Add CONSTANT attribute to Q_PROPERTY()

This will be used by the declarative module to determine if a property lacking a NOTIFY signal is truly constant, or just missing a NOTIFY signal.

Reviewed-by: Roberto Raggi

8 files changed, 86 insertions, 4 deletions

diff --git a/doc/src/properties.qdoc b/doc/src/properties.qdoc
index 5490dd0..cac5016 100644
--- a/doc/src/properties.qdoc
+++ b/doc/src/properties.qdoc
@@ -122,6 +122,12 @@
     editable property for (checkable) buttons. Note that QItemDelegate
     gets and sets a widget's \c USER property.
 
+    \o The presence of the \c CONSTANT attibute indicates that the property 
+    value is constant.  For a given object instance, the READ method of a 
+    constant property must return the same value every time it is called.  This
+    constant value may be different for different instances of the object.  A
+    constant property cannot have a WRTE method or a NOTIFY signal.
+
     \endlist
 
     The \c READ, \c WRITE, and \c RESET functions can be inherited.
diff --git a/doc/src/snippets/code/doc_src_properties.qdoc b/doc/src/snippets/code/doc_src_properties.qdoc
index 377cc9c..64e5377 100644
--- a/doc/src/snippets/code/doc_src_properties.qdoc
+++ b/doc/src/snippets/code/doc_src_properties.qdoc
@@ -7,7 +7,8 @@ Q_PROPERTY(type name
            [DESIGNABLE bool]
            [SCRIPTABLE bool]
            [STORED bool]
-	   [USER bool])
+	   [USER bool]
+           [CONSTANT])
 //! [0]
 
 
diff --git a/src/corelib/kernel/qmetaobject.cpp b/src/corelib/kernel/qmetaobject.cpp
index 08cecaf..fee2da9 100644
--- a/src/corelib/kernel/qmetaobject.cpp
+++ b/src/corelib/kernel/qmetaobject.cpp
@@ -159,7 +159,9 @@ enum PropertyFlags  {
     ResolveEditable = 0x00080000,
     User = 0x00100000,
     ResolveUser = 0x00200000,
-    Notify = 0x00400000
+    Notify = 0x00400000,
+    Dynamic = 0x00800000,
+    Constant = 0x00000400
 };
 
 enum MethodFlags  {
@@ -2439,6 +2441,31 @@ bool QMetaProperty::isUser(const QObject *object) const
 }
 
 /*!
+    \internal
+*/
+bool QMetaProperty::isDynamic() const
+{
+    if (!mobj)
+        return false;
+    int flags = mobj->d.data[handle + 2];
+    return flags & Dynamic;
+}
+
+/*!
+    Returns true if the property is constant; otherwise returns false.
+
+    A property is constant if the \c{Q_PROPERTY()}'s \c CONSTANT attribute
+    is set.
+*/
+bool QMetaProperty::isConstant() const
+{
+    if (!mobj)
+        return false;
+    int flags = mobj->d.data[handle + 2];
+    return flags & Constant;
+}
+
+/*!
     \obsolete
 
     Returns true if the property is editable for the given \a object;
diff --git a/src/corelib/kernel/qmetaobject.h b/src/corelib/kernel/qmetaobject.h
index 000ba6e..73b52a9 100644
--- a/src/corelib/kernel/qmetaobject.h
+++ b/src/corelib/kernel/qmetaobject.h
@@ -187,6 +187,8 @@ public:
     bool isStored(const QObject *obj = 0) const;
     bool isEditable(const QObject *obj = 0) const;
     bool isUser(const QObject *obj = 0) const;
+    bool isDynamic() const;
+    bool isConstant() const;
 
     bool isFlagType() const;
     bool isEnumType() const;
diff --git a/src/tools/moc/generator.cpp b/src/tools/moc/generator.cpp
index b872dfd..e4086e6 100644
--- a/src/tools/moc/generator.cpp
+++ b/src/tools/moc/generator.cpp
@@ -66,7 +66,9 @@ enum PropertyFlags  {
     ResolveEditable = 0x00080000,
     User = 0x00100000,
     ResolveUser = 0x00200000,
-    Notify = 0x00400000
+    Notify = 0x00400000,
+    Dynamic = 0x00800000,
+    Constant = 0x00000400
 };
 enum MethodFlags {
     AccessPrivate = 0x00,
@@ -597,6 +599,9 @@ void Generator::generateProperties()
         if (p.notifyId != -1)
             flags |= Notify;
 
+        if (p.constant)
+            flags |= Constant;
+
         fprintf(out, "    %4d, %4d, ",
                 strreg(p.name),
                 strreg(p.type));
diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index 797595f..66012ca 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -908,6 +908,12 @@ void Moc::parseProperty(ClassDef *def)
     propDef.name = lexem();
     while (test(IDENTIFIER)) {
         QByteArray l = lexem();
+
+        if (l[0] == 'C' && l == "CONSTANT") {
+            propDef.constant = true;
+            continue;
+        }
+
         QByteArray v, v2;
         if (test(LPAREN)) {
             v = lexemUntil(RPAREN);
@@ -963,6 +969,23 @@ void Moc::parseProperty(ClassDef *def)
         msg += " has no READ accessor function. The property will be invalid.";
         warning(msg.constData());
     }
+    if (propDef.constant && !propDef.write.isNull()) {
+        QByteArray msg;
+        msg += "Property declaration ";
+        msg += propDef.name;
+        msg += " is both WRITEable and CONSTANT. CONSTANT will be ignored.";
+        propDef.constant = false;
+        warning(msg.constData());
+    }
+    if (propDef.constant && !propDef.notify.isNull()) {
+        QByteArray msg;
+        msg += "Property declaration ";
+        msg += propDef.name;
+        msg += " is both NOTIFYable and CONSTANT. CONSTANT will be ignored.";
+        propDef.constant = false;
+        warning(msg.constData());
+    }
+
     if(!propDef.notify.isEmpty())
         def->notifyableProperties++;
 
diff --git a/src/tools/moc/moc.h b/src/tools/moc/moc.h
index 9fa9ac2..494d53e 100644
--- a/src/tools/moc/moc.h
+++ b/src/tools/moc/moc.h
@@ -115,9 +115,10 @@ struct FunctionDef
 
 struct PropertyDef
 {
-    PropertyDef():notifyId(-1), gspec(ValueSpec){}
+    PropertyDef():notifyId(-1), constant(false), gspec(ValueSpec){}
     QByteArray name, type, read, write, reset, designable, scriptable, editable, stored, user, notify;
     int notifyId;
+    bool constant;
     enum Specification  { ValueSpec, ReferenceSpec, PointerSpec };
     Specification gspec;
     bool stdCppSet() const {
diff --git a/tests/auto/qmetaobject/tst_qmetaobject.cpp b/tests/auto/qmetaobject/tst_qmetaobject.cpp
index dea0ffb..f4cff2b 100644
--- a/tests/auto/qmetaobject/tst_qmetaobject.cpp
+++ b/tests/auto/qmetaobject/tst_qmetaobject.cpp
@@ -108,6 +108,7 @@ class tst_QMetaObject : public QObject
     Q_PROPERTY(int value6 READ value6 NOTIFY value6Changed)
     Q_PROPERTY(MyStruct value7 READ value7 WRITE setVal7 NOTIFY value7Changed)
     Q_PROPERTY(int value8 READ value8 NOTIFY value8Changed)
+    Q_PROPERTY(int value9 READ value9 CONSTANT)
 
 public:
     enum EnumType { EnumType1 };
@@ -137,6 +138,8 @@ public:
 
     int value8() const { return 1; }
 
+    int value9() const { return 1; }
+
     QList<QVariant> value4;
     QVariantList value5;
 
@@ -159,6 +162,7 @@ private slots:
     void customPropertyType();
     void checkScope();
     void propertyNotify();
+    void propertyConstant();
 
     void stdSet();
     void classInfo();
@@ -785,6 +789,19 @@ void tst_QMetaObject::propertyNotify()
     QCOMPARE(signal.signature(), (const char *)0);
 }
 
+void tst_QMetaObject::propertyConstant()
+{
+    const QMetaObject *mo = metaObject();
+
+    QMetaProperty prop = mo->property(mo->indexOfProperty("value8"));
+    QVERIFY(prop.isValid());
+    QVERIFY(!prop.isConstant());
+
+    prop = mo->property(mo->indexOfProperty("value9"));
+    QVERIFY(prop.isValid());
+    QVERIFY(prop.isConstant());
+}
+
 class ClassInfoTestObjectA : public QObject
 {
     Q_OBJECT