move event handler verification to the Event class

include/SFML/Window/Event.hpp

@@ -339,15 +339,15 @@ public:
     [[nodiscard]] const TEventSubtype* getIf() const;
 
     ////////////////////////////////////////////////////////////
-    /// \brief Apply a visitor to the event
+    /// \brief Apply visitors to the event
     ///
-    /// \param visitor The visitor to apply
+    /// \param visitors Visitors to apply
     ///
-    /// \return The result of applying the visitor to the event
+    /// \return The result of applying visitors to the event
     ///
     ////////////////////////////////////////////////////////////
-    template <typename T>
+    template <typename... Ts>
-    decltype(auto) visit(T&& visitor) const;
+    decltype(auto) visit(Ts&&... visitors) const;
 
 private:
     ////////////////////////////////////////////////////////////
@@ -396,12 +396,8 @@ private:
         return (std::is_invocable_v<Handler, const Ts&> || ...);
     }
 
-public:
     template <typename Handler>
-    static constexpr bool isValidHandler()
+    static constexpr bool isValidHandler = isInvokableWithAnyOf<Handler>(static_cast<decltype(m_data)*>(nullptr));
-    {
-        return isInvokableWithAnyOf<Handler>(static_cast<decltype(m_data)*>(nullptr));
-    }
 };
 
 } // namespace sf

include/SFML/Window/Event.inl

@@ -38,6 +38,28 @@
 
 namespace sf
 {
+namespace priv
+{
+template <typename... Ts>
+struct OverloadSet : Ts...
+{
+    using Ts::operator()...;
+#if defined(_MSC_VER) && !defined(__clang__)
+    unsigned char dummy; // Dummy variable to ensure that this struct is not empty thus avoiding a crash due to an MSVC bug
+#endif
+};
+template <typename... Ts>
+OverloadSet(Ts...) -> OverloadSet<Ts...>;
+
+struct DelayOverloadResolution
+{
+    template <typename T>
+    DelayOverloadResolution(const T&)
+    {
+    }
+};
+} // namespace priv
+
 ////////////////////////////////////////////////////////////
 template <typename TEventSubtype>
 Event::Event(const TEventSubtype& eventSubtype)
@@ -79,10 +101,21 @@ const TEventSubtype* Event::getIf() const
 
 
 ////////////////////////////////////////////////////////////
-template <typename T>
+template <typename... Ts>
-decltype(auto) Event::visit(T&& visitor) const
+decltype(auto) Event::visit(Ts&&... visitors) const
 {
-    return std::visit(std::forward<T>(visitor), m_data);
+    static_assert(sizeof...(Ts) > 0, "Must provide at least one handler");
+    static_assert((isValidHandler<Ts> && ...),
+                  "All event handlers must accept a single parameter, either a const reference or a value");
+
+    // Disable misc-const-correctness for this line since clang-tidy
+    // complains about it even though the code would become uncompilable
+
+    // NOLINTNEXTLINE(misc-const-correctness)
+    return std::visit(priv::OverloadSet{std::forward<Ts>(visitors)...,
+                                        [](const priv::DelayOverloadResolution&) { /* ignore */ }},
+                      m_data);
 }
 
+
 } // namespace sf

include/SFML/Window/WindowBase.inl

@@ -28,50 +28,15 @@
 #include <SFML/Window/Event.hpp>
 #include <SFML/Window/WindowBase.hpp> // NOLINT(misc-header-include-cycle)
 
-#include <utility>
-
 
 namespace sf
 {
-namespace priv
-{
-template <typename... Ts>
-struct OverloadSet : Ts...
-{
-    using Ts::operator()...;
-#if defined(_MSC_VER) && !defined(__clang__)
-    unsigned char dummy; // Dummy variable to ensure that this struct is not empty thus avoiding a crash due to an MSVC bug
-#endif
-};
-template <typename... Ts>
-OverloadSet(Ts...) -> OverloadSet<Ts...>;
-
-struct DelayOverloadResolution
-{
-    template <typename T>
-    DelayOverloadResolution(const T&)
-    {
-    }
-};
-} // namespace priv
-
-
 ////////////////////////////////////////////////////////////
 template <typename... Ts>
 void WindowBase::handleEvents(Ts&&... handlers) // NOLINT(cppcoreguidelines-missing-std-forward)
 {
-    static_assert(sizeof...(Ts) > 0, "Must provide at least one handler");
-    static_assert((Event::isValidHandler<Ts>() && ...),
-                  "All event handlers must accept a single parameter, either a const reference or a value");
-
-    // Disable misc-const-correctness for this line since clang-tidy
-    // complains about it even though the code would become uncompilable
-
-    // NOLINTNEXTLINE(misc-const-correctness)
-    priv::OverloadSet overloadSet{std::forward<Ts>(handlers)..., [](const priv::DelayOverloadResolution&) { /* ignore */ }};
-
     while (const std::optional event = pollEvent())
-        event->visit(overloadSet);
+        event->visit(handlers...);
 }
 
 } // namespace sf