MMDevice: Add ActionLambda

This is like CPropertyAction[Ex], but takes an arbitrary copyable
callable (such as a lambda).

Defining a property action using a lambda allows one to put all the code
related to a single property in one place.

MMDevice/Property.h

@@ -24,11 +24,13 @@
 #define _MMPROPERTY_H_
 
 #include "MMDeviceConstants.h"
-#include <string>
-#include <cstring>
+
 #include <cstdlib>
-#include <vector>
+#include <cstring>
+#include <functional>
 #include <map>
+#include <string>
+#include <vector>
 
 namespace MM {
 
@@ -120,6 +122,24 @@ class ActionEx : public ActionFunctor
       { return (*pObj_.*fpt_)(pProp, eAct, param_);};
 };
 
+/**
+ * Action implementation using std::function to wrap arbitrary callables.
+ *
+ * (It is named "lambda" after its intended use, but can wrap any C++
+ * callable.)
+ */
+class ActionLambda final : public ActionFunctor
+{
+    std::function<int(PropertyBase*, ActionType)> func_;
+
+public:
+    template <typename F> explicit ActionLambda(F func) : func_(func) {}
+
+    int Execute(PropertyBase* pProp, ActionType eAct) final {
+        return func_(pProp, eAct);
+    }
+};
+
 /**
  * Property API with most of the Property mechanism implemented.
  */