diff --git a/src/declarativeimports/calendar/calendar.cpp b/src/declarativeimports/calendar/calendar.cpp
index 790833b8d..ea636947d 100644
--- a/src/declarativeimports/calendar/calendar.cpp
+++ b/src/declarativeimports/calendar/calendar.cpp
@@ -127,7 +127,7 @@ void Calendar::setDays(int days)
     }
 }
 
-int Calendar::weeks()
+int Calendar::weeks() const
 {
     return m_weeks;
 }
@@ -141,7 +141,7 @@ void Calendar::setWeeks(int weeks)
     }
 }
 
-int Calendar::firstDayOfWeek()
+int Calendar::firstDayOfWeek() const
 {
     // QML has Sunday as 0, so we need to accomodate here
     return m_firstDayOfWeek == 7 ? 0 : m_firstDayOfWeek;
diff --git a/src/declarativeimports/calendar/calendar.h b/src/declarativeimports/calendar/calendar.h
index 17783a4bc..a746bd915 100644
--- a/src/declarativeimports/calendar/calendar.h
+++ b/src/declarativeimports/calendar/calendar.h
@@ -156,11 +156,11 @@ public:
     void setDays(int days);
 
     // Weeks
-    int weeks();
+    int weeks() const;
     void setWeeks(int weeks);
 
     // Start day
-    int firstDayOfWeek();
+    int firstDayOfWeek() const;
     void setFirstDayOfWeek(int day);
 
     // Error message
diff --git a/src/declarativeimports/calendar/daysmodel.cpp b/src/declarativeimports/calendar/daysmodel.cpp
index 6961b6b1b..273eab917 100644
--- a/src/declarativeimports/calendar/daysmodel.cpp
+++ b/src/declarativeimports/calendar/daysmodel.cpp
@@ -29,7 +29,7 @@
 
 DaysModel::DaysModel(QObject *parent) :
     QAbstractListModel(parent),
-    m_pluginsManager(0),
+    m_pluginsManager(nullptr),
     m_lastRequestedEventsStartDate(QDate()),
     m_agendaNeedsUpdate(false)
 {
diff --git a/src/declarativeimports/calendar/daysmodel.h b/src/declarativeimports/calendar/daysmodel.h
index 636beb5a8..3906eb4ae 100644
--- a/src/declarativeimports/calendar/daysmodel.h
+++ b/src/declarativeimports/calendar/daysmodel.h
@@ -70,8 +70,8 @@ private Q_SLOTS:
 private:
     QModelIndex indexForDate(const QDate &date);
 
-    EventPluginsManager *m_pluginsManager;
-    QList<DayData> *m_data;
+    EventPluginsManager *m_pluginsManager = nullptr;
+    QList<DayData> *m_data = nullptr;
     QList<QObject*> m_qmlData;
     QDate m_lastRequestedAgendaDate;
     QList<CalendarEvents::CalendarEventsPlugin*> m_eventPlugins;
diff --git a/src/declarativeimports/calendar/eventpluginsmanager.h b/src/declarativeimports/calendar/eventpluginsmanager.h
index e414e1869..1642e61db 100644
--- a/src/declarativeimports/calendar/eventpluginsmanager.h
+++ b/src/declarativeimports/calendar/eventpluginsmanager.h
@@ -67,7 +67,7 @@ private:
     void loadPlugin(const QString &absolutePath);
 
     friend class EventPluginsModel;
-    EventPluginsModel *m_model;
+    EventPluginsModel *m_model = nullptr;
     QList<CalendarEvents::CalendarEventsPlugin*> m_plugins;
     struct PluginData {
         QString name;
diff --git a/src/declarativeimports/core/colorscope.cpp b/src/declarativeimports/core/colorscope.cpp
index f6cefcce0..b46f2e3da 100644
--- a/src/declarativeimports/core/colorscope.cpp
+++ b/src/declarativeimports/core/colorscope.cpp
@@ -94,7 +94,7 @@ void ColorScope::setParentScope(ColorScope* parentScope)
 
 ColorScope *ColorScope::findParentScope()
 {
-    QObject *p = 0;
+    QObject *p = nullptr;
     if (m_parent) {
         QQuickItem *gp = qobject_cast<QQuickItem *>(m_parent);
         if (gp) {
@@ -106,7 +106,7 @@ ColorScope *ColorScope::findParentScope()
 
     if (!p || !m_parent) {
         setParentScope(nullptr);
-        return 0;
+        return nullptr;
     }
 
     ColorScope *c = qobject_cast<ColorScope *>(p);
diff --git a/src/declarativeimports/core/datamodel.cpp b/src/declarativeimports/core/datamodel.cpp
index 224e19460..7664cb747 100644
--- a/src/declarativeimports/core/datamodel.cpp
+++ b/src/declarativeimports/core/datamodel.cpp
@@ -151,7 +151,7 @@ void SortFilterModel::setFilterCallback(const QJSValue& callback)
     m_filterCallback = callback;
     invalidateFilter();
 
-    emit filterCallbackChanged(callback);
+    Q_EMIT filterCallbackChanged(callback);
 }
 
 void SortFilterModel::setFilterRole(const QString &role)
diff --git a/src/declarativeimports/core/datasource.cpp b/src/declarativeimports/core/datasource.cpp
index e2ac96dfe..52d842284 100644
--- a/src/declarativeimports/core/datasource.cpp
+++ b/src/declarativeimports/core/datasource.cpp
@@ -28,9 +28,7 @@ DataSource::DataSource(QObject *parent)
     : QObject(parent),
       m_ready(false),
       m_interval(0),
-      m_intervalAlignment(Plasma::Types::NoAlignment),
-      m_dataEngine(0),
-      m_dataEngineConsumer(0)
+      m_intervalAlignment(Plasma::Types::NoAlignment)
 {
     m_models = new QQmlPropertyMap(this);
     m_data = new QQmlPropertyMap(this);
@@ -104,7 +102,7 @@ void DataSource::setEngine(const QString &e)
         m_dataEngine->disconnect(this);
         // Deleting the consumer triggers the reference counting
         delete m_dataEngineConsumer;
-        m_dataEngineConsumer = 0;
+        m_dataEngineConsumer = nullptr;
     }
 
     /*
@@ -222,7 +220,7 @@ QObject *DataSource::serviceForSource(const QString &source)
     if (!m_services.contains(source)) {
         Plasma::Service *service = m_dataEngine->serviceForSource(source);
         if (!service) {
-            return 0;
+            return nullptr;
         }
         m_services[source] = service;
     }
diff --git a/src/declarativeimports/core/datasource.h b/src/declarativeimports/core/datasource.h
index dedbc43e1..42b662a54 100644
--- a/src/declarativeimports/core/datasource.h
+++ b/src/declarativeimports/core/datasource.h
@@ -185,10 +185,10 @@ private:
     int m_interval;
     Plasma::Types::IntervalAlignment m_intervalAlignment;
     QString m_engine;
-    QQmlPropertyMap *m_data;
-    QQmlPropertyMap *m_models;
-    Plasma::DataEngine *m_dataEngine;
-    Plasma::DataEngineConsumer *m_dataEngineConsumer;
+    QQmlPropertyMap *m_data = nullptr;
+    QQmlPropertyMap *m_models = nullptr;
+    Plasma::DataEngine *m_dataEngine = nullptr;
+    Plasma::DataEngineConsumer *m_dataEngineConsumer = nullptr;
     QStringList m_sources;
     QStringList m_connectedSources;
     QStringList m_oldSources;
diff --git a/src/declarativeimports/core/fadingnode.cpp b/src/declarativeimports/core/fadingnode.cpp
index 6347dbdba..9c2c93d4f 100644
--- a/src/declarativeimports/core/fadingnode.cpp
+++ b/src/declarativeimports/core/fadingnode.cpp
@@ -25,8 +25,8 @@
 
 struct FadingMaterialState
 {
-   QSGTexture *source;
-   QSGTexture *target;
+   QSGTexture *source = nullptr;
+   QSGTexture *target = nullptr;
    qreal progress;
 };
 
@@ -41,7 +41,7 @@ public:
 
     void initialize() Q_DECL_OVERRIDE;
 private:
-    QOpenGLFunctions *glFuncs = 0;
+    QOpenGLFunctions *glFuncs  = nullptr;
     int m_progressId = 0;
 };
 
diff --git a/src/declarativeimports/core/tooltip.cpp b/src/declarativeimports/core/tooltip.cpp
index 7ebe39c54..735f456ea 100644
--- a/src/declarativeimports/core/tooltip.cpp
+++ b/src/declarativeimports/core/tooltip.cpp
@@ -30,7 +30,7 @@
 #include <kwindoweffects.h>
 #include <KDirWatch>
 
-ToolTipDialog *ToolTip::s_dialog = 0;
+ToolTipDialog *ToolTip::s_dialog = nullptr;
 int ToolTip::s_dialogUsers  = 0;
 
 ToolTip::ToolTip(QQuickItem *parent)
@@ -70,7 +70,7 @@ ToolTip::~ToolTip()
 
     if (s_dialogUsers == 0) {
         delete s_dialog;
-        s_dialog = 0;
+        s_dialog = nullptr;
     }
 }
 
diff --git a/src/declarativeimports/plasmacomponents/plasmacomponentsplugin.cpp b/src/declarativeimports/plasmacomponents/plasmacomponentsplugin.cpp
index 891476565..64f6feaeb 100644
--- a/src/declarativeimports/plasmacomponents/plasmacomponentsplugin.cpp
+++ b/src/declarativeimports/plasmacomponents/plasmacomponentsplugin.cpp
@@ -55,7 +55,7 @@ QQmlEngine *EngineBookKeeping::engine() const
     //for components creation, any engine will do, as long is valid
     if (m_engines.isEmpty()) {
         qWarning() << "No engines found, this should never happen";
-        return 0;
+        return nullptr;
     } else {
         return *m_engines.constBegin();
     }
diff --git a/src/declarativeimports/plasmacomponents/qmenu.cpp b/src/declarativeimports/plasmacomponents/qmenu.cpp
index 96249a8db..793445af6 100644
--- a/src/declarativeimports/plasmacomponents/qmenu.cpp
+++ b/src/declarativeimports/plasmacomponents/qmenu.cpp
@@ -37,7 +37,7 @@ QMenuProxy::QMenuProxy(QObject *parent)
       m_placement(Plasma::Types::LeftPosedTopAlignedPopup)
 {
     if (qobject_cast<QApplication *>(QCoreApplication::instance())) {
-        m_menu = new QMenu(0);
+        m_menu = new QMenu(nullptr);
         // Breeze and Oxygen have rounded corners on menus. They set this attribute in polish()
         // but at that time the underlying surface has already been created where setting this
         // flag makes no difference anymore (Bug 385311)
@@ -91,7 +91,7 @@ void QMenuProxy::setVisualParent(QObject *parent)
     //if the old parent was a QAction, disconnect the menu from it
     QAction *action = qobject_cast<QAction *>(m_visualParent.data());
     if (action) {
-        action->setMenu(0);
+        action->setMenu(nullptr);
         m_menu->clear();
     }
     //if parent is a QAction, become a submenu
@@ -336,7 +336,7 @@ void QMenuProxy::open(int x, int y)
     openInternal(pos.toPoint());
 }
 
-Q_INVOKABLE void QMenuProxy::openRelative()
+void QMenuProxy::openRelative()
 {
     QQuickItem *parentItem = nullptr;
 
diff --git a/src/plasma/applet.cpp b/src/plasma/applet.cpp
index 2a0481245..10230ff48 100644
--- a/src/plasma/applet.cpp
+++ b/src/plasma/applet.cpp
@@ -126,7 +126,7 @@ Applet::Applet(QObject *parentObject, const QVariantList &args)
 }
 
 Applet::Applet(const QString &packagePath, uint appletId)
-    : QObject(0),
+    : QObject(nullptr),
       d(new AppletPrivate(appletMetadataForDirectory(packagePath), appletId, this))
 {
     d->init(packagePath);