +50,7 @@ class Q_WIDGETS_EXPORT QGraphicsTransform : public QObject
 {
     Q_OBJECT
 public:
-    QGraphicsTransform(QObject *parent = 0);
+    QGraphicsTransform(QObject *parent = Q_NULLPTR);
     ~QGraphicsTransform();
 
     virtual void applyTo(QMatrix4x4 *matrix) const = 0;
@@ -78,7 +78,7 @@ class Q_WIDGETS_EXPORT QGraphicsScale : public QGraphicsTransform
     Q_PROPERTY(qreal yScale READ yScale WRITE setYScale NOTIFY yScaleChanged)
     Q_PROPERTY(qreal zScale READ zScale WRITE setZScale NOTIFY zScaleChanged)
 public:
-    QGraphicsScale(QObject *parent = 0);
+    QGraphicsScale(QObject *parent = Q_NULLPTR);
     ~QGraphicsScale();
 
     QVector3D origin() const;
@@ -116,7 +116,7 @@ class Q_WIDGETS_EXPORT QGraphicsRotation : public QGraphicsTransform
     Q_PROPERTY(qreal angle READ angle WRITE setAngle NOTIFY angleChanged)
     Q_PROPERTY(QVector3D axis READ axis WRITE setAxis NOTIFY axisChanged)
 public:
-    QGraphicsRotation(QObject *parent = 0);
+    QGraphicsRotation(QObject *parent = Q_NULLPTR);
     ~QGraphicsRotation();
 
     QVector3D origin() const;
diff --git a/src/widgets/graphicsview/qgraphicsview.h b/src/widgets/graphicsview/qgraphicsview.h
index d426273d97..667fa76fe7 100644
--- a/src/widgets/graphicsview/qgraphicsview.h
+++ b/src/widgets/graphicsview/qgraphicsview.h
@@ -108,8 +108,8 @@ public:
     };
     Q_DECLARE_FLAGS(OptimizationFlags, OptimizationFlag)
 
-    QGraphicsView(QWidget *parent = 0);
-    QGraphicsView(QGraphicsScene *scene, QWidget *parent = 0);
+    QGraphicsView(QWidget *parent = Q_NULLPTR);
+    QGraphicsView(QGraphicsScene *scene, QWidget *parent = Q_NULLPTR);
     ~QGraphicsView();
 
     QSize sizeHint() const Q_DECL_OVERRIDE;
@@ -230,7 +230,7 @@ protected Q_SLOTS:
     void setupViewport(QWidget *widget) Q_DECL_OVERRIDE;
 
 protected:
-    QGraphicsView(QGraphicsViewPrivate &, QWidget *parent = 0);
+    QGraphicsView(QGraphicsViewPrivate &, QWidget *parent = Q_NULLPTR);
     bool event(QEvent *event) Q_DECL_OVERRIDE;
     bool viewportEvent(QEvent *event) Q_DECL_OVERRIDE;
 
diff --git a/src/widgets/graphicsview/qgraphicswidget.h b/src/widgets/graphicsview/qgraphicswidget.h
index cf617b6d3f..0878e020bc 100644
--- a/src/widgets/graphicsview/qgraphicswidget.h
+++ b/src/widgets/graphicsview/qgraphicswidget.h
@@ -156,8 +156,8 @@ public:
     };
     int type() const Q_DECL_OVERRIDE;
 
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0) Q_DECL_OVERRIDE;
-    virtual void paintWindowFrame(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = 0);
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR) Q_DECL_OVERRIDE;
+    virtual void paintWindowFrame(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = Q_NULLPTR);
     QRectF boundingRect() const Q_DECL_OVERRIDE;
     QPainterPath shape() const Q_DECL_OVERRIDE;
 
diff --git a/src/widgets/itemviews/qabstractitemdelegate.h b/src/widgets/itemviews/qabstractitemdelegate.h
index c250179087..b29717d1e1 100644
--- a/src/widgets/itemviews/qabstractitemdelegate.h
+++ b/src/widgets/itemviews/qabstractitemdelegate.h
@@ -63,7 +63,7 @@ public:
         RevertModelCache
     };
 
-    explicit QAbstractItemDelegate(QObject *parent = 0);
+    explicit QAbstractItemDelegate(QObject *parent = Q_NULLPTR);
     virtual ~QAbstractItemDelegate();
 
     // painting
@@ -113,7 +113,7 @@ Q_SIGNALS:
     void sizeHintChanged(const QModelIndex &);
 
 protected:
-    QAbstractItemDelegate(QObjectPrivate &, QObject *parent = 0);
+    QAbstractItemDelegate(QObjectPrivate &, QObject *parent = Q_NULLPTR);
 private:
     Q_DECLARE_PRIVATE(QAbstractItemDelegate)
     Q_DISABLE_COPY(QAbstractItemDelegate)
diff --git a/src/widgets/itemviews/qabstractitemview.h b/src/widgets/itemviews/qabstractitemview.h
index 1be17b6c0e..ff1848b149 100644
--- a/src/widgets/itemviews/qabstractitemview.h
+++ b/src/widgets/itemviews/qabstractitemview.h
@@ -115,7 +115,7 @@ public:
     };
     Q_ENUM(ScrollMode)
 
-    explicit QAbstractItemView(QWidget *parent = 0);
+    explicit QAbstractItemView(QWidget *parent = Q_NULLPTR);
     ~QAbstractItemView();
 
     virtual void setModel(QAbstractItemModel *model);
@@ -258,7 +258,7 @@ Q_SIGNALS:
     void iconSizeChanged(const QSize &size);
 
 protected:
-    QAbstractItemView(QAbstractItemViewPrivate &, QWidget *parent = 0);
+    QAbstractItemView(QAbstractItemViewPrivate &, QWidget *parent = Q_NULLPTR);
 
     void setHorizontalStepsPerItem(int steps);
     int horizontalStepsPerItem() const;
@@ -283,7 +283,7 @@ protected:
     virtual bool edit(const QModelIndex &index, EditTrigger trigger, QEvent *event);
 
     virtual QItemSelectionModel::SelectionFlags selectionCommand(const QModelIndex &index,
-                                                                 const QEvent *event = 0) const;
+                                                                 const QEvent *event = Q_NULLPTR) const;
 
 #ifndef QT_NO_DRAGANDDROP
     virtual void startDrag(Qt::DropActions supportedActions);
diff --git a/src/widgets/itemviews/qcolumnview.h b/src/widgets/itemviews/qcolumnview.h
index 792ae04eb6..58472ddd8e 100644
--- a/src/widgets/itemviews/qcolumnview.h
+++ b/src/widgets/itemviews/qcolumnview.h
@@ -52,7 +52,7 @@ Q_SIGNALS:
     void updatePreviewWidget(const QModelIndex &index);
 
 public:
-    explicit QColumnView(QWidget *parent = 0);
+    explicit QColumnView(QWidget *parent = Q_NULLPTR);
     ~QColumnView();
 
     // QAbstractItemView overloads
@@ -76,7 +76,7 @@ public:
     QList<int> columnWidths() const;
 
 protected:
-    QColumnView(QColumnViewPrivate &dd, QWidget *parent = 0);
+    QColumnView(QColumnViewPrivate &dd, QWidget *parent = Q_NULLPTR);
 
     // QAbstractItemView overloads
     bool isIndexHidden(const QModelIndex &index) const Q_DECL_OVERRIDE;
diff --git a/src/widgets/itemviews/qdatawidgetmapper.h b/src/widgets/itemviews/qdatawidgetmapper.h
index 5ccbee4d68..4dd5e0e14c 100644
--- a/src/widgets/itemviews/qdatawidgetmapper.h
+++ b/src/widgets/itemviews/qdatawidgetmapper.h
@@ -55,7 +55,7 @@ class Q_WIDGETS_EXPORT QDataWidgetMapper: public QObject
     Q_PROPERTY(SubmitPolicy submitPolicy READ submitPolicy WRITE setSubmitPolicy)
 
 public:
-    explicit QDataWidgetMapper(QObject *parent = 0);
+    explicit QDataWidgetMapper(QObject *parent = Q_NULLPTR);
     ~QDataWidgetMapper();
 
     void setModel(QAbstractItemModel *model);
diff --git a/src/widgets/itemviews/qdirmodel.h b/src/widgets/itemviews/qdirmodel.h
index dcc337244c..536e5299a2 100644
--- a/src/widgets/itemviews/qdirmodel.h
+++ b/src/widgets/itemviews/qdirmodel.h
@@ -60,8 +60,8 @@ public:
     };
 
     QDirModel(const QStringList &nameFilters, QDir::Filters filters,
-              QDir::SortFlags sort, QObject *parent = 0);
-    explicit QDirModel(QObject *parent = 0);
+              QDir::SortFlags sort, QObject *parent = Q_NULLPTR);
+    explicit QDirModel(QObject *parent = Q_NULLPTR);
     ~QDirModel();
 
     QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
@@ -127,7 +127,7 @@ public Q_SLOTS:
     void refresh(const QModelIndex &parent = QModelIndex());
 
 protected:
-    QDirModel(QDirModelPrivate &, QObject *parent = 0);
+    QDirModel(QDirModelPrivate &, QObject *parent = Q_NULLPTR);
     friend class QFileDialogPrivate;
 
 private:
diff --git a/src/widgets/itemviews/qheaderview.h b/src/widgets/itemviews/qheaderview.h
index e0f57130c0..d892614a39 100644
--- a/src/widgets/itemviews/qheaderview.h
+++ b/src/widgets/itemviews/qheaderview.h
@@ -68,7 +68,7 @@ public:
     };
     Q_ENUM(ResizeMode)
 
-    explicit QHeaderView(Qt::Orientation orientation, QWidget *parent = 0);
+    explicit QHeaderView(Qt::Orientation orientation, QWidget *parent = Q_NULLPTR);
     virtual ~QHeaderView();
 
     void setModel(QAbstractItemModel *model) Q_DECL_OVERRIDE;
@@ -202,7 +202,7 @@ protected Q_SLOTS:
     void sectionsAboutToBeRemoved(const QModelIndex &parent, int logicalFirst, int logicalLast);
 
 protected:
-    QHeaderView(QHeaderViewPrivate &dd, Qt::Orientation orientation, QWidget *parent = 0);
+    QHeaderView(QHeaderViewPrivate &dd, Qt::Orientation orientation, QWidget *parent = Q_NULLPTR);
     void initialize();
 
     void initializeSections();
diff --git a/src/widgets/itemviews/qitemdelegate.h b/src/widgets/itemviews/qitemdelegate.h
index edc224b0f3..beba6b90fb 100644
--- a/src/widgets/itemviews/qitemdelegate.h
+++ b/src/widgets/itemviews/qitemdelegate.h
@@ -53,7 +53,7 @@ class Q_WIDGETS_EXPORT QItemDelegate : public QAbstractItemDelegate
     Q_PROPERTY(bool clipping READ hasClipping WRITE setClipping)
 
 public:
-    explicit QItemDelegate(QObject *parent = 0);
+    explicit QItemDelegate(QObject *parent = Q_NULLPTR);
     ~QItemDelegate();
 
     bool hasClipping() const;
diff --git a/src/widgets/itemviews/qlistview.h b/src/widgets/itemviews/qlistview.h
index ac65a47d9f..433933b500 100644
--- a/src/widgets/itemviews/qlistview.h
+++ b/src/widgets/itemviews/qlistview.h
@@ -72,7 +72,7 @@ public:
     enum ViewMode { ListMode, IconMode };
     Q_ENUM(ViewMode)
 
-    explicit QListView(QWidget *parent = 0);
+    explicit QListView(QWidget *parent = Q_NULLPTR);
     ~QListView();
 
     void setMovement(Movement movement);
@@ -131,7 +131,7 @@ Q_SIGNALS:
     void indexesMoved(const QModelIndexList &indexes);
 
 protected:
-    QListView(QListViewPrivate &, QWidget *parent = 0);
+    QListView(QListViewPrivate &, QWidget *parent = Q_NULLPTR);
 
     bool event(QEvent *e) Q_DECL_OVERRIDE;
 
diff --git a/src/widgets/itemviews/qlistwidget.h b/src/widgets/itemviews/qlistwidget.h
index 8ab864c930..1fbdc472db 100644
--- a/src/widgets/itemviews/qlistwidget.h
+++ b/src/widgets/itemviews/qlistwidget.h
@@ -55,10 +55,10 @@ class Q_WIDGETS_EXPORT QListWidgetItem
     friend class QListWidget;
 public:
     enum ItemType { Type = 0, UserType = 1000 };
-    explicit QListWidgetItem(QListWidget *view = 0, int type = Type);
-    explicit QListWidgetItem(const QString &text, QListWidget *view = 0, int type = Type);
+    explicit QListWidgetItem(QListWidget *view = Q_NULLPTR, int type = Type);
+    explicit QListWidgetItem(const QString &text, QListWidget *view = Q_NULLPTR, int type = Type);
     explicit QListWidgetItem(const QIcon &icon, const QString &text,
-                             QListWidget *view = 0, int type = Type);
+                             QListWidget *view = Q_NULLPTR, int type = Type);
     QListWidgetItem(const QListWidgetItem &other);
     virtual ~QListWidgetItem();
 
@@ -198,7 +198,7 @@ class Q_WIDGETS_EXPORT QListWidget : public QListView
     friend class QListWidgetItem;
     friend class QListModel;
 public:
-    explicit QListWidget(QWidget *parent = 0);
+    explicit QListWidget(QWidget *parent = Q_NULLPTR);
     ~QListWidget();
 
     QListWidgetItem *item(int row) const;
@@ -299,7 +299,7 @@ private:
 };
 
 inline void QListWidget::removeItemWidget(QListWidgetItem *aItem)
-{ setItemWidget(aItem, 0); }
+{ setItemWidget(aItem, Q_NULLPTR); }
 
 inline void QListWidget::addItem(QListWidgetItem *aitem)
 { insertItem(count(), aitem); }
diff --git a/src/widgets/itemviews/qstyleditemdelegate.h b/src/widgets/itemviews/qstyleditemdelegate.h
index 590ddf6614..541830239a 100644
--- a/src/widgets/itemviews/qstyleditemdelegate.h
+++ b/src/widgets/itemviews/qstyleditemdelegate.h
@@ -52,7 +52,7 @@ class Q_WIDGETS_EXPORT QStyledItemDelegate : public QAbstractItemDelegate
     Q_OBJECT
 
 public:
-    explicit QStyledItemDelegate(QObject *parent = 0);
+    explicit QStyledItemDelegate(QObject *parent = Q_NULLPTR);
     ~QStyledItemDelegate();
 
     // painting
diff --git a/src/widgets/itemviews/qtableview.h b/src/widgets/itemviews/qtableview.h
index d69b78c6fe..1bb23844cc 100644
--- a/src/widgets/itemviews/qtableview.h
+++ b/src/widgets/itemviews/qtableview.h
@@ -54,7 +54,7 @@ class Q_WIDGETS_EXPORT QTableView : public QAbstractItemView
     Q_PROPERTY(bool cornerButtonEnabled READ isCornerButtonEnabled WRITE setCornerButtonEnabled)
 
 public:
-    explicit QTableView(QWidget *parent = 0);
+    explicit QTableView(QWidget *parent = Q_NULLPTR);
     ~QTableView();
 
     void setModel(QAbstractItemModel *model) Q_DECL_OVERRIDE;
diff --git a/src/widgets/itemviews/qtablewidget.h b/src/widgets/itemviews/qtablewidget.h
index 93639f0753..9acdc19863 100644
--- a/src/widgets/itemviews/qtablewidget.h
+++ b/src/widgets/itemviews/qtablewidget.h
@@ -214,8 +214,8 @@ class Q_WIDGETS_EXPORT QTableWidget : public QTableView
 
     friend class QTableModel;
 public:
-    explicit QTableWidget(QWidget *parent = 0);
-    QTableWidget(int rows, int columns, QWidget *parent = 0);
+    explicit QTableWidget(QWidget *parent = Q_NULLPTR);
+    QTableWidget(int rows, int columns, QWidget *parent = Q_NULLPTR);
     ~QTableWidget();
 
     void setRowCount(int rows);
@@ -344,7 +344,7 @@ private:
 };
 
 inline void QTableWidget::removeCellWidget(int arow, int acolumn)
-{ setCellWidget(arow, acolumn, 0); }
+{ setCellWidget(arow, acolumn, Q_NULLPTR); }
 
 inline QTableWidgetItem *QTableWidget::itemAt(int ax, int ay) const
 { return itemAt(QPoint(ax, ay)); }
diff --git a/src/widgets/itemviews/qtreeview.h b/src/widgets/itemviews/qtreeview.h
index e9e2e78e17..546cc488cb 100644
--- a/src/widgets/itemviews/qtreeview.h
+++ b/src/widgets/itemviews/qtreeview.h
@@ -60,7 +60,7 @@ class Q_WIDGETS_EXPORT QTreeView : public QAbstractItemView
     Q_PROPERTY(bool expandsOnDoubleClick READ expandsOnDoubleClick WRITE setExpandsOnDoubleClick)
 
 public:
-    explicit QTreeView(QWidget *parent = 0);
+    explicit QTreeView(QWidget *parent = Q_NULLPTR);
     ~QTreeView();
 
     void setModel(QAbstractItemModel *model) Q_DECL_OVERRIDE;
@@ -163,7 +163,7 @@ protected Q_SLOTS:
     void rowsRemoved(const QModelIndex &parent, int first, int last);
 
 protected:
-    QTreeView(QTreeViewPrivate &dd, QWidget *parent = 0);
+    QTreeView(QTreeViewPrivate &dd, QWidget *parent = Q_NULLPTR);
     void scrollContentsBy(int dx, int dy) Q_DECL_OVERRIDE;
     void rowsInserted(const QModelIndex &parent, int start, int end) Q_DECL_OVERRIDE;
     void rowsAboutToBeRemoved(const QModelIndex &parent, int start, int end) Q_DECL_OVERRIDE;
diff --git a/src/widgets/itemviews/qtreewidget.h b/src/widgets/itemviews/qtreewidget.h
index 564e10ac1a..995528fe37 100644
--- a/src/widgets/itemviews/qtreewidget.h
+++ b/src/widgets/itemviews/qtreewidget.h
@@ -172,7 +172,7 @@ public:
     inline QTreeWidgetItem *parent() const { return par; }
     inline QTreeWidgetItem *child(int index) const {
         if (index < 0 || index >= children.size())
-            return 0;
+            return Q_NULLPTR;
         executePendingSort();
         return children.at(index);
     }
@@ -255,7 +255,7 @@ class Q_WIDGETS_EXPORT QTreeWidget : public QTreeView
     friend class QTreeModel;
     friend class QTreeWidgetItem;
 public:
-    explicit QTreeWidget(QWidget *parent = 0);
+    explicit QTreeWidget(QWidget *parent = Q_NULLPTR);
     ~QTreeWidget();
 
     int columnCount() const;
@@ -375,7 +375,7 @@ private:
 };
 
 inline void QTreeWidget::removeItemWidget(QTreeWidgetItem *item, int column)
-{ setItemWidget(item, column, 0); }
+{ setItemWidget(item, column, Q_NULLPTR); }
 
 inline QTreeWidgetItem *QTreeWidget::itemAt(int ax, int ay) const
 { return itemAt(QPoint(ax, ay)); }
diff --git a/src/widgets/kernel/qaction.h b/src/widgets/kernel/qaction.h
index 1d69694699..8ef26b60bf 100644
--- a/src/widgets/kernel/qaction.h
+++ b/src/widgets/kernel/qaction.h
@@ -153,7 +153,7 @@ public:
 
     enum ActionEvent { Trigger, Hover };
     void activate(ActionEvent event);
-    bool showStatusText(QWidget *widget=0);
+    bool showStatusText(QWidget *widget = Q_NULLPTR);
 
     void setMenuRole(MenuRole menuRole);
     MenuRole menuRole() const;
diff --git a/src/widgets/kernel/qapplication.h b/src/widgets/kernel/qapplication.h
index d4b2326afd..7aaea2a947 100644
--- a/src/widgets/kernel/qapplication.h
+++ b/src/widgets/kernel/qapplication.h
@@ -104,11 +104,11 @@ public:
     using QGuiApplication::palette;
     static QPalette palette(const QWidget *);
     static QPalette palette(const char *className);
-    static void setPalette(const QPalette &, const char* className = 0);
+    static void setPalette(const QPalette &, const char* className = Q_NULLPTR);
     static QFont font();
     static QFont font(const QWidget*);
     static QFont font(const char *className);
-    static void setFont(const QFont &, const char* className = 0);
+    static void setFont(const QFont &, const char* className = Q_NULLPTR);
     static QFontMetrics fontMetrics();
 
 #if QT_VERSION < 0x060000 // remove these forwarders in Qt 6
diff --git a/src/widgets/kernel/qboxlayout.h b/src/widgets/kernel/qboxlayout.h
index 5ce9ca26f6..02c4b47343 100644
--- a/src/widgets/kernel/qboxlayout.h
+++ b/src/widgets/kernel/qboxlayout.h
@@ -54,7 +54,7 @@ public:
     enum Direction { LeftToRight, RightToLeft, TopToBottom, BottomToTop,
                      Down = TopToBottom, Up = BottomToTop };
 
-    explicit QBoxLayout(Direction, QWidget *parent = 0);
+    explicit QBoxLayout(Direction, QWidget *parent = Q_NULLPTR);
 
     ~QBoxLayout();
 
diff --git a/src/widgets/kernel/qdesktopwidget.h b/src/widgets/kernel/qdesktopwidget.h
index 5412c5bc4a..c0cc4f1b81 100644
--- a/src/widgets/kernel/qdesktopwidget.h
+++ b/src/widgets/kernel/qdesktopwidget.h
@@ -58,7 +58,7 @@ public:
     int screenCount() const;
     int primaryScreen() const;
 
-    int screenNumber(const QWidget *widget = 0) const;
+    int screenNumber(const QWidget *widget = Q_NULLPTR) const;
     int screenNumber(const QPoint &) const;
 
     QWidget *screen(int screen = -1);
diff --git a/src/widgets/kernel/qformlayout.h b/src/widgets/kernel/qformlayout.h
index 18f3c84354..0767d78ce6 100644
--- a/src/widgets/kernel/qformlayout.h
+++ b/src/widgets/kernel/qformlayout.h
@@ -74,7 +74,7 @@ public:
     };
     Q_ENUM(ItemRole)
 
-    explicit QFormLayout(QWidget *parent = 0);
+    explicit QFormLayout(QWidget *parent = Q_NULLPTR);
     ~QFormLayout();
 
     void setFieldGrowthPolicy(FieldGrowthPolicy policy);
diff --git a/src/widgets/kernel/qgesture.h b/src/widgets/kernel/qgesture.h
index dfe9450365..bcf583a507 100644
--- a/src/widgets/kernel/qgesture.h
+++ b/src/widgets/kernel/qgesture.h
@@ -63,7 +63,7 @@ class Q_WIDGETS_EXPORT QGesture : public QObject
     Q_PROPERTY(bool hasHotSpot READ hasHotSpot)
 
 public:
-    explicit QGesture(QObject *parent = 0);
+    explicit QGesture(QObject *parent = Q_NULLPTR);
     ~QGesture();
 
     Qt::GestureType gestureType() const;
@@ -107,7 +107,7 @@ class Q_WIDGETS_EXPORT QPanGesture : public QGesture
     Q_PRIVATE_PROPERTY(QPanGesture::d_func(), qreal verticalVelocity READ verticalVelocity WRITE setVerticalVelocity)
 
 public:
-    explicit QPanGesture(QObject *parent = 0);
+    explicit QPanGesture(QObject *parent = Q_NULLPTR);
     ~QPanGesture();
 
     QPointF lastOffset() const;
@@ -154,7 +154,7 @@ public:
     Q_PROPERTY(QPointF centerPoint READ centerPoint WRITE setCenterPoint)
 
 public:
-    explicit QPinchGesture(QObject *parent = 0);
+    explicit QPinchGesture(QObject *parent = Q_NULLPTR);
     ~QPinchGesture();
 
     ChangeFlags totalChangeFlags() const;
@@ -210,7 +210,7 @@ public:
     enum SwipeDirection { NoDirection, Left, Right, Up, Down };
     Q_ENUM(SwipeDirection)
 
-    explicit QSwipeGesture(QObject *parent = 0);
+    explicit QSwipeGesture(QObject *parent = Q_NULLPTR);
     ~QSwipeGesture();
 
     SwipeDirection horizontalDirection() const;
@@ -231,7 +231,7 @@ class Q_WIDGETS_EXPORT QTapGesture : public QGesture
     Q_PROPERTY(QPointF position READ position WRITE setPosition)
 
 public:
-    explicit QTapGesture(QObject *parent = 0);
+    explicit QTapGesture(QObject *parent = Q_NULLPTR);
     ~QTapGesture();
 
     QPointF position() const;
@@ -249,7 +249,7 @@ class Q_WIDGETS_EXPORT QTapAndHoldGesture : public QGesture
     Q_PROPERTY(QPointF position READ position WRITE setPosition)
 
 public:
-    explicit QTapAndHoldGesture(QObject *parent = 0);
+    explicit QTapAndHoldGesture(QObject *parent = Q_NULLPTR);
     ~QTapAndHoldGesture();
 
     QPointF position() const;
diff --git a/src/widgets/kernel/qshortcut.h b/src/widgets/kernel/qshortcut.h
index 9171f855ba..e816bbe06d 100644
--- a/src/widgets/kernel/qshortcut.h
+++ b/src/widgets/kernel/qshortcut.h
@@ -55,7 +55,7 @@ class Q_WIDGETS_EXPORT QShortcut : public QObject
 public:
     explicit QShortcut(QWidget *parent);
     QShortcut(const QKeySequence& key, QWidget *parent,
-              const char *member = 0, const char *ambiguousMember = 0,
+              const char *member = Q_NULLPTR, const char *ambiguousMember = Q_NULLPTR,
               Qt::ShortcutContext context = Qt::WindowShortcut);
     ~QShortcut();
 
diff --git a/src/widgets/kernel/qtooltip.h b/src/widgets/kernel/qtooltip.h
index 286d8fb327..54cf71d2f0 100644
--- a/src/widgets/kernel/qtooltip.h
+++ b/src/widgets/kernel/qtooltip.h
@@ -46,7 +46,7 @@ class Q_WIDGETS_EXPORT QToolTip
     QToolTip() Q_DECL_EQ_DELETE;
 public:
     // ### Qt 6 - merge the three showText functions below
-    static void showText(const QPoint &pos, const QString &text, QWidget *w = 0);
+    static void showText(const QPoint &pos, const QString &text, QWidget *w = Q_NULLPTR);
     static void showText(const QPoint &pos, const QString &text, QWidget *w, const QRect &rect);
     static void showText(const QPoint &pos, const QString &text, QWidget *w, const QRect &rect, int msecShowTime);
     static inline void hideText() { showText(QPoint(), QString()); }
diff --git a/src/widgets/kernel/qwhatsthis.h b/src/widgets/kernel/qwhatsthis.h
index 999c66486c..367b8aab3c 100644
--- a/src/widgets/kernel/qwhatsthis.h
+++ b/src/widgets/kernel/qwhatsthis.h
@@ -53,10 +53,10 @@ public:
     static bool inWhatsThisMode();
     static void leaveWhatsThisMode();
 
-    static void showText(const QPoint &pos, const QString &text, QWidget *w = 0);
+    static void showText(const QPoint &pos, const QString &text, QWidget *w = Q_NULLPTR);
     static void hideText();
 
-    static QAction *createAction(QObject *parent = 0);
+    static QAction *createAction(QObject *parent = Q_NULLPTR);
 
 };
 
diff --git a/src/widgets/kernel/qwidget.h b/src/widgets/kernel/qwidget.h
index 9370e20086..a56f6e1133 100644
--- a/src/widgets/kernel/qwidget.h
+++ b/src/widgets/kernel/qwidget.h
@@ -734,12 +734,12 @@ Q_DECLARE_OPERATORS_FOR_FLAGS(QWidget::RenderFlags)
 #ifndef Q_QDOC
 template <> inline QWidget *qobject_cast<QWidget*>(QObject *o)
 {
-    if (!o || !o->isWidgetType()) return 0;
+    if (!o || !o->isWidgetType()) return Q_NULLPTR;
     return static_cast<QWidget*>(o);
 }
 template <> inline const QWidget *qobject_cast<const QWidget*>(const QObject *o)
 {
-    if (!o || !o->isWidgetType()) return 0;
+    if (!o || !o->isWidgetType()) return Q_NULLPTR;
     return static_cast<const QWidget*>(o);
 }
 #endif // !Q_QDOC
diff --git a/src/widgets/statemachine/qkeyeventtransition.h b/src/widgets/statemachine/qkeyeventtransition.h
index 5dd0685d0b..ad159eaa22 100644
--- a/src/widgets/statemachine/qkeyeventtransition.h
+++ b/src/widgets/statemachine/qkeyeventtransition.h
@@ -48,9 +48,9 @@ class Q_WIDGETS_EXPORT QKeyEventTransition : public QEventTransition
     Q_PROPERTY(int key READ key WRITE setKey)
     Q_PROPERTY(Qt::KeyboardModifiers modifierMask READ modifierMask WRITE setModifierMask)
 public:
-    QKeyEventTransition(QState *sourceState = 0);
+    QKeyEventTransition(QState *sourceState = Q_NULLPTR);
     QKeyEventTransition(QObject *object, QEvent::Type type, int key,
-                        QState *sourceState = 0);
+                        QState *sourceState = Q_NULLPTR);
     ~QKeyEventTransition();
 
     int key() const;
diff --git a/src/widgets/statemachine/qmouseeventtransition.h b/src/widgets/statemachine/qmouseeventtransition.h
index d9bac9e1a0..b4db61279d 100644
--- a/src/widgets/statemachine/qmouseeventtransition.h
+++ b/src/widgets/statemachine/qmouseeventtransition.h
@@ -49,9 +49,9 @@ class Q_WIDGETS_EXPORT QMouseEventTransition : public QEventTransition
     Q_PROPERTY(Qt::MouseButton button READ button WRITE setButton)
     Q_PROPERTY(Qt::KeyboardModifiers modifierMask READ modifierMask WRITE setModifierMask)
 public:
-    QMouseEventTransition(QState *sourceState = 0);
+    QMouseEventTransition(QState *sourceState = Q_NULLPTR);
     QMouseEventTransition(QObject *object, QEvent::Type type,
-                          Qt::MouseButton button, QState *sourceState = 0);
+                          Qt::MouseButton button, QState *sourceState = Q_NULLPTR);
     ~QMouseEventTransition();
 
     Qt::MouseButton button() const;
diff --git a/src/widgets/styles/qcommonstyle.h b/src/widgets/styles/qcommonstyle.h
index 06fd755fa1..0d040f1b3e 100644
--- a/src/widgets/styles/qcommonstyle.h
+++ b/src/widgets/styles/qcommonstyle.h
@@ -49,34 +49,34 @@ public:
     ~QCommonStyle();
 
     void drawPrimitive(PrimitiveElement pe, const QStyleOption *opt, QPainter *p,
-                       const QWidget *w = 0) const Q_DECL_OVERRIDE;
+                       const QWidget *w = Q_NULLPTR) const Q_DECL_OVERRIDE;
     void drawControl(ControlElement element, const QStyleOption *opt, QPainter *p,
-                     const QWidget *w = 0) const Q_DECL_OVERRIDE;
-    QRect subElementRect(SubElement r, const QStyleOption *opt, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
+                     const QWidget *w = Q_NULLPTR) const Q_DECL_OVERRIDE;
+    QRect subElementRect(SubElement r, const QStyleOption *opt, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
     void drawComplexControl(ComplexControl cc, const QStyleOptionComplex *opt, QPainter *p,
-                            const QWidget *w = 0) const Q_DECL_OVERRIDE;
+                            const QWidget *w = Q_NULLPTR) const Q_DECL_OVERRIDE;
     SubControl hitTestComplexControl(ComplexControl cc, const QStyleOptionComplex *opt,
-                                     const QPoint &pt, const QWidget *w = 0) const Q_DECL_OVERRIDE;
+                                     const QPoint &pt, const QWidget *w = Q_NULLPTR) const Q_DECL_OVERRIDE;
     QRect subControlRect(ComplexControl cc, const QStyleOptionComplex *opt, SubControl sc,
-                         const QWidget *w = 0) const Q_DECL_OVERRIDE;
+                         const QWidget *w = Q_NULLPTR) const Q_DECL_OVERRIDE;
     QSize sizeFromContents(ContentsType ct, const QStyleOption *opt,
-                           const QSize &contentsSize, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
+                           const QSize &contentsSize, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
 
-    int pixelMetric(PixelMetric m, const QStyleOption *opt = 0, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
+    int pixelMetric(PixelMetric m, const QStyleOption *opt = Q_NULLPTR, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
 
-    int styleHint(StyleHint sh, const QStyleOption *opt = 0, const QWidget *w = 0,
-                  QStyleHintReturn *shret = 0) const Q_DECL_OVERRIDE;
+    int styleHint(StyleHint sh, const QStyleOption *opt = Q_NULLPTR, const QWidget *w = Q_NULLPTR,
+                  QStyleHintReturn *shret = Q_NULLPTR) const Q_DECL_OVERRIDE;
 
-    QIcon standardIcon(StandardPixmap standardIcon, const QStyleOption *opt = 0,
-                       const QWidget *widget = 0) const Q_DECL_OVERRIDE;
-    QPixmap standardPixmap(StandardPixmap sp, const QStyleOption *opt = 0,
-                           const QWidget *widget = 0) const Q_DECL_OVERRIDE;
+    QIcon standardIcon(StandardPixmap standardIcon, const QStyleOption *opt = Q_NULLPTR,
+                       const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
+    QPixmap standardPixmap(StandardPixmap sp, const QStyleOption *opt = Q_NULLPTR,
+                           const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
 
     QPixmap generatedIconPixmap(QIcon::Mode iconMode, const QPixmap &pixmap,
                                 const QStyleOption *opt) const Q_DECL_OVERRIDE;
     int layoutSpacing(QSizePolicy::ControlType control1, QSizePolicy::ControlType control2,
-                      Qt::Orientation orientation, const QStyleOption *option = 0,
-                      const QWidget *widget = 0) const Q_DECL_OVERRIDE;
+                      Qt::Orientation orientation, const QStyleOption *option = Q_NULLPTR,
+                      const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
 
     void polish(QPalette &) Q_DECL_OVERRIDE;
     void polish(QApplication *app) Q_DECL_OVERRIDE;
diff --git a/src/widgets/styles/qdrawutil.h b/src/widgets/styles/qdrawutil.h
index 1f2078a931..5b6d57b76f 100644
--- a/src/widgets/styles/qdrawutil.h
+++ b/src/widgets/styles/qdrawutil.h
@@ -63,42 +63,42 @@ Q_WIDGETS_EXPORT void qDrawShadeLine(QPainter *p, const QPoint &p1, const QPoint
 Q_WIDGETS_EXPORT void qDrawShadeRect(QPainter *p, int x, int y, int w, int h,
                               const QPalette &pal, bool sunken = false,
                               int lineWidth = 1, int midLineWidth = 0,
-                              const QBrush *fill = 0);
+                              const QBrush *fill = Q_NULLPTR);
 
 Q_WIDGETS_EXPORT void qDrawShadeRect(QPainter *p, const QRect &r,
                               const QPalette &pal, bool sunken = false,
                               int lineWidth = 1, int midLineWidth = 0,
-                              const QBrush *fill = 0);
+                              const QBrush *fill = Q_NULLPTR);
 
 Q_WIDGETS_EXPORT void qDrawShadePanel(QPainter *p, int x, int y, int w, int h,
                                const QPalette &pal, bool sunken = false,
-                               int lineWidth = 1, const QBrush *fill = 0);
+                               int lineWidth = 1, const QBrush *fill = Q_NULLPTR);
 
 Q_WIDGETS_EXPORT void qDrawShadePanel(QPainter *p, const QRect &r,
                                const QPalette &pal, bool sunken = false,
-                               int lineWidth = 1, const QBrush *fill = 0);
+                               int lineWidth = 1, const QBrush *fill = Q_NULLPTR);
 
 Q_WIDGETS_EXPORT void qDrawWinButton(QPainter *p, int x, int y, int w, int h,
                               const QPalette &pal, bool sunken = false,
-                              const QBrush *fill = 0);
+                              const QBrush *fill = Q_NULLPTR);
 
 Q_WIDGETS_EXPORT void qDrawWinButton(QPainter *p, const QRect &r,
                               const QPalette &pal, bool sunken = false,
-                              const QBrush *fill = 0);
+                              const QBrush *fill = Q_NULLPTR);
 
 Q_WIDGETS_EXPORT void qDrawWinPanel(QPainter *p, int x, int y, int w, int h,
                               const QPalette &pal, bool sunken = false,
-                             const QBrush *fill = 0);
+                             const QBrush *fill = Q_NULLPTR);
 
 Q_WIDGETS_EXPORT void qDrawWinPanel(QPainter *p, const QRect &r,
                               const QPalette &pal, bool sunken = false,
-                             const QBrush *fill = 0);
+                             const QBrush *fill = Q_NULLPTR);
 
 Q_WIDGETS_EXPORT void qDrawPlainRect(QPainter *p, int x, int y, int w, int h, const QColor &,
-                              int lineWidth = 1, const QBrush *fill = 0);
+                              int lineWidth = 1, const QBrush *fill = Q_NULLPTR);
 
 Q_WIDGETS_EXPORT void qDrawPlainRect(QPainter *p, const QRect &r, const QColor &,
-                              int lineWidth = 1, const QBrush *fill = 0);
+                              int lineWidth = 1, const QBrush *fill = Q_NULLPTR);
 
 
 
diff --git a/src/widgets/styles/qproxystyle.h b/src/widgets/styles/qproxystyle.h
index cac4cde0f2..072965bbd7 100644
--- a/src/widgets/styles/qproxystyle.h
+++ b/src/widgets/styles/qproxystyle.h
@@ -47,16 +47,16 @@ class Q_WIDGETS_EXPORT QProxyStyle : public QCommonStyle
     Q_OBJECT
 
 public:
-    QProxyStyle(QStyle *style = 0);
+    QProxyStyle(QStyle *style = Q_NULLPTR);
     QProxyStyle(const QString &key);
     ~QProxyStyle();
 
     QStyle *baseStyle() const;
     void setBaseStyle(QStyle *style);
 
-    void drawPrimitive(PrimitiveElement element, const QStyleOption *option, QPainter *painter, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
-    void drawControl(ControlElement element, const QStyleOption *option, QPainter *painter, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
-    void drawComplexControl(ComplexControl control, const QStyleOptionComplex *option, QPainter *painter, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
+    void drawPrimitive(PrimitiveElement element, const QStyleOption *option, QPainter *painter, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
+    void drawControl(ControlElement element, const QStyleOption *option, QPainter *painter, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
+    void drawComplexControl(ComplexControl control, const QStyleOptionComplex *option, QPainter *painter, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
     void drawItemText(QPainter *painter, const QRect &rect, int flags, const QPalette &pal, bool enabled,
                       const QString &text, QPalette::ColorRole textRole = QPalette::NoRole) const Q_DECL_OVERRIDE;
     virtual void drawItemPixmap(QPainter *painter, const QRect &rect, int alignment, const QPixmap &pixmap) const Q_DECL_OVERRIDE;
@@ -68,14 +68,14 @@ public:
     QRect itemTextRect(const QFontMetrics &fm, const QRect &r, int flags, bool enabled, const QString &text) const Q_DECL_OVERRIDE;
     QRect itemPixmapRect(const QRect &r, int flags, const QPixmap &pixmap) const Q_DECL_OVERRIDE;
 
-    SubControl hitTestComplexControl(ComplexControl control, const QStyleOptionComplex *option, const QPoint &pos, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
-    int styleHint(StyleHint hint, const QStyleOption *option = 0, const QWidget *widget = 0, QStyleHintReturn *returnData = 0) const Q_DECL_OVERRIDE;
-    int pixelMetric(PixelMetric metric, const QStyleOption *option = 0, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
+    SubControl hitTestComplexControl(ComplexControl control, const QStyleOptionComplex *option, const QPoint &pos, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
+    int styleHint(StyleHint hint, const QStyleOption *option = Q_NULLPTR, const QWidget *widget = Q_NULLPTR, QStyleHintReturn *returnData = Q_NULLPTR) const Q_DECL_OVERRIDE;
+    int pixelMetric(PixelMetric metric, const QStyleOption *option = Q_NULLPTR, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
     int layoutSpacing(QSizePolicy::ControlType control1, QSizePolicy::ControlType control2,
-                      Qt::Orientation orientation, const QStyleOption *option = 0, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
+                      Qt::Orientation orientation, const QStyleOption *option = Q_NULLPTR, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
 
-    QIcon standardIcon(StandardPixmap standardIcon, const QStyleOption *option = 0, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
-    QPixmap standardPixmap(StandardPixmap standardPixmap, const QStyleOption *opt, const QWidget *widget = 0) const Q_DECL_OVERRIDE;
+    QIcon standardIcon(StandardPixmap standardIcon, const QStyleOption *option = Q_NULLPTR, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
+    QPixmap standardPixmap(StandardPixmap standardPixmap, const QStyleOption *opt, const QWidget *widget = Q_NULLPTR) const Q_DECL_OVERRIDE;
     QPixmap generatedIconPixmap(QIcon::Mode iconMode, const QPixmap &pixmap, const QStyleOption *opt) const Q_DECL_OVERRIDE;
     QPalette standardPalette() const Q_DECL_OVERRIDE;
 
diff --git a/src/widgets/styles/qstyle.h b/src/widgets/styles/qstyle.h
index b41762795d..1e9d15c993 100644
--- a/src/widgets/styles/qstyle.h
+++ b/src/widgets/styles/qstyle.h
@@ -192,7 +192,7 @@ public:
     Q_ENUM(PrimitiveElement)
 
     virtual void drawPrimitive(PrimitiveElement pe, const QStyleOption *opt, QPainter *p,
-                               const QWidget *w = 0) const = 0;
+                               const QWidget *w = Q_NULLPTR) const = 0;
     enum ControlElement {
         CE_PushButton,
         CE_PushButtonBevel,
@@ -263,7 +263,7 @@ public:
     Q_ENUM(ControlElement)
 
     virtual void drawControl(ControlElement element, const QStyleOption *opt, QPainter *p,
-                             const QWidget *w = 0) const = 0;
+                             const QWidget *w = Q_NULLPTR) const = 0;
 
     enum SubElement {
         SE_PushButtonContents,
@@ -347,7 +347,7 @@ public:
     Q_ENUM(SubElement)
 
     virtual QRect subElementRect(SubElement subElement, const QStyleOption *option,
-                                 const QWidget *widget = 0) const = 0;
+                                 const QWidget *widget = Q_NULLPTR) const = 0;
 
 
     enum ComplexControl {
@@ -426,11 +426,11 @@ public:
 
 
     virtual void drawComplexControl(ComplexControl cc, const QStyleOptionComplex *opt, QPainter *p,
-                                    const QWidget *widget = 0) const = 0;
+                                    const QWidget *widget = Q_NULLPTR) const = 0;
     virtual SubControl hitTestComplexControl(ComplexControl cc, const QStyleOptionComplex *opt,
-                                             const QPoint &pt, const QWidget *widget = 0) const = 0;
+                                             const QPoint &pt, const QWidget *widget = Q_NULLPTR) const = 0;
     virtual QRect subControlRect(ComplexControl cc, const QStyleOptionComplex *opt,
-                                 SubControl sc, const QWidget *widget = 0) const = 0;
+                                 SubControl sc, const QWidget *widget = Q_NULLPTR) const = 0;
 
     enum PixelMetric {
         PM_ButtonMargin,
@@ -561,8 +561,8 @@ public:
     };
     Q_ENUM(PixelMetric)
 
-    virtual int pixelMetric(PixelMetric metric, const QStyleOption *option = 0,
-                            const QWidget *widget = 0) const = 0;
+    virtual int pixelMetric(PixelMetric metric, const QStyleOption *option = Q_NULLPTR,
+                            const QWidget *widget = Q_NULLPTR) const = 0;
 
     enum ContentsType {
         CT_PushButton,
@@ -594,7 +594,7 @@ public:
     Q_ENUM(ContentsType)
 
     virtual QSize sizeFromContents(ContentsType ct, const QStyleOption *opt,
-                                   const QSize &contentsSize, const QWidget *w = 0) const = 0;
+                                   const QSize &contentsSize, const QWidget *w = Q_NULLPTR) const = 0;
 
     enum RequestSoftwareInputPanel {
         RSIP_OnMouseClickAndAlreadyFocused,
@@ -724,8 +724,8 @@ public:
     };
     Q_ENUM(StyleHint)
 
-    virtual int styleHint(StyleHint stylehint, const QStyleOption *opt = 0,
-                          const QWidget *widget = 0, QStyleHintReturn* returnData = 0) const = 0;
+    virtual int styleHint(StyleHint stylehint, const QStyleOption *opt = Q_NULLPTR,
+                          const QWidget *widget = Q_NULLPTR, QStyleHintReturn* returnData = Q_NULLPTR) const = 0;
 
     enum StandardPixmap {
         SP_TitleBarMenuButton,
@@ -804,11 +804,11 @@ public:
     };
     Q_ENUM(StandardPixmap)
 
-    virtual QPixmap standardPixmap(StandardPixmap standardPixmap, const QStyleOption *opt = 0,
-                                   const QWidget *widget = 0) const = 0;
+    virtual QPixmap standardPixmap(StandardPixmap standardPixmap, const QStyleOption *opt = Q_NULLPTR,
+                                   const QWidget *widget = Q_NULLPTR) const = 0;
 
-    virtual QIcon standardIcon(StandardPixmap standardIcon, const QStyleOption *option = 0,
-                               const QWidget *widget = 0) const = 0;
+    virtual QIcon standardIcon(StandardPixmap standardIcon, const QStyleOption *option = Q_NULLPTR,
+                               const QWidget *widget = Q_NULLPTR) const = 0;
 
     virtual QPixmap generatedIconPixmap(QIcon::Mode iconMode, const QPixmap &pixmap,
                                         const QStyleOption *opt) const = 0;
@@ -827,10 +827,10 @@ public:
 
     virtual int layoutSpacing(QSizePolicy::ControlType control1,
                               QSizePolicy::ControlType control2, Qt::Orientation orientation,
-                              const QStyleOption *option = 0, const QWidget *widget = 0) const = 0;
+                              const QStyleOption *option = Q_NULLPTR, const QWidget *widget = Q_NULLPTR) const = 0;
     int combinedLayoutSpacing(QSizePolicy::ControlTypes controls1,
                               QSizePolicy::ControlTypes controls2, Qt::Orientation orientation,
-                              QStyleOption *option = 0, QWidget *widget = 0) const;
+                              QStyleOption *option = Q_NULLPTR, QWidget *widget = Q_NULLPTR) const;
 
     const QStyle * proxy() const;
 
diff --git a/src/widgets/styles/qstylepainter.h b/src/widgets/styles/qstylepainter.h
index 33d17d42b9..8492d231ae 100644
--- a/src/widgets/styles/qstylepainter.h
+++ b/src/widgets/styles/qstylepainter.h
@@ -44,7 +44,7 @@ QT_BEGIN_NAMESPACE
 class QStylePainter : public QPainter
 {
 public:
-    inline QStylePainter() : QPainter(), widget(0), wstyle(0) {}
+    inline QStylePainter() : QPainter(), widget(Q_NULLPTR), wstyle(Q_NULLPTR) {}
     inline explicit QStylePainter(QWidget *w) { begin(w, w); }
     inline QStylePainter(QPaintDevice *pd, QWidget *w) { begin(pd, w); }
     inline bool begin(QWidget *w) { return begin(w, w); }
diff --git a/src/widgets/styles/qstyleplugin.h b/src/widgets/styles/qstyleplugin.h
index b83774a39d..c8f6344758 100644
--- a/src/widgets/styles/qstyleplugin.h
+++ b/src/widgets/styles/qstyleplugin.h
@@ -48,7 +48,7 @@ class Q_WIDGETS_EXPORT QStylePlugin : public QObject
 {
     Q_OBJECT
 public:
-    explicit QStylePlugin(QObject *parent = 0);
+    explicit QStylePlugin(QObject *parent = Q_NULLPTR);
     ~QStylePlugin();
 
     virtual QStyle *create(const QString &key) = 0;
diff --git a/src/widgets/util/qcompleter.h b/src/widgets/util/qcompleter.h
index 22230fc39e..32ee6296ca 100644
--- a/src/widgets/util/qcompleter.h
+++ b/src/widgets/util/qcompleter.h
@@ -76,10 +76,10 @@ public:
         CaseInsensitivelySortedModel
     };
 
-    QCompleter(QObject *parent = 0);
-    QCompleter(QAbstractItemModel *model, QObject *parent = 0);
+    QCompleter(QObject *parent = Q_NULLPTR);
+    QCompleter(QAbstractItemModel *model, QObject *parent = Q_NULLPTR);
 #ifndef QT_NO_STRINGLISTMODEL
-    QCompleter(const QStringList& completions, QObject *parent = 0);
+    QCompleter(const QStringList& completions, QObject *parent = Q_NULLPTR);
 #endif
     ~QCompleter();
 
diff --git a/src/widgets/util/qsystemtrayicon.h b/src/widgets/util/qsystemtrayicon.h
index a4da0861e9..aba126b4fc 100644
--- a/src/widgets/util/qsystemtrayicon.h
+++ b/src/widgets/util/qsystemtrayicon.h
@@ -59,8 +59,8 @@ class Q_WIDGETS_EXPORT QSystemTrayIcon : public QObject
     Q_PROPERTY(bool visible READ isVisible WRITE setVisible DESIGNABLE false)
 
 public:
-    QSystemTrayIcon(QObject *parent = 0);
-    QSystemTrayIcon(const QIcon &icon, QObject *parent = 0);
+    QSystemTrayIcon(QObject *parent = Q_NULLPTR);
+    QSystemTrayIcon(const QIcon &icon, QObject *parent = Q_NULLPTR);
     ~QSystemTrayIcon();
 
     enum ActivationReason {
diff --git a/src/widgets/util/qundogroup.h b/src/widgets/util/qundogroup.h
index ea4b226a18..ec6e67f4d3 100644
--- a/src/widgets/util/qundogroup.h
+++ b/src/widgets/util/qundogroup.h
@@ -52,7 +52,7 @@ class Q_WIDGETS_EXPORT QUndoGroup : public QObject
     Q_DECLARE_PRIVATE(QUndoGroup)
 
 public:
-    explicit QUndoGroup(QObject *parent = 0);
+    explicit QUndoGroup(QObject *parent = Q_NULLPTR);
     ~QUndoGroup();
 
     void addStack(QUndoStack *stack);
diff --git a/src/widgets/util/qundostack.h b/src/widgets/util/qundostack.h
index f6589da4ec..0b14a442c2 100644
--- a/src/widgets/util/qundostack.h
+++ b/src/widgets/util/qundostack.h
@@ -51,8 +51,8 @@ class Q_WIDGETS_EXPORT QUndoCommand
     QUndoCommandPrivate *d;
 
 public:
-    explicit QUndoCommand(QUndoCommand *parent = 0);
-    explicit QUndoCommand(const QString &text, QUndoCommand *parent = 0);
+    explicit QUndoCommand(QUndoCommand *parent = Q_NULLPTR);
+    explicit QUndoCommand(const QString &text, QUndoCommand *parent = Q_NULLPTR);
     virtual ~QUndoCommand();
 
     virtual void undo();
@@ -85,7 +85,7 @@ class Q_WIDGETS_EXPORT QUndoStack : public QObject
     Q_PROPERTY(int undoLimit READ undoLimit WRITE setUndoLimit)
 
 public:
-    explicit QUndoStack(QObject *parent = 0);
+    explicit QUndoStack(QObject *parent = Q_NULLPTR);
     ~QUndoStack();
     void clear();
 
diff --git a/src/widgets/util/qundoview.h b/src/widgets/util/qundoview.h
index a239d9b38e..2a15207ca5 100644
--- a/src/widgets/util/qundoview.h
+++ b/src/widgets/util/qundoview.h
@@ -55,10 +55,10 @@ class Q_WIDGETS_EXPORT QUndoView : public QListView
     Q_PROPERTY(QIcon cleanIcon READ cleanIcon WRITE setCleanIcon)
 
 public:
-    explicit QUndoView(QWidget *parent = 0);
-    explicit QUndoView(QUndoStack *stack, QWidget *parent = 0);
+    explicit QUndoView(QWidget *parent = Q_NULLPTR);
+    explicit QUndoView(QUndoStack *stack, QWidget *parent = Q_NULLPTR);
 #ifndef QT_NO_UNDOGROUP
-    explicit QUndoView(QUndoGroup *group, QWidget *parent = 0);
+    explicit QUndoView(QUndoGroup *group, QWidget *parent = Q_NULLPTR);
 #endif
     ~QUndoView();
 
diff --git a/src/widgets/widgets/qabstractbutton.h b/src/widgets/widgets/qabstractbutton.h
index 4b397e2396..5f3e82a2e6 100644
--- a/src/widgets/widgets/qabstractbutton.h
+++ b/src/widgets/widgets/qabstractbutton.h
@@ -63,7 +63,7 @@ class Q_WIDGETS_EXPORT QAbstractButton : public QWidget
     Q_PROPERTY(bool down READ isDown WRITE setDown DESIGNABLE false)
 
 public:
-    explicit QAbstractButton(QWidget* parent=0);
+    explicit QAbstractButton(QWidget *parent = Q_NULLPTR);
     ~QAbstractButton();
 
     void setText(const QString &text);
@@ -135,7 +135,7 @@ protected:
 
 
 protected:
-    QAbstractButton(QAbstractButtonPrivate &dd, QWidget* parent = 0);
+    QAbstractButton(QAbstractButtonPrivate &dd, QWidget* parent = Q_NULLPTR);
 
 private:
     Q_DECLARE_PRIVATE(QAbstractButton)
diff --git a/src/widgets/widgets/qabstractscrollarea.h b/src/widgets/widgets/qabstractscrollarea.h
index 13dafd547b..8bc32b1c78 100644
--- a/src/widgets/widgets/qabstractscrollarea.h
+++ b/src/widgets/widgets/qabstractscrollarea.h
@@ -54,7 +54,7 @@ class Q_WIDGETS_EXPORT QAbstractScrollArea : public QFrame
     Q_PROPERTY(SizeAdjustPolicy sizeAdjustPolicy READ sizeAdjustPolicy WRITE setSizeAdjustPolicy)
 
 public:
-    explicit QAbstractScrollArea(QWidget* parent=0);
+    explicit QAbstractScrollArea(QWidget *parent = Q_NULLPTR);
     ~QAbstractScrollArea();
 
     enum SizeAdjustPolicy {
@@ -94,7 +94,7 @@ public:
     void setSizeAdjustPolicy(SizeAdjustPolicy policy);
 
 protected:
-    QAbstractScrollArea(QAbstractScrollAreaPrivate &dd, QWidget *parent = 0);
+    QAbstractScrollArea(QAbstractScrollAreaPrivate &dd, QWidget *parent = Q_NULLPTR);
     void setViewportMargins(int left, int top, int right, int bottom);
     void setViewportMargins(const QMargins &margins);
     QMargins viewportMargins() const;
diff --git a/src/widgets/widgets/qabstractslider.h b/src/widgets/widgets/qabstractslider.h
index 2f649e3d3d..6faca5ea3c 100644
--- a/src/widgets/widgets/qabstractslider.h
+++ b/src/widgets/widgets/qabstractslider.h
@@ -58,7 +58,7 @@ class Q_WIDGETS_EXPORT QAbstractSlider : public QWidget
     Q_PROPERTY(bool sliderDown READ isSliderDown WRITE setSliderDown DESIGNABLE false)
 
 public:
-    explicit QAbstractSlider(QWidget *parent=0);
+    explicit QAbstractSlider(QWidget *parent = Q_NULLPTR);
     ~QAbstractSlider();
 
     Qt::Orientation orientation() const;
@@ -144,7 +144,7 @@ protected:
 
 
 protected:
-    QAbstractSlider(QAbstractSliderPrivate &dd, QWidget *parent=0);
+    QAbstractSlider(QAbstractSliderPrivate &dd, QWidget *parent = Q_NULLPTR);
 
 private:
     Q_DISABLE_COPY(QAbstractSlider)
diff --git a/src/widgets/widgets/qabstractspinbox.h b/src/widgets/widgets/qabstractspinbox.h
index a80a89c894..046036b9a8 100644
--- a/src/widgets/widgets/qabstractspinbox.h
+++ b/src/widgets/widgets/qabstractspinbox.h
@@ -64,7 +64,7 @@ class Q_WIDGETS_EXPORT QAbstractSpinBox : public QWidget
     Q_PROPERTY(bool keyboardTracking READ keyboardTracking WRITE setKeyboardTracking)
     Q_PROPERTY(bool showGroupSeparator READ isGroupSeparatorShown WRITE setGroupSeparatorShown)
 public:
-    explicit QAbstractSpinBox(QWidget *parent = 0);
+    explicit QAbstractSpinBox(QWidget *parent = Q_NULLPTR);
     ~QAbstractSpinBox();
 
     enum StepEnabledFlag { StepNone = 0x00, StepUpEnabled = 0x01,
@@ -154,7 +154,7 @@ protected:
 Q_SIGNALS:
     void editingFinished();
 protected:
-    QAbstractSpinBox(QAbstractSpinBoxPrivate &dd, QWidget *parent = 0);
+    QAbstractSpinBox(QAbstractSpinBoxPrivate &dd, QWidget *parent = Q_NULLPTR);
 
 private:
     Q_PRIVATE_SLOT(d_func(), void _q_editorTextChanged(const QString &))
diff --git a/src/widgets/widgets/qbuttongroup.h b/src/widgets/widgets/qbuttongroup.h
index 01de03ac84..ba4f8e26c1 100644
--- a/src/widgets/widgets/qbuttongroup.h
+++ b/src/widgets/widgets/qbuttongroup.h
@@ -51,7 +51,7 @@ class Q_WIDGETS_EXPORT QButtonGroup : public QObject
 
     Q_PROPERTY(bool exclusive READ exclusive WRITE setExclusive)
 public:
-    explicit QButtonGroup(QObject *parent = 0);
+    explicit QButtonGroup(QObject *parent = Q_NULLPTR);
     ~QButtonGroup();
 
     void setExclusive(bool);
diff --git a/src/widgets/widgets/qcalendarwidget.h b/src/widgets/widgets/qcalendarwidget.h
index c456cc2161..df54985351 100644
--- a/src/widgets/widgets/qcalendarwidget.h
+++ b/src/widgets/widgets/qcalendarwidget.h
@@ -83,7 +83,7 @@ public:
     };
     Q_ENUM(SelectionMode)
 
-    explicit QCalendarWidget(QWidget *parent = 0);
+    explicit QCalendarWidget(QWidget *parent = Q_NULLPTR);
     ~QCalendarWidget();
 
     virtual QSize sizeHint() const Q_DECL_OVERRIDE;
diff --git a/src/widgets/widgets/qcheckbox.h b/src/widgets/widgets/qcheckbox.h
index b614659f02..61d03eb8e6 100644
--- a/src/widgets/widgets/qcheckbox.h
+++ b/src/widgets/widgets/qcheckbox.h
@@ -49,8 +49,8 @@ class Q_WIDGETS_EXPORT QCheckBox : public QAbstractButton
     Q_PROPERTY(bool tristate READ isTristate WRITE setTristate)
 
 public:
-    explicit QCheckBox(QWidget *parent=0);
-    explicit QCheckBox(const QString &text, QWidget *parent=0);
+    explicit QCheckBox(QWidget *parent = Q_NULLPTR);
+    explicit QCheckBox(const QString &text, QWidget *parent = Q_NULLPTR);
     ~QCheckBox();
 
     QSize sizeHint() const Q_DECL_OVERRIDE;
diff --git a/src/widgets/widgets/qcombobox.h b/src/widgets/widgets/qcombobox.h
index ae35f7a89a..3182a0a3aa 100644
--- a/src/widgets/widgets/qcombobox.h
+++ b/src/widgets/widgets/qcombobox.h
@@ -74,7 +74,7 @@ class Q_WIDGETS_EXPORT QComboBox : public QWidget
     Q_PROPERTY(int modelColumn READ modelColumn WRITE setModelColumn)
 
 public:
-    explicit QComboBox(QWidget *parent = 0);
+    explicit QComboBox(QWidget *parent = Q_NULLPTR);
     ~QComboBox();
 
     int maxVisibleItems() const;
diff --git a/src/widgets/widgets/qcommandlinkbutton.h b/src/widgets/widgets/qcommandlinkbutton.h
index 486c48af5d..9ddb14270d 100644
--- a/src/widgets/widgets/qcommandlinkbutton.h
+++ b/src/widgets/widgets/qcommandlinkbutton.h
@@ -49,9 +49,9 @@ class Q_WIDGETS_EXPORT QCommandLinkButton: public QPushButton
     Q_PROPERTY(bool flat READ isFlat WRITE setFlat DESIGNABLE false)
 
 public:
-    explicit QCommandLinkButton(QWidget *parent=0);
-    explicit QCommandLinkButton(const QString &text, QWidget *parent=0);
-    explicit QCommandLinkButton(const QString &text, const QString &description, QWidget *parent=0);
+    explicit QCommandLinkButton(QWidget *parent = Q_NULLPTR);
+    explicit QCommandLinkButton(const QString &text, QWidget *parent = Q_NULLPTR);
+    explicit QCommandLinkButton(const QString &text, const QString &description, QWidget *parent = Q_NULLPTR);
     ~QCommandLinkButton();
 
     QString description() const;
diff --git a/src/widgets/widgets/qdatetimeedit.h b/src/widgets/widgets/qdatetimeedit.h
index 4e77713fd0..829ce205be 100644
--- a/src/widgets/widgets/qdatetimeedit.h
+++ b/src/widgets/widgets/qdatetimeedit.h
@@ -86,10 +86,10 @@ public:
 
     Q_DECLARE_FLAGS(Sections, Section)
 
-    explicit QDateTimeEdit(QWidget *parent = 0);
-    explicit QDateTimeEdit(const QDateTime &dt, QWidget *parent = 0);
-    explicit QDateTimeEdit(const QDate &d, QWidget *parent = 0);
-    explicit QDateTimeEdit(const QTime &t, QWidget *parent = 0);
+    explicit QDateTimeEdit(QWidget *parent = Q_NULLPTR);
+    explicit QDateTimeEdit(const QDateTime &dt, QWidget *parent = Q_NULLPTR);
+    explicit QDateTimeEdit(const QDate &d, QWidget *parent = Q_NULLPTR);
+    explicit QDateTimeEdit(const QTime &t, QWidget *parent = Q_NULLPTR);
     ~QDateTimeEdit();
 
     QDateTime dateTime() const;
@@ -185,7 +185,7 @@ protected:
     virtual void paintEvent(QPaintEvent *event);
     void initStyleOption(QStyleOptionSpinBox *option) const;
 
-    QDateTimeEdit(const QVariant &val, QVariant::Type parserType, QWidget *parent = 0);
+    QDateTimeEdit(const QVariant &val, QVariant::Type parserType, QWidget *parent = Q_NULLPTR);
 private:
     Q_DECLARE_PRIVATE(QDateTimeEdit)
     Q_DISABLE_COPY(QDateTimeEdit)
@@ -198,8 +198,8 @@ class Q_WIDGETS_EXPORT QTimeEdit : public QDateTimeEdit
     Q_OBJECT
     Q_PROPERTY(QTime time READ time WRITE setTime NOTIFY userTimeChanged USER true)
 public:
-    explicit QTimeEdit(QWidget *parent = 0);
-    explicit QTimeEdit(const QTime &time, QWidget *parent = 0);
+    explicit QTimeEdit(QWidget *parent = Q_NULLPTR);
+    explicit QTimeEdit(const QTime &time, QWidget *parent = Q_NULLPTR);
     ~QTimeEdit();
 
 Q_SIGNALS:
@@ -211,8 +211,8 @@ class Q_WIDGETS_EXPORT QDateEdit : public QDateTimeEdit
     Q_OBJECT
     Q_PROPERTY(QDate date READ date WRITE setDate NOTIFY userDateChanged USER true)
 public:
-    explicit QDateEdit(QWidget *parent = 0);
-    explicit QDateEdit(const QDate &date, QWidget *parent = 0);
+    explicit QDateEdit(QWidget *parent = Q_NULLPTR);
+    explicit QDateEdit(const QDate &date, QWidget *parent = Q_NULLPTR);
     ~QDateEdit();
 
 Q_SIGNALS:
diff --git a/src/widgets/widgets/qdial.h b/src/widgets/widgets/qdial.h
index 7e01aefce3..cb69e02301 100644
--- a/src/widgets/widgets/qdial.h
+++ b/src/widgets/widgets/qdial.h
@@ -54,7 +54,7 @@ class Q_WIDGETS_EXPORT QDial: public QAbstractSlider
     Q_PROPERTY(qreal notchTarget READ notchTarget WRITE setNotchTarget)
     Q_PROPERTY(bool notchesVisible READ notchesVisible WRITE setNotchesVisible)
 public:
-    explicit QDial(QWidget *parent = 0);
+    explicit QDial(QWidget *parent = Q_NULLPTR);
 
     ~QDial();
 
diff --git a/src/widgets/widgets/qdialogbuttonbox.h b/src/widgets/widgets/qdialogbuttonbox.h
index 02960b5b79..83c1fd66fd 100644
--- a/src/widgets/widgets/qdialogbuttonbox.h
+++ b/src/widgets/widgets/qdialogbuttonbox.h
@@ -106,11 +106,11 @@ public:
         GnomeLayout
     };
 
-    QDialogButtonBox(QWidget *parent = 0);
-    QDialogButtonBox(Qt::Orientation orientation, QWidget *parent = 0);
-    explicit QDialogButtonBox(StandardButtons buttons, QWidget *parent = 0);
+    QDialogButtonBox(QWidget *parent = Q_NULLPTR);
+    QDialogButtonBox(Qt::Orientation orientation, QWidget *parent = Q_NULLPTR);
+    explicit QDialogButtonBox(StandardButtons buttons, QWidget *parent = Q_NULLPTR);
     QDialogButtonBox(StandardButtons buttons, Qt::Orientation orientation,
-                     QWidget *parent = 0);
+                     QWidget *parent = Q_NULLPTR);
     ~QDialogButtonBox();
 
     void setOrientation(Qt::Orientation orientation);
diff --git a/src/widgets/widgets/qfocusframe.h b/src/widgets/widgets/qfocusframe.h
index f976ba9827..bbd639c2f9 100644
--- a/src/widgets/widgets/qfocusframe.h
+++ b/src/widgets/widgets/qfocusframe.h
@@ -46,7 +46,7 @@ class Q_WIDGETS_EXPORT QFocusFrame : public QWidget
 {
     Q_OBJECT
 public:
-    QFocusFrame(QWidget *parent=0);
+    QFocusFrame(QWidget *parent = Q_NULLPTR);
     ~QFocusFrame();
 
     void setWidget(QWidget *widget);
diff --git a/src/widgets/widgets/qfontcombobox.h b/src/widgets/widgets/qfontcombobox.h
index 0c8cf5d58d..412acd041e 100644
--- a/src/widgets/widgets/qfontcombobox.h
+++ b/src/widgets/widgets/qfontcombobox.h
@@ -53,7 +53,7 @@ class Q_WIDGETS_EXPORT QFontComboBox : public QComboBox
     Q_PROPERTY(QFont currentFont READ currentFont WRITE setCurrentFont NOTIFY currentFontChanged)
 
 public:
-    explicit QFontComboBox(QWidget *parent = 0);
+    explicit QFontComboBox(QWidget *parent = Q_NULLPTR);
     ~QFontComboBox();
 
     void setWritingSystem(QFontDatabase::WritingSystem);
diff --git a/src/widgets/widgets/qgroupbox.h b/src/widgets/widgets/qgroupbox.h
index 8100fadff4..57ebdce8dd 100644
--- a/src/widgets/widgets/qgroupbox.h
+++ b/src/widgets/widgets/qgroupbox.h
@@ -53,8 +53,8 @@ class Q_WIDGETS_EXPORT QGroupBox : public QWidget
     Q_PROPERTY(bool checkable READ isCheckable WRITE setCheckable)
     Q_PROPERTY(bool checked READ isChecked WRITE setChecked DESIGNABLE isCheckable NOTIFY toggled USER true)
 public:
-    explicit QGroupBox(QWidget* parent=0);
-    explicit QGroupBox(const QString &title, QWidget* parent=0);
+    explicit QGroupBox(QWidget *parent = Q_NULLPTR);
+    explicit QGroupBox(const QString &title, QWidget *parent = Q_NULLPTR);
     ~QGroupBox();
 
     QString title() const;
diff --git a/src/widgets/widgets/qkeysequenceedit.h b/src/widgets/widgets/qkeysequenceedit.h
index 1887a40bfc..ad60bcc513 100644
--- a/src/widgets/widgets/qkeysequenceedit.h
+++ b/src/widgets/widgets/qkeysequenceedit.h
@@ -48,8 +48,8 @@ class Q_WIDGETS_EXPORT QKeySequenceEdit : public QWidget
     Q_PROPERTY(QKeySequence keySequence READ keySequence WRITE setKeySequence NOTIFY keySequenceChanged USER true)
 
 public:
-    explicit QKeySequenceEdit(QWidget *parent = 0);
-    explicit QKeySequenceEdit(const QKeySequence &keySequence, QWidget *parent = 0);
+    explicit QKeySequenceEdit(QWidget *parent = Q_NULLPTR);
+    explicit QKeySequenceEdit(const QKeySequence &keySequence, QWidget *parent = Q_NULLPTR);
     ~QKeySequenceEdit();
 
     QKeySequence keySequence() const;
diff --git a/src/widgets/widgets/qlcdnumber.h b/src/widgets/widgets/qlcdnumber.h
index d93edc75ca..9a7904a8bb 100644
--- a/src/widgets/widgets/qlcdnumber.h
+++ b/src/widgets/widgets/qlcdnumber.h
@@ -53,8 +53,8 @@ class Q_WIDGETS_EXPORT QLCDNumber : public QFrame // LCD number widget
     Q_PROPERTY(int intValue READ intValue WRITE display)
 
 public:
-    explicit QLCDNumber(QWidget* parent = 0);
-    explicit QLCDNumber(uint numDigits, QWidget* parent = 0);
+    explicit QLCDNumber(QWidget* parent = Q_NULLPTR);
+    explicit QLCDNumber(uint numDigits, QWidget* parent = Q_NULLPTR);
     ~QLCDNumber();
 
     enum Mode {
diff --git a/src/widgets/widgets/qlineedit.h b/src/widgets/widgets/qlineedit.h
index e006f1c0d8..ac192f0da8 100644
--- a/src/widgets/widgets/qlineedit.h
+++ b/src/widgets/widgets/qlineedit.h
@@ -84,8 +84,8 @@ public:
     };
     Q_ENUM(ActionPosition)
 
-    explicit QLineEdit(QWidget* parent=0);
-    explicit QLineEdit(const QString &, QWidget* parent=0);
+    explicit QLineEdit(QWidget *parent = Q_NULLPTR);
+    explicit QLineEdit(const QString &, QWidget *parent = Q_NULLPTR);
     ~QLineEdit();
 
     QString text() const;
diff --git a/src/widgets/widgets/qmaccocoaviewcontainer_mac.h b/src/widgets/widgets/qmaccocoaviewcontainer_mac.h
index 5920c1f8bf..a27d8f8690 100644
--- a/src/widgets/widgets/qmaccocoaviewcontainer_mac.h
+++ b/src/widgets/widgets/qmaccocoaviewcontainer_mac.h
@@ -45,7 +45,7 @@ class Q_WIDGETS_EXPORT QMacCocoaViewContainer : public QWidget
 {
     Q_OBJECT
 public:
-    QMacCocoaViewContainer(NSView *cocoaViewToWrap, QWidget *parent = 0);
+    QMacCocoaViewContainer(NSView *cocoaViewToWrap, QWidget *parent = Q_NULLPTR);
     virtual ~QMacCocoaViewContainer();
 
     void setCocoaView(NSView *view);
diff --git a/src/widgets/widgets/qmacnativewidget_mac.h b/src/widgets/widgets/qmacnativewidget_mac.h
index 761e55656b..5e82872faa 100644
--- a/src/widgets/widgets/qmacnativewidget_mac.h
+++ b/src/widgets/widgets/qmacnativewidget_mac.h
@@ -45,7 +45,7 @@ class Q_WIDGETS_EXPORT QMacNativeWidget : public QWidget
 {
     Q_OBJECT
 public:
-    QMacNativeWidget(NSView *parentView = 0);
+    QMacNativeWidget(NSView *parentView = Q_NULLPTR);
     ~QMacNativeWidget();
 
     QSize sizeHint() const;
diff --git a/src/widgets/widgets/qmdiarea.h b/src/widgets/widgets/qmdiarea.h
index f1361fffc6..e05535b2af 100644
--- a/src/widgets/widgets/qmdiarea.h
+++ b/src/widgets/widgets/qmdiarea.h
@@ -79,7 +79,7 @@ public:
     };
     Q_ENUM(ViewMode)
 
-    QMdiArea(QWidget *parent = 0);
+    QMdiArea(QWidget *parent = Q_NULLPTR);
     ~QMdiArea();
 
     QSize sizeHint() const Q_DECL_OVERRIDE;
diff --git a/src/widgets/widgets/qmenu.h b/src/widgets/widgets/qmenu.h
index 21e1432d2a..6bbe54186e 100644
--- a/src/widgets/widgets/qmenu.h
+++ b/src/widgets/widgets/qmenu.h
@@ -68,8 +68,8 @@ private:
     Q_PROPERTY(bool toolTipsVisible READ toolTipsVisible WRITE setToolTipsVisible)
 
 public:
-    explicit QMenu(QWidget *parent = 0);
-    explicit QMenu(const QString &title, QWidget *parent = 0);
+    explicit QMenu(QWidget *parent = Q_NULLPTR);
+    explicit QMenu(const QString &title, QWidget *parent = Q_NULLPTR);
     ~QMenu();
 
     using QWidget::addAction;
@@ -173,14 +173,14 @@ public:
     void setActiveAction(QAction *act);
     QAction *activeAction() const;
 
-    void popup(const QPoint &pos, QAction *at=0);
+    void popup(const QPoint &pos, QAction *at = Q_NULLPTR);
     QAction *exec();
-    QAction *exec(const QPoint &pos, QAction *at=0);
+    QAction *exec(const QPoint &pos, QAction *at = Q_NULLPTR);
 
 #if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
-    static QAction *exec(const QList<QAction *> &actions, const QPoint &pos, QAction *at = 0, QWidget *parent = 0);
+    static QAction *exec(const QList<QAction *> &actions, const QPoint &pos, QAction *at = Q_NULLPTR, QWidget *parent = Q_NULLPTR);
 #else
-    static QAction *exec(QList<QAction*> actions, const QPoint &pos, QAction *at=0, QWidget *parent=0);
+    static QAction *exec(QList<QAction*> actions, const QPoint &pos, QAction *at = Q_NULLPTR, QWidget *parent = Q_NULLPTR);
 #endif
 
     QSize sizeHint() const Q_DECL_OVERRIDE;
@@ -255,7 +255,7 @@ private:
     Q_PRIVATE_SLOT(d_func(), void _q_platformMenuAboutToShow())
 
 protected:
-    QMenu(QMenuPrivate &dd, QWidget* parent = 0);
+    QMenu(QMenuPrivate &dd, QWidget* parent = Q_NULLPTR);
 
 private:
     Q_DISABLE_COPY(QMenu)
diff --git a/src/widgets/widgets/qmenubar.h b/src/widgets/widgets/qmenubar.h
index 461dec8a94..3b3980c860 100644
--- a/src/widgets/widgets/qmenubar.h
+++ b/src/widgets/widgets/qmenubar.h
@@ -54,7 +54,7 @@ class Q_WIDGETS_EXPORT QMenuBar : public QWidget
     Q_PROPERTY(bool nativeMenuBar READ isNativeMenuBar WRITE setNativeMenuBar)
 
 public:
-    explicit QMenuBar(QWidget *parent = 0);
+    explicit QMenuBar(QWidget *parent = Q_NULLPTR);
     ~QMenuBar();
 
     using QWidget::addAction;
diff --git a/src/widgets/widgets/qplaintextedit.h b/src/widgets/widgets/qplaintextedit.h
index 69bd2ab647..fc378c6ab9 100644
--- a/src/widgets/widgets/qplaintextedit.h
+++ b/src/widgets/widgets/qplaintextedit.h
@@ -82,8 +82,8 @@ public:
     };
     Q_ENUM(LineWrapMode)
 
-    explicit QPlainTextEdit(QWidget *parent = 0);
-    explicit QPlainTextEdit(const QString &text, QWidget *parent = 0);
+    explicit QPlainTextEdit(QWidget *parent = Q_NULLPTR);
+    explicit QPlainTextEdit(const QString &text, QWidget *parent = Q_NULLPTR);
     virtual ~QPlainTextEdit();
 
     void setDocument(QTextDocument *document);
diff --git a/src/widgets/widgets/qprogressbar.h b/src/widgets/widgets/qprogressbar.h
index 0c3200f82c..e17e01c17b 100644
--- a/src/widgets/widgets/qprogressbar.h
+++ b/src/widgets/widgets/qprogressbar.h
@@ -62,7 +62,7 @@ public:
     enum Direction { TopToBottom, BottomToTop };
     Q_ENUM(Direction)
 
-    explicit QProgressBar(QWidget *parent = 0);
+    explicit QProgressBar(QWidget *parent = Q_NULLPTR);
     ~QProgressBar();
 
     int minimum() const;
diff --git a/src/widgets/widgets/qpushbutton.h b/src/widgets/widgets/qpushbutton.h
index 2521c0982e..3db12be380 100644
--- a/src/widgets/widgets/qpushbutton.h
+++ b/src/widgets/widgets/qpushbutton.h
@@ -52,9 +52,9 @@ class Q_WIDGETS_EXPORT QPushButton : public QAbstractButton
     Q_PROPERTY(bool flat READ isFlat WRITE setFlat)
 
 public:
-    explicit QPushButton(QWidget *parent=0);
-    explicit QPushButton(const QString &text, QWidget *parent=0);
-    QPushButton(const QIcon& icon, const QString &text, QWidget *parent=0);
+    explicit QPushButton(QWidget *parent = Q_NULLPTR);
+    explicit QPushButton(const QString &text, QWidget *parent = Q_NULLPTR);
+    QPushButton(const QIcon& icon, const QString &text, QWidget *parent = Q_NULLPTR);
     ~QPushButton();
 
     QSize sizeHint() const Q_DECL_OVERRIDE;
@@ -88,7 +88,7 @@ protected:
     void focusInEvent(QFocusEvent *) Q_DECL_OVERRIDE;
     void focusOutEvent(QFocusEvent *) Q_DECL_OVERRIDE;
     void initStyleOption(QStyleOptionButton *option) const;
-    QPushButton(QPushButtonPrivate &dd, QWidget* parent = 0);
+    QPushButton(QPushButtonPrivate &dd, QWidget* parent = Q_NULLPTR);
 
 public:
 
diff --git a/src/widgets/widgets/qradiobutton.h b/src/widgets/widgets/qradiobutton.h
index f323f5af99..df0b1051bf 100644
--- a/src/widgets/widgets/qradiobutton.h
+++ b/src/widgets/widgets/qradiobutton.h
@@ -47,8 +47,8 @@ class Q_WIDGETS_EXPORT QRadioButton : public QAbstractButton
     Q_OBJECT
 
 public:
-    explicit QRadioButton(QWidget *parent=0);
-    explicit QRadioButton(const QString &text, QWidget *parent=0);
+    explicit QRadioButton(QWidget *parent = Q_NULLPTR);
+    explicit QRadioButton(const QString &text, QWidget *parent = Q_NULLPTR);
     ~QRadioButton();
 
     QSize sizeHint() const Q_DECL_OVERRIDE;
diff --git a/src/widgets/widgets/qrubberband.h b/src/widgets/widgets/qrubberband.h
index 3ff6eb47fa..b0dc14ed98 100644
--- a/src/widgets/widgets/qrubberband.h
+++ b/src/widgets/widgets/qrubberband.h
@@ -50,7 +50,7 @@ class Q_WIDGETS_EXPORT QRubberBand : public QWidget
 
 public:
     enum Shape { Line, Rectangle };
-    explicit QRubberBand(Shape, QWidget * =0);
+    explicit QRubberBand(Shape, QWidget * = Q_NULLPTR);
     ~QRubberBand();
 
     Shape shape() const;
diff --git a/src/widgets/widgets/qscrollarea.h b/src/widgets/widgets/qscrollarea.h
index cafb1ec6de..1658236034 100644
--- a/src/widgets/widgets/qscrollarea.h
+++ b/src/widgets/widgets/qscrollarea.h
@@ -50,7 +50,7 @@ class Q_WIDGETS_EXPORT QScrollArea : public QAbstractScrollArea
     Q_PROPERTY(Qt::Alignment alignment READ alignment WRITE setAlignment)
 
 public:
-    explicit QScrollArea(QWidget* parent=0);
+    explicit QScrollArea(QWidget *parent = Q_NULLPTR);
     ~QScrollArea();
 
     QWidget *widget() const;
@@ -71,7 +71,7 @@ public:
     void ensureWidgetVisible(QWidget *childWidget, int xmargin = 50, int ymargin = 50);
 
 protected:
-    QScrollArea(QScrollAreaPrivate &dd, QWidget *parent = 0);
+    QScrollArea(QScrollAreaPrivate &dd, QWidget *parent = Q_NULLPTR);
     bool event(QEvent *) Q_DECL_OVERRIDE;
     bool eventFilter(QObject *, QEvent *) Q_DECL_OVERRIDE;
     void resizeEvent(QResizeEvent *) Q_DECL_OVERRIDE;
diff --git a/src/widgets/widgets/qscrollbar.h b/src/widgets/widgets/qscrollbar.h
index 5934469045..4af5fb4a55 100644
--- a/src/widgets/widgets/qscrollbar.h
+++ b/src/widgets/widgets/qscrollbar.h
@@ -49,8 +49,8 @@ class Q_WIDGETS_EXPORT QScrollBar : public QAbstractSlider
 {
     Q_OBJECT
 public:
-    explicit QScrollBar(QWidget *parent=0);
-    explicit QScrollBar(Qt::Orientation, QWidget *parent=0);
+    explicit QScrollBar(QWidget *parent = Q_NULLPTR);
+    explicit QScrollBar(Qt::Orientation, QWidget *parent = Q_NULLPTR);
     ~QScrollBar();
 
     QSize sizeHint() const Q_DECL_OVERRIDE;
diff --git a/src/widgets/widgets/qslider.h b/src/widgets/widgets/qslider.h
index 3a528382a7..801a684fdf 100644
--- a/src/widgets/widgets/qslider.h
+++ b/src/widgets/widgets/qslider.h
@@ -61,8 +61,8 @@ public:
     };
     Q_ENUM(TickPosition)
 
-    explicit QSlider(QWidget *parent = 0);
-    explicit QSlider(Qt::Orientation orientation, QWidget *parent = 0);
+    explicit QSlider(QWidget *parent = Q_NULLPTR);
+    explicit QSlider(Qt::Orientation orientation, QWidget *parent = Q_NULLPTR);
 
     ~QSlider();
 
diff --git a/src/widgets/widgets/qspinbox.h b/src/widgets/widgets/qspinbox.h
index 606206d4f0..066fe88562 100644
--- a/src/widgets/widgets/qspinbox.h
+++ b/src/widgets/widgets/qspinbox.h
@@ -56,7 +56,7 @@ class Q_WIDGETS_EXPORT QSpinBox : public QAbstractSpinBox
     Q_PROPERTY(int displayIntegerBase READ displayIntegerBase WRITE setDisplayIntegerBase)
 
 public:
-    explicit QSpinBox(QWidget *parent = 0);
+    explicit QSpinBox(QWidget *parent = Q_NULLPTR);
     ~QSpinBox();
 
     int value() const;
@@ -117,7 +117,7 @@ class Q_WIDGETS_EXPORT QDoubleSpinBox : public QAbstractSpinBox
     Q_PROPERTY(double singleStep READ singleStep WRITE setSingleStep)
     Q_PROPERTY(double value READ value WRITE setValue NOTIFY valueChanged USER true)
 public:
-    explicit QDoubleSpinBox(QWidget *parent = 0);
+    explicit QDoubleSpinBox(QWidget *parent = Q_NULLPTR);
     ~QDoubleSpinBox();
 
     double value() const;
diff --git a/src/widgets/widgets/qsplitter.h b/src/widgets/widgets/qsplitter.h
index 4da92acd22..84010c236b 100644
--- a/src/widgets/widgets/qsplitter.h
+++ b/src/widgets/widgets/qsplitter.h
@@ -58,8 +58,8 @@ class Q_WIDGETS_EXPORT QSplitter : public QFrame
     Q_PROPERTY(bool childrenCollapsible READ childrenCollapsible WRITE setChildrenCollapsible)
 
 public:
-    explicit QSplitter(QWidget* parent = 0);
-    explicit QSplitter(Qt::Orientation, QWidget* parent = 0);
+    explicit QSplitter(QWidget* parent = Q_NULLPTR);
+    explicit QSplitter(Qt::Orientation, QWidget* parent = Q_NULLPTR);
     ~QSplitter();
 
     void addWidget(QWidget *widget);
diff --git a/src/widgets/widgets/qstackedwidget.h b/src/widgets/widgets/qstackedwidget.h
index 4267d8241f..9fcdf80833 100644
--- a/src/widgets/widgets/qstackedwidget.h
+++ b/src/widgets/widgets/qstackedwidget.h
@@ -50,7 +50,7 @@ class Q_WIDGETS_EXPORT QStackedWidget : public QFrame
     Q_PROPERTY(int currentIndex READ currentIndex WRITE setCurrentIndex NOTIFY currentChanged)
     Q_PROPERTY(int count READ count)
 public:
-    explicit QStackedWidget(QWidget *parent=0);
+    explicit QStackedWidget(QWidget *parent = Q_NULLPTR);
     ~QStackedWidget();
 
     int addWidget(QWidget *w);
diff --git a/src/widgets/widgets/qstatusbar.h b/src/widgets/widgets/qstatusbar.h
index 42248d7958..92785aa4c4 100644
--- a/src/widgets/widgets/qstatusbar.h
+++ b/src/widgets/widgets/qstatusbar.h
@@ -50,7 +50,7 @@ class Q_WIDGETS_EXPORT QStatusBar: public QWidget
     Q_PROPERTY(bool sizeGripEnabled READ isSizeGripEnabled WRITE setSizeGripEnabled)
 
 public:
-    explicit QStatusBar(QWidget* parent=0);
+    explicit QStatusBar(QWidget *parent = Q_NULLPTR);
     virtual ~QStatusBar();
 
     void addWidget(QWidget *widget, int stretch = 0);
diff --git a/src/widgets/widgets/qtabbar.h b/src/widgets/widgets/qtabbar.h
index 6d8bdb0c86..94a83142b0 100644
--- a/src/widgets/widgets/qtabbar.h
+++ b/src/widgets/widgets/qtabbar.h
@@ -65,7 +65,7 @@ class Q_WIDGETS_EXPORT QTabBar: public QWidget
     Q_PROPERTY(bool changeCurrentOnDrag READ changeCurrentOnDrag WRITE setChangeCurrentOnDrag)
 
 public:
-    explicit QTabBar(QWidget* parent=0);
+    explicit QTabBar(QWidget *parent = Q_NULLPTR);
     ~QTabBar();
 
     enum Shape { RoundedNorth, RoundedSouth, RoundedWest, RoundedEast,
diff --git a/src/widgets/widgets/qtabwidget.h b/src/widgets/widgets/qtabwidget.h
index 702563127d..f12d584475 100644
--- a/src/widgets/widgets/qtabwidget.h
+++ b/src/widgets/widgets/qtabwidget.h
@@ -62,7 +62,7 @@ class Q_WIDGETS_EXPORT QTabWidget : public QWidget
     Q_PROPERTY(bool tabBarAutoHide READ tabBarAutoHide WRITE setTabBarAutoHide)
 
 public:
-    explicit QTabWidget(QWidget *parent = 0);
+    explicit QTabWidget(QWidget *parent = Q_NULLPTR);
     ~QTabWidget();
 
     int addTab(QWidget *widget, const QString &);
diff --git a/src/widgets/widgets/qtextbrowser.h b/src/widgets/widgets/qtextbrowser.h
index 4d4d9f4880..339814e948 100644
--- a/src/widgets/widgets/qtextbrowser.h
+++ b/src/widgets/widgets/qtextbrowser.h
@@ -57,7 +57,7 @@ class Q_WIDGETS_EXPORT QTextBrowser : public QTextEdit
     Q_PROPERTY(bool openLinks READ openLinks WRITE setOpenLinks)
 
 public:
-    explicit QTextBrowser(QWidget* parent = 0);
+    explicit QTextBrowser(QWidget* parent = Q_NULLPTR);
     virtual ~QTextBrowser();
 
     QUrl source() const;
diff --git a/src/widgets/widgets/qtextedit.h b/src/widgets/widgets/qtextedit.h
index 689f45bea9..8519bf1163 100644
--- a/src/widgets/widgets/qtextedit.h
+++ b/src/widgets/widgets/qtextedit.h
@@ -94,8 +94,8 @@ public:
 
     Q_DECLARE_FLAGS(AutoFormatting, AutoFormattingFlag)
 
-    explicit QTextEdit(QWidget *parent = 0);
-    explicit QTextEdit(const QString &text, QWidget *parent = 0);
+    explicit QTextEdit(QWidget *parent = Q_NULLPTR);
+    explicit QTextEdit(const QString &text, QWidget *parent = Q_NULLPTR);
     virtual ~QTextEdit();
 
     void setDocument(QTextDocument *document);
diff --git a/src/widgets/widgets/qtoolbar.h b/src/widgets/widgets/qtoolbar.h
index f4ed13d399..9eeb7ccd71 100644
--- a/src/widgets/widgets/qtoolbar.h
+++ b/src/widgets/widgets/qtoolbar.h
@@ -69,8 +69,8 @@ class Q_WIDGETS_EXPORT QToolBar : public QWidget
     Q_PROPERTY(bool floatable READ isFloatable WRITE setFloatable)
 
 public:
-    explicit QToolBar(const QString &title, QWidget *parent = 0);
-    explicit QToolBar(QWidget *parent = 0);
+    explicit QToolBar(const QString &title, QWidget *parent = Q_NULLPTR);
+    explicit QToolBar(QWidget *parent = Q_NULLPTR);
     ~QToolBar();
 
     void setMovable(bool movable);
diff --git a/src/widgets/widgets/qtoolbutton.h b/src/widgets/widgets/qtoolbutton.h
index 69ad032324..c76f58577b 100644
--- a/src/widgets/widgets/qtoolbutton.h
+++ b/src/widgets/widgets/qtoolbutton.h
@@ -64,7 +64,7 @@ public:
     };
     Q_ENUM(ToolButtonPopupMode)
 
-    explicit QToolButton(QWidget * parent=0);
+    explicit QToolButton(QWidget *parent = Q_NULLPTR);
     ~QToolButton();
 
     QSize sizeHint() const Q_DECL_OVERRIDE;