diff --git a/src/declarativeimports/calendar/daysmodel.cpp b/src/declarativeimports/calendar/daysmodel.cpp
index 273eab917..1f701440c 100644
--- a/src/declarativeimports/calendar/daysmodel.cpp
+++ b/src/declarativeimports/calendar/daysmodel.cpp
@@ -218,9 +218,9 @@ void DaysModel::setPluginsManager(QObject *manager)
         return;
     }
 
-    if (m_pluginsManager != 0) {
+    if (m_pluginsManager) {
         m_pluginsManager->deleteLater();
-        m_pluginsManager = 0;
+        m_pluginsManager = nullptr;
     }
 
     m_pluginsManager = m;
diff --git a/src/declarativeimports/calendar/eventpluginsmanager.cpp b/src/declarativeimports/calendar/eventpluginsmanager.cpp
index c4b46063e..c7301c413 100644
--- a/src/declarativeimports/calendar/eventpluginsmanager.cpp
+++ b/src/declarativeimports/calendar/eventpluginsmanager.cpp
@@ -42,7 +42,7 @@ public:
         m_roles.insert(Qt::EditRole, QByteArrayLiteral("checked"));
         m_roles.insert(Qt::UserRole, QByteArrayLiteral("configUi"));
         m_roles.insert(Qt::UserRole + 1, QByteArrayLiteral("pluginPath"));
-    };
+    }
 
     // make these two available to the manager
     void beginResetModel()
diff --git a/src/declarativeimports/core/colorscope.cpp b/src/declarativeimports/core/colorscope.cpp
index c427221eb..56e379ec0 100644
--- a/src/declarativeimports/core/colorscope.cpp
+++ b/src/declarativeimports/core/colorscope.cpp
@@ -57,7 +57,7 @@ ColorScope *ColorScope::qmlAttachedProperties(QObject *object)
         return cs;
     }
 
-    ColorScope *s = new ColorScope(0, object);
+    ColorScope *s = new ColorScope(nullptr, object);
     s_attachedScopes[object] = s;
     s->m_inherit = true;
     s->setParent(object);
diff --git a/src/declarativeimports/core/colorscope.h b/src/declarativeimports/core/colorscope.h
index ce4d85ec2..2596352dc 100644
--- a/src/declarativeimports/core/colorscope.h
+++ b/src/declarativeimports/core/colorscope.h
@@ -88,7 +88,7 @@ class ColorScope : public QQuickItem
 public:
 /// @cond INTERNAL_DOCS
     explicit ColorScope(QQuickItem *parent = nullptr, QObject *parentObject = nullptr);
-    ~ColorScope();
+    ~ColorScope() Q_DECL_OVERRIDE;
 
     void setColorGroup(Plasma::Theme::ColorGroup group);
     Plasma::Theme::ColorGroup colorGroup() const;
diff --git a/src/declarativeimports/core/datamodel.cpp b/src/declarativeimports/core/datamodel.cpp
index 7664cb747..b0257d866 100644
--- a/src/declarativeimports/core/datamodel.cpp
+++ b/src/declarativeimports/core/datamodel.cpp
@@ -217,7 +217,7 @@ int SortFilterModel::mapRowFromSource(int row) const
 
 DataModel::DataModel(QObject *parent)
     : QAbstractItemModel(parent),
-      m_dataSource(0),
+      m_dataSource(nullptr),
       m_maxRoleId(Qt::UserRole + 1)
 {
     //There is one reserved role name: DataEngineSource
@@ -293,7 +293,7 @@ void DataModel::setDataSource(QObject *object)
     }
 
     if (m_dataSource) {
-        disconnect(m_dataSource, 0, this, 0);
+        disconnect(m_dataSource, nullptr, this, nullptr);
     }
 
     m_dataSource = source;
diff --git a/src/declarativeimports/core/framesvgitem.cpp b/src/declarativeimports/core/framesvgitem.cpp
index 7449a81c4..47d116750 100644
--- a/src/declarativeimports/core/framesvgitem.cpp
+++ b/src/declarativeimports/core/framesvgitem.cpp
@@ -514,7 +514,7 @@ QSGNode *FrameSvgItem::updatePaintNode(QSGNode *oldNode, QQuickItem::UpdatePaint
     if (m_fastPath) {
         if (m_textureChanged) {
             delete oldNode;
-            oldNode = 0;
+            oldNode = nullptr;
         }
 
         if (!oldNode) {
diff --git a/src/declarativeimports/core/iconitem.cpp b/src/declarativeimports/core/iconitem.cpp
index d8b060f17..c554f8673 100644
--- a/src/declarativeimports/core/iconitem.cpp
+++ b/src/declarativeimports/core/iconitem.cpp
@@ -37,7 +37,7 @@
 
 IconItem::IconItem(QQuickItem *parent)
     : QQuickItem(parent),
-      m_svgIcon(0),
+      m_svgIcon(nullptr),
       m_status(Plasma::Svg::Normal),
       m_smooth(true),
       m_active(false),
@@ -163,7 +163,7 @@ void IconItem::setSource(const QVariant &source)
             m_imageIcon = QImage(localFile);
             m_svgIconName.clear();
             delete m_svgIcon;
-            m_svgIcon = 0;
+            m_svgIcon = nullptr;
         } else {
             if (!m_svgIcon) {
                 m_svgIcon = new Plasma::Svg(this);
@@ -209,7 +209,7 @@ void IconItem::setSource(const QVariant &source)
                     }
                     m_svgIconName.clear();
                     delete m_svgIcon;
-                    m_svgIcon = 0;
+                    m_svgIcon = nullptr;
                     m_imageIcon = QImage();
                 }
             }
@@ -220,19 +220,19 @@ void IconItem::setSource(const QVariant &source)
         m_imageIcon = QImage();
         m_svgIconName.clear();
         delete m_svgIcon;
-        m_svgIcon = 0;
+        m_svgIcon = nullptr;
     } else if (source.canConvert<QImage>()) {
         m_icon = QIcon();
         m_imageIcon = source.value<QImage>();
         m_svgIconName.clear();
         delete m_svgIcon;
-        m_svgIcon = 0;
+        m_svgIcon = nullptr;
     } else {
         m_icon = QIcon();
         m_imageIcon = QImage();
         m_svgIconName.clear();
         delete m_svgIcon;
-        m_svgIcon = 0;
+        m_svgIcon = nullptr;
     }
 
     if (width() > 0 && height() > 0) {
@@ -470,7 +470,7 @@ QSGNode* IconItem::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *update
 {
     Q_UNUSED(updatePaintNodeData)
 
-    if (m_iconPixmap.isNull() || width() == 0 || height() == 0) {
+    if (m_iconPixmap.isNull() || width() == 0.0 || height() == 0.0) {
         delete oldNode;
         return nullptr;
     }
diff --git a/src/declarativeimports/core/iconitem.h b/src/declarativeimports/core/iconitem.h
index 9ae0837d7..bf7ff25dc 100644
--- a/src/declarativeimports/core/iconitem.h
+++ b/src/declarativeimports/core/iconitem.h
@@ -126,7 +126,7 @@ class IconItem : public QQuickItem
 
 public:
     explicit IconItem(QQuickItem *parent = nullptr);
-    ~IconItem();
+    ~IconItem() Q_DECL_OVERRIDE;
 
     void setSource(const QVariant &source);
     QVariant source() const;
diff --git a/src/declarativeimports/core/serviceoperationstatus.cpp b/src/declarativeimports/core/serviceoperationstatus.cpp
index e22cc55c1..ed355b6cb 100644
--- a/src/declarativeimports/core/serviceoperationstatus.cpp
+++ b/src/declarativeimports/core/serviceoperationstatus.cpp
@@ -36,7 +36,7 @@ void ServiceOperationStatus::setService(Plasma::Service *service)
     }
 
     if (m_service) {
-        disconnect(m_service.data(), 0, this, 0);
+        disconnect(m_service.data(), nullptr, this, nullptr);
     }
     if (service) {
         connect(service, &Plasma::Service::operationEnabledChanged,
diff --git a/src/declarativeimports/core/svgitem.cpp b/src/declarativeimports/core/svgitem.cpp
index 9ebc7c334..d1b37b9f4 100644
--- a/src/declarativeimports/core/svgitem.cpp
+++ b/src/declarativeimports/core/svgitem.cpp
@@ -86,7 +86,7 @@ QSizeF SvgItem::naturalSize() const
 void SvgItem::setSvg(Plasma::Svg *svg)
 {
     if (m_svg) {
-        disconnect(m_svg.data(), 0, this, 0);
+        disconnect(m_svg.data(), nullptr, this, nullptr);
     }
     m_svg = svg;
     updateDevicePixelRatio();
@@ -138,7 +138,7 @@ QSGNode *SvgItem::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *updateP
     }
 
     //this is more than just an optimisation, uploading a null image to QSGAtlasTexture causes a crash
-    if (width() == 0 || height() == 0) {
+    if (width() == 0.0 || height() == 0.0) {
         delete oldNode;
         return nullptr;
     }
diff --git a/src/declarativeimports/core/tooltip.h b/src/declarativeimports/core/tooltip.h
index b37c467c5..543b6c5c6 100644
--- a/src/declarativeimports/core/tooltip.h
+++ b/src/declarativeimports/core/tooltip.h
@@ -127,8 +127,8 @@ class ToolTip : public QQuickItem
 
 public:
 /// @cond INTERNAL_DOCS
-    ToolTip(QQuickItem *parent = nullptr);
-    ~ToolTip();
+    explicit ToolTip(QQuickItem *parent = nullptr);
+    ~ToolTip() Q_DECL_OVERRIDE;
 
     QQuickItem *mainItem() const;
     void setMainItem(QQuickItem *mainItem);
diff --git a/src/declarativeimports/core/tooltipdialog.cpp b/src/declarativeimports/core/tooltipdialog.cpp
index e5f629c4e..787f19fde 100644
--- a/src/declarativeimports/core/tooltipdialog.cpp
+++ b/src/declarativeimports/core/tooltipdialog.cpp
@@ -29,7 +29,7 @@
 
 ToolTipDialog::ToolTipDialog(QQuickItem  *parent)
     : Dialog(parent),
-      m_qmlObject(0),
+      m_qmlObject(nullptr),
       m_hideTimeout(4000),
       m_interactive(false),
       m_owner(nullptr)
diff --git a/src/declarativeimports/core/tooltipdialog.h b/src/declarativeimports/core/tooltipdialog.h
index 2652fc9ae..ce9011f7a 100644
--- a/src/declarativeimports/core/tooltipdialog.h
+++ b/src/declarativeimports/core/tooltipdialog.h
@@ -43,8 +43,8 @@ class ToolTipDialog : public PlasmaQuick::Dialog
     Q_OBJECT
 
 public:
-    ToolTipDialog(QQuickItem *parent = nullptr);
-    ~ToolTipDialog();
+    explicit ToolTipDialog(QQuickItem *parent = nullptr);
+    ~ToolTipDialog() Q_DECL_OVERRIDE;
 
     QQuickItem *loadDefaultItem();
 
diff --git a/src/declarativeimports/core/units.h b/src/declarativeimports/core/units.h
index e93270cc7..a0a7e9f28 100644
--- a/src/declarativeimports/core/units.h
+++ b/src/declarativeimports/core/units.h
@@ -32,8 +32,8 @@ class SharedAppFilter : public QObject
 {
    Q_OBJECT
 public:
-    SharedAppFilter(QObject *parent = nullptr);
-    ~SharedAppFilter();
+    explicit SharedAppFilter(QObject *parent = nullptr);
+    ~SharedAppFilter() Q_DECL_OVERRIDE;
 
 Q_SIGNALS:
     void fontChanged();
diff --git a/src/declarativeimports/plasmacomponents/qmenu.h b/src/declarativeimports/plasmacomponents/qmenu.h
index 34e20f64f..8a40b7751 100644
--- a/src/declarativeimports/plasmacomponents/qmenu.h
+++ b/src/declarativeimports/plasmacomponents/qmenu.h
@@ -102,7 +102,7 @@ class QMenuProxy : public QObject
 
 public:
     explicit QMenuProxy(QObject *parent = nullptr);
-    ~QMenuProxy();
+    ~QMenuProxy() Q_DECL_OVERRIDE;
 
     QQmlListProperty<QMenuItem> content();
     int actionCount() const;
diff --git a/src/declarativeimports/plasmacomponents/qmenuitem.cpp b/src/declarativeimports/plasmacomponents/qmenuitem.cpp
index f773a26d4..0d598491a 100644
--- a/src/declarativeimports/plasmacomponents/qmenuitem.cpp
+++ b/src/declarativeimports/plasmacomponents/qmenuitem.cpp
@@ -22,7 +22,7 @@
 
 QMenuItem::QMenuItem(QQuickItem *parent)
     : QQuickItem(parent),
-      m_action(0),
+      m_action(nullptr),
       m_section(false)
 {
     setAction(new QAction(this));
@@ -37,7 +37,7 @@ void QMenuItem::setAction(QAction *a)
 {
     if (m_action != a) {
         if (m_action) {
-            disconnect(m_action, 0, this, 0);
+            disconnect(m_action, nullptr, this, nullptr);
 
             if (m_action->parent() == this) {
                 delete m_action;
diff --git a/src/declarativeimports/plasmacomponents/qmenuitem.h b/src/declarativeimports/plasmacomponents/qmenuitem.h
index c52ca36c2..c42d52000 100644
--- a/src/declarativeimports/plasmacomponents/qmenuitem.h
+++ b/src/declarativeimports/plasmacomponents/qmenuitem.h
@@ -48,7 +48,7 @@ class QMenuItem : public QQuickItem
     Q_PROPERTY(bool checked READ checked WRITE setChecked NOTIFY toggled)
 
 public:
-    QMenuItem(QQuickItem *parent = nullptr);
+    explicit QMenuItem(QQuickItem *parent = nullptr);
 
     QAction *action() const;
     void setAction(QAction *a);
diff --git a/src/declarativeimports/plasmacomponents/qrangemodel.cpp b/src/declarativeimports/plasmacomponents/qrangemodel.cpp
index f57b3233d..1fa2a9ac1 100644
--- a/src/declarativeimports/plasmacomponents/qrangemodel.cpp
+++ b/src/declarativeimports/plasmacomponents/qrangemodel.cpp
@@ -104,7 +104,7 @@ qreal QRangeModelPrivate::publicPosition(qreal position) const
     const qreal positionValueRatio = valueRange ? (max - min) / valueRange : 0;
     const qreal positionStep = stepSize * positionValueRatio;
 
-    if (positionStep == 0) {
+    if (positionStep == 0.0) {
         return (min < max) ? qBound(min, position, max) : qBound(max, position, min);
     }
 
@@ -146,7 +146,7 @@ qreal QRangeModelPrivate::publicValue(qreal value) const
     // QML bindings; a position that is initially invalid because it lays
     // outside the range, might become valid later if the range changes.
 
-    if (stepSize == 0) {
+    if (stepSize == 0.0) {
         return qBound(minimum, value, maximum);
     }
 
@@ -215,7 +215,7 @@ QRangeModel::QRangeModel(QRangeModelPrivate &dd, QObject *parent)
 QRangeModel::~QRangeModel()
 {
     delete d_ptr;
-    d_ptr = 0;
+    d_ptr = nullptr;
 }
 
 /*!
diff --git a/src/declarativeimports/plasmaextracomponents/appbackgroundprovider_p.h b/src/declarativeimports/plasmaextracomponents/appbackgroundprovider_p.h
index ea4f07aa8..fbd1d5655 100644
--- a/src/declarativeimports/plasmaextracomponents/appbackgroundprovider_p.h
+++ b/src/declarativeimports/plasmaextracomponents/appbackgroundprovider_p.h
@@ -37,7 +37,7 @@ class AppBackgroundProvider : public QQuickImageProvider
 
 public:
     AppBackgroundProvider();
-    ~AppBackgroundProvider();
+    ~AppBackgroundProvider() Q_DECL_OVERRIDE;
     QImage requestImage(const QString &id, QSize *size, const QSize &requestedSize) Q_DECL_OVERRIDE;
 private:
     Plasma::Theme *m_theme;