Allow V4 bindings to be assigned to aliases

V4 bindings must be able to be retargetted for them to be assignable
to aliases.

Change-Id: I4d3addd0fdc90b9bf472c781d316f7f406eaf1d7
Reviewed-by: Chris Adams <christopher.adams@nokia.com>

6 files changed, 54 insertions, 32 deletions

diff --git a/src/qml/qml/qqmlabstractbinding_p.h b/src/qml/qml/qqmlabstractbinding_p.h
index 8c4aa4affc..ed414964f8 100644
--- a/src/qml/qml/qqmlabstractbinding_p.h
+++ b/src/qml/qml/qqmlabstractbinding_p.h
@@ -99,9 +99,8 @@ protected:
     void clear();
 
     // Called by QQmlPropertyPrivate to "move" a binding to a different property.
-    // This is only used for alias properties, and only used by QQmlBinding not
-    // V8 or V4 bindings.  The default implementation qFatal()'s to ensure that the
-    // method is never called for V4 or V8 bindings.
+    // This is only used for alias properties. The default implementation qFatal()'s
+    // to ensure that the method is never called for binding types that don't support it.
     virtual void retargetBinding(QObject *, int);
 private:
     Pointer weakPointer();
diff --git a/src/qml/qml/qqmlcompiler.cpp b/src/qml/qml/qqmlcompiler.cpp
index e409544c96..d5775b63f4 100644
--- a/src/qml/qml/qqmlcompiler.cpp
+++ b/src/qml/qml/qqmlcompiler.cpp
@@ -3428,6 +3428,7 @@ void QQmlCompiler::genBindingAssignment(QQmlScript::Value *binding,
         store.value = js.compiledIndex;
         store.context = js.bindingContext.stack;
         store.owner = js.bindingContext.owner;
+        store.isAlias = prop->isAlias;
         if (valueTypeProperty) {
             store.property = (valueTypeProperty->index & 0xFFFF) |
                              ((valueTypeProperty->type & 0xFF)) << 16 |
@@ -3542,21 +3543,18 @@ bool QQmlCompiler::completeComponentBuild()
 
         JSBindingReference &binding = *b;
 
-        // ### We don't currently optimize for bindings on alias's - because 
-        // of the solution to QTBUG-13719
-        if (!binding.property->isAlias) {
-            expr.context = binding.bindingContext.object;
-            expr.property = binding.property;
-            expr.expression = binding.expression;
-
-            int index = bindingCompiler.compile(expr, enginePrivate);
-            if (index != -1) {
-                binding.dataType = BindingReference::V4;
-                binding.compiledIndex = index;
-                if (componentStats)
-                    componentStats->componentStat.optimizedBindings.append(b->value->location);
-                continue;
-            } 
+        // First try v4
+        expr.context = binding.bindingContext.object;
+        expr.property = binding.property;
+        expr.expression = binding.expression;
+
+        int index = bindingCompiler.compile(expr, enginePrivate);
+        if (index != -1) {
+            binding.dataType = BindingReference::V4;
+            binding.compiledIndex = index;
+            if (componentStats)
+                componentStats->componentStat.optimizedBindings.append(b->value->location);
+            continue;
         }
 
         // Pre-rewrite the expression
diff --git a/src/qml/qml/qqmlinstruction_p.h b/src/qml/qml/qqmlinstruction_p.h
index cfc530df04..533734b622 100644
--- a/src/qml/qml/qqmlinstruction_p.h
+++ b/src/qml/qml/qqmlinstruction_p.h
@@ -240,6 +240,7 @@ union QQmlInstruction
         short context;
         short owner;
         bool isRoot;
+        bool isAlias;
         ushort line;
         ushort column;
     };
diff --git a/src/qml/qml/qqmlvme.cpp b/src/qml/qml/qqmlvme.cpp
index 898f598af4..093b6d1575 100644
--- a/src/qml/qml/qqmlvme.cpp
+++ b/src/qml/qml/qqmlvme.cpp
@@ -831,12 +831,21 @@ QObject *QQmlVME::run(QList<QQmlError> *errors,
             bindValues.push(binding);
             binding->m_mePtr = &bindValues.top();
 
-            Q_ASSERT(binding->propertyIndex() == (property & 0xFF00FFFF));
-            Q_ASSERT(binding->object() == target);
+            if (instr.isAlias) {
+                QQmlAbstractBinding *old =
+                    QQmlPropertyPrivate::setBindingNoEnable(target,
+                                                            instr.property & 0xFFFF,
+                                                            instr.property >> 24,
+                                                            binding);
+                if (old) { old->destroy(); }
+            } else {
+                Q_ASSERT(binding->propertyIndex() == (property & 0xFF00FFFF));
+                Q_ASSERT(binding->object() == target);
 
-            CLEAN_PROPERTY(target, property & 0xFF00FFFF);
+                CLEAN_PROPERTY(target, property & 0xFF00FFFF);
 
-            binding->addToObject();
+                binding->addToObject();
+            }
         QML_END_INSTR(StoreV4Binding)
 
         QML_BEGIN_INSTR(StoreV8Binding)
diff --git a/src/qml/qml/v4/qv4bindings.cpp b/src/qml/qml/v4/qv4bindings.cpp
index 944d4de210..e19d74370c 100644
--- a/src/qml/qml/v4/qv4bindings.cpp
+++ b/src/qml/qml/v4/qv4bindings.cpp
@@ -319,13 +319,21 @@ void QV4Bindings::Binding::destroy()
 
 int QV4Bindings::Binding::propertyIndex() const
 {
+    if (target.hasValue()) return target.constValue()->targetProperty;
     //mask out the type information set for value types
-    return property & 0xFF00FFFF;
+    else return property & 0xFF00FFFF;
 }
 
 QObject *QV4Bindings::Binding::object() const
 {
-    return target;
+    if (target.hasValue()) return target.constValue()->target;
+    return *target;
+}
+
+void QV4Bindings::Binding::retargetBinding(QObject *t, int i)
+{
+    target.value().target = t;
+    target.value().targetProperty = i;
 }
 
 void QV4Bindings::Subscription::subscriptionCallback(QQmlNotifierEndpoint *e, void **)
@@ -359,7 +367,7 @@ void QV4Bindings::run(Binding *binding, QQmlPropertyPrivate::WriteFlags flags)
         return;
 
     // Check that the target has not been deleted
-    if (QQmlData::wasDeleted(binding->target))
+    if (QQmlData::wasDeleted(*binding->target))
         return;
 
     QQmlTrace trace("V4 Binding Update");
@@ -383,7 +391,7 @@ void QV4Bindings::run(Binding *binding, QQmlPropertyPrivate::WriteFlags flags)
         } else {
             name = QLatin1String(binding->target->metaObject()->property(binding->property).name());
         }
-        qmlInfo(binding->target) << tr("Binding loop detected for property \"%1\"").arg(name);
+        qmlInfo(*binding->target) << tr("Binding loop detected for property \"%1\"").arg(name);
         return;
     }
 
@@ -393,14 +401,14 @@ void QV4Bindings::run(Binding *binding, QQmlPropertyPrivate::WriteFlags flags)
 
         QQmlValueType *vt = ep->valueTypes[(binding->property >> 16) & 0xFF];
         Q_ASSERT(vt);
-        vt->read(binding->target, binding->property & 0xFFFF);
+        vt->read(*binding->target, binding->property & 0xFFFF);
 
         QObject *target = vt;
         run(binding->index, binding->executedBlocks, context, binding, binding->scope, target, flags);
 
-        vt->write(binding->target, binding->property & 0xFFFF, flags);
+        vt->write(*binding->target, binding->property & 0xFFFF, flags);
     } else {
-        QQmlData *data = QQmlData::get(binding->target);
+        QQmlData *data = QQmlData::get(*binding->target);
         QQmlPropertyData *propertyData = (data && data->propertyCache ? data->propertyCache->property(binding->property) : 0);
 
         if (propertyData && propertyData->isVMEProperty()) {
@@ -408,9 +416,9 @@ void QV4Bindings::run(Binding *binding, QQmlPropertyPrivate::WriteFlags flags)
             v8::HandleScope handle_scope;
             v8::Context::Scope context_scope(QQmlEnginePrivate::get(context->engine)->v8engine()->context());
 
-            run(binding->index, binding->executedBlocks, context, binding, binding->scope, binding->target, flags);
+            run(binding->index, binding->executedBlocks, context, binding, binding->scope, *binding->target, flags);
         } else {
-            run(binding->index, binding->executedBlocks, context, binding, binding->scope, binding->target, flags);
+            run(binding->index, binding->executedBlocks, context, binding, binding->scope, *binding->target, flags);
         }
     }
     binding->updating = false;
diff --git a/src/qml/qml/v4/qv4bindings_p.h b/src/qml/qml/v4/qv4bindings_p.h
index 78a3f9bab3..8ceccbb731 100644
--- a/src/qml/qml/v4/qv4bindings_p.h
+++ b/src/qml/qml/v4/qv4bindings_p.h
@@ -56,6 +56,7 @@
 #include "private/qqmlexpression_p.h"
 #include "private/qqmlbinding_p.h"
 #include "private/qv4instruction_p.h"
+#include "private/qpointervaluepair_p.h"
 
 QT_BEGIN_HEADER
 
@@ -91,8 +92,14 @@ private:
         virtual void update(QQmlPropertyPrivate::WriteFlags flags);
         virtual void destroy();
         virtual int propertyIndex() const;
+        virtual void retargetBinding(QObject *, int);
         virtual QObject *object() const;
 
+        struct Retarget {
+            QObject *target;
+            int targetProperty;
+        };
+
         int index:30;
         bool enabled:1;
         bool updating:1;
@@ -102,7 +109,7 @@ private:
         QObject *scope;
         int line;
         int column;
-        QObject *target;
+        QPointerValuePair<QObject, Retarget> target;
         quint32 executedBlocks;
 
         QV4Bindings *parent;