kcmkwin/kwincompositing: add option to toggle tearing on Wayland

src/core/renderloop.cpp

@@ -263,7 +263,7 @@ void RenderLoop::setFullscreenSurface(Item *surfaceItem)
 {
     d->fullscreenItem = surfaceItem;
     if (SurfaceItemWayland *wayland = qobject_cast<SurfaceItemWayland *>(surfaceItem)) {
-        d->allowTearing = d->canDoTearing && wayland->surface()->presentationHint() == KWaylandServer::PresentationHint::Async;
+        d->allowTearing = d->canDoTearing && options->allowTearing() && wayland->surface()->presentationHint() == KWaylandServer::PresentationHint::Async;
     } else {
         d->allowTearing = false;
     }

src/kcmkwin/kwincompositing/compositing.ui

@@ -207,6 +207,16 @@ you can reset this protection but be aware that this might result in an immediat
      </item>
     </widget>
    </item>
+   <item row="15" column="1">
+    <widget class="QCheckBox" name="kcfg_AllowTearing">
+     <property name="toolTip">
+      <string>Allows applications to cause screen tearing in fullscreen.</string>
+     </property>
+     <property name="text">
+      <string>Allow tearing in fullscreen</string>
+     </property>
+    </widget>
+   </item>
   </layout>
  </widget>
  <customwidgets>

src/kcmkwin/kwincompositing/kwincompositing_setting.kcfg

@@ -45,6 +45,10 @@
            <default>LatencyMedium</default>
        </entry>
 
+       <entry name="AllowTearing" type="Bool">
+           <default>true</default>
+       </entry>
+
     </group>
 
 </kcfg>

src/kcmkwin/kwincompositing/main.cpp

@@ -85,6 +85,7 @@ KWinCompositingKCM::KWinCompositingKCM(QWidget *parent, const QVariantList &args
     m_form.kcfg_Enabled->setVisible(!compositingRequired());
     m_form.kcfg_WindowsBlockCompositing->setVisible(!compositingRequired());
     m_form.compositingLabel->setVisible(!compositingRequired());
+    m_form.kcfg_AllowTearing->setVisible(compositingRequired());
 
     connect(this, &KWinCompositingKCM::defaultsIndicatorsVisibleChanged, this, &KWinCompositingKCM::updateUnmanagedItemStatus);
 

src/kwin.kcfg

@@ -278,6 +278,9 @@
             </choices>
             <default>RenderTimeEstimatorMaximum</default>
         </entry>
+        <entry name="AllowTearing" type="Bool">
+            <default>true</default>
+        </entry>
     </group>
     <group name="TabBox">
         <entry name="ShowDelay" type="Bool">

src/options.cpp

@@ -653,6 +653,19 @@ void Options::setRenderTimeEstimator(RenderTimeEstimator estimator)
     Q_EMIT renderTimeEstimatorChanged();
 }
 
+bool Options::allowTearing() const
+{
+    return m_allowTearing;
+}
+
+void Options::setAllowTearing(bool allow)
+{
+    if (allow != m_allowTearing) {
+        m_allowTearing = allow;
+        Q_EMIT allowTearingChanged();
+    }
+}
+
 void Options::setGlPlatformInterface(OpenGLPlatformInterface interface)
 {
     // check environment variable
@@ -793,6 +806,7 @@ void Options::syncFromKcfgc()
     setMoveMinimizedWindowsToEndOfTabBoxFocusChain(m_settings->moveMinimizedWindowsToEndOfTabBoxFocusChain());
     setLatencyPolicy(m_settings->latencyPolicy());
     setRenderTimeEstimator(m_settings->renderTimeEstimator());
+    setAllowTearing(m_settings->allowTearing());
 }
 
 bool Options::loadCompositingConfig(bool force)

src/options.h

@@ -214,6 +214,7 @@ class KWIN_EXPORT Options : public QObject
     Q_PROPERTY(bool windowsBlockCompositing READ windowsBlockCompositing WRITE setWindowsBlockCompositing NOTIFY windowsBlockCompositingChanged)
     Q_PROPERTY(LatencyPolicy latencyPolicy READ latencyPolicy WRITE setLatencyPolicy NOTIFY latencyPolicyChanged)
     Q_PROPERTY(RenderTimeEstimator renderTimeEstimator READ renderTimeEstimator WRITE setRenderTimeEstimator NOTIFY renderTimeEstimatorChanged)
+    Q_PROPERTY(bool allowTearing READ allowTearing WRITE setAllowTearing NOTIFY allowTearingChanged)
 public:
     explicit Options(QObject *parent = nullptr);
     ~Options() override;
@@ -704,6 +705,7 @@ public:
     QStringList modifierOnlyDBusShortcut(Qt::KeyboardModifier mod) const;
     LatencyPolicy latencyPolicy() const;
     RenderTimeEstimator renderTimeEstimator() const;
+    bool allowTearing() const;
 
     // setters
     void setFocusPolicy(FocusPolicy focusPolicy);
@@ -763,6 +765,7 @@ public:
     void setMoveMinimizedWindowsToEndOfTabBoxFocusChain(bool set);
     void setLatencyPolicy(LatencyPolicy policy);
     void setRenderTimeEstimator(RenderTimeEstimator estimator);
+    void setAllowTearing(bool allow);
 
     // default values
     static WindowOperation defaultOperationTitlebarDblClick()
@@ -969,6 +972,7 @@ Q_SIGNALS:
     void latencyPolicyChanged();
     void configChanged();
     void renderTimeEstimatorChanged();
+    void allowTearingChanged();
 
 private:
     void setElectricBorders(int borders);
@@ -1042,6 +1046,8 @@ private:
     bool borderless_maximized_windows;
     bool condensed_title;
 
+    bool m_allowTearing = true;
+
     QHash<Qt::KeyboardModifier, QStringList> m_modifierOnlyShortcuts;
 
     MouseCommand wheelToMouseCommand(MouseWheelCommand com, int delta) const;