Use std::function for onEntry and onExit return types

This allows us to drop the C++14 requirement. As onEntry and onExit are
template functions we don't need to care about (not) using the standard
library for them.

Change-Id: Ie776e04f7e1771914c9f48d2440ef445d87d64c0
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>

8 files changed, 27 insertions, 55 deletions

diff --git a/examples/scxml/ftpclient/ftpclient.pro b/examples/scxml/ftpclient/ftpclient.pro
index 7aa266e..3ba8adf 100644
--- a/examples/scxml/ftpclient/ftpclient.pro
+++ b/examples/scxml/ftpclient/ftpclient.pro
@@ -1,6 +1,5 @@
 QT = core scxml
 
-CONFIG += c++14
 TARGET = ftpclient
 
 TEMPLATE = app
diff --git a/examples/scxml/ftpclient/main.cpp b/examples/scxml/ftpclient/main.cpp
index 3a99bd4..25102d2 100644
--- a/examples/scxml/ftpclient/main.cpp
+++ b/examples/scxml/ftpclient/main.cpp
@@ -62,7 +62,6 @@ struct Command {
 
 int main(int argc, char *argv[])
 {
-#if defined(__cpp_return_type_deduction) && __cpp_return_type_deduction == 201304
     if (argc != 3) {
         qDebug() << "Usage: ftpclient <server> <file>";
         return 1;
@@ -127,9 +126,4 @@ int main(int argc, char *argv[])
     });
 
     return app.exec();
-#else
-    qDebug() << "The ftpclient example uses the C++14 return type deduction feature and will only "
-                "work with compilers that support it.";
-    return 2;
-#endif
 }
diff --git a/src/scxml/qscxmlstatemachine.cpp b/src/scxml/qscxmlstatemachine.cpp
index e6137e0..8cb94ad 100644
--- a/src/scxml/qscxmlstatemachine.cpp
+++ b/src/scxml/qscxmlstatemachine.cpp
@@ -178,8 +178,8 @@ Q_LOGGING_CATEGORY(scxmlLog, "scxml.statemachine")
 */
 
 /*!
-    \fn auto QScxmlStateMachine::onEntry(const QObject *receiver,
-                                         const char *method)
+    \fn QScxmlStateMachine::onEntry(const QObject *receiver,
+                                    const char *method)
 
     Returns a functor that accepts a boolean argument and calls the given
     \a method on \a receiver using QMetaObject::invokeMethod() if that argument
@@ -190,14 +190,10 @@ Q_LOGGING_CATEGORY(scxmlLog, "scxml.statemachine")
 
     This is useful to wrap handlers for connectToState() that should only
     be executed when the state is entered.
-
-    onEntry() is only available if the compiler supports return type
-    deduction for functions.
-*/
+ */
 
 /*!
-    \fn auto QScxmlStateMachine::onExit(const QObject *receiver,
-                                        const char *method)
+    \fn QScxmlStateMachine::onExit(const QObject *receiver, const char *method)
 
     Returns a functor that accepts a boolean argument and calls the given
     \a method on \a receiver using QMetaObject::invokeMethod() if that argument
@@ -208,10 +204,7 @@ Q_LOGGING_CATEGORY(scxmlLog, "scxml.statemachine")
 
     This is useful to wrap handlers for connectToState() that should only
     be executed when the state is left.
-
-    onExit() is only available if the compiler supports return type
-    deduction for functions.
-*/
+ */
 
 /*!
     \fn QScxmlStateMachine::onEntry(Functor functor)
@@ -222,9 +215,6 @@ Q_LOGGING_CATEGORY(scxmlLog, "scxml.statemachine")
 
     This is useful to wrap handlers for connectToState() that should only
     be executed when the state is entered.
-
-    onEntry() is only available if the compiler supports return type
-    deduction for functions.
  */
 
 /*!
@@ -236,9 +226,6 @@ Q_LOGGING_CATEGORY(scxmlLog, "scxml.statemachine")
 
     This is useful to wrap handlers for connectToState() that should only
     be executed when the state is left.
-
-    onExit() is only available if the compiler supports return type
-    deduction for functions.
  */
 
 /*!
@@ -252,9 +239,6 @@ Q_LOGGING_CATEGORY(scxmlLog, "scxml.statemachine")
 
     This is useful to wrap handlers for connectToState() that should only
     be executed when the state is entered.
-
-    onEntry() is only available if the compiler supports return type
-    deduction for functions.
  */
 
 /*!
@@ -268,9 +252,6 @@ Q_LOGGING_CATEGORY(scxmlLog, "scxml.statemachine")
 
     This is useful to wrap handlers for connectToState() that should only
     be executed when the state is left.
-
-    onExit() is only available if the compiler supports return type
-    deduction for functions.
  */
 
 namespace QScxmlInternal {
diff --git a/src/scxml/qscxmlstatemachine.h b/src/scxml/qscxmlstatemachine.h
index 4f813e4..16bd3d0 100644
--- a/src/scxml/qscxmlstatemachine.h
+++ b/src/scxml/qscxmlstatemachine.h
@@ -52,6 +52,8 @@
 #include <QVariantList>
 #include <QPointer>
 
+#include <functional>
+
 QT_BEGIN_NAMESPACE
 class QIODevice;
 class QXmlStreamWriter;
@@ -170,22 +172,24 @@ public:
 #endif
 
 #ifdef Q_QDOC
-    static auto onEntry(const QObject *receiver, const char *method);
-    static auto onExit(const QObject *receiver, const char *method);
+    static std::function<void(bool)> onEntry(const QObject *receiver, const char *method);
+    static std::function<void(bool)> onExit(const QObject *receiver, const char *method);
 
     template<typename Functor>
-    static auto onEntry(Functor functor);
+    static std::function<void(bool)> onEntry(Functor functor);
 
     template<typename Functor>
-    static auto onExit(Functor functor);
+    static std::function<void(bool)> onExit(Functor functor);
 
     template<typename PointerToMemberFunction>
-    static auto onEntry(const QObject *receiver, PointerToMemberFunction method);
+    static std::function<void(bool)> onEntry(const QObject *receiver,
+                                             PointerToMemberFunction method);
 
     template<typename PointerToMemberFunction>
-    static auto onExit(const QObject *receiver, PointerToMemberFunction method);
-#elif defined(__cpp_return_type_deduction) && __cpp_return_type_deduction == 201304
-    static auto onEntry(const QObject *receiver, const char *method)
+    static std::function<void(bool)> onExit(const QObject *receiver,
+                                            PointerToMemberFunction method);
+#else
+    static std::function<void(bool)> onEntry(const QObject *receiver, const char *method)
     {
         const QPointer<QObject> receiverPointer(const_cast<QObject *>(receiver));
         return [receiverPointer, method](bool isEnteringState) {
@@ -194,7 +198,7 @@ public:
         };
     }
 
-    static auto onExit(const QObject *receiver, const char *method)
+    static std::function<void(bool)> onExit(const QObject *receiver, const char *method)
     {
         const QPointer<QObject> receiverPointer(const_cast<QObject *>(receiver));
         return [receiverPointer, method](bool isEnteringState) {
@@ -204,7 +208,7 @@ public:
     }
 
     template<typename Functor>
-    static auto onEntry(Functor functor)
+    static std::function<void(bool)> onEntry(Functor functor)
     {
         return [functor](bool isEnteringState) {
             if (isEnteringState)
@@ -213,7 +217,7 @@ public:
     }
 
     template<typename Functor>
-    static auto onExit(Functor functor)
+    static std::function<void(bool)> onExit(Functor functor)
     {
         return [functor](bool isEnteringState) {
             if (!isEnteringState)
@@ -222,8 +226,8 @@ public:
     }
 
     template<typename Func1>
-    static auto onEntry(const typename QtPrivate::FunctionPointer<Func1>::Object *receiver,
-                        Func1 slot)
+    static std::function<void(bool)> onEntry(
+            const typename QtPrivate::FunctionPointer<Func1>::Object *receiver, Func1 slot)
     {
         typedef typename QtPrivate::FunctionPointer<Func1>::Object Object;
         const QPointer<Object> receiverPointer(const_cast<Object *>(receiver));
@@ -234,8 +238,8 @@ public:
     }
 
     template<typename Func1>
-    static auto onExit(const typename QtPrivate::FunctionPointer<Func1>::Object *receiver,
-                       Func1 slot)
+    static std::function<void(bool)> onExit(
+            const typename QtPrivate::FunctionPointer<Func1>::Object *receiver, Func1 slot)
     {
         typedef typename QtPrivate::FunctionPointer<Func1>::Object Object;
         const QPointer<Object> receiverPointer(const_cast<Object *>(receiver));
@@ -244,7 +248,7 @@ public:
                 (receiverPointer->*slot)();
         };
     }
-#endif // defined(__cpp_return_type_deduction) && __cpp_return_type_deduction == 201304
+#endif // !Q_QDOC
 
     QMetaObject::Connection connectToEvent(const QString &scxmlEventSpec,
                                            const QObject *receiver, const char *method,
diff --git a/tests/auto/compiled/compiled.pro b/tests/auto/compiled/compiled.pro
index c13cbf4..713f484 100644
--- a/tests/auto/compiled/compiled.pro
+++ b/tests/auto/compiled/compiled.pro
@@ -1,5 +1,5 @@
 QT = core gui qml testlib scxml
-CONFIG += testcase c++14
+CONFIG += testcase
 
 TARGET = tst_compiled
 CONFIG += console
diff --git a/tests/auto/compiled/tst_compiled.cpp b/tests/auto/compiled/tst_compiled.cpp
index 27e4a80..6ee181d 100644
--- a/tests/auto/compiled/tst_compiled.cpp
+++ b/tests/auto/compiled/tst_compiled.cpp
@@ -168,15 +168,12 @@ void tst_Compiled::connection()
     QMetaObject::Connection conB     = stateMachine.connectToState("b",     &receiverB,     SLOT(receive(bool)));
     QMetaObject::Connection conFinal = stateMachine.connectToState("final", &receiverFinal, SLOT(receive(bool)));
 
-#if defined(__cpp_return_type_deduction) && __cpp_return_type_deduction == 201304
-    // C++14 available: test for onEntry and onExit
     typedef QScxmlStateMachine QXSM;
     QMetaObject::Connection aEntry = stateMachine.connectToState("a", QXSM::onEntry(&receiverA, "enter"));
     QMetaObject::Connection aExit  = stateMachine.connectToState("a", QXSM::onExit(&receiverA, "exit"));
 
     QVERIFY(aEntry);
     QVERIFY(aExit);
-#endif
 
     QVERIFY(conA);
     QVERIFY(conA1);
diff --git a/tests/auto/statemachine/statemachine.pro b/tests/auto/statemachine/statemachine.pro
index 95bf9a8..0e4de1a 100644
--- a/tests/auto/statemachine/statemachine.pro
+++ b/tests/auto/statemachine/statemachine.pro
@@ -1,5 +1,5 @@
 QT = core gui qml testlib scxml-private
-CONFIG += testcase c++14
+CONFIG += testcase
 
 TARGET = tst_statemachine
 CONFIG += console
diff --git a/tests/auto/statemachine/tst_statemachine.cpp b/tests/auto/statemachine/tst_statemachine.cpp
index 1cf0518..9c757e7 100644
--- a/tests/auto/statemachine/tst_statemachine.cpp
+++ b/tests/auto/statemachine/tst_statemachine.cpp
@@ -183,8 +183,6 @@ void tst_StateMachine::connections()
     });
     QVERIFY(final);
 
-#if defined(__cpp_return_type_deduction) && __cpp_return_type_deduction == 201304
-    // C++14 available, test onEntry and onExit
     bool a1Entered = false;
     bool a1Exited = false;
     bool finalEntered = false;
@@ -219,7 +217,6 @@ void tst_StateMachine::connections()
         finalExited = true;
     }));
     QVERIFY(finalExit);
-#endif
 
     stateMachine->start();