signal: add value wrapper signal

signal.hpp

@@ -60,6 +60,17 @@ namespace util {
             typedef std::list<callback> group;
             group m_children;
     };
+
+    template <typename T>
+    class value_signal : public signal<void(T)> {
+    public:
+        operator const T&() const;
+
+        value_signal<T>& operator= (const T&);
+
+    private:
+        T m_value;
+    };
 }
 
 #include "signal.ipp"

signal.ipp

@@ -167,5 +167,23 @@ namespace util {
             (*current)(std::forward<Args> (tail)...);
         } while (looping);
     }
+
+
+    ///////////////////////////////////////////////////////////////////////////
+    template <typename T>
+    value_signal<T>::operator const T&() const
+    {
+        return m_value;
+    }
+
+
+    template <typename T>
+    value_signal<T>&
+    value_signal<T>::operator= (const T &t)
+    {
+        m_value = t;
+        (*this) (m_value);
+        return *this;
+    }
 }
 

test/signal.cpp

@@ -60,6 +60,19 @@ test_linking_pointers (void)
 }
 
 
+///////////////////////////////////////////////////////////////////////////////
+void
+test_value_signal (void)
+{
+    util::value_signal<unsigned> val;
+    auto raii = val.connect ([] (unsigned v) { CHECK_EQ (v, 42); });
+    val = 42u;
+
+    unsigned check = val;
+    CHECK_EQ (check, 42);
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 int
 main (int, char **)
@@ -67,6 +80,7 @@ main (int, char **)
     test_null   ();
     test_single ();
     test_double ();
+    test_value_signal ();
 
     return EXIT_SUCCESS;
 }