Use a templated approach for InputRedirection::processFilters

Summary:
An improvement from the introduction of InputEventSpy. Instead of
specifying a std::function as argument, we let the compiler decide what
is the best argument.

Reviewers: #kwin, #plasma, mart

Reviewed By: mart

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D3877

input.cpp

@@ -1882,11 +1882,6 @@ bool InputRedirection::isBreakingPointerConstraints() const
     return m_pointerConstraintsFilter ? m_pointerConstraintsFilter->isActive() : false;
 }
 
-void InputRedirection::processFilters(std::function<bool(InputEventFilter*)> function)
-{
-    std::any_of(m_filters.constBegin(), m_filters.constEnd(), function);
-}
-
 InputDeviceHandler::InputDeviceHandler(InputRedirection *input)
     : QObject(input)
     , m_input(input)

input.h

@@ -173,10 +173,19 @@ public:
      * The method @p function is invoked on each input filter. Processing is stopped if
      * a filter returns @c true for @p function.
      *
+     * The UnaryPredicate is defined like the UnaryPredicate of std::any_of.
+     * The signature of the function should be equivalent to the following:
+     * @code
+     * bool function(const InputEventFilter *spy);
+     * @endcode
+     *
      * The intended usage is to std::bind the method to invoke on the filter with all arguments
      * bind.
      **/
-    void processFilters(std::function<bool(InputEventFilter*)> function);
+    template <class UnaryPredicate>
+    void processFilters(UnaryPredicate function) {
+        std::any_of(m_filters.constBegin(), m_filters.constEnd(), function);
+    }
 
     /**
      * Sends an event through all input event spies.