Add Workspace::findToplevel

Like findClient and findUnmanaged, just a little bit more generic.
Toplevel::findInList got adjusted to support it.

activation.cpp

@@ -731,7 +731,7 @@ xcb_timestamp_t Client::readUserTimeMapTimestamp(const KStartupInfoId *asn_id, c
                     ; // is transient for currently active window, even though it's not
                 // the same app (e.g. kcookiejar dialog) -> allow activation
                 else if (groupTransient() &&
-                        findInList<Client>(mainClients(), sameApplicationActiveHackPredicate) == NULL)
+                        findInList<Client, Client>(mainClients(), sameApplicationActiveHackPredicate) == NULL)
                     ; // standalone transient
                 else
                     first_window = false;

toplevel.h

@@ -361,8 +361,8 @@ public:
      * @param func The condition function (compare std::find_if)
      * @return T* The found Toplevel or @c null if there is no matching Toplevel
      */
-    template <class T>
-    static T *findInList(const QList<T*> &list, std::function<bool (const T*)> func);
+    template <class T, class U>
+    static T *findInList(const QList<T*> &list, std::function<bool (const U*)> func);
 
 Q_SIGNALS:
     void opacityChanged(KWin::Toplevel* toplevel, qreal oldOpacity);
@@ -718,9 +718,11 @@ inline quint32 Toplevel::surfaceId() const
     return m_surfaceId;
 }
 
-template <class T>
-inline T *Toplevel::findInList(const QList<T*> &list, std::function<bool (const T*)> func)
+template <class T, class U>
+inline T *Toplevel::findInList(const QList<T*> &list, std::function<bool (const U*)> func)
 {
+    static_assert(std::is_base_of<U, T>::value,
+                 "U must be derived from T");
     const auto it = std::find_if(list.begin(), list.end(), func);
     if (it == list.end()) {
         return nullptr;

workspace.cpp

@@ -1576,6 +1576,20 @@ Client *Workspace::findClient(Predicate predicate, xcb_window_t w) const
     return nullptr;
 }
 
+Toplevel *Workspace::findToplevel(std::function<bool (const Toplevel*)> func) const
+{
+    if (Client *ret = Toplevel::findInList(clients, func)) {
+        return ret;
+    }
+    if (Client *ret = Toplevel::findInList(desktops, func)) {
+        return ret;
+    }
+    if (Unmanaged *ret = Toplevel::findInList(unmanaged, func)) {
+        return ret;
+    }
+    return nullptr;
+}
+
 } // namespace
 
 #include "workspace.moc"

workspace.h

@@ -122,6 +122,7 @@ public:
      */
     Unmanaged *findUnmanaged(xcb_window_t w) const;
     void forEachUnmanaged(std::function<void (Unmanaged*)> func);
+    Toplevel *findToplevel(std::function<bool (const Toplevel*)> func) const;
 
     QRect clientArea(clientAreaOption, const QPoint& p, int desktop) const;
     QRect clientArea(clientAreaOption, const Client* c) const;