QDeclarativeEnginePrivate: fix and encapsulate the usage of scopeChainValue

Reduce the places that we make a direct reference to the
scopeChainValue (and the "-3" position) by providing a higher level
function that gets the scopeNode of the Declarative Context that
is in the current execution.

This commit also fixes the offset of the wanted nodes in the scope
chain. In the long term we still need to get rid of this scope chain
direct manipulation if possible.

Reviewed-by: Olivier Goffart

Author: Caio Marcelo de Oliveira Filho

src/declarative/qml/qdeclarativeengine.cpp

@@ -1262,9 +1262,8 @@ QScriptValue QDeclarativeEnginePrivate::qmlScriptObject(QObject* object,
 */
 QDeclarativeContextData *QDeclarativeEnginePrivate::getContext(QScriptContext *ctxt)
 {
-    QScriptValue scopeNode = QScriptDeclarativeClass::scopeChainValue(ctxt, -3);
+    QScriptValue scopeNode = getEvaluationContextScopeNode(ctxt);
     Q_ASSERT(scopeNode.isValid());
-    Q_ASSERT(QScriptDeclarativeClass::scriptClass(scopeNode) == contextClass);
     return contextClass->contextFromValue(scopeNode);
 }
 
@@ -1274,12 +1273,24 @@ QDeclarativeContextData *QDeclarativeEnginePrivate::getContext(QScriptContext *c
 */
 QUrl QDeclarativeEnginePrivate::getUrl(QScriptContext *ctxt)
 {
-    QScriptValue scopeNode = QScriptDeclarativeClass::scopeChainValue(ctxt, -3);
+    QScriptValue scopeNode = getEvaluationContextScopeNode(ctxt);
     Q_ASSERT(scopeNode.isValid());
-    Q_ASSERT(QScriptDeclarativeClass::scriptClass(scopeNode) == contextClass);
     return contextClass->urlFromValue(scopeNode);
 }
 
+/*!
+    When valid, the returned QScriptValue contains the object that represents the
+    outer QDeclarativeContext of the current execution.
+*/
+QScriptValue QDeclarativeEnginePrivate::getEvaluationContextScopeNode(QScriptContext *context)
+{
+    Q_ASSERT(context);
+    QScriptValue scopeNode = QScriptDeclarativeClass::scopeChainValue(context, -4);
+    if (scopeNode.isValid())
+        Q_ASSERT(QScriptDeclarativeClass::scriptClass(scopeNode) == contextClass);
+    return scopeNode;
+}
+
 QString QDeclarativeEnginePrivate::urlToLocalFileOrQrc(const QUrl& url)
 {
     if (url.scheme().compare(QLatin1String("qrc"), Qt::CaseInsensitive) == 0) {

src/declarative/qml/qdeclarativeengine_p.h

@@ -340,6 +340,7 @@ class Q_AUTOTEST_EXPORT QDeclarativeEnginePrivate : public QObjectPrivate
     static QDeclarativeEngine *get(QDeclarativeEnginePrivate *p) { return p->q_func(); }
     QDeclarativeContextData *getContext(QScriptContext *);
     QUrl getUrl(QScriptContext *);
+    QScriptValue getEvaluationContextScopeNode(QScriptContext *);
 
     static QString urlToLocalFileOrQrc(const QUrl& url);
 

src/declarative/qml/qdeclarativeinclude.cpp

@@ -57,10 +57,11 @@ QDeclarativeInclude::QDeclarativeInclude(const QUrl &url,
 : QObject(engine), m_engine(engine), m_network(0), m_reply(0), m_http://github.com/url(url), m_redirectCount(0)
 {
     QDeclarativeEnginePrivate *ep = QDeclarativeEnginePrivate::get(engine);
-    m_context = ep->contextClass->contextFromValue(QScriptDeclarativeClass::scopeChainValue(ctxt, -3));
+    m_context = ep->contextClass->contextFromValue(ep->getEvaluationContextScopeNode(ctxt));
+    // ### Can/Should we assume m_context != 0? If so, why not use ep->getContext?
 
-    m_scope[0] = QScriptDeclarativeClass::scopeChainValue(ctxt, -4);
-    m_scope[1] = QScriptDeclarativeClass::scopeChainValue(ctxt, -5);
+    m_scope[0] = QScriptDeclarativeClass::scopeChainValue(ctxt, -5);
+    m_scope[1] = QScriptDeclarativeClass::scopeChainValue(ctxt, -6);
 
     m_scriptEngine = QDeclarativeEnginePrivate::getScriptEngine(engine);
     m_network = QDeclarativeScriptEngine::get(m_scriptEngine)->networkAccessManager();
@@ -181,8 +182,7 @@ QScriptValue QDeclarativeInclude::include(QScriptContext *ctxt, QScriptEngine *e
         return engine->undefinedValue();
 
     QDeclarativeEnginePrivate *ep = QDeclarativeEnginePrivate::get(engine);
-
-    QUrl contextUrl = ep->contextClass->urlFromValue(QScriptDeclarativeClass::scopeChainValue(ctxt, -3));
+    QUrl contextUrl = ep->contextClass->urlFromValue(ep->getEvaluationContextScopeNode(ctxt));
     if (contextUrl.isEmpty()) 
         return ctxt->throwError(QLatin1String("Qt.include(): Can only be called from JavaScript files"));
 
@@ -216,12 +216,13 @@ QScriptValue QDeclarativeInclude::include(QScriptContext *ctxt, QScriptEngine *e
             QString code = QString::fromUtf8(data);
 
             QDeclarativeContextData *context = 
-                ep->contextClass->contextFromValue(QScriptDeclarativeClass::scopeChainValue(ctxt, -3));
+                ep->contextClass->contextFromValue(ep->getEvaluationContextScopeNode(ctxt));
+            // ### Can/Should we assume context != 0, if so we can use ep->getContext()
 
             QScriptContext *scriptContext = QScriptDeclarativeClass::pushCleanContext(engine);
             scriptContext->pushScope(ep->contextClass->newUrlContext(context, 0, urlString));
             scriptContext->pushScope(ep->globalClass->staticGlobalObject());
-            QScriptValue scope = QScriptDeclarativeClass::scopeChainValue(ctxt, -5);
+            QScriptValue scope = QScriptDeclarativeClass::scopeChainValue(ctxt, -6);
             scriptContext->pushScope(scope);
             scriptContext->setActivationObject(scope);
             QDeclarativeScriptParser::extractPragmas(code);
@@ -255,7 +256,7 @@ QScriptValue QDeclarativeInclude::worker_include(QScriptContext *ctxt, QScriptEn
     QString urlString = ctxt->argument(0).toString();
     QUrl url(ctxt->argument(0).toString());
     if (url.isRelative()) {
-        QString contextUrl = QScriptDeclarativeClass::scopeChainValue(ctxt, -3).data().toString();
+        QString contextUrl = QScriptDeclarativeClass::scopeChainValue(ctxt, -4).data().toString();
         Q_ASSERT(!contextUrl.isEmpty());
 
         url = QUrl(contextUrl).resolved(url);
@@ -281,7 +282,7 @@ QScriptValue QDeclarativeInclude::worker_include(QScriptContext *ctxt, QScriptEn
             urlContext.setData(QScriptValue(engine, urlString));
             scriptContext->pushScope(urlContext);
 
-            QScriptValue scope = QScriptDeclarativeClass::scopeChainValue(ctxt, -4);
+            QScriptValue scope = QScriptDeclarativeClass::scopeChainValue(ctxt, -5);
             scriptContext->pushScope(scope);
             scriptContext->setActivationObject(scope);
             QDeclarativeScriptParser::extractPragmas(code);

src/declarative/qml/qdeclarativeobjectscriptclass.cpp

@@ -177,13 +177,9 @@ QDeclarativeObjectScriptClass::queryProperty(QObject *obj, const Identifier &nam
 
     if (!(hints & SkipAttachedProperties)) {
         if (!evalContext && context()) {
-            // Global object, QScriptContext activation object, QDeclarativeContext object
-            QScriptValue scopeNode = scopeChainValue(context(), -3);
-            if (scopeNode.isValid()) {
-                Q_ASSERT(scriptClass(scopeNode) == enginePrivate->contextClass);
-
+            QScriptValue scopeNode = enginePrivate->getEvaluationContextScopeNode(context());
+            if (scopeNode.isValid())
                 evalContext = enginePrivate->contextClass->contextFromValue(scopeNode);
-            }
         }
 
         if (evalContext && evalContext->imports) {
@@ -351,13 +347,9 @@ void QDeclarativeObjectScriptClass::setProperty(QObject *obj,
     QDeclarativeEnginePrivate *enginePriv = QDeclarativeEnginePrivate::get(engine);
 
     if (!evalContext) {
-        // Global object, QScriptContext activation object, QDeclarativeContext object
-        QScriptValue scopeNode = scopeChainValue(context, -3);
-        if (scopeNode.isValid()) {
-            Q_ASSERT(scriptClass(scopeNode) == enginePriv->contextClass);
-
+        QScriptValue scopeNode = enginePriv->getEvaluationContextScopeNode(context);
+        if (scopeNode.isValid())
             evalContext = enginePriv->contextClass->contextFromValue(scopeNode);
-        }
     }
 
     QDeclarativeBinding *newBinding = 0;