Inspector: Fetch objects lazily

QML objects are fetched lazily when constructing the object tree.
Incase parents have not been previously fetched, we fetch the
required data to construct only the relevant branch of the tree.

Task-number: QTCREATORBUG-8246
Change-Id: Id529c3b2334d33ff4eb46b14f50cf042ad2960e2
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/debugger/qml/qmlinspectoragent.cpp

@@ -62,6 +62,7 @@ QmlInspectorAgent::QmlInspectorAgent(DebuggerEngine *engine, QObject *parent)
     , m_objectToSelect(-1)
     , m_newObjectsCreated(false)
 {
+    m_debugIdToIname.insert(-1, QByteArray("inspect"));
     connect(debuggerCore()->action(ShowQmlObjectTree),
             SIGNAL(valueChanged(QVariant)), SLOT(updateStatus()));
     m_delayQueryTimer.setSingleShot(true);
@@ -452,17 +453,17 @@ void QmlInspectorAgent::onResult(quint32 queryId, const QVariant &value,
     }
 
     if (m_objectTreeQueryIds.contains(queryId)) {
+        m_objectTreeQueryIds.removeOne(queryId);
         if (value.type() == QVariant::List) {
             QVariantList objList = value.toList();
             foreach (QVariant var, objList) {
                 // TODO: check which among the list is the actual
                 // object that needs to be selected.
-                insertObjectInTree(qvariant_cast<ObjectReference>(var));
+                verifyAndInsertObjectInTree(qvariant_cast<ObjectReference>(var));
             }
         } else {
-            insertObjectInTree(qvariant_cast<ObjectReference>(value));
+            verifyAndInsertObjectInTree(qvariant_cast<ObjectReference>(value));
         }
-        m_objectTreeQueryIds.removeOne(queryId);
     } else if (queryId == m_engineQueryId) {
         m_engineQueryId = 0;
         QList<EngineReference> engines = qvariant_cast<QList<EngineReference> >(value);
@@ -608,13 +609,13 @@ void QmlInspectorAgent::updateObjectTree(const ContextReference &context)
         return;
 
     foreach (const ObjectReference & obj, context.objects())
-        insertObjectInTree(obj);
+        verifyAndInsertObjectInTree(obj);
 
     foreach (const ContextReference &child, context.contexts())
         updateObjectTree(child);
 }
 
-void QmlInspectorAgent::insertObjectInTree(const ObjectReference &object)
+void QmlInspectorAgent::verifyAndInsertObjectInTree(const ObjectReference &object)
 {
     if (debug)
         qDebug() << __FUNCTION__ << '(' << object << ')';
@@ -622,17 +623,56 @@ void QmlInspectorAgent::insertObjectInTree(const ObjectReference &object)
     if (!object.isValid())
         return;
 
+    // Find out the correct position in the tree
+    // Objects are inserted to the tree if they satisfy one of the two conditions.
+    // Condition 1: Object is a root object i.e. parentId == -1.
+    // Condition 2: Object has an expanded parent i.e. siblings are known.
+    // If the two conditions are not met then we push the object to a stack and recursively
+    // fetch parents till we find a previously expanded parent.
+
+    WatchHandler *handler = m_debuggerEngine->watchHandler();
+    const int parentId = object.parentId();
+    const int objectDebugId = object.debugId();
+    if (m_debugIdToIname.contains(parentId)) {
+        QByteArray parentIname = m_debugIdToIname.value(parentId);
+        if (parentId != -1 && !handler->isExpandedIName(parentIname)) {
+            m_objectStack.push(object);
+            handler->model()->fetchMore(handler->watchDataIndex(parentIname));
+            return; // recursive
+        }
+        insertObjectInTree(object);
+
+    } else {
+        m_objectStack.push(object);
+        fetchObject(parentId);
+        return; // recursive
+    }
+    if (!m_objectStack.isEmpty()) {
+        const ObjectReference &top = m_objectStack.top();
+        // We want to expand only a particular branch and not the whole tree. Hence, we do not
+        // expand siblings.
+        if (object.children().contains(top)) {
+            QByteArray objectIname = m_debugIdToIname.value(objectDebugId);
+            if (!handler->isExpandedIName(objectIname)) {
+                handler->model()->fetchMore(handler->watchDataIndex(objectIname));
+            } else {
+                verifyAndInsertObjectInTree(m_objectStack.pop());
+                return; // recursive
+            }
+        }
+    }
+}
+
+void QmlInspectorAgent::insertObjectInTree(const ObjectReference &object)
+{
+    if (debug)
+        qDebug() << __FUNCTION__ << '(' << object << ')';
+
+    const int objectDebugId = object.debugId();
+    const int parentId = parentIdForIname(m_debugIdToIname.value(objectDebugId));
+
     QElapsedTimer timeElapsed;
-    // sync tree with watchhandler
     QList<WatchData> watchData;
-    int objectDebugId = object.debugId();
-
-    // When root items are inserted in the object tree, m_objectTreeQueryIds = 0
-    if (!m_debugIdToIname.contains(objectDebugId) && m_objectTreeQueryIds.count())
-        return;
-
-    int parentId = parentIdForIname(m_debugIdToIname.value(objectDebugId));
-
     if (debug)
         timeElapsed.start();
     watchData.append(buildWatchData(object, m_debugIdToIname.value(parentId), true));
@@ -829,6 +869,7 @@ void QmlInspectorAgent::clearObjectTree()
     m_debugIdHash.clear();
     m_debugIdHash.reserve(old_count + 1);
     m_debugIdToIname.clear();
+    m_debugIdToIname.insert(-1, QByteArray("inspect"));
     m_objectStack.clear();
     // reset only for qt > 4.8.3.
     if (m_engineClient->objectName() != QLatin1String(QDECLARATIVE_ENGINE))