diff --git a/kcm/src/collapsablebutton.h b/kcm/src/collapsablebutton.h
--- a/kcm/src/collapsablebutton.h
+++ b/kcm/src/collapsablebutton.h
@@ -29,7 +29,7 @@
     Q_OBJECT
 
   public:
-    explicit CollapsableButton(const QString &text, QWidget *parent = 0);
+    explicit CollapsableButton(const QString &text, QWidget *parent = nullptr);
     virtual ~CollapsableButton();
 
     void setCollapsed(bool collapsed);
diff --git a/kcm/src/controlpanel.cpp b/kcm/src/controlpanel.cpp
--- a/kcm/src/controlpanel.cpp
+++ b/kcm/src/controlpanel.cpp
@@ -30,7 +30,7 @@
 
 ControlPanel::ControlPanel(QWidget *parent)
     : QFrame(parent)
-    , mUnifiedOutputCfg(0)
+    , mUnifiedOutputCfg(nullptr)
 {
     setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Expanding);
     setFrameStyle(QFrame::StyledPanel | QFrame::Sunken);
@@ -46,7 +46,7 @@
     qDeleteAll(mOutputConfigs);
     mOutputConfigs.clear();
     delete mUnifiedOutputCfg;
-    mUnifiedOutputCfg = 0;
+    mUnifiedOutputCfg = nullptr;
 
     if (mConfig) {
         mConfig->disconnect(this);
@@ -108,12 +108,12 @@
             continue;
         }
 
-        config->setVisible(output == 0);
+        config->setVisible(output == nullptr);
     }
 
     if (output.isNull()) {
         mUnifiedOutputCfg->deleteLater();
-        mUnifiedOutputCfg = 0;
+        mUnifiedOutputCfg = nullptr;
     } else {
         mUnifiedOutputCfg = new UnifiedOutputConfig(mConfig, this);
         mUnifiedOutputCfg->setOutput(output);
diff --git a/kcm/src/kcm_kscreen.cpp b/kcm/src/kcm_kscreen.cpp
--- a/kcm/src/kcm_kscreen.cpp
+++ b/kcm/src/kcm_kscreen.cpp
@@ -49,7 +49,7 @@
 
 KCMKScreen::KCMKScreen(QWidget* parent, const QVariantList& args)
     : KCModule(parent, args)
-    , mKScreenWidget(0)
+    , mKScreenWidget(nullptr)
 {
     Log::instance();
 
@@ -74,7 +74,7 @@
     mMainLayout->setMargin(0);
 
     if (op->hasError()) {
-        mKScreenWidget = 0;
+        mKScreenWidget = nullptr;
         delete mKScreenWidget;
         QLabel *errorLabel = new QLabel(this);
         mMainLayout->addWidget(errorLabel);
diff --git a/kcm/src/outputconfig.cpp b/kcm/src/outputconfig.cpp
--- a/kcm/src/outputconfig.cpp
+++ b/kcm/src/outputconfig.cpp
@@ -42,7 +42,7 @@
 
 OutputConfig::OutputConfig(QWidget *parent)
     : QWidget(parent)
-    , mOutput(0)
+    , mOutput(nullptr)
 {
 }
 
diff --git a/kcm/src/previewwidget.cpp b/kcm/src/previewwidget.cpp
--- a/kcm/src/previewwidget.cpp
+++ b/kcm/src/previewwidget.cpp
@@ -33,7 +33,7 @@
     m_internalPreview(new QWidget) // deliberately no parent, we don't want it to have a screen
 {
     Ui::StylePreview ui;
-    ui.setupUi(m_internalPreview );
+    ui.setupUi(m_internalPreview);
 }
 
 PreviewWidget::~PreviewWidget()
diff --git a/kcm/src/resolutionslider.cpp b/kcm/src/resolutionslider.cpp
--- a/kcm/src/resolutionslider.cpp
+++ b/kcm/src/resolutionslider.cpp
@@ -39,11 +39,11 @@
 ResolutionSlider::ResolutionSlider(const KScreen::OutputPtr &output, QWidget *parent)
     : QWidget(parent)
     , mOutput(output)
-    , mSmallestLabel(0)
-    , mBiggestLabel(0)
-    , mCurrentLabel(0)
-    , mSlider(0)
-    , mComboBox(0)
+    , mSmallestLabel(nullptr)
+    , mBiggestLabel(nullptr)
+    , mCurrentLabel(nullptr)
+    , mSlider(nullptr)
+    , mComboBox(nullptr)
 {
     connect(output.data(), &KScreen::Output::currentModeIdChanged,
             this, &ResolutionSlider::slotOutputModeChanged);
diff --git a/kcm/src/widget.cpp b/kcm/src/widget.cpp
--- a/kcm/src/widget.cpp
+++ b/kcm/src/widget.cpp
@@ -53,9 +53,9 @@
 
 Widget::Widget(QWidget *parent):
     QWidget(parent),
-    mScreen(0),
-    mConfig(0),
-    mPrevConfig(0)
+    mScreen(nullptr),
+    mConfig(nullptr),
+    mPrevConfig(nullptr)
 {
     qRegisterMetaType<QQuickView*>();
 
diff --git a/kded/daemon.cpp b/kded/daemon.cpp
--- a/kded/daemon.cpp
+++ b/kded/daemon.cpp
@@ -46,7 +46,7 @@
 
 KScreenDaemon::KScreenDaemon(QObject* parent, const QList< QVariant >& )
  : KDEDModule(parent)
- , m_monitoredConfig(0)
+ , m_monitoredConfig(nullptr)
  , m_iteration(Generator::None)
  , m_monitoring(false)
  , m_changeCompressor(new QTimer(this))
diff --git a/kded/device.cpp b/kded/device.cpp
--- a/kded/device.cpp
+++ b/kded/device.cpp
@@ -23,7 +23,7 @@
 
 #include <QLoggingCategory>
 
-Device* Device::m_instance = 0;
+Device* Device::m_instance = nullptr;
 
 Device* Device::self()
 {
@@ -37,7 +37,7 @@
 void Device::destroy()
 {
     delete m_instance;
-    m_instance = 0;
+    m_instance = nullptr;
 }
 
 Device::Device(QObject* parent) 
diff --git a/kded/generator.cpp b/kded/generator.cpp
--- a/kded/generator.cpp
+++ b/kded/generator.cpp
@@ -41,7 +41,7 @@
     }
 #endif
 
-Generator* Generator::instance = 0;
+Generator* Generator::instance = nullptr;
 
 bool operator<(const QSize &s1, const QSize &s2)
 {
@@ -69,7 +69,7 @@
 void Generator::destroy()
 {
     delete Generator::instance;
-    Generator::instance = 0;
+    Generator::instance = nullptr;
 }
 
 Generator::~Generator()
@@ -298,7 +298,6 @@
     QSet<QSize> commonSizes;
     const QSize maxScreenSize  = m_currentConfig->screen()->maxSize();
 
-    QList<QSet<QSize>> modes;
     Q_FOREACH(const KScreen::OutputPtr &output, connectedOutputs) {
         QSet<QSize> modeSizes;
         Q_FOREACH(const KScreen::ModePtr &mode, output->modes()) {