Add support for initializer_list construction in QFlags

[ChangeLog][QtCore][QFlags] Added initializer_list constructor

Task-number: QTBUG-39786
Change-Id: I36967c67b489c2a893fb031954f46f5243aba2c4
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 51 insertions, 0 deletions

diff --git a/src/corelib/global/qflags.h b/src/corelib/global/qflags.h
index 9e97724fec..d7b673bc1f 100644
--- a/src/corelib/global/qflags.h
+++ b/src/corelib/global/qflags.h
@@ -47,6 +47,10 @@
 #include <QtCore/qtypeinfo.h>
 #include <QtCore/qtypetraits.h>
 
+#ifdef Q_COMPILER_INITIALIZER_LISTS
+#include <initializer_list>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 class QFlag
@@ -107,6 +111,11 @@ public:
     Q_DECL_CONSTEXPR inline QFlags(Zero = 0) : i(0) {}
     Q_DECL_CONSTEXPR inline QFlags(QFlag f) : i(f) {}
 
+#ifdef Q_COMPILER_INITIALIZER_LISTS
+    Q_DECL_CONSTEXPR inline QFlags(std::initializer_list<Enum> flags)
+        : i(initializer_list_helper(flags.begin(), flags.end())) {}
+#endif
+
     inline QFlags &operator&=(int mask) { i &= mask; return *this; }
     inline QFlags &operator&=(uint mask) { i &= mask; return *this; }
     inline QFlags &operator&=(Enum mask) { i &= Int(mask); return *this; }
@@ -130,6 +139,14 @@ public:
 
     Q_DECL_CONSTEXPR inline bool testFlag(Enum f) const { return (i & Int(f)) == Int(f) && (Int(f) != 0 || i == Int(f) ); }
 private:
+#ifdef Q_COMPILER_INITIALIZER_LISTS
+    Q_DECL_CONSTEXPR static inline Int initializer_list_helper(typename std::initializer_list<Enum>::const_iterator it,
+                                                               typename std::initializer_list<Enum>::const_iterator end)
+    {
+        return (it == end ? Int(0) : (Int(*it) | initializer_list_helper(it + 1, end)));
+    }
+#endif
+
     Int i;
 };
 
diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index 98460481ca..56d8ea197f 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -270,6 +270,16 @@ Q_STATIC_ASSERT_X(UCHAR_MAX == 255, "Qt assumes that char is 8 bits");
 */
 
 /*!
+    \fn QFlags::QFlags(std::initializer_list<Enum> flags)
+    \since 5.4
+
+    Constructs a QFlags object initialized with all \a flags
+    combined using the bitwise OR operator.
+
+    \sa operator|=(), operator|()
+*/
+
+/*!
     \fn QFlags &QFlags::operator=(const QFlags &other)
 
     Assigns \a other to this object and returns a reference to this
diff --git a/tests/auto/corelib/global/qflags/tst_qflags.cpp b/tests/auto/corelib/global/qflags/tst_qflags.cpp
index 73a69a1309..42add6150a 100644
--- a/tests/auto/corelib/global/qflags/tst_qflags.cpp
+++ b/tests/auto/corelib/global/qflags/tst_qflags.cpp
@@ -50,6 +50,7 @@ private slots:
     void constExpr();
     void signedness();
     void classEnum();
+    void initializerLists();
 };
 
 void tst_QFlags::testFlag() const
@@ -143,6 +144,9 @@ enum class MyStrictEnum { StrictZero, StrictOne, StrictTwo, StrictFour=4 };
 Q_DECLARE_FLAGS( MyStrictFlags, MyStrictEnum )
 Q_DECLARE_OPERATORS_FOR_FLAGS( MyStrictFlags )
 
+enum class MyStrictNoOpEnum { StrictZero, StrictOne, StrictTwo, StrictFour=4 };
+Q_DECLARE_FLAGS( MyStrictNoOpFlags, MyStrictNoOpEnum )
+
 Q_STATIC_ASSERT( !QTypeInfo<MyStrictFlags>::isComplex );
 Q_STATIC_ASSERT( !QTypeInfo<MyStrictFlags>::isStatic );
 Q_STATIC_ASSERT( !QTypeInfo<MyStrictFlags>::isLarge );
@@ -253,6 +257,26 @@ void tst_QFlags::classEnum()
 #endif
 }
 
+void tst_QFlags::initializerLists()
+{
+#if defined(Q_COMPILER_INITIALIZER_LISTS)
+    Qt::MouseButtons bts = { Qt::LeftButton, Qt::RightButton };
+    QVERIFY(bts.testFlag(Qt::LeftButton));
+    QVERIFY(bts.testFlag(Qt::RightButton));
+    QVERIFY(!bts.testFlag(Qt::MiddleButton));
+
+#if defined(Q_COMPILER_CLASS_ENUM)
+    MyStrictNoOpFlags flags = { MyStrictNoOpEnum::StrictOne, MyStrictNoOpEnum::StrictFour };
+    QVERIFY(flags.testFlag(MyStrictNoOpEnum::StrictOne));
+    QVERIFY(flags.testFlag(MyStrictNoOpEnum::StrictFour));
+    QVERIFY(!flags.testFlag(MyStrictNoOpEnum::StrictTwo));
+#endif // Q_COMPILER_CLASS_ENUM
+
+#else
+    QSKIP("This test requires C++11 initializer_list support.");
+#endif // Q_COMPILER_INITIALIZER_LISTS
+}
+
 // (statically) check QTypeInfo for QFlags instantiations:
 enum MyEnum { Zero, One, Two, Four=4 };
 Q_DECLARE_FLAGS( MyFlags, MyEnum )