Provide default implementation for AbstractClient::updateDecoration()

Not all client types support server-side decorations, for example it's
typically the case for popup windows. This change provides a default
implementation for the updateDecoration() method in order to reduce the
amount of boilerplate code in client types that have no support for ssd.

abstract_client.cpp

@@ -3451,4 +3451,11 @@ void AbstractClient::changeMaximize(bool horizontal, bool vertical, bool adjust)
     qCWarning(KWIN_CORE, "%s doesn't support setting maximized state", metaObject()->className());
 }
 
+void AbstractClient::updateDecoration(bool check_workspace_pos, bool force)
+{
+    Q_UNUSED(check_workspace_pos)
+    Q_UNUSED(force)
+    qCWarning(KWIN_CORE, "%s doesn't support server side decorations", metaObject()->className());
+}
+
 }

abstract_client.h

@@ -723,7 +723,7 @@ public:
     /**
      * TODO: fix boolean traps
      */
-    virtual void updateDecoration(bool check_workspace_pos, bool force = false) = 0;
+    virtual void updateDecoration(bool check_workspace_pos, bool force = false);
 
     /**
      * Returns whether the window provides context help or not. If it does,

xdgshellclient.cpp

@@ -2027,12 +2027,6 @@ void XdgPopupClient::setNoBorder(bool set)
     Q_UNUSED(set)
 }
 
-void XdgPopupClient::updateDecoration(bool check_workspace_pos, bool force)
-{
-    Q_UNUSED(check_workspace_pos)
-    Q_UNUSED(force)
-}
-
 void XdgPopupClient::showOnScreenEdge()
 {
 }

xdgshellclient.h

@@ -249,7 +249,6 @@ public:
     bool noBorder() const override;
     bool userCanSetNoBorder() const override;
     void setNoBorder(bool set) override;
-    void updateDecoration(bool check_workspace_pos, bool force = false) override;
     void showOnScreenEdge() override;
     bool wantsInput() const override;
     bool takeFocus() override;