Make Toplevel::opacity virtual and copy it to Deleted

Toplevel::opacity() accesses the WinInfo, but for a Wayland client
we won't have the opacity through the WinInfo, so let's have it as
a virtual method that a subclass can override. Also it needs to be
copied to Deleted to not have a Deleted of a Wayland client crash
because it accesses the not existing WinInfo.

deleted.cpp

@@ -79,6 +79,7 @@ void Deleted::copyToDeleted(Toplevel* c)
     transparent_rect = c->transparentRect();
     m_layer = c->layer();
     m_frame = c->frameId();
+    m_opacity = c->opacity();
     if (WinInfo* cinfo = dynamic_cast< WinInfo* >(info))
         cinfo->disable();
     Client* client = dynamic_cast<Client*>(c);
@@ -185,6 +186,11 @@ xcb_window_t Deleted::frameId() const
     return m_frame;
 }
 
+double Deleted::opacity() const
+{
+    return m_opacity;
+}
+
 } // namespace
 
 #include "deleted.moc"

deleted.h

@@ -71,6 +71,7 @@ public:
     bool wasClient() const {
         return m_wasClient;
     }
+    double opacity() const override;
 
     const Decoration::Renderer *decorationRenderer() const {
         return m_decorationRenderer;
@@ -103,6 +104,7 @@ private:
     ClientList m_mainClients;
     bool m_wasClient;
     Decoration::Renderer *m_decorationRenderer;
+    double m_opacity;
 };
 
 inline void Deleted::refWindow()

toplevel.h

@@ -269,7 +269,7 @@ public:
     xcb_visualid_t visual() const;
     bool shape() const;
     void setOpacity(double opacity);
-    double opacity() const;
+    virtual double opacity() const;
     int depth() const;
     bool hasAlpha() const;
     virtual bool setupCompositing();