Move AbstractClient::isShade() to Toplevel

This simplifies rendering code and allows to cache properly the shaded
state for Deleted windows.

src/abstract_client.h

@@ -521,7 +521,7 @@ public:
     /**
      * @c true only for @c ShadeNormal
      */
-    bool isShade() const {
+    bool isShade() const override {
         return shadeMode() == ShadeNormal;
     }
     ShadeMode shadeMode() const; // Prefer isShade()
@@ -918,7 +918,6 @@ Q_SIGNALS:
     void desktopChanged();
     void activitiesChanged(KWin::AbstractClient* client);
     void x11DesktopIdsChanged();
-    void shadeChanged();
     void minimizedChanged();
     void clientMinimized(KWin::AbstractClient* client, bool animate);
     void clientUnminimized(KWin::AbstractClient* client, bool animate);

src/deleted.cpp

@@ -25,6 +25,7 @@ Deleted::Deleted()
     , delete_refcount(1)
     , m_frame(XCB_WINDOW_NONE)
     , m_layer(UnknownLayer)
+    , m_shade(false)
     , m_minimized(false)
     , m_modal(false)
     , m_wasClient(false)
@@ -78,6 +79,7 @@ void Deleted::copyToDeleted(Toplevel* c)
     m_frame = c->frameId();
     m_type = c->windowType();
     m_windowRole = c->windowRole();
+    m_shade = c->isShade();
     if (WinInfo* cinfo = dynamic_cast< WinInfo* >(info))
         cinfo->disable();
     if (AbstractClient *client = dynamic_cast<AbstractClient*>(c)) {

src/deleted.h

@@ -40,6 +40,9 @@ public:
     Layer layer() const override {
         return m_layer;
     }
+    bool isShade() const override {
+        return m_shade;
+    }
     bool isMinimized() const {
         return m_minimized;
     }
@@ -113,6 +116,7 @@ private:
     QRect decoration_top;
     QRect decoration_bottom;
     Layer m_layer;
+    bool m_shade;
     bool m_minimized;
     bool m_modal;
     QList<AbstractClient*> m_mainClients;

src/scene.cpp

@@ -836,9 +836,7 @@ bool Scene::Window::isOpaque() const
 
 bool Scene::Window::isShaded() const
 {
-    if (AbstractClient *client = qobject_cast<AbstractClient *>(toplevel))
-        return client->isShade();
-    return false;
+    return toplevel->isShade();
 }
 
 bool Scene::Window::isPaintingEnabled() const

src/toplevel.h

@@ -562,7 +562,13 @@ public:
         return m_internalId;
     }
 
+    /**
+     * Returns @c true if the window is shaded; otherwise returns @c false.
+     */
+    virtual bool isShade() const { return false; }
+
 Q_SIGNALS:
+    void shadeChanged();
     void markedAsZombie();
     void opacityChanged(KWin::Toplevel* toplevel, qreal oldOpacity);
     void damaged(KWin::Toplevel* toplevel, const QRegion& damage);