diff --git a/autotests/mock_effectshandler.h b/autotests/mock_effectshandler.h
--- a/autotests/mock_effectshandler.h
+++ b/autotests/mock_effectshandler.h
@@ -124,7 +124,7 @@
         return 0;
     }
     void doneOpenGLContextCurrent() override {}
-    void drawWindow(KWin::EffectWindow *, int, QRegion, KWin::WindowPaintData &) override {}
+    void drawWindow(KWin::EffectWindow *, int, const QRegion &, KWin::WindowPaintData &) override {}
     KWin::EffectFrame *effectFrame(KWin::EffectFrameStyle, bool, const QPoint &, Qt::Alignment) const override {
         return nullptr;
     }
@@ -173,9 +173,9 @@
     bool optionRollOverDesktops() const override {
         return false;
     }
-    void paintEffectFrame(KWin::EffectFrame *, QRegion, double, double) override {}
-    void paintScreen(int, QRegion, KWin::ScreenPaintData &) override {}
-    void paintWindow(KWin::EffectWindow *, int, QRegion, KWin::WindowPaintData &) override {}
+    void paintEffectFrame(KWin::EffectFrame *, const QRegion &, double, double) override {}
+    void paintScreen(int, const QRegion &, KWin::ScreenPaintData &) override {}
+    void paintWindow(KWin::EffectWindow *, int, const QRegion &, KWin::WindowPaintData &) override {}
     void postPaintScreen() override {}
     void postPaintWindow(KWin::EffectWindow *) override {}
     void prePaintScreen(KWin::ScreenPrePaintData &, int) override {}
diff --git a/effects.h b/effects.h
--- a/effects.h
+++ b/effects.h
@@ -74,20 +74,20 @@
     EffectsHandlerImpl(Compositor *compositor, Scene *scene);
     ~EffectsHandlerImpl() override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     /**
      * Special hook to perform a paintScreen but just with the windows on @p desktop.
      */
     void paintDesktop(int desktop, int mask, QRegion region, ScreenPaintData& data);
     void postPaintScreen() override;
     void prePaintWindow(EffectWindow* w, WindowPrePaintData& data, int time) override;
-    void paintWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) override;
+    void paintWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data) override;
     void postPaintWindow(EffectWindow* w) override;
-    void paintEffectFrame(EffectFrame* frame, QRegion region, double opacity, double frameOpacity) override;
+    void paintEffectFrame(EffectFrame* frame, const QRegion &region, double opacity, double frameOpacity) override;
 
     Effect *provides(Effect::Feature ef);
 
-    void drawWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) override;
+    void drawWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data) override;
 
     void buildQuads(EffectWindow* w, WindowQuadList& quadList) override;
 
@@ -541,7 +541,7 @@
     ~EffectFrameImpl() override;
 
     void free() override;
-    void render(QRegion region = infiniteRegion(), double opacity = 1.0, double frameOpacity = 1.0) override;
+    void render(const QRegion &region = infiniteRegion(), double opacity = 1.0, double frameOpacity = 1.0) override;
     Qt::Alignment alignment() const override;
     void setAlignment(Qt::Alignment alignment) override;
     const QFont& font() const override;
diff --git a/effects.cpp b/effects.cpp
--- a/effects.cpp
+++ b/effects.cpp
@@ -397,7 +397,7 @@
     // no special final code
 }
 
-void EffectsHandlerImpl::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void EffectsHandlerImpl::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     if (m_currentPaintScreenIterator != m_activeEffects.constEnd()) {
         (*m_currentPaintScreenIterator++)->paintScreen(mask, region, data);
@@ -440,16 +440,16 @@
     // no special final code
 }
 
-void EffectsHandlerImpl::paintWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data)
+void EffectsHandlerImpl::paintWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data)
 {
     if (m_currentPaintWindowIterator != m_activeEffects.constEnd()) {
         (*m_currentPaintWindowIterator++)->paintWindow(w, mask, region, data);
         --m_currentPaintWindowIterator;
     } else
         m_scene->finalPaintWindow(static_cast<EffectWindowImpl*>(w), mask, region, data);
 }
 
-void EffectsHandlerImpl::paintEffectFrame(EffectFrame* frame, QRegion region, double opacity, double frameOpacity)
+void EffectsHandlerImpl::paintEffectFrame(EffectFrame* frame, const QRegion &region, double opacity, double frameOpacity)
 {
     if (m_currentPaintEffectFrameIterator != m_activeEffects.constEnd()) {
         (*m_currentPaintEffectFrameIterator++)->paintEffectFrame(frame, region, opacity, frameOpacity);
@@ -477,7 +477,7 @@
     return nullptr;
 }
 
-void EffectsHandlerImpl::drawWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data)
+void EffectsHandlerImpl::drawWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data)
 {
     if (m_currentDrawWindowIterator != m_activeEffects.constEnd()) {
         (*m_currentDrawWindowIterator++)->drawWindow(w, mask, region, data);
@@ -2280,7 +2280,7 @@
     free();
 }
 
-void EffectFrameImpl::render(QRegion region, double opacity, double frameOpacity)
+void EffectFrameImpl::render(const QRegion &region, double opacity, double frameOpacity)
 {
     if (m_geometry.isEmpty()) {
         return; // Nothing to display
diff --git a/effects/backgroundcontrast/contrast.h b/effects/backgroundcontrast/contrast.h
--- a/effects/backgroundcontrast/contrast.h
+++ b/effects/backgroundcontrast/contrast.h
@@ -55,8 +55,8 @@
     void reconfigure(ReconfigureFlags flags) override;
     void prePaintScreen(ScreenPrePaintData &data, int time) override;
     void prePaintWindow(EffectWindow *w, WindowPrePaintData &data, int time) override;
-    void drawWindow(EffectWindow *w, int mask, QRegion region, WindowPaintData &data) override;
-    void paintEffectFrame(EffectFrame *frame, QRegion region, double opacity, double frameOpacity) override;
+    void drawWindow(EffectWindow *w, int mask, const QRegion &region, WindowPaintData &data) override;
+    void paintEffectFrame(EffectFrame *frame, const QRegion &region, double opacity, double frameOpacity) override;
 
     bool provides(Feature feature) override;
 
diff --git a/effects/backgroundcontrast/contrast.cpp b/effects/backgroundcontrast/contrast.cpp
--- a/effects/backgroundcontrast/contrast.cpp
+++ b/effects/backgroundcontrast/contrast.cpp
@@ -431,7 +431,7 @@
     return true;
 }
 
-void ContrastEffect::drawWindow(EffectWindow *w, int mask, QRegion region, WindowPaintData &data)
+void ContrastEffect::drawWindow(EffectWindow *w, int mask, const QRegion &region, WindowPaintData &data)
 {
     const QRect screen = GLRenderTarget::virtualScreenGeometry();
     if (shouldContrast(w, mask, data)) {
@@ -467,7 +467,7 @@
     effects->drawWindow(w, mask, region, data);
 }
 
-void ContrastEffect::paintEffectFrame(EffectFrame *frame, QRegion region, double opacity, double frameOpacity)
+void ContrastEffect::paintEffectFrame(EffectFrame *frame, const QRegion &region, double opacity, double frameOpacity)
 {
     //FIXME: this is a no-op for now, it should figure out the right contrast, intensity, saturation
     effects->paintEffectFrame(frame, region, opacity, frameOpacity);
diff --git a/effects/blur/blur.h b/effects/blur/blur.h
--- a/effects/blur/blur.h
+++ b/effects/blur/blur.h
@@ -58,8 +58,8 @@
     void reconfigure(ReconfigureFlags flags) override;
     void prePaintScreen(ScreenPrePaintData &data, int time) override;
     void prePaintWindow(EffectWindow* w, WindowPrePaintData& data, int time) override;
-    void drawWindow(EffectWindow *w, int mask, QRegion region, WindowPaintData &data) override;
-    void paintEffectFrame(EffectFrame *frame, QRegion region, double opacity, double frameOpacity) override;
+    void drawWindow(EffectWindow *w, int mask, const QRegion &region, WindowPaintData &data) override;
+    void paintEffectFrame(EffectFrame *frame, const QRegion &region, double opacity, double frameOpacity) override;
 
     bool provides(Feature feature) override;
 
diff --git a/effects/blur/blur.cpp b/effects/blur/blur.cpp
--- a/effects/blur/blur.cpp
+++ b/effects/blur/blur.cpp
@@ -580,7 +580,7 @@
     return true;
 }
 
-void BlurEffect::drawWindow(EffectWindow *w, int mask, QRegion region, WindowPaintData &data)
+void BlurEffect::drawWindow(EffectWindow *w, int mask, const QRegion &region, WindowPaintData &data)
 {
     const QRect screen = GLRenderTarget::virtualScreenGeometry();
     if (shouldBlur(w, mask, data)) {
@@ -616,7 +616,7 @@
     effects->drawWindow(w, mask, region, data);
 }
 
-void BlurEffect::paintEffectFrame(EffectFrame *frame, QRegion region, double opacity, double frameOpacity)
+void BlurEffect::paintEffectFrame(EffectFrame *frame, const QRegion &region, double opacity, double frameOpacity)
 {
     const QRect screen = effects->virtualScreenGeometry();
     bool valid = m_renderTargetsValid && m_shader && m_shader->isValid();
diff --git a/effects/colorpicker/colorpicker.h b/effects/colorpicker/colorpicker.h
--- a/effects/colorpicker/colorpicker.h
+++ b/effects/colorpicker/colorpicker.h
@@ -37,7 +37,7 @@
 public:
     ColorPickerEffect();
     ~ColorPickerEffect() override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     void postPaintScreen() override;
     bool isActive() const override;
 
diff --git a/effects/colorpicker/colorpicker.cpp b/effects/colorpicker/colorpicker.cpp
--- a/effects/colorpicker/colorpicker.cpp
+++ b/effects/colorpicker/colorpicker.cpp
@@ -61,7 +61,7 @@
 
 ColorPickerEffect::~ColorPickerEffect() = default;
 
-void ColorPickerEffect::paintScreen(int mask, QRegion region, ScreenPaintData &data)
+void ColorPickerEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {
     m_cachedOutputGeometry = data.outputGeometry();
     effects->paintScreen(mask, region, data);
diff --git a/effects/coverswitch/coverswitch.h b/effects/coverswitch/coverswitch.h
--- a/effects/coverswitch/coverswitch.h
+++ b/effects/coverswitch/coverswitch.h
@@ -54,7 +54,7 @@
 
     void reconfigure(ReconfigureFlags) override;
     void prePaintScreen(ScreenPrePaintData &data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     void postPaintScreen() override;
     void paintWindow(EffectWindow *w, int mask, QRegion region, WindowPaintData &data) override;
     void windowInputMouseEvent(QEvent *e) override;
diff --git a/effects/coverswitch/coverswitch.cpp b/effects/coverswitch/coverswitch.cpp
--- a/effects/coverswitch/coverswitch.cpp
+++ b/effects/coverswitch/coverswitch.cpp
@@ -129,7 +129,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void CoverSwitchEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void CoverSwitchEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);
 
diff --git a/effects/cube/cube.h b/effects/cube/cube.h
--- a/effects/cube/cube.h
+++ b/effects/cube/cube.h
@@ -59,7 +59,7 @@
     ~CubeEffect() override;
     void reconfigure(ReconfigureFlags) override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     void prePaintWindow(EffectWindow* w, WindowPrePaintData& data, int time) override;
     void paintWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) override;
diff --git a/effects/cube/cube.cpp b/effects/cube/cube.cpp
--- a/effects/cube/cube.cpp
+++ b/effects/cube/cube.cpp
@@ -397,7 +397,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void CubeEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void CubeEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     if (activated) {
         QRect rect = effects->clientArea(FullArea, activeScreen, effects->currentDesktop());
diff --git a/effects/cubeslide/cubeslide.h b/effects/cubeslide/cubeslide.h
--- a/effects/cubeslide/cubeslide.h
+++ b/effects/cubeslide/cubeslide.h
@@ -43,7 +43,7 @@
     ~CubeSlideEffect() override;
     void reconfigure(ReconfigureFlags) override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     void prePaintWindow(EffectWindow* w, WindowPrePaintData& data, int time) override;
     void paintWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) override;
diff --git a/effects/cubeslide/cubeslide.cpp b/effects/cubeslide/cubeslide.cpp
--- a/effects/cubeslide/cubeslide.cpp
+++ b/effects/cubeslide/cubeslide.cpp
@@ -87,7 +87,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void CubeSlideEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void CubeSlideEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     if (isActive()) {
         glEnable(GL_CULL_FACE);
diff --git a/effects/desktopgrid/desktopgrid.h b/effects/desktopgrid/desktopgrid.h
--- a/effects/desktopgrid/desktopgrid.h
+++ b/effects/desktopgrid/desktopgrid.h
@@ -70,7 +70,7 @@
     ~DesktopGridEffect() override;
     void reconfigure(ReconfigureFlags) override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     void prePaintWindow(EffectWindow* w, WindowPrePaintData& data, int time) override;
     void paintWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) override;
diff --git a/effects/desktopgrid/desktopgrid.cpp b/effects/desktopgrid/desktopgrid.cpp
--- a/effects/desktopgrid/desktopgrid.cpp
+++ b/effects/desktopgrid/desktopgrid.cpp
@@ -181,7 +181,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void DesktopGridEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void DesktopGridEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     if (timeline.currentValue() == 0 && !isUsingPresentWindows()) {
         effects->paintScreen(mask, region, data);
diff --git a/effects/flipswitch/flipswitch.h b/effects/flipswitch/flipswitch.h
--- a/effects/flipswitch/flipswitch.h
+++ b/effects/flipswitch/flipswitch.h
@@ -47,7 +47,7 @@
 
     void reconfigure(ReconfigureFlags) override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     void prePaintWindow(EffectWindow *w, WindowPrePaintData &data, int time) override;
     void paintWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) override;
diff --git a/effects/flipswitch/flipswitch.cpp b/effects/flipswitch/flipswitch.cpp
--- a/effects/flipswitch/flipswitch.cpp
+++ b/effects/flipswitch/flipswitch.cpp
@@ -120,7 +120,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void FlipSwitchEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void FlipSwitchEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);
     if (m_active) {
diff --git a/effects/invert/invert.h b/effects/invert/invert.h
--- a/effects/invert/invert.h
+++ b/effects/invert/invert.h
@@ -40,8 +40,8 @@
     InvertEffect();
     ~InvertEffect() override;
 
-    void drawWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) override;
-    void paintEffectFrame(KWin::EffectFrame* frame, QRegion region, double opacity, double frameOpacity) override;
+    void drawWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data) override;
+    void paintEffectFrame(KWin::EffectFrame* frame, const QRegion &region, double opacity, double frameOpacity) override;
     bool isActive() const override;
     bool provides(Feature) override;
 
diff --git a/effects/invert/invert.cpp b/effects/invert/invert.cpp
--- a/effects/invert/invert.cpp
+++ b/effects/invert/invert.cpp
@@ -82,7 +82,7 @@
     return true;
 }
 
-void InvertEffect::drawWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data)
+void InvertEffect::drawWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data)
 {
     // Load if we haven't already
     if (m_valid && !m_inited)
@@ -103,7 +103,7 @@
     }
 }
 
-void InvertEffect::paintEffectFrame(KWin::EffectFrame* frame, QRegion region, double opacity, double frameOpacity)
+void InvertEffect::paintEffectFrame(KWin::EffectFrame* frame, const QRegion &region, double opacity, double frameOpacity)
 {
     if (m_valid && m_allWindows) {
         frame->setShader(m_shader);
diff --git a/effects/lookingglass/lookingglass.h b/effects/lookingglass/lookingglass.h
--- a/effects/lookingglass/lookingglass.h
+++ b/effects/lookingglass/lookingglass.h
@@ -46,7 +46,7 @@
     void reconfigure(ReconfigureFlags) override;
 
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     bool isActive() const override;
 
     static bool supported();
diff --git a/effects/lookingglass/lookingglass.cpp b/effects/lookingglass/lookingglass.cpp
--- a/effects/lookingglass/lookingglass.cpp
+++ b/effects/lookingglass/lookingglass.cpp
@@ -225,7 +225,7 @@
     }
 }
 
-void LookingGlassEffect::paintScreen(int mask, QRegion region, ScreenPaintData &data)
+void LookingGlassEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {
     // Call the next effect.
     effects->paintScreen(mask, region, data);
diff --git a/effects/magnifier/magnifier.h b/effects/magnifier/magnifier.h
--- a/effects/magnifier/magnifier.h
+++ b/effects/magnifier/magnifier.h
@@ -42,7 +42,7 @@
     ~MagnifierEffect() override;
     void reconfigure(ReconfigureFlags) override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     bool isActive() const override;
     static bool supported();
diff --git a/effects/magnifier/magnifier.cpp b/effects/magnifier/magnifier.cpp
--- a/effects/magnifier/magnifier.cpp
+++ b/effects/magnifier/magnifier.cpp
@@ -138,7 +138,7 @@
         data.paint |= magnifierArea().adjusted(-FRAME_WIDTH, -FRAME_WIDTH, FRAME_WIDTH, FRAME_WIDTH);
 }
 
-void MagnifierEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void MagnifierEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);   // paint normal screen
     if (zoom != 1.0) {
diff --git a/effects/mouseclick/mouseclick.h b/effects/mouseclick/mouseclick.h
--- a/effects/mouseclick/mouseclick.h
+++ b/effects/mouseclick/mouseclick.h
@@ -104,7 +104,7 @@
     ~MouseClickEffect() override;
     void reconfigure(ReconfigureFlags) override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     bool isActive() const override;
 
diff --git a/effects/mouseclick/mouseclick.cpp b/effects/mouseclick/mouseclick.cpp
--- a/effects/mouseclick/mouseclick.cpp
+++ b/effects/mouseclick/mouseclick.cpp
@@ -111,7 +111,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void MouseClickEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void MouseClickEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);
 
diff --git a/effects/mousemark/mousemark.h b/effects/mousemark/mousemark.h
--- a/effects/mousemark/mousemark.h
+++ b/effects/mousemark/mousemark.h
@@ -40,7 +40,7 @@
     MouseMarkEffect();
     ~MouseMarkEffect() override;
     void reconfigure(ReconfigureFlags) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     bool isActive() const override;
 
     // for properties
diff --git a/effects/mousemark/mousemark.cpp b/effects/mousemark/mousemark.cpp
--- a/effects/mousemark/mousemark.cpp
+++ b/effects/mousemark/mousemark.cpp
@@ -111,7 +111,7 @@
 }
 #endif
 
-void MouseMarkEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void MouseMarkEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);   // paint normal screen
     if (marks.isEmpty() && drawing.isEmpty())
diff --git a/effects/presentwindows/presentwindows.h b/effects/presentwindows/presentwindows.h
--- a/effects/presentwindows/presentwindows.h
+++ b/effects/presentwindows/presentwindows.h
@@ -98,7 +98,7 @@
 
     // Screen painting
     void prePaintScreen(ScreenPrePaintData &data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     void postPaintScreen() override;
 
     // Window painting
diff --git a/effects/presentwindows/presentwindows.cpp b/effects/presentwindows/presentwindows.cpp
--- a/effects/presentwindows/presentwindows.cpp
+++ b/effects/presentwindows/presentwindows.cpp
@@ -218,7 +218,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void PresentWindowsEffect::paintScreen(int mask, QRegion region, ScreenPaintData &data)
+void PresentWindowsEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {
     effects->paintScreen(mask, region, data);
 
diff --git a/effects/screenedge/screenedgeeffect.h b/effects/screenedge/screenedgeeffect.h
--- a/effects/screenedge/screenedgeeffect.h
+++ b/effects/screenedge/screenedgeeffect.h
@@ -37,7 +37,7 @@
     ScreenEdgeEffect();
     ~ScreenEdgeEffect() override;
     void prePaintScreen(ScreenPrePaintData &data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     bool isActive() const override;
 
     int requestedEffectChainPosition() const override {
diff --git a/effects/screenedge/screenedgeeffect.cpp b/effects/screenedge/screenedgeeffect.cpp
--- a/effects/screenedge/screenedgeeffect.cpp
+++ b/effects/screenedge/screenedgeeffect.cpp
@@ -89,7 +89,7 @@
     }
 }
 
-void ScreenEdgeEffect::paintScreen(int mask, QRegion region, ScreenPaintData &data)
+void ScreenEdgeEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {
     effects->paintScreen(mask, region, data);
     for (QHash<ElectricBorder, Glow*>::iterator it = m_borders.begin();
diff --git a/effects/screenshot/screenshot.h b/effects/screenshot/screenshot.h
--- a/effects/screenshot/screenshot.h
+++ b/effects/screenshot/screenshot.h
@@ -44,7 +44,7 @@
     ScreenShotEffect();
     ~ScreenShotEffect() override;
 
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     void postPaintScreen() override;
     bool isActive() const override;
 
diff --git a/effects/screenshot/screenshot.cpp b/effects/screenshot/screenshot.cpp
--- a/effects/screenshot/screenshot.cpp
+++ b/effects/screenshot/screenshot.cpp
@@ -156,7 +156,7 @@
     return pixmap;
 }
 
-void ScreenShotEffect::paintScreen(int mask, QRegion region, ScreenPaintData &data)
+void ScreenShotEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {
     m_cachedOutputGeometry = data.outputGeometry();
     effects->paintScreen(mask, region, data);
diff --git a/effects/showfps/showfps.h b/effects/showfps/showfps.h
--- a/effects/showfps/showfps.h
+++ b/effects/showfps/showfps.h
@@ -46,7 +46,7 @@
     ShowFpsEffect();
     void reconfigure(ReconfigureFlags) override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void paintWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) override;
     void postPaintScreen() override;
     enum { INSIDE_GRAPH, NOWHERE, TOP_LEFT, TOP_RIGHT, BOTTOM_LEFT, BOTTOM_RIGHT }; // fps text position
diff --git a/effects/showfps/showfps.cpp b/effects/showfps/showfps.cpp
--- a/effects/showfps/showfps.cpp
+++ b/effects/showfps/showfps.cpp
@@ -151,7 +151,7 @@
     paint_size[ paints_pos ] += winsize;
 }
 
-void ShowFpsEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void ShowFpsEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);
     int fps = 0;
diff --git a/effects/showpaint/showpaint.h b/effects/showpaint/showpaint.h
--- a/effects/showpaint/showpaint.h
+++ b/effects/showpaint/showpaint.h
@@ -33,7 +33,7 @@
 public:
     ShowPaintEffect();
 
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     void paintWindow(EffectWindow *w, int mask, QRegion region, WindowPaintData &data) override;
 
     bool isActive() const override;
diff --git a/effects/showpaint/showpaint.cpp b/effects/showpaint/showpaint.cpp
--- a/effects/showpaint/showpaint.cpp
+++ b/effects/showpaint/showpaint.cpp
@@ -58,7 +58,7 @@
     connect(toggleAction, &QAction::triggered, this, &ShowPaintEffect::toggle);
 }
 
-void ShowPaintEffect::paintScreen(int mask, QRegion region, ScreenPaintData &data)
+void ShowPaintEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {
     m_painted = QRegion();
     effects->paintScreen(mask, region, data);
diff --git a/effects/slide/slide.h b/effects/slide/slide.h
--- a/effects/slide/slide.h
+++ b/effects/slide/slide.h
@@ -45,7 +45,7 @@
     void reconfigure(ReconfigureFlags) override;
 
     void prePaintScreen(ScreenPrePaintData &data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     void postPaintScreen() override;
 
     void prePaintWindow(EffectWindow *w, WindowPrePaintData &data, int time) override;
diff --git a/effects/slide/slide.cpp b/effects/slide/slide.cpp
--- a/effects/slide/slide.cpp
+++ b/effects/slide/slide.cpp
@@ -128,7 +128,7 @@
     return r;
 }
 
-void SlideEffect::paintScreen(int mask, QRegion region, ScreenPaintData &data)
+void SlideEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {
     const bool wrap = effects->optionRollOverDesktops();
     const int w = workspaceWidth();
diff --git a/effects/snaphelper/snaphelper.h b/effects/snaphelper/snaphelper.h
--- a/effects/snaphelper/snaphelper.h
+++ b/effects/snaphelper/snaphelper.h
@@ -38,7 +38,7 @@
     void reconfigure(ReconfigureFlags flags) override;
 
     void prePaintScreen(ScreenPrePaintData &data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     void postPaintScreen() override;
 
     bool isActive() const override;
diff --git a/effects/snaphelper/snaphelper.cpp b/effects/snaphelper/snaphelper.cpp
--- a/effects/snaphelper/snaphelper.cpp
+++ b/effects/snaphelper/snaphelper.cpp
@@ -105,7 +105,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void SnapHelperEffect::paintScreen(int mask, QRegion region, ScreenPaintData &data)
+void SnapHelperEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {
     effects->paintScreen(mask, region, data);
 
diff --git a/effects/startupfeedback/startupfeedback.h b/effects/startupfeedback/startupfeedback.h
--- a/effects/startupfeedback/startupfeedback.h
+++ b/effects/startupfeedback/startupfeedback.h
@@ -40,7 +40,7 @@
 
     void reconfigure(ReconfigureFlags flags) override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     bool isActive() const override;
 
diff --git a/effects/startupfeedback/startupfeedback.cpp b/effects/startupfeedback/startupfeedback.cpp
--- a/effects/startupfeedback/startupfeedback.cpp
+++ b/effects/startupfeedback/startupfeedback.cpp
@@ -169,7 +169,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void StartupFeedbackEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void StartupFeedbackEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);
     if (m_active) {
diff --git a/effects/thumbnailaside/thumbnailaside.h b/effects/thumbnailaside/thumbnailaside.h
--- a/effects/thumbnailaside/thumbnailaside.h
+++ b/effects/thumbnailaside/thumbnailaside.h
@@ -46,7 +46,7 @@
 public:
     ThumbnailAsideEffect();
     void reconfigure(ReconfigureFlags) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void paintWindow(EffectWindow *w, int mask, QRegion region, WindowPaintData &data) override;
 
     // for properties
diff --git a/effects/thumbnailaside/thumbnailaside.cpp b/effects/thumbnailaside/thumbnailaside.cpp
--- a/effects/thumbnailaside/thumbnailaside.cpp
+++ b/effects/thumbnailaside/thumbnailaside.cpp
@@ -60,7 +60,7 @@
     arrange();
 }
 
-void ThumbnailAsideEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void ThumbnailAsideEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     painted = QRegion();
     effects->paintScreen(mask, region, data);
diff --git a/effects/touchpoints/touchpoints.h b/effects/touchpoints/touchpoints.h
--- a/effects/touchpoints/touchpoints.h
+++ b/effects/touchpoints/touchpoints.h
@@ -39,7 +39,7 @@
     TouchPointsEffect();
     ~TouchPointsEffect() override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     bool isActive() const override;
     bool touchDown(qint32 id, const QPointF &pos, quint32 time) override;
diff --git a/effects/touchpoints/touchpoints.cpp b/effects/touchpoints/touchpoints.cpp
--- a/effects/touchpoints/touchpoints.cpp
+++ b/effects/touchpoints/touchpoints.cpp
@@ -127,7 +127,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void TouchPointsEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void TouchPointsEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);
 
diff --git a/effects/trackmouse/trackmouse.h b/effects/trackmouse/trackmouse.h
--- a/effects/trackmouse/trackmouse.h
+++ b/effects/trackmouse/trackmouse.h
@@ -41,7 +41,7 @@
     TrackMouseEffect();
     ~TrackMouseEffect() override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     void reconfigure(ReconfigureFlags) override;
     bool isActive() const override;
diff --git a/effects/trackmouse/trackmouse.cpp b/effects/trackmouse/trackmouse.cpp
--- a/effects/trackmouse/trackmouse.cpp
+++ b/effects/trackmouse/trackmouse.cpp
@@ -115,7 +115,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void TrackMouseEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void TrackMouseEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);   // paint normal screen
 
diff --git a/effects/windowgeometry/windowgeometry.h b/effects/windowgeometry/windowgeometry.h
--- a/effects/windowgeometry/windowgeometry.h
+++ b/effects/windowgeometry/windowgeometry.h
@@ -39,7 +39,7 @@
         return ef == Effect::GeometryTip;
     }
     void reconfigure(ReconfigureFlags) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData &data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData &data) override;
     bool isActive() const override;
 
     int requestedEffectChainPosition() const override {
diff --git a/effects/windowgeometry/windowgeometry.cpp b/effects/windowgeometry/windowgeometry.cpp
--- a/effects/windowgeometry/windowgeometry.cpp
+++ b/effects/windowgeometry/windowgeometry.cpp
@@ -92,7 +92,7 @@
     iHandleResizes = WindowGeometryConfiguration::resize();
 }
 
-void WindowGeometry::paintScreen(int mask, QRegion region, ScreenPaintData &data)
+void WindowGeometry::paintScreen(int mask, const QRegion &region, ScreenPaintData &data)
 {
     effects->paintScreen(mask, region, data);
     if (iAmActivated && iAmActive) {
diff --git a/effects/zoom/zoom.h b/effects/zoom/zoom.h
--- a/effects/zoom/zoom.h
+++ b/effects/zoom/zoom.h
@@ -49,7 +49,7 @@
     ~ZoomEffect() override;
     void reconfigure(ReconfigureFlags flags) override;
     void prePaintScreen(ScreenPrePaintData& data, int time) override;
-    void paintScreen(int mask, QRegion region, ScreenPaintData& data) override;
+    void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) override;
     void postPaintScreen() override;
     bool isActive() const override;
     // for properties
diff --git a/effects/zoom/zoom.cpp b/effects/zoom/zoom.cpp
--- a/effects/zoom/zoom.cpp
+++ b/effects/zoom/zoom.cpp
@@ -271,7 +271,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void ZoomEffect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void ZoomEffect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     if (zoom != 1.0) {
         data *= QVector2D(zoom, zoom);
diff --git a/kcmkwin/kwindecoration/declarative-plugin/previewbutton.h b/kcmkwin/kwindecoration/declarative-plugin/previewbutton.h
--- a/kcmkwin/kwindecoration/declarative-plugin/previewbutton.h
+++ b/kcmkwin/kwindecoration/declarative-plugin/previewbutton.h
@@ -59,7 +59,7 @@
     void setType(int type);
 
     const QColor &color() const { return m_color; }
-    void setColor(const QColor color);
+    void setColor(const QColor &color);
 
 Q_SIGNALS:
     void bridgeChanged();
diff --git a/kcmkwin/kwindecoration/declarative-plugin/previewbutton.cpp b/kcmkwin/kwindecoration/declarative-plugin/previewbutton.cpp
--- a/kcmkwin/kwindecoration/declarative-plugin/previewbutton.cpp
+++ b/kcmkwin/kwindecoration/declarative-plugin/previewbutton.cpp
@@ -138,7 +138,7 @@
     painter->fillRect(size, m_color);
 }
 
-void PreviewButtonItem::setColor(const QColor color)
+void PreviewButtonItem::setColor(const QColor &color)
 {
     m_color = color;
     m_color.setAlpha(127);
diff --git a/kcmkwin/kwinrules/ruleswidget.h b/kcmkwin/kwinrules/ruleswidget.h
--- a/kcmkwin/kwinrules/ruleswidget.h
+++ b/kcmkwin/kwinrules/ruleswidget.h
@@ -107,7 +107,7 @@
     int desktopToCombo(int d) const;
     int comboToDesktop(int val) const;
 #ifdef KWIN_BUILD_ACTIVITIES
-    int activityToCombo(QString d) const;
+    int activityToCombo(const QString &d) const;
     QString comboToActivity(int val) const;
     void updateActivitiesList();
     KActivities::Consumer *m_activities;
diff --git a/kcmkwin/kwinrules/ruleswidget.cpp b/kcmkwin/kwinrules/ruleswidget.cpp
--- a/kcmkwin/kwinrules/ruleswidget.cpp
+++ b/kcmkwin/kwinrules/ruleswidget.cpp
@@ -315,7 +315,7 @@
 }
 
 #ifdef KWIN_BUILD_ACTIVITIES
-int RulesWidget::activityToCombo(QString d) const
+int RulesWidget::activityToCombo(const QString &d) const
 {
     // TODO: ivan - do a multiselection list
     for (int i = 0; i < activity->count(); i++) {
diff --git a/libkwineffects/anidata.cpp b/libkwineffects/anidata.cpp
--- a/libkwineffects/anidata.cpp
+++ b/libkwineffects/anidata.cpp
@@ -86,10 +86,10 @@
  , to(to_)
  , meta(meta_)
  , startTime(AnimationEffect::clock() + delay)
- , fullScreenEffectLock(fullScreenEffectLock_)
+ , fullScreenEffectLock(std::move(fullScreenEffectLock_))
  , waitAtSource(waitAtSource_)
  , keepAlive(keepAlive)
- , previousWindowPixmapLock(previousWindowPixmapLock_)
+ , previousWindowPixmapLock(std::move(previousWindowPixmapLock_))
 {
 }
 
diff --git a/libkwineffects/anidata_p.h b/libkwineffects/anidata_p.h
--- a/libkwineffects/anidata_p.h
+++ b/libkwineffects/anidata_p.h
@@ -76,7 +76,7 @@
     AniData();
     AniData(AnimationEffect::Attribute a, int meta, const FPx2 &to,
             int delay, const FPx2 &from, bool waitAtSource,
-            FullScreenEffectLockPtr=FullScreenEffectLockPtr(),
+            FullScreenEffectLockPtr =FullScreenEffectLockPtr(),
             bool keepAlive = true, PreviousWindowPixmapLockPtr previousWindowPixmapLock = {});
 
     bool isActive() const;
diff --git a/libkwineffects/kwinanimationeffect.h b/libkwineffects/kwinanimationeffect.h
--- a/libkwineffects/kwinanimationeffect.h
+++ b/libkwineffects/kwinanimationeffect.h
@@ -258,7 +258,7 @@
      * @returns An ID that you can use to cancel a running animation.
      * @since 4.8
      */
-    quint64 animate( EffectWindow *w, Attribute a, uint meta, int ms, FPx2 to, QEasingCurve curve = QEasingCurve(), int delay = 0, FPx2 from = FPx2(), bool fullScreen = false, bool keepAlive = true)
+    quint64 animate( EffectWindow *w, Attribute a, uint meta, int ms, const FPx2 &to, const QEasingCurve &curve = QEasingCurve(), int delay = 0, const FPx2 &from = FPx2(), bool fullScreen = false, bool keepAlive = true)
     { return p_animate(w, a, meta, ms, to, curve, delay, from, false, fullScreen, keepAlive); }
 
     /**
@@ -288,7 +288,7 @@
      * @returns An ID that you need to use to cancel this manipulation.
      * @since 4.11
      */
-    quint64 set( EffectWindow *w, Attribute a, uint meta, int ms, FPx2 to, QEasingCurve curve = QEasingCurve(), int delay = 0, FPx2 from = FPx2(), bool fullScreen = false, bool keepAlive = true)
+    quint64 set( EffectWindow *w, Attribute a, uint meta, int ms, const FPx2 &to, const QEasingCurve &curve = QEasingCurve(), int delay = 0, const FPx2 &from = FPx2(), bool fullScreen = false, bool keepAlive = true)
     { return p_animate(w, a, meta, ms, to, curve, delay, from, true, fullScreen, keepAlive); }
 
     /**
@@ -386,7 +386,7 @@
     AniMap state() const;
 
 private:
-    quint64 p_animate(EffectWindow *w, Attribute a, uint meta, int ms, FPx2 to, QEasingCurve curve, int delay, FPx2 from, bool keepAtTarget, bool fullScreenEffect, bool keepAlive);
+    quint64 p_animate(EffectWindow *w, Attribute a, uint meta, int ms, FPx2 to, const QEasingCurve &curve, int delay, FPx2 from, bool keepAtTarget, bool fullScreenEffect, bool keepAlive);
     QRect clipRect(const QRect &windowRect, const AniData&) const;
     void clipWindow(const EffectWindow *, const AniData &, WindowQuadList &) const;
     float interpolated( const AniData&, int i = 0 ) const;
diff --git a/libkwineffects/kwinanimationeffect.cpp b/libkwineffects/kwinanimationeffect.cpp
--- a/libkwineffects/kwinanimationeffect.cpp
+++ b/libkwineffects/kwinanimationeffect.cpp
@@ -217,7 +217,7 @@
     }
 }
 
-quint64 AnimationEffect::p_animate( EffectWindow *w, Attribute a, uint meta, int ms, FPx2 to, QEasingCurve curve, int delay, FPx2 from, bool keepAtTarget, bool fullScreenEffect, bool keepAlive)
+quint64 AnimationEffect::p_animate( EffectWindow *w, Attribute a, uint meta, int ms, FPx2 to, const QEasingCurve &curve, int delay, FPx2 from, bool keepAtTarget, bool fullScreenEffect, bool keepAlive)
 {
     const bool waitAtSource = from.isValid();
     validate(a, meta, &from, &to, w);
diff --git a/libkwineffects/kwineffects.h b/libkwineffects/kwineffects.h
--- a/libkwineffects/kwineffects.h
+++ b/libkwineffects/kwineffects.h
@@ -428,7 +428,7 @@
      * In OpenGL based compositing, the frameworks ensures that the context is current
      * when this method is invoked.
      */
-    virtual void paintScreen(int mask, QRegion region, ScreenPaintData& data);
+    virtual void paintScreen(int mask, const QRegion &region, ScreenPaintData& data);
     /**
      * Called after all the painting has been finished.
      * In this method you can:
@@ -487,7 +487,7 @@
      * In OpenGL based compositing, the frameworks ensures that the context is current
      * when this method is invoked.
      */
-    virtual void paintEffectFrame(EffectFrame* frame, QRegion region, double opacity, double frameOpacity);
+    virtual void paintEffectFrame(EffectFrame* frame, const QRegion &region, double opacity, double frameOpacity);
 
     /**
      * Called on Transparent resizes.
@@ -516,7 +516,7 @@
      * In OpenGL based compositing, the frameworks ensures that the context is current
      * when this method is invoked.
      */
-    virtual void drawWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data);
+    virtual void drawWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data);
 
     /**
      * Define new window quads so that they can be transformed by other effects.
@@ -832,13 +832,13 @@
     ~EffectsHandler() override;
     // for use by effects
     virtual void prePaintScreen(ScreenPrePaintData& data, int time) = 0;
-    virtual void paintScreen(int mask, QRegion region, ScreenPaintData& data) = 0;
+    virtual void paintScreen(int mask, const QRegion &region, ScreenPaintData& data) = 0;
     virtual void postPaintScreen() = 0;
     virtual void prePaintWindow(EffectWindow* w, WindowPrePaintData& data, int time) = 0;
-    virtual void paintWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) = 0;
+    virtual void paintWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data) = 0;
     virtual void postPaintWindow(EffectWindow* w) = 0;
-    virtual void paintEffectFrame(EffectFrame* frame, QRegion region, double opacity, double frameOpacity) = 0;
-    virtual void drawWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data) = 0;
+    virtual void paintEffectFrame(EffectFrame* frame, const QRegion &region, double opacity, double frameOpacity) = 0;
+    virtual void drawWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data) = 0;
     virtual void buildQuads(EffectWindow* w, WindowQuadList& quadList) = 0;
     virtual QVariant kwinOption(KWinOption kwopt) = 0;
     /**
@@ -2140,7 +2140,7 @@
     virtual bool hasAlpha() const = 0;
 
     bool isOnCurrentActivity() const;
-    Q_SCRIPTABLE bool isOnActivity(QString id) const;
+    Q_SCRIPTABLE bool isOnActivity(const QString &id) const;
     bool isOnAllActivities() const;
     virtual QStringList activities() const = 0;
 
@@ -3226,7 +3226,7 @@
     /**
      * Register a list of windows for managing.
      */
-    inline void manage(EffectWindowList list) {
+    inline void manage(const EffectWindowList &list) {
         for (int i = 0; i < list.size(); i++)
             manage(list.at(i));
     }
@@ -3380,7 +3380,7 @@
     /**
      * Render the frame.
      */
-    virtual void render(QRegion region = infiniteRegion(), double opacity = 1.0, double frameOpacity = 1.0) = 0;
+    virtual void render(const QRegion &region = infiniteRegion(), double opacity = 1.0, double frameOpacity = 1.0) = 0;
 
     virtual void setPosition(const QPoint& point) = 0;
     /**
diff --git a/libkwineffects/kwineffects.cpp b/libkwineffects/kwineffects.cpp
--- a/libkwineffects/kwineffects.cpp
+++ b/libkwineffects/kwineffects.cpp
@@ -565,7 +565,7 @@
     effects->prePaintScreen(data, time);
 }
 
-void Effect::paintScreen(int mask, QRegion region, ScreenPaintData& data)
+void Effect::paintScreen(int mask, const QRegion &region, ScreenPaintData& data)
 {
     effects->paintScreen(mask, region, data);
 }
@@ -590,7 +590,7 @@
     effects->postPaintWindow(w);
 }
 
-void Effect::paintEffectFrame(KWin::EffectFrame* frame, QRegion region, double opacity, double frameOpacity)
+void Effect::paintEffectFrame(KWin::EffectFrame* frame, const QRegion &region, double opacity, double frameOpacity)
 {
     effects->paintEffectFrame(frame, region, opacity, frameOpacity);
 }
@@ -610,7 +610,7 @@
     return QString();
 }
 
-void Effect::drawWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data)
+void Effect::drawWindow(EffectWindow* w, int mask, const QRegion &region, WindowPaintData& data)
 {
     effects->drawWindow(w, mask, region, data);
 }
@@ -778,7 +778,7 @@
 {
 }
 
-bool EffectWindow::isOnActivity(QString activity) const
+bool EffectWindow::isOnActivity(const QString &activity) const
 {
     const QStringList _activities = activities();
     return _activities.isEmpty() || _activities.contains(activity);
diff --git a/libkwineffects/kwinglplatform.cpp b/libkwineffects/kwinglplatform.cpp
--- a/libkwineffects/kwinglplatform.cpp
+++ b/libkwineffects/kwinglplatform.cpp
@@ -680,7 +680,7 @@
     // Parse the Mesa version
     const int mesaIndex = versionTokens.indexOf("Mesa");
     if (mesaIndex != -1) {
-        const QByteArray version = versionTokens.at(mesaIndex + 1);
+        const QByteArray &version = versionTokens.at(mesaIndex + 1);
         m_mesaVersion = parseVersionString(version);
     }
 
@@ -718,7 +718,7 @@
     if (m_renderer.startsWith("Mesa DRI R")) {
         // Sample renderer string: Mesa DRI R600 (RV740 94B3) 20090101 x86/MMX/SSE2 TCL DRI2
         const QList<QByteArray> tokens = m_renderer.split(' ');
-        const QByteArray chipClass = tokens.at(2);
+        const QByteArray &chipClass = tokens.at(2);
         m_chipset = tokens.at(3).mid(1, -1); // Strip the leading '('
 
         if (chipClass == "R100")
diff --git a/libkwineffects/kwingltexture.h b/libkwineffects/kwingltexture.h
--- a/libkwineffects/kwingltexture.h
+++ b/libkwineffects/kwingltexture.h
@@ -106,7 +106,7 @@
     virtual void discard();
     void bind();
     void unbind();
-    void render(QRegion region, const QRect& rect, bool hardwareClipping = false);
+    void render(const QRegion &region, const QRect& rect, bool hardwareClipping = false);
 
     GLuint texture() const;
     GLenum target() const;
diff --git a/libkwineffects/kwingltexture.cpp b/libkwineffects/kwingltexture.cpp
--- a/libkwineffects/kwingltexture.cpp
+++ b/libkwineffects/kwingltexture.cpp
@@ -467,7 +467,7 @@
     glBindTexture(d->m_target, 0);
 }
 
-void GLTexture::render(QRegion region, const QRect& rect, bool hardwareClipping)
+void GLTexture::render(const QRegion &region, const QRect& rect, bool hardwareClipping)
 {
     Q_D(GLTexture);
     if (rect.isEmpty())
diff --git a/libkwineffects/kwinglutils.h b/libkwineffects/kwinglutils.h
--- a/libkwineffects/kwinglutils.h
+++ b/libkwineffects/kwinglutils.h
@@ -52,7 +52,7 @@
 //  well as checking for GL version and extensions
 //  Note that GL context has to be created by the time this function is called
 typedef void (*resolveFuncPtr)();
-void KWINGLUTILS_EXPORT initGL(std::function<resolveFuncPtr(const char*)> resolveFunction);
+void KWINGLUTILS_EXPORT initGL(const std::function<resolveFuncPtr(const char*)> &resolveFunction);
 // Cleans up all resources hold by the GL Context
 void KWINGLUTILS_EXPORT cleanupGL();
 
diff --git a/libkwineffects/kwinglutils.cpp b/libkwineffects/kwinglutils.cpp
--- a/libkwineffects/kwinglutils.cpp
+++ b/libkwineffects/kwinglutils.cpp
@@ -61,7 +61,7 @@
 
 // Functions
 
-void initGL(std::function<resolveFuncPtr(const char*)> resolveFunction)
+void initGL(const std::function<resolveFuncPtr(const char*)> &resolveFunction)
 {
     // Get list of supported OpenGL extensions
     if (hasGLVersion(3, 0)) {
diff --git a/libkwineffects/kwinglutils_funcs.h b/libkwineffects/kwinglutils_funcs.h
--- a/libkwineffects/kwinglutils_funcs.h
+++ b/libkwineffects/kwinglutils_funcs.h
@@ -43,7 +43,7 @@
 {
 
 typedef void (*resolveFuncPtr)();
-void KWINGLUTILS_EXPORT glResolveFunctions(std::function<resolveFuncPtr(const char*)> resolveFunction);
+void KWINGLUTILS_EXPORT glResolveFunctions(const std::function<resolveFuncPtr(const char*)> &resolveFunction);
 
 // GL_ARB_robustness / GL_EXT_robustness
 using glGetGraphicsResetStatus_func = GLenum (*)();
diff --git a/libkwineffects/kwinglutils_funcs.cpp b/libkwineffects/kwinglutils_funcs.cpp
--- a/libkwineffects/kwinglutils_funcs.cpp
+++ b/libkwineffects/kwinglutils_funcs.cpp
@@ -40,7 +40,7 @@
 glReadnPixels_func            glReadnPixels;
 glGetnUniformfv_func          glGetnUniformfv;
 
-void glResolveFunctions(std::function<resolveFuncPtr(const char*)> resolveFunction)
+void glResolveFunctions(const std::function<resolveFuncPtr(const char*)> &resolveFunction)
 {
     const bool haveArbRobustness = hasGLExtension(QByteArrayLiteral("GL_ARB_robustness"));
     const bool haveExtRobustness = hasGLExtension(QByteArrayLiteral("GL_EXT_robustness"));
diff --git a/main.h b/main.h
--- a/main.h
+++ b/main.h
@@ -84,21 +84,21 @@
         return m_config;
     }
     void setConfig(KSharedConfigPtr config) {
-        m_config = config;
+        m_config = std::move(config);
     }
 
     KSharedConfigPtr kxkbConfig() const {
         return m_kxkbConfig;
     }
     void setKxkbConfig(KSharedConfigPtr config) {
-        m_kxkbConfig = config;
+        m_kxkbConfig = std::move(config);
     }
 
     KSharedConfigPtr inputConfig() const {
         return m_inputConfig;
     }
     void setInputConfig(KSharedConfigPtr config) {
-        m_inputConfig = config;
+        m_inputConfig = std::move(config);
     }
 
     void start();
diff --git a/orientation_sensor.h b/orientation_sensor.h
--- a/orientation_sensor.h
+++ b/orientation_sensor.h
@@ -61,7 +61,7 @@
     }
 
     void setConfig(KSharedConfig::Ptr config) {
-        m_config = config;
+        m_config = std::move(config);
     }
 
     bool isUserEnabled() const {
diff --git a/virtualdesktops.h b/virtualdesktops.h
--- a/virtualdesktops.h
+++ b/virtualdesktops.h
@@ -710,7 +710,7 @@
 inline
 void VirtualDesktopManager::setConfig(KSharedConfig::Ptr config)
 {
-    m_config = config;
+    m_config = std::move(config);
 }
 
 inline
diff --git a/xkb.h b/xkb.h
--- a/xkb.h
+++ b/xkb.h
@@ -56,10 +56,10 @@
     Xkb(QObject *parent = nullptr);
     ~Xkb() override;
     void setConfig(KSharedConfigPtr config) {
-        m_config = config;
+        m_config = std::move(config);
     }
     void setNumLockConfig(KSharedConfigPtr config) {
-        m_numLockConfig = config;
+        m_numLockConfig = std::move(config);
     }
     void reconfigure();