Improve support for var properties

This commit changes the semantics of function assignment in QML.
Previously, function assignment was interpreted as binding assignment.
Now, function assignment is interpreted as function assignment, and
therefore fails for all property types other than "var" properties.

To support imperative binding assignment, a new function was added to
the Qt object: Qt.binding(function) which takes a single function
parameter and returns a function object which will be interpreted as
an assignable binding expression by the QML engine.

Finally, this commit also slightly changes the semantics of var
properties in that the "special" JavaScript values of null and
undefined may be assigned to var properties, rather than being
interpreted as reset requests.

Task-number: QTBUG-21842
Change-Id: Iee99a878b9badf0fb76e983da7ebfa493f55ceb5
Reviewed-by: Matthew Vogt <matthew.vogt@nokia.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/qml/qml/v8/qv8engine_p.h b/src/qml/qml/v8/qv8engine_p.h
index bc57b27085..825d7a3583 100644
--- a/src/qml/qml/v8/qv8engine_p.h
+++ b/src/qml/qml/v8/qv8engine_p.h
@@ -357,6 +357,9 @@ public:
     // a QVariant wrapper
     inline v8::Handle<v8::Value> newQVariant(const QVariant &);
 
+    // Return the JS string key for the "function is a binding" flag
+    inline v8::Handle<v8::String> bindingFlagKey() const;
+
     // Return the network access manager for this engine.  By default this returns the network
     // access manager of the QQmlEngine.  It is overridden in the case of a threaded v8
     // instance (like in WorkerScript).
@@ -461,6 +464,8 @@ protected:
     v8::Persistent<v8::Context> m_context;
     QScriptOriginalGlobalObject m_originalGlobalObject;
 
+    v8::Persistent<v8::String> m_bindingFlagKey;
+
     QV8StringWrapper m_stringWrapper;
     QV8ContextWrapper m_contextWrapper;
     QV8QObjectWrapper m_qobjectWrapper;
@@ -609,6 +614,11 @@ v8::Handle<v8::Value> QV8Engine::newSequence(int sequenceType, QObject *object,
     return m_sequenceWrapper.newSequence(sequenceType, object, property, succeeded);
 }
 
+v8::Handle<v8::String> QV8Engine::bindingFlagKey() const
+{
+    return m_bindingFlagKey;
+}
+
 // XXX Can this be made more optimal?  It is called prior to resolving each and every 
 // unqualified name in QV8ContextWrapper.
 bool QV8Engine::startsWithUpper(v8::Handle<v8::String> string)