Moved the QML Observer Service and related functionality into Qt

This code was previously developed as part of Qt Creator in
share/qtcreator/qml/qmljsdebugger/

Moving it into Qt will allow us to simplify the setup required before
you can debug QML applications.

To avoid adding too much weight to the QtDeclarative module, a
declarativeobserver plugin was introduced that contains the
QDeclarativeViewObserver and related classes. The
QDeclarativeObserverService is just a stub service that loads this
plugin once a QML debugging client connects. The plugin implements the
QDeclarativeObserverInterface

A QJSDebugService was separated out of QJSDebuggerAgent, so
that the service can be active while the agent is instantiated lazily.
Each QDeclarativeEngine adds itself to the QJSDebugService. Currently
only the first one is used when instantiating the agent.

QDeclarativeObserverService is hooked into QDeclarativeView, with the
view registering itself to the service, allowing the
QDeclarativeViewObserver to be created for the view once somebody
connects to the service. Again, only the first view is used at the
moment.

Change-Id: Ib50579c6d24361c2b39528e5556410d3446c2e90
Reviewed-by: Martin Jones
Reviewed-by: Michael Brasser

7 files changed, 1314 insertions, 2 deletions

diff --git a/src/declarative/debugger/debugger.pri b/src/declarative/debugger/debugger.pri
index 75287b4563..044db3c756 100644
--- a/src/declarative/debugger/debugger.pri
+++ b/src/declarative/debugger/debugger.pri
@@ -8,7 +8,10 @@ SOURCES += \
     $$PWD/qdeclarativedebug.cpp \
     $$PWD/qdeclarativedebugtrace.cpp \
     $$PWD/qdeclarativedebughelper.cpp \
-    $$PWD/qdeclarativedebugserver.cpp
+    $$PWD/qdeclarativedebugserver.cpp \
+    $$PWD/qdeclarativeobserverservice.cpp \
+    $$PWD/qjsdebuggeragent.cpp \
+    $$PWD/qjsdebugservice.cpp
 
 HEADERS += \
     $$PWD/qdeclarativedebuggerstatus_p.h \
@@ -20,4 +23,8 @@ HEADERS += \
     $$PWD/qdeclarativedebugtrace_p.h \
     $$PWD/qdeclarativedebughelper_p.h \
     $$PWD/qdeclarativedebugserver_p.h \
-    debugger/qdeclarativedebugserverconnection_p.h
+    $$PWD/qdeclarativedebugserverconnection_p.h \
+    $$PWD/qdeclarativeobserverservice_p.h \
+    $$PWD/qdeclarativeobserverinterface_p.h \
+    $$PWD/qjsdebuggeragent_p.h \
+    $$PWD/qjsdebugservice_p.h
diff --git a/src/declarative/debugger/qdeclarativeobserverservice.cpp b/src/declarative/debugger/qdeclarativeobserverservice.cpp
new file mode 100644
index 0000000000..a623c55d05
--- /dev/null
+++ b/src/declarative/debugger/qdeclarativeobserverservice.cpp
@@ -0,0 +1,137 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "private/qdeclarativeobserverservice_p.h"
+#include "private/qdeclarativeobserverinterface_p.h"
+
+#include <QtCore/QCoreApplication>
+#include <QtCore/QDebug>
+#include <QtCore/QDir>
+#include <QtCore/QPluginLoader>
+
+#include <QtDeclarative/QDeclarativeView>
+
+QT_BEGIN_NAMESPACE
+
+Q_GLOBAL_STATIC(QDeclarativeObserverService, serviceInstance)
+
+QDeclarativeObserverService::QDeclarativeObserverService()
+    : QDeclarativeDebugService(QLatin1String("QDeclarativeObserverMode"))
+    , m_observer(0)
+{
+}
+
+QDeclarativeObserverService *QDeclarativeObserverService::instance()
+{
+    return serviceInstance();
+}
+
+void QDeclarativeObserverService::addView(QDeclarativeView *view)
+{
+    m_views.append(view);
+}
+
+void QDeclarativeObserverService::removeView(QDeclarativeView *view)
+{
+    m_views.removeAll(view);
+}
+
+void QDeclarativeObserverService::sendMessage(const QByteArray &message)
+{
+    if (status() != Enabled)
+        return;
+
+    QDeclarativeDebugService::sendMessage(message);
+}
+
+void QDeclarativeObserverService::statusChanged(Status status)
+{
+    if (m_views.isEmpty())
+        return;
+
+    if (status == Enabled) {
+        if (!m_observer)
+            m_observer = loadObserverPlugin();
+
+        if (!m_observer) {
+            qWarning() << "Error while loading observer plugin";
+            return;
+        }
+
+        m_observer->activate();
+    } else {
+        if (m_observer)
+            m_observer->deactivate();
+    }
+}
+
+void QDeclarativeObserverService::messageReceived(const QByteArray &message)
+{
+    emit gotMessage(message);
+}
+
+QDeclarativeObserverInterface *QDeclarativeObserverService::loadObserverPlugin()
+{
+    QStringList pluginCandidates;
+    const QStringList paths = QCoreApplication::libraryPaths();
+    foreach (const QString &libPath, paths) {
+        const QDir dir(libPath + QLatin1String("/qmltooling"));
+        if (dir.exists())
+            foreach (const QString &pluginPath, dir.entryList(QDir::Files))
+                pluginCandidates << dir.absoluteFilePath(pluginPath);
+    }
+
+    foreach (const QString &pluginPath, pluginCandidates) {
+        QPluginLoader loader(pluginPath);
+        if (!loader.load())
+            continue;
+
+        QDeclarativeObserverInterface *observer =
+                qobject_cast<QDeclarativeObserverInterface*>(loader.instance());
+
+        if (observer)
+            return observer;
+        loader.unload();
+    }
+    return 0;
+}
+
+QT_END_NAMESPACE
diff --git a/src/declarative/debugger/qdeclarativeobserverservice_p.h b/src/declarative/debugger/qdeclarativeobserverservice_p.h
new file mode 100644
index 0000000000..36f31dc510
--- /dev/null
+++ b/src/declarative/debugger/qdeclarativeobserverservice_p.h
@@ -0,0 +1,91 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QDECLARATIVEOBSERVERSERVICE_H
+#define QDECLARATIVEOBSERVERSERVICE_H
+
+#include "private/qdeclarativedebugservice_p.h"
+#include <private/qdeclarativeglobal_p.h>
+
+#include <QtCore/QList>
+
+QT_BEGIN_HEADER
+
+QT_BEGIN_NAMESPACE
+
+QT_MODULE(Declarative)
+
+class QDeclarativeView;
+class QDeclarativeObserverInterface;
+
+class Q_DECLARATIVE_EXPORT QDeclarativeObserverService : public QDeclarativeDebugService
+{
+    Q_OBJECT
+
+public:
+    QDeclarativeObserverService();
+    static QDeclarativeObserverService *instance();
+
+    void addView(QDeclarativeView *);
+    void removeView(QDeclarativeView *);
+    QList<QDeclarativeView*> views() const { return m_views; }
+
+    void sendMessage(const QByteArray &message);
+
+Q_SIGNALS:
+    void gotMessage(const QByteArray &message);
+
+protected:
+    virtual void statusChanged(Status status);
+    virtual void messageReceived(const QByteArray &);
+
+private:
+    static QDeclarativeObserverInterface *loadObserverPlugin();
+
+    QList<QDeclarativeView*> m_views;
+    QDeclarativeObserverInterface *m_observer;
+};
+
+QT_END_NAMESPACE
+
+QT_END_HEADER
+
+#endif // QDECLARATIVEOBSERVERSERVICE_H
diff --git a/src/declarative/debugger/qjsdebuggeragent.cpp b/src/declarative/debugger/qjsdebuggeragent.cpp
new file mode 100644
index 0000000000..601c8c8ce8
--- /dev/null
+++ b/src/declarative/debugger/qjsdebuggeragent.cpp
@@ -0,0 +1,576 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "private/qjsdebuggeragent_p.h"
+#include "private/qdeclarativedebughelper_p.h"
+
+#include <QtCore/qdatetime.h>
+#include <QtCore/qcoreapplication.h>
+#include <QtCore/qset.h>
+#include <QtCore/qurl.h>
+#include <QtScript/qscriptcontextinfo.h>
+#include <QtScript/qscriptengine.h>
+#include <QtScript/qscriptvalueiterator.h>
+
+QT_BEGIN_NAMESPACE
+
+class QJSDebuggerAgentPrivate
+{
+public:
+    QJSDebuggerAgentPrivate(QJSDebuggerAgent *q)
+        : q(q), state(NoState)
+    {}
+
+    void continueExec();
+    void recordKnownObjects(const QList<JSAgentWatchData> &);
+    QList<JSAgentWatchData> getLocals(QScriptContext *);
+    void positionChange(qint64 scriptId, int lineNumber, int columnNumber);
+    QScriptEngine *engine() { return q->engine(); }
+    void stopped();
+
+public:
+    QJSDebuggerAgent *q;
+    JSDebuggerState state;
+    int stepDepth;
+    int stepCount;
+
+    QEventLoop loop;
+    QHash<qint64, QString> filenames;
+    JSAgentBreakpoints breakpoints;
+    // breakpoints by filename (without path)
+    QHash<QString, JSAgentBreakpointData> fileNameToBreakpoints;
+    QStringList watchExpressions;
+    QSet<qint64> knownObjectIds;
+};
+
+namespace {
+
+class SetupExecEnv
+{
+public:
+    SetupExecEnv(QJSDebuggerAgentPrivate *a)
+        : agent(a),
+          previousState(a->state),
+          hadException(a->engine()->hasUncaughtException())
+    {
+        agent->state = StoppedState;
+    }
+
+    ~SetupExecEnv()
+    {
+        if (!hadException && agent->engine()->hasUncaughtException())
+            agent->engine()->clearExceptions();
+        agent->state = previousState;
+    }
+
+private:
+    QJSDebuggerAgentPrivate *agent;
+    JSDebuggerState previousState;
+    bool hadException;
+};
+
+} // anonymous namespace
+
+static JSAgentWatchData fromScriptValue(const QString &expression,
+                                        const QScriptValue &value)
+{
+    static const QString arrayStr = QCoreApplication::translate
+            ("Debugger::JSAgentWatchData", "[Array of length %1]");
+    static const QString undefinedStr = QCoreApplication::translate
+            ("Debugger::JSAgentWatchData", "<undefined>");
+
+    JSAgentWatchData data;
+    data.exp = expression.toUtf8();
+    data.name = data.exp;
+    data.hasChildren = false;
+    data.value = value.toString().toUtf8();
+    data.objectId = value.objectId();
+    if (value.isArray()) {
+        data.type = "Array";
+        data.value = arrayStr.arg(value.property(QLatin1String("length")).toString()).toUtf8();
+        data.hasChildren = true;
+    } else if (value.isBool()) {
+        data.type = "Bool";
+        // data.value = value.toBool() ? "true" : "false";
+    } else if (value.isDate()) {
+        data.type = "Date";
+        data.value = value.toDateTime().toString().toUtf8();
+    } else if (value.isError()) {
+        data.type = "Error";
+    } else if (value.isFunction()) {
+        data.type = "Function";
+    } else if (value.isUndefined()) {
+        data.type = undefinedStr.toUtf8();
+    } else if (value.isNumber()) {
+        data.type = "Number";
+    } else if (value.isRegExp()) {
+        data.type = "RegExp";
+    } else if (value.isString()) {
+        data.type = "String";
+    } else if (value.isVariant()) {
+        data.type = "Variant";
+    } else if (value.isQObject()) {
+        const QObject *obj = value.toQObject();
+        data.type = "Object";
+        data.value += '[';
+        data.value += obj->metaObject()->className();
+        data.value += ']';
+        data.hasChildren = true;
+    } else if (value.isObject()) {
+        data.type = "Object";
+        data.hasChildren = true;
+        data.value = "[Object]";
+    } else if (value.isNull()) {
+        data.type = "<null>";
+    } else {
+        data.type = "<unknown>";
+    }
+    return data;
+}
+
+static QList<JSAgentWatchData> expandObject(const QScriptValue &object)
+{
+    QList<JSAgentWatchData> result;
+    QScriptValueIterator it(object);
+    while (it.hasNext()) {
+        it.next();
+        if (it.flags() & QScriptValue::SkipInEnumeration)
+            continue;
+        if (/*object.isQObject() &&*/ it.value().isFunction()) {
+            // Cosmetics: skip all functions and slot, there are too many of them,
+            // and it is not useful information in the debugger.
+            continue;
+        }
+        JSAgentWatchData data = fromScriptValue(it.name(), it.value());
+        result.append(data);
+    }
+    if (result.isEmpty()) {
+        JSAgentWatchData data;
+        data.name = "<no initialized data>";
+        data.hasChildren = false;
+        data.value = " ";
+        data.objectId = 0;
+        result.append(data);
+    }
+    return result;
+}
+
+static QString fileName(const QString &fileUrl)
+{
+    int lastDelimiterPos = fileUrl.lastIndexOf(QLatin1Char('/'));
+    return fileUrl.mid(lastDelimiterPos, fileUrl.size() - lastDelimiterPos);
+}
+
+void QJSDebuggerAgentPrivate::recordKnownObjects(const QList<JSAgentWatchData>& list)
+{
+    foreach (const JSAgentWatchData &data, list)
+        knownObjectIds << data.objectId;
+}
+
+QList<JSAgentWatchData> QJSDebuggerAgentPrivate::getLocals(QScriptContext *ctx)
+{
+    QList<JSAgentWatchData> locals;
+    if (ctx) {
+        QScriptValue activationObject = ctx->activationObject();
+        QScriptValue thisObject = ctx->thisObject();
+        locals = expandObject(activationObject);
+        if (thisObject.isObject()
+                && thisObject.objectId() != engine()->globalObject().objectId()
+                && QScriptValueIterator(thisObject).hasNext())
+            locals.prepend(fromScriptValue(QLatin1String("this"), thisObject));
+        recordKnownObjects(locals);
+        knownObjectIds << activationObject.objectId();
+    }
+    return locals;
+}
+
+/*!
+  Constructs a new agent for the given \a engine. The agent will
+  report debugging-related events (e.g. step completion) to the given
+  \a backend.
+*/
+QJSDebuggerAgent::QJSDebuggerAgent(QScriptEngine *engine, QObject *parent)
+    : QObject(parent)
+    , QScriptEngineAgent(engine)
+    , d(new QJSDebuggerAgentPrivate(this))
+{
+    QJSDebuggerAgent::engine()->setAgent(this);
+}
+
+QJSDebuggerAgent::QJSDebuggerAgent(QDeclarativeEngine *engine, QObject *parent)
+    : QObject(parent)
+    , QScriptEngineAgent(QDeclarativeDebugHelper::getScriptEngine(engine))
+    , d(new QJSDebuggerAgentPrivate(this))
+{
+    QJSDebuggerAgent::engine()->setAgent(this);
+}
+
+/*!
+  Destroys this QJSDebuggerAgent.
+*/
+QJSDebuggerAgent::~QJSDebuggerAgent()
+{
+    engine()->setAgent(0);
+    delete d;
+}
+
+void QJSDebuggerAgent::setBreakpoints(const JSAgentBreakpoints &breakpoints)
+{
+    d->breakpoints = breakpoints;
+
+    d->fileNameToBreakpoints.clear();
+    foreach (const JSAgentBreakpointData &bp, breakpoints)
+        d->fileNameToBreakpoints.insertMulti(fileName(QString::fromUtf8(bp.fileUrl)), bp);
+}
+
+void QJSDebuggerAgent::setWatchExpressions(const QStringList &watchExpressions)
+{
+    d->watchExpressions = watchExpressions;
+}
+
+void QJSDebuggerAgent::stepOver()
+{
+    d->stepDepth = 0;
+    d->state = SteppingOverState;
+    d->continueExec();
+}
+
+void QJSDebuggerAgent::stepInto()
+{
+    d->stepDepth = 0;
+    d->state = SteppingIntoState;
+    d->continueExec();
+}
+
+void QJSDebuggerAgent::stepOut()
+{
+    d->stepDepth = 0;
+    d->state = SteppingOutState;
+    d->continueExec();
+}
+
+void QJSDebuggerAgent::continueExecution()
+{
+    d->state = NoState;
+    d->continueExec();
+}
+
+JSAgentWatchData QJSDebuggerAgent::executeExpression(const QString &expr)
+{
+    SetupExecEnv execEnv(d);
+
+    JSAgentWatchData data = fromScriptValue(expr, engine()->evaluate(expr));
+    d->knownObjectIds << data.objectId;
+    return data;
+}
+
+QList<JSAgentWatchData> QJSDebuggerAgent::expandObjectById(quint64 objectId)
+{
+    SetupExecEnv execEnv(d);
+
+    QScriptValue v;
+    if (d->knownObjectIds.contains(objectId))
+        v = engine()->objectById(objectId);
+
+    QList<JSAgentWatchData> result = expandObject(v);
+    d->recordKnownObjects(result);
+    return result;
+}
+
+QList<JSAgentWatchData> QJSDebuggerAgent::locals()
+{
+    SetupExecEnv execEnv(d);
+    return d->getLocals(engine()->currentContext());
+}
+
+QList<JSAgentWatchData> QJSDebuggerAgent::localsAtFrame(int frameId)
+{
+    SetupExecEnv execEnv(d);
+
+    int deep = 0;
+    QScriptContext *ctx = engine()->currentContext();
+    while (ctx && deep < frameId) {
+        ctx = ctx->parentContext();
+        deep++;
+    }
+
+    return d->getLocals(ctx);
+}
+
+QList<JSAgentStackData> QJSDebuggerAgent::backtrace()
+{
+    SetupExecEnv execEnv(d);
+
+    QList<JSAgentStackData> backtrace;
+
+    for (QScriptContext *ctx = engine()->currentContext(); ctx; ctx = ctx->parentContext()) {
+        QScriptContextInfo info(ctx);
+
+        JSAgentStackData frame;
+        frame.functionName = info.functionName().toUtf8();
+        if (frame.functionName.isEmpty()) {
+            if (ctx->parentContext()) {
+                switch (info.functionType()) {
+                case QScriptContextInfo::ScriptFunction:
+                    frame.functionName = "<anonymous>";
+                    break;
+                case QScriptContextInfo::NativeFunction:
+                    frame.functionName = "<native>";
+                    break;
+                case QScriptContextInfo::QtFunction:
+                case QScriptContextInfo::QtPropertyFunction:
+                    frame.functionName = "<native slot>";
+                    break;
+                }
+            } else {
+                frame.functionName = "<global>";
+            }
+        }
+        frame.lineNumber = info.lineNumber();
+        // if the line number is unknown, fallback to the function line number
+        if (frame.lineNumber == -1)
+            frame.lineNumber = info.functionStartLineNumber();
+
+        frame.fileUrl = info.fileName().toUtf8();
+        backtrace.append(frame);
+    }
+
+    return backtrace;
+}
+
+QList<JSAgentWatchData> QJSDebuggerAgent::watches()
+{
+    SetupExecEnv execEnv(d);
+
+    QList<JSAgentWatchData> watches;
+    foreach (const QString &expr, d->watchExpressions)
+        watches << fromScriptValue(expr, engine()->evaluate(expr));
+    d->recordKnownObjects(watches);
+    return watches;
+}
+
+void QJSDebuggerAgent::setProperty(qint64 objectId,
+                                   const QString &property,
+                                   const QString &value)
+{
+    SetupExecEnv execEnv(d);
+
+    if (d->knownObjectIds.contains(objectId)) {
+        QScriptValue object = engine()->objectById(objectId);
+        if (object.isObject()) {
+            QScriptValue result = engine()->evaluate(value);
+            object.setProperty(property, result);
+        }
+    }
+}
+
+/*!
+  \reimp
+*/
+void QJSDebuggerAgent::scriptLoad(qint64 id, const QString &program,
+                                  const QString &fileName, int)
+{
+    Q_UNUSED(program);
+    d->filenames.insert(id, fileName);
+}
+
+/*!
+  \reimp
+*/
+void QJSDebuggerAgent::scriptUnload(qint64 id)
+{
+    d->filenames.remove(id);
+}
+
+/*!
+  \reimp
+*/
+void QJSDebuggerAgent::contextPush()
+{
+}
+
+/*!
+  \reimp
+*/
+void QJSDebuggerAgent::contextPop()
+{
+}
+
+/*!
+  \reimp
+*/
+void QJSDebuggerAgent::functionEntry(qint64 scriptId)
+{
+    Q_UNUSED(scriptId);
+    d->stepDepth++;
+}
+
+/*!
+  \reimp
+*/
+void QJSDebuggerAgent::functionExit(qint64 scriptId, const QScriptValue &returnValue)
+{
+    Q_UNUSED(scriptId);
+    Q_UNUSED(returnValue);
+    d->stepDepth--;
+}
+
+/*!
+  \reimp
+*/
+void QJSDebuggerAgent::positionChange(qint64 scriptId, int lineNumber, int columnNumber)
+{
+    d->positionChange(scriptId, lineNumber, columnNumber);
+}
+
+void QJSDebuggerAgentPrivate::positionChange(qint64 scriptId, int lineNumber, int columnNumber)
+{
+    Q_UNUSED(columnNumber);
+
+    if (state == StoppedState)
+        return; //no re-entrency
+
+    // check breakpoints
+    if (!breakpoints.isEmpty()) {
+        QHash<qint64, QString>::const_iterator it = filenames.constFind(scriptId);
+        QScriptContext *ctx = engine()->currentContext();
+        QScriptContextInfo info(ctx);
+        if (it == filenames.constEnd()) {
+            // It is possible that the scripts are loaded before the agent is attached
+            QString filename = info.fileName();
+
+            JSAgentStackData frame;
+            frame.functionName = info.functionName().toUtf8();
+
+            QPair<QString, qint32> key = qMakePair(filename, lineNumber);
+            it = filenames.insert(scriptId, filename);
+        }
+
+        const QString filePath = it.value();
+        JSAgentBreakpoints bps = fileNameToBreakpoints.values(fileName(filePath)).toSet();
+
+        foreach (const JSAgentBreakpointData &bp, bps) {
+            if (bp.lineNumber == lineNumber) {
+                stopped();
+                return;
+            }
+        }
+    }
+
+    switch (state) {
+    case NoState:
+    case StoppedState:
+        // Do nothing
+        break;
+    case SteppingOutState:
+        if (stepDepth >= 0)
+            break;
+        //fallthough
+    case SteppingOverState:
+        if (stepDepth > 0)
+            break;
+        //fallthough
+    case SteppingIntoState:
+        stopped();
+        break;
+    }
+
+}
+
+/*!
+  \reimp
+*/
+void QJSDebuggerAgent::exceptionThrow(qint64 scriptId,
+                                     const QScriptValue &exception,
+                                     bool hasHandler)
+{
+    Q_UNUSED(scriptId);
+    Q_UNUSED(exception);
+    Q_UNUSED(hasHandler);
+//    qDebug() << Q_FUNC_INFO << exception.toString() << hasHandler;
+#if 0 //sometimes, we get exceptions that we should just ignore.
+    if (!hasHandler && state != StoppedState)
+        stopped(true, exception);
+#endif
+}
+
+/*!
+  \reimp
+*/
+void QJSDebuggerAgent::exceptionCatch(qint64 scriptId, const QScriptValue &exception)
+{
+    Q_UNUSED(scriptId);
+    Q_UNUSED(exception);
+}
+
+bool QJSDebuggerAgent::supportsExtension(Extension extension) const
+{
+    return extension == QScriptEngineAgent::DebuggerInvocationRequest;
+}
+
+QVariant QJSDebuggerAgent::extension(Extension extension, const QVariant &argument)
+{
+    if (extension == QScriptEngineAgent::DebuggerInvocationRequest) {
+        d->stopped();
+        return QVariant();
+    }
+    return QScriptEngineAgent::extension(extension, argument);
+}
+
+void QJSDebuggerAgentPrivate::stopped()
+{
+    bool becauseOfException = false;
+    const QScriptValue &exception = QScriptValue();
+
+    knownObjectIds.clear();
+    state = StoppedState;
+
+    emit q->stopped(becauseOfException, exception.toString());
+
+    loop.exec(QEventLoop::ExcludeUserInputEvents);
+}
+
+void QJSDebuggerAgentPrivate::continueExec()
+{
+    loop.quit();
+}
+
+QT_END_NAMESPACE
diff --git a/src/declarative/debugger/qjsdebuggeragent_p.h b/src/declarative/debugger/qjsdebuggeragent_p.h
new file mode 100644
index 0000000000..ce5a0449eb
--- /dev/null
+++ b/src/declarative/debugger/qjsdebuggeragent_p.h
@@ -0,0 +1,204 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QJSDEBUGGERAGENT_P_H
+#define QJSDEBUGGERAGENT_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtScript/qscriptengineagent.h>
+#include <QtCore/qset.h>
+
+QT_BEGIN_NAMESPACE
+class QScriptValue;
+class QDeclarativeEngine;
+QT_END_NAMESPACE
+
+QT_BEGIN_HEADER
+
+QT_BEGIN_NAMESPACE
+
+QT_MODULE(Declarative)
+
+class QJSDebuggerAgentPrivate;
+
+enum JSDebuggerState
+{
+    NoState,
+    SteppingIntoState,
+    SteppingOverState,
+    SteppingOutState,
+    StoppedState
+};
+
+struct JSAgentWatchData
+{
+    QByteArray exp;
+    QByteArray name;
+    QByteArray value;
+    QByteArray type;
+    bool hasChildren;
+    quint64 objectId;
+};
+
+inline QDataStream &operator<<(QDataStream &s, const JSAgentWatchData &data)
+{
+    return s << data.exp << data.name << data.value
+             << data.type << data.hasChildren << data.objectId;
+}
+
+struct JSAgentStackData
+{
+    QByteArray functionName;
+    QByteArray fileUrl;
+    qint32 lineNumber;
+};
+
+inline QDataStream &operator<<(QDataStream &s, const JSAgentStackData &data)
+{
+    return s << data.functionName << data.fileUrl << data.lineNumber;
+}
+
+struct JSAgentBreakpointData
+{
+    QByteArray functionName;
+    QByteArray fileUrl;
+    qint32 lineNumber;
+};
+
+typedef QSet<JSAgentBreakpointData> JSAgentBreakpoints;
+
+inline QDataStream &operator<<(QDataStream &s, const JSAgentBreakpointData &data)
+{
+    return s << data.functionName << data.fileUrl << data.lineNumber;
+}
+
+inline QDataStream &operator>>(QDataStream &s, JSAgentBreakpointData &data)
+{
+    return s >> data.functionName >> data.fileUrl >> data.lineNumber;
+}
+
+inline bool operator==(const JSAgentBreakpointData &b1, const JSAgentBreakpointData &b2)
+{
+    return b1.lineNumber == b2.lineNumber && b1.fileUrl == b2.fileUrl;
+}
+
+inline uint qHash(const JSAgentBreakpointData &b)
+{
+    return b.lineNumber ^ qHash(b.fileUrl);
+}
+
+
+class QJSDebuggerAgent : public QObject, public QScriptEngineAgent
+{
+    Q_OBJECT
+
+public:
+    QJSDebuggerAgent(QScriptEngine *engine, QObject *parent = 0);
+    QJSDebuggerAgent(QDeclarativeEngine *engine, QObject *parent = 0);
+    ~QJSDebuggerAgent();
+
+    void setBreakpoints(const JSAgentBreakpoints &);
+    void setWatchExpressions(const QStringList &);
+
+    void stepOver();
+    void stepInto();
+    void stepOut();
+    void continueExecution();
+
+    JSAgentWatchData executeExpression(const QString &expr);
+    QList<JSAgentWatchData> expandObjectById(quint64 objectId);
+    QList<JSAgentWatchData> locals();
+    QList<JSAgentWatchData> localsAtFrame(int frameId);
+    QList<JSAgentStackData> backtrace();
+    QList<JSAgentWatchData> watches();
+    void setProperty(qint64 objectId,
+                     const QString &property,
+                     const QString &value);
+
+    // reimplemented
+    void scriptLoad(qint64 id, const QString &program,
+                    const QString &fileName, int baseLineNumber);
+    void scriptUnload(qint64 id);
+
+    void contextPush();
+    void contextPop();
+
+    void functionEntry(qint64 scriptId);
+    void functionExit(qint64 scriptId,
+                      const QScriptValue &returnValue);
+
+    void positionChange(qint64 scriptId,
+                        int lineNumber, int columnNumber);
+
+    void exceptionThrow(qint64 scriptId,
+                        const QScriptValue &exception,
+                        bool hasHandler);
+    void exceptionCatch(qint64 scriptId,
+                        const QScriptValue &exception);
+
+    bool supportsExtension(Extension extension) const;
+    QVariant extension(Extension extension,
+                       const QVariant &argument = QVariant());
+
+Q_SIGNALS:
+    void stopped(bool becauseOfException,
+                 const QString &exception);
+
+private:
+    friend class QJSDebuggerAgentPrivate;
+    QJSDebuggerAgentPrivate *d;
+};
+
+QT_END_NAMESPACE
+
+QT_END_HEADER
+
+#endif // QJSDEBUGGERAGENT_P_H
diff --git a/src/declarative/debugger/qjsdebugservice.cpp b/src/declarative/debugger/qjsdebugservice.cpp
new file mode 100644
index 0000000000..f8cd095943
--- /dev/null
+++ b/src/declarative/debugger/qjsdebugservice.cpp
@@ -0,0 +1,198 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "private/qjsdebugservice_p.h"
+#include "private/qjsdebuggeragent_p.h"
+
+#include <QtCore/qdatastream.h>
+#include <QtCore/qdebug.h>
+#include <QtCore/qstringlist.h>
+#include <QtDeclarative/qdeclarativeengine.h>
+
+Q_GLOBAL_STATIC(QJSDebugService, serviceInstance)
+
+QJSDebugService::QJSDebugService(QObject *parent)
+    : QDeclarativeDebugService(QLatin1String("JSDebugger"), parent)
+    , m_agent(0)
+{
+}
+
+QJSDebugService::~QJSDebugService()
+{
+    delete m_agent;
+}
+
+QJSDebugService *QJSDebugService::instance()
+{
+    return serviceInstance();
+}
+
+void QJSDebugService::addEngine(QDeclarativeEngine *engine)
+{
+    Q_ASSERT(engine);
+    Q_ASSERT(!m_engines.contains(engine));
+
+    m_engines.append(engine);
+}
+
+void QJSDebugService::removeEngine(QDeclarativeEngine *engine)
+{
+    Q_ASSERT(engine);
+    Q_ASSERT(m_engines.contains(engine));
+
+    m_engines.removeAll(engine);
+}
+
+void QJSDebugService::statusChanged(Status status)
+{
+    if (status == Enabled && !m_engines.isEmpty() && !m_agent) {
+        // Multiple engines are currently unsupported
+        QDeclarativeEngine *engine = m_engines.first();
+        m_agent = new QJSDebuggerAgent(engine, engine);
+
+        connect(m_agent, SIGNAL(stopped(bool,QString)),
+                this, SLOT(executionStopped(bool,QString)));
+
+    } else if (status != Enabled && m_agent) {
+        delete m_agent;
+        m_agent = 0;
+    }
+}
+
+void QJSDebugService::messageReceived(const QByteArray &message)
+{
+    if (!m_agent) {
+        qWarning() << "QJSDebugService::messageReceived: No QJSDebuggerAgent available";
+        return;
+    }
+
+    QDataStream ds(message);
+    QByteArray command;
+    ds >> command;
+    if (command == "BREAKPOINTS") {
+        JSAgentBreakpoints breakpoints;
+        ds >> breakpoints;
+        m_agent->setBreakpoints(breakpoints);
+
+        //qDebug() << "BREAKPOINTS";
+        //foreach (const JSAgentBreakpointData &bp, breakpoints)
+        //    qDebug() << "BREAKPOINT: " << bp.fileUrl << bp.lineNumber;
+    } else if (command == "WATCH_EXPRESSIONS") {
+        QStringList watchExpressions;
+        ds >> watchExpressions;
+        m_agent->setWatchExpressions(watchExpressions);
+    } else if (command == "STEPOVER") {
+        m_agent->stepOver();
+    } else if (command == "STEPINTO" || command == "INTERRUPT") {
+        m_agent->stepInto();
+    } else if (command == "STEPOUT") {
+        m_agent->stepOut();
+    } else if (command == "CONTINUE") {
+        m_agent->continueExecution();
+    } else if (command == "EXEC") {
+        QByteArray id;
+        QString expr;
+        ds >> id >> expr;
+
+        JSAgentWatchData data = m_agent->executeExpression(expr);
+
+        QByteArray reply;
+        QDataStream rs(&reply, QIODevice::WriteOnly);
+        rs << QByteArray("RESULT") << id << data;
+        sendMessage(reply);
+    } else if (command == "EXPAND") {
+        QByteArray requestId;
+        quint64 objectId;
+        ds >> requestId >> objectId;
+
+        QList<JSAgentWatchData> result = m_agent->expandObjectById(objectId);
+
+        QByteArray reply;
+        QDataStream rs(&reply, QIODevice::WriteOnly);
+        rs << QByteArray("EXPANDED") << requestId << result;
+        sendMessage(reply);
+    } else if (command == "ACTIVATE_FRAME") {
+        int frameId;
+        ds >> frameId;
+
+        QList<JSAgentWatchData> locals = m_agent->localsAtFrame(frameId);
+
+        QByteArray reply;
+        QDataStream rs(&reply, QIODevice::WriteOnly);
+        rs << QByteArray("LOCALS") << frameId << locals;
+        sendMessage(reply);
+    } else if (command == "SET_PROPERTY") {
+        QByteArray id;
+        qint64 objectId;
+        QString property;
+        QString value;
+        ds >> id >> objectId >> property >> value;
+
+        m_agent->setProperty(objectId, property, value);
+
+        //TODO: feedback
+    } else if (command == "PING") {
+        int ping;
+        ds >> ping;
+        QByteArray reply;
+        QDataStream rs(&reply, QIODevice::WriteOnly);
+        rs << QByteArray("PONG") << ping;
+        sendMessage(reply);
+    } else {
+        qDebug() << Q_FUNC_INFO << "Unknown command" << command;
+    }
+
+    QDeclarativeDebugService::messageReceived(message);
+}
+
+void QJSDebugService::executionStopped(bool becauseOfException,
+                                       const QString &exception)
+{
+    const QList<JSAgentStackData> backtrace = m_agent->backtrace();
+    const QList<JSAgentWatchData> watches = m_agent->watches();
+    const QList<JSAgentWatchData> locals = m_agent->locals();
+
+    QByteArray reply;
+    QDataStream rs(&reply, QIODevice::WriteOnly);
+    rs << QByteArray("STOPPED") << backtrace << watches << locals
+       << becauseOfException << exception;
+    sendMessage(reply);
+}
diff --git a/src/declarative/debugger/qjsdebugservice_p.h b/src/declarative/debugger/qjsdebugservice_p.h
new file mode 100644
index 0000000000..6839ca8ffd
--- /dev/null
+++ b/src/declarative/debugger/qjsdebugservice_p.h
@@ -0,0 +1,99 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtDeclarative module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QJSDEBUGSERVICE_P_H
+#define QJSDEBUGSERVICE_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtCore/QPointer>
+
+#include "private/qdeclarativedebugservice_p.h"
+
+QT_BEGIN_HEADER
+
+QT_BEGIN_NAMESPACE
+
+QT_MODULE(Declarative)
+
+class QDeclarativeEngine;
+class QJSDebuggerAgent;
+
+class QJSDebugService : public QDeclarativeDebugService
+{
+    Q_OBJECT
+
+public:
+    QJSDebugService(QObject *parent = 0);
+    ~QJSDebugService();
+
+    static QJSDebugService *instance();
+
+    void addEngine(QDeclarativeEngine *);
+    void removeEngine(QDeclarativeEngine *);
+
+protected:
+    void statusChanged(Status status);
+    void messageReceived(const QByteArray &);
+
+private Q_SLOTS:
+    void executionStopped(bool becauseOfException,
+                          const QString &exception);
+
+private:
+    QList<QDeclarativeEngine *> m_engines;
+    QPointer<QJSDebuggerAgent> m_agent;
+};
+
+QT_END_NAMESPACE
+
+QT_END_HEADER
+
+#endif // QJSDEBUGSERVICE_P_H