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diff --git a/src/scripttools/debugging/qscriptdebuggerbackend.cpp b/src/scripttools/debugging/qscriptdebuggerbackend.cpp
new file mode 100644
index 0000000..8e739af
--- /dev/null
+++ b/src/scripttools/debugging/qscriptdebuggerbackend.cpp
@@ -0,0 +1,993 @@
+/****************************************************************************
+**
+** 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 QtSCriptTools 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 "qscriptdebuggerbackend_p.h"
+#include "qscriptdebuggerbackend_p_p.h"
+#include "qscriptdebuggeragent_p.h"
+#include "qscriptdebuggercommandexecutor_p.h"
+#include "qscriptdebuggerevent_p.h"
+#include "qscriptdebuggervalue_p.h"
+#include "qscriptscriptdata_p.h"
+#include "qscriptbreakpointdata_p.h"
+#include "qscriptobjectsnapshot_p.h"
+
+#include <QtScript/qscriptengine.h>
+#include <QtScript/qscriptcontextinfo.h>
+#include <QtScript/qscriptvalueiterator.h>
+
+#include <QtCore/qcoreapplication.h>
+#include <QtCore/qdebug.h>
+
+Q_DECLARE_METATYPE(QScriptDebuggerValue)
+Q_DECLARE_METATYPE(QScriptDebuggerBackendPrivate*)
+
+QT_BEGIN_NAMESPACE
+
+/*!
+  \since 4.5
+  \class QScriptDebuggerBackend
+  \internal
+
+  \brief The QScriptDebuggerBackend class is the base class of debugger back-ends.
+
+  QScriptDebuggerBackend builds on the QScriptDebuggerAgent class.
+
+  This class is usually used together with the QScriptDebuggerFrontend
+  class, in order to form a (front-end, back-end) pair.
+
+  Call attachTo() to attach to a QScriptEngine object. Call detach()
+  to detach from the current engine.
+
+  Call stepInto() to step into the next script statement; call stepOver()
+  to step over the next script statement; and call stepOut() to step out
+  of the currently executing script function. An event() will be generated
+  when the stepping is completed.
+
+  Call runToLocation() to execute script statements until a certain
+  location has been reached. An event() will be generated when the location
+  has been reached.
+
+  Call interruptEvaluation() to request that evaluation should be
+  interrupted. An event() will be generated upon the next script
+  statement that is reached.
+
+  Call continueEvalution() to allow script evaluation to continue.
+
+  Call setBreakpoint() to set a breakpoint. A breakpoint event() will
+  be generated when a breakpoint is hit. Call deleteBreakpoint() to
+  delete a breakpoint. Call modifyBreakpoint() to change the state of
+  an existing breakpoint.
+
+  Call contextCount() to obtain the number of active contexts
+  (frames). Call context() to obtain a pointer to a QScriptContext.
+
+  \section1 Subclassing
+
+  When subclassing QScriptDebuggerBackend, you must implement the pure
+  virtual event() function. This function typically forwards the event
+  to a QScriptDebuggerFrontend object. For most type of events,
+  event() should block until the back-end is instructed to resume
+  execution (e.g. until continueEvalution() is called). You must
+  implement resume(), which is responsible for making event() return.
+
+  \sa QScriptDebuggerFrontend, QScriptDebuggerEvent
+*/
+
+// helper class that's used to handle our custom Qt events
+class QScriptDebuggerBackendEventReceiver : public QObject
+{
+public:
+    QScriptDebuggerBackendEventReceiver(QScriptDebuggerBackendPrivate *backend,
+                                        QObject *parent = 0)
+        : QObject(parent), m_backend(backend) {}
+    ~QScriptDebuggerBackendEventReceiver() {}
+
+    bool event(QEvent *e)
+    {
+        return m_backend->event(e);
+    }
+
+private:
+    QScriptDebuggerBackendPrivate *m_backend;
+};
+
+
+QScriptDebuggerBackendPrivate::QScriptDebuggerBackendPrivate()
+    : agent(0), commandExecutor(0),
+        pendingEvaluateContextIndex(-1), pendingEvaluateLineNumber(-1),
+        ignoreExceptions(false),
+        nextScriptValueIteratorId(0), nextScriptObjectSnapshotId(0),
+        eventReceiver(0),
+        q_ptr(0) // q_ptr will be set later by QScriptDebuggerBackend constructor
+{
+}
+
+QScriptDebuggerBackendPrivate::~QScriptDebuggerBackendPrivate()
+{
+    if (agent)
+        agent->nullifyBackendPointer();
+    delete commandExecutor;
+    delete eventReceiver;
+    qDeleteAll(scriptValueIterators);
+    qDeleteAll(scriptObjectSnapshots);
+}
+
+void QScriptDebuggerBackendPrivate::postEvent(QEvent *e)
+{
+    if (!eventReceiver) {
+        eventReceiver = new QScriptDebuggerBackendEventReceiver(this);
+        eventReceiver->moveToThread(agent->engine()->thread());
+    }
+    QCoreApplication::postEvent(eventReceiver, e);
+}
+
+bool QScriptDebuggerBackendPrivate::event(QEvent *e)
+{
+    if (e->type() == QEvent::User+1) {
+        QScriptDebuggerEventEvent *de = static_cast<QScriptDebuggerEventEvent*>(e);
+        q_func()->event(de->event());
+        return true;
+    }
+    return false;
+}
+
+void QScriptDebuggerBackendPrivate::agentDestroyed(QScriptDebuggerAgent *ag)
+{
+    // Since agents are owned by the script engine, this in practice means
+    // that the engine has been destroyed. Invalidate our pointer so we
+    // don't crash later.
+    if (agent == ag)
+        agent = 0;
+}
+
+/*!
+  The agent calls this function when it has completed a step
+  operation.
+*/
+void QScriptDebuggerBackendPrivate::stepped(qint64 scriptId,
+                                            int lineNumber,
+                                            int columnNumber,
+                                            const QScriptValue &result)
+{
+    Q_Q(QScriptDebuggerBackend);
+    QScriptDebuggerEvent e(QScriptDebuggerEvent::SteppingFinished,
+                           scriptId, lineNumber, columnNumber);
+    e.setFileName(agent->scriptData(scriptId).fileName());
+    QScriptDebuggerValue value(result);
+    e.setScriptValue(value);
+    if (!result.isUndefined())
+        e.setMessage(result.toString()); // for convenience -- we always need it
+    q->event(e);
+}
+
+/*!
+  The agent calls this function when it has run to a particular
+  location.
+*/
+void QScriptDebuggerBackendPrivate::locationReached(qint64 scriptId,
+                                                    int lineNumber,
+                                                    int columnNumber)
+{
+    Q_Q(QScriptDebuggerBackend);
+    QScriptDebuggerEvent e(QScriptDebuggerEvent::LocationReached,
+                           scriptId, lineNumber, columnNumber);
+    e.setFileName(agent->scriptData(scriptId).fileName());
+    q->event(e);
+}
+
+/*!
+  The agent calls this function when evaluation has been interrupted.
+*/
+void QScriptDebuggerBackendPrivate::interrupted(qint64 scriptId,
+                                                int lineNumber,
+                                                int columnNumber)
+{
+    Q_Q(QScriptDebuggerBackend);
+    QScriptDebuggerEvent e(QScriptDebuggerEvent::Interrupted,
+                           scriptId, lineNumber, columnNumber);
+    e.setFileName(agent->scriptData(scriptId).fileName());
+    q->event(e);
+}
+
+/*!
+  The agent calls this function when a breakpoint has been triggered.
+*/
+void QScriptDebuggerBackendPrivate::breakpoint(qint64 scriptId,
+                                               int lineNumber,
+                                               int columnNumber,
+                                               int breakpointId)
+{
+    Q_Q(QScriptDebuggerBackend);
+    QScriptDebuggerEvent e(QScriptDebuggerEvent::Breakpoint,
+                           scriptId, lineNumber, columnNumber);
+    e.setFileName(agent->scriptData(scriptId).fileName());
+    e.setBreakpointId(breakpointId);
+    q->event(e);
+}
+
+/*!
+  The agent calls this function when an uncaught exception has
+  occurred.
+*/
+void QScriptDebuggerBackendPrivate::exception(qint64 scriptId,
+                                              const QScriptValue &exception,
+                                              bool hasHandler)
+{
+    Q_Q(QScriptDebuggerBackend);
+    if (ignoreExceptions) {
+        // don't care (it's caught by us)
+        return;
+    }
+    QScriptDebuggerEvent e(QScriptDebuggerEvent::Exception);
+    e.setScriptId(scriptId);
+    e.setFileName(agent->scriptData(scriptId).fileName());
+    e.setMessage(exception.toString());
+    e.setHasExceptionHandler(hasHandler);
+    int lineNumber = -1;
+    QString fileName;
+    if (exception.property(QLatin1String("lineNumber")).isNumber())
+        lineNumber = exception.property(QLatin1String("lineNumber")).toInt32();
+    if (exception.property(QLatin1String("fileName")).isString())
+        fileName = exception.property(QLatin1String("fileName")).toString();
+    if (lineNumber == -1) {
+        QScriptContextInfo info(q->engine()->currentContext());
+        lineNumber = info.lineNumber();
+        fileName = info.fileName();
+    }
+    if (lineNumber != -1)
+        e.setLineNumber(lineNumber);
+    if (!fileName.isEmpty())
+        e.setFileName(fileName);
+    QScriptDebuggerValue value(exception);
+    e.setScriptValue(value);
+    q->event(e);
+}
+
+QScriptValue QScriptDebuggerBackendPrivate::trace(QScriptContext *context,
+                                                  QScriptEngine *engine)
+{
+    QScriptValue data = context->callee().data();
+    QScriptDebuggerBackendPrivate *self = qscriptvalue_cast<QScriptDebuggerBackendPrivate*>(data);
+    if (!self)
+        return engine->undefinedValue();
+    QString str;
+    for (int i = 0; i < context->argumentCount(); ++i) {
+        if (i > 0)
+            str.append(QLatin1Char(' '));
+        str.append(context->argument(i).toString());
+    }
+    QScriptDebuggerEvent e(QScriptDebuggerEvent::Trace);
+    e.setMessage(str);
+    self->q_func()->event(e);
+    return engine->undefinedValue();
+}
+
+QScriptValue QScriptDebuggerBackendPrivate::qsassert(QScriptContext *context,
+                                                     QScriptEngine *engine)
+{
+    QScriptValue arg = context->argument(0);
+    if (arg.toBoolean())
+        return arg;
+    QScriptContextInfo info(context->parentContext());
+    QString msg;
+    QString fileName = info.fileName();
+    if (fileName.isEmpty())
+        fileName = QString::fromLatin1("<anonymous script, id=%0>").arg(info.scriptId());
+    msg.append(fileName);
+    msg.append(QLatin1Char(':'));
+    msg.append(QString::number(info.lineNumber()));
+    msg.append(QString::fromLatin1(": Assertion failed"));
+    for (int i = 1; i < context->argumentCount(); ++i) {
+        if (i == 1)
+            msg.append(QLatin1Char(':'));
+        msg.append(QLatin1Char(' '));
+        msg.append(context->argument(i).toString());
+    }
+    QScriptValue err = context->throwError(msg);
+    err.setProperty(QString::fromLatin1("name"), QScriptValue(engine, QString::fromLatin1("AssertionError")));
+    return err;
+}
+
+QScriptValue QScriptDebuggerBackendPrivate::fileName(QScriptContext *context,
+                                                     QScriptEngine *engine)
+{
+    QScriptContextInfo info(context->parentContext());
+    QString fn = info.fileName();
+    if (fn.isEmpty())
+        return engine->undefinedValue();
+    return QScriptValue(engine, fn);
+}
+
+QScriptValue QScriptDebuggerBackendPrivate::lineNumber(QScriptContext *context,
+                                                       QScriptEngine *engine)
+{
+    QScriptContextInfo info(context->parentContext());
+    return QScriptValue(engine, info.lineNumber());
+}
+
+/*!
+  The agent calls this function when the engine has reached a
+  "debugger" statement.
+*/
+void QScriptDebuggerBackendPrivate::debuggerInvocationRequest(
+    qint64 scriptId, int lineNumber, int columnNumber)
+{
+    Q_Q(QScriptDebuggerBackend);
+    QScriptDebuggerEvent e(QScriptDebuggerEvent::DebuggerInvocationRequest,
+                           scriptId, lineNumber, columnNumber);
+    e.setFileName(agent->scriptData(scriptId).fileName());
+    q->event(e);
+}
+
+void QScriptDebuggerBackendPrivate::forcedReturn(
+    qint64 scriptId, int lineNumber, int columnNumber,
+    const QScriptValue &value)
+{
+    Q_Q(QScriptDebuggerBackend);
+    QScriptDebuggerEvent e(QScriptDebuggerEvent::ForcedReturn,
+                           scriptId, lineNumber, columnNumber);
+    e.setFileName(agent->scriptData(scriptId).fileName());
+    e.setScriptValue(QScriptDebuggerValue(value));
+    q->event(e);
+}
+
+/*!
+  Creates a QScriptDebuggerBackend object.
+*/
+QScriptDebuggerBackend::QScriptDebuggerBackend()
+    : d_ptr(new QScriptDebuggerBackendPrivate)
+{
+    d_ptr->q_ptr = this;
+}
+
+/*!
+  Destroys this QScriptDebuggerBackend.
+*/
+QScriptDebuggerBackend::~QScriptDebuggerBackend()
+{
+    detach();
+}
+
+/*!
+  \internal
+*/
+QScriptDebuggerBackend::QScriptDebuggerBackend(QScriptDebuggerBackendPrivate &dd)
+    : d_ptr(&dd)
+{
+    d_ptr->q_ptr = this;
+}
+
+/*!
+  Attaches this backend to the given \a engine.
+  The backend automatically detaches from the old engine, if any.
+
+  This function installs its own agent on the \a engine using
+  QScriptEngine::setAgent(); any existing agent will be replaced.
+
+  \sa detach(). engine()
+*/
+void QScriptDebuggerBackend::attachTo(QScriptEngine *engine)
+{
+    Q_D(QScriptDebuggerBackend);
+    detach();
+    d->agent = new QScriptDebuggerAgent(d, engine);
+    QScriptValue global = engine->globalObject();
+    d->origTraceFunction = global.property(QString::fromLatin1("print"));
+    global.setProperty(QString::fromLatin1("print"), traceFunction());
+//    global.setProperty(QString::fromLatin1("qAssert"), assertFunction());
+    d->origFileNameFunction = global.property(QString::fromLatin1("__FILE__"));
+    global.setProperty(QString::fromLatin1("__FILE__"), fileNameFunction(),
+                       QScriptValue::PropertyGetter | QScriptValue::ReadOnly);
+    d->origLineNumberFunction = global.property(QString::fromLatin1("__LINE__"));
+    global.setProperty(QString::fromLatin1("__LINE__"), lineNumberFunction(),
+                       QScriptValue::PropertyGetter | QScriptValue::ReadOnly);
+    engine->setAgent(d->agent);
+}
+
+/*!
+  Detaches this backend from the current script engine.
+  The backend's state (including breakpoints and information on loaded
+  scripts) will be invalidated.
+
+  \sa attach()
+*/
+void QScriptDebuggerBackend::detach()
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent) {
+        QScriptEngine *eng = d->agent->engine();
+        if (eng && eng->agent() == d->agent) {
+            eng->setAgent(0);
+            QScriptValue global = eng->globalObject();
+            global.setProperty(QString::fromLatin1("print"), d->origTraceFunction);
+            d->origTraceFunction = QScriptValue();
+//            global.setProperty(QString::fromLatin1("qAssert"), QScriptValue());
+            global.setProperty(QString::fromLatin1("__FILE__"), QScriptValue(),
+                               QScriptValue::PropertyGetter);
+            global.setProperty(QString::fromLatin1("__FILE__"), d->origFileNameFunction);
+            d->origFileNameFunction = QScriptValue();
+            global.setProperty(QString::fromLatin1("__LINE__"), QScriptValue(),
+                               QScriptValue::PropertyGetter);
+            global.setProperty(QString::fromLatin1("__LINE__"), d->origLineNumberFunction);
+            d->origLineNumberFunction = QScriptValue();
+            d->agent->nullifyBackendPointer();
+            d->agent = 0; // agent is owned by engine
+        }
+    }
+
+    d->pendingEvaluateLineNumber = -1;
+    d->ignoreExceptions = false;
+    d->nextScriptValueIteratorId = 0;
+    qDeleteAll(d->scriptValueIterators);
+    d->scriptValueIterators.clear();
+    qDeleteAll(d->scriptObjectSnapshots);
+    d->scriptObjectSnapshots.clear();
+}
+
+/*!
+  Returns the script engine that this backend is attached to, or 0 if
+  the backend is not attached to an engine.
+
+  \sa attachTo()
+*/
+QScriptEngine *QScriptDebuggerBackend::engine() const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (!d->agent)
+        return 0;
+    return d->agent->engine();
+}
+
+/*!
+  Steps into the next script statement.
+  When stepping is complete, an event() will be generated.
+*/
+void QScriptDebuggerBackend::stepInto(int count)
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent) {
+        d->agent->enterStepIntoMode(count);
+        resume();
+    }
+}
+
+/*!
+  Steps over the next script statement.
+  When stepping is complete, an event() will be generated.
+*/
+void QScriptDebuggerBackend::stepOver(int count)
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent) {
+        d->agent->enterStepOverMode(count);
+        resume();
+    }
+}
+
+/*!
+  Steps out of the current script function.
+  When stepping is complete, an event() will be generated.
+*/
+void QScriptDebuggerBackend::stepOut()
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent) {
+        d->agent->enterStepOutMode();
+        resume();
+    }
+}
+
+/*!
+  Continues script evaluation. Evaluation will proceed without
+  interruption until either 1) an uncaught exception occurs, 2) a
+  breakpoint is triggered, or 3) interruptEvaluation() is called.
+  In each case, a proper event() will be generated.
+*/
+void QScriptDebuggerBackend::continueEvalution()
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent) {
+        d->agent->enterContinueMode();
+        resume();
+    }
+}
+
+/*!
+  Interrupts script evaluation. When the next script statement is
+  reached, an event() will be generated.
+*/
+void QScriptDebuggerBackend::interruptEvaluation()
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent)
+        d->agent->enterInterruptMode();
+}
+
+/*!
+  Continues evaluation until the location defined by the given \a
+  fileName and \a lineNumber is reached. When the location is reached,
+  an event() will be generated.
+*/
+void QScriptDebuggerBackend::runToLocation(const QString &fileName, int lineNumber)
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent) {
+        d->agent->enterRunToLocationMode(fileName, lineNumber);
+        resume();
+    }
+}
+
+/*!
+  Continues evaluation until the location defined by the given \a
+  scriptId and \a lineNumber is reached. When the location is reached,
+  an event() will be generated.
+*/
+void QScriptDebuggerBackend::runToLocation(qint64 scriptId, int lineNumber)
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent) {
+        d->agent->enterRunToLocationMode(scriptId, lineNumber);
+        resume();
+    }
+}
+
+void QScriptDebuggerBackend::returnToCaller(int contextIndex, const QScriptValue &value)
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent) {
+        d->agent->enterReturnByForceMode(contextIndex, value);
+        resume();
+    }
+}
+
+/*!
+  Evaluates the given \a program. When evaluation is complete, an
+  event() is generated.
+*/
+void QScriptDebuggerBackend::evaluate(int contextIndex, const QString &program,
+                                      const QString &fileName, int lineNumber)
+{
+    Q_D(QScriptDebuggerBackend);
+    d->pendingEvaluateContextIndex = contextIndex;
+    d->pendingEvaluateProgram = program;
+    d->pendingEvaluateFileName = fileName;
+    d->pendingEvaluateLineNumber = lineNumber;
+    if (!engine()->isEvaluating())
+        doPendingEvaluate(/*postEvent=*/true);
+    else
+        resume();
+}
+
+/*!
+  Executes the pending evaluate, if any.
+*/
+void QScriptDebuggerBackend::doPendingEvaluate(bool postEvent)
+{
+    Q_D(QScriptDebuggerBackend);
+    QString program = d->pendingEvaluateProgram;
+    if (program.isEmpty())
+        return;
+    int contextIndex = d->pendingEvaluateContextIndex;
+    QScriptContext *ctx = context(contextIndex);
+    Q_ASSERT(ctx != 0);
+    QString fileName = d->pendingEvaluateFileName;
+    int lineNumber = d->pendingEvaluateLineNumber;
+    d->pendingEvaluateProgram = QString();
+    d->pendingEvaluateFileName = QString();
+    d->pendingEvaluateLineNumber = -1;
+    d->pendingEvaluateContextIndex = -1;
+
+    // push a new context and initialize its scope chain etc.
+    {
+        QScriptContext *evalContext = engine()->pushContext();
+        QScriptValueList scopeChain = ctx->scopeChain();
+        if (scopeChain.isEmpty())
+            scopeChain.append(engine()->globalObject());
+        while (!scopeChain.isEmpty())
+            evalContext->pushScope(scopeChain.takeLast());
+        evalContext->setActivationObject(ctx->activationObject());
+        evalContext->setThisObject(ctx->thisObject());
+    }
+
+    d->agent->enterContinueMode();
+    // set a flag so that any exception that happens in
+    // the evaluate() is not sent to the debugger
+    d->ignoreExceptions = true;
+    bool hadException = engine()->hasUncaughtException();
+    QScriptValue ret = engine()->evaluate(program, fileName, lineNumber);
+    d->ignoreExceptions = false;
+    if (!hadException && engine()->hasUncaughtException())
+        engine()->clearExceptions();
+    engine()->popContext();
+
+    QScriptDebuggerValue retret(ret);
+    QScriptDebuggerEvent e(QScriptDebuggerEvent::InlineEvalFinished);
+    e.setScriptValue(retret);
+    if (!ret.isUndefined())
+        e.setMessage(ret.toString()); // for convenience -- we always need it
+
+    e.setNestedEvaluate(engine()->isEvaluating());
+
+    if (postEvent) {
+        QScriptDebuggerEventEvent *de = new QScriptDebuggerEventEvent(e);
+        d->postEvent(de);
+    } else {
+        event(e);
+    }
+}
+
+/*!
+  Sets a breakpoint defined by the given \a data, and returns a unique
+  identifier for the new breakpoint.
+
+  If the conditions of the breakpoint is satisfied at some point
+  during script evaluation, a breakpoint event() will be generated.
+
+  \sa deleteBreakpoint(), breakpoints()
+*/
+int QScriptDebuggerBackend::setBreakpoint(const QScriptBreakpointData &data)
+{
+    Q_D(QScriptDebuggerBackend);
+    if (!d->agent)
+        return -1;
+    if (!data.isValid())
+        return -1;
+    return d->agent->setBreakpoint(data);
+}
+
+/*!
+  Deletes the breakpoint identified by the given \a id.  Returns true
+  if the breakpoint was deleted (i.e. the \a id was valid), otherwise
+  returns false.
+
+  \sa setBreakpoint()
+*/
+bool QScriptDebuggerBackend::deleteBreakpoint(int id)
+{
+    Q_D(QScriptDebuggerBackend);
+    if (!d->agent)
+        return false;
+    return d->agent->deleteBreakpoint(id);
+}
+
+/*!
+  Deletes all breakpoints.
+*/
+void QScriptDebuggerBackend::deleteAllBreakpoints()
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent)
+        d->agent->deleteAllBreakpoints();
+}
+
+/*!
+  Returns the data associated with the breakpoint identified by the
+  given \a id.
+*/
+QScriptBreakpointData QScriptDebuggerBackend::breakpointData(int id) const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (!d->agent)
+        return QScriptBreakpointData();
+    return d->agent->breakpointData(id);
+}
+
+/*!
+  Sets the \a data associated with the breakpoint identified by the
+  given \a id.
+*/
+bool QScriptDebuggerBackend::setBreakpointData(int id, const QScriptBreakpointData &data)
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent)
+        return d->agent->setBreakpointData(id, data);
+    return false;
+}
+
+/*!
+  Returns this backend's breakpoints.
+
+  \sa setBreakpoint()
+*/
+QScriptBreakpointMap QScriptDebuggerBackend::breakpoints() const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (!d->agent)
+        return QScriptBreakpointMap();
+    return d->agent->breakpoints();
+}
+
+/*!
+  Returns the scripts that this backend knows about.
+
+  \sa scriptData()
+*/
+QScriptScriptMap QScriptDebuggerBackend::scripts() const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (!d->agent)
+        return QScriptScriptMap();
+    return d->agent->scripts();
+}
+
+/*!
+  Returns the data for the script identified by the given \a id.
+
+  \sa scripts()
+*/
+QScriptScriptData QScriptDebuggerBackend::scriptData(qint64 id) const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (!d->agent)
+        return QScriptScriptData();
+    return d->agent->scriptData(id);
+}
+
+/*!
+  Makes a checkpoint of the currently loaded scripts.
+
+  \sa scriptsDelta()
+*/
+void QScriptDebuggerBackend::scriptsCheckpoint()
+{
+    Q_D(QScriptDebuggerBackend);
+    if (d->agent)
+        d->agent->scriptsCheckpoint();
+}
+
+/*!
+  Returns the difference between the latest scripts checkpoint and the
+  previous checkpoint.  The first item in the pair is a list
+  containing the identifiers of the scripts that were added. The
+  second item in the pair is a list containing the identifiers of the
+  scripts that were removed.
+
+  \sa scriptsCheckpoint()
+*/
+QScriptScriptsDelta QScriptDebuggerBackend::scriptsDelta() const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (!d->agent)
+        return QPair<QList<qint64>, QList<qint64> >();
+    return d->agent->scriptsDelta();
+}
+
+qint64 QScriptDebuggerBackend::resolveScript(const QString &fileName) const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (!d->agent)
+        return -1;
+    return d->agent->resolveScript(fileName);
+}
+
+/*!
+  Returns the number of contexts (frames).
+*/
+int QScriptDebuggerBackend::contextCount() const
+{
+    if (!engine())
+        return 0;
+    return contextIds().count();
+}
+
+/*!
+  Returns the context for the frame with the given \a index.
+*/
+QScriptContext *QScriptDebuggerBackend::context(int index) const
+{
+    if (index < 0)
+        return 0;
+    QScriptContext *ctx = engine()->currentContext();
+    while (ctx) {
+        if (index == 0)
+            return ctx;
+        ctx = ctx->parentContext();
+        --index;
+    }
+    return 0;
+}
+
+/*!
+  Returns a backtrace of the current execution.
+*/
+QStringList QScriptDebuggerBackend::backtrace() const
+{
+    if (!engine())
+        return QStringList();
+    return engine()->currentContext()->backtrace();
+}
+
+QList<qint64> QScriptDebuggerBackend::contextIds() const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (!d->agent)
+        return QList<qint64>();
+    return d->agent->contextIds();
+}
+
+QScriptContextsDelta QScriptDebuggerBackend::contextsCheckpoint()
+{
+    Q_D(QScriptDebuggerBackend);
+    if (!d->agent)
+        return QScriptContextsDelta();
+    return d->agent->contextsCheckpoint();
+}
+
+int QScriptDebuggerBackend::newScriptObjectSnapshot()
+{
+    Q_D(QScriptDebuggerBackend);
+    int id = d->nextScriptObjectSnapshotId;
+    ++d->nextScriptObjectSnapshotId;
+    d->scriptObjectSnapshots[id] = new QScriptObjectSnapshot();
+    return id;
+}
+
+QScriptObjectSnapshot *QScriptDebuggerBackend::scriptObjectSnapshot(int id) const
+{
+    Q_D(const QScriptDebuggerBackend);
+    return d->scriptObjectSnapshots.value(id);
+}
+
+void QScriptDebuggerBackend::deleteScriptObjectSnapshot(int id)
+{
+    Q_D(QScriptDebuggerBackend);
+    QScriptObjectSnapshot *snap = d->scriptObjectSnapshots.take(id);
+    delete snap;
+}
+
+int QScriptDebuggerBackend::newScriptValueIterator(const QScriptValue &object)
+{
+    Q_D(QScriptDebuggerBackend);
+    int id = d->nextScriptValueIteratorId;
+    ++d->nextScriptValueIteratorId;
+    d->scriptValueIterators[id] = new QScriptValueIterator(object);
+    return id;
+}
+
+QScriptValueIterator *QScriptDebuggerBackend::scriptValueIterator(int id) const
+{
+    Q_D(const QScriptDebuggerBackend);
+    return d->scriptValueIterators.value(id);
+}
+
+void QScriptDebuggerBackend::deleteScriptValueIterator(int id)
+{
+    Q_D(QScriptDebuggerBackend);
+    QScriptValueIterator *it = d->scriptValueIterators.take(id);
+    delete it;
+}
+
+bool QScriptDebuggerBackend::ignoreExceptions() const
+{
+    Q_D(const QScriptDebuggerBackend);
+    return d->ignoreExceptions;
+}
+
+void QScriptDebuggerBackend::setIgnoreExceptions(bool ignore)
+{
+    Q_D(QScriptDebuggerBackend);
+    d->ignoreExceptions = ignore;
+}
+
+/*!
+  Returns a trace function. The trace function has similar semantics
+  to the built-in print() function; however, instead of writing text
+  to standard output, it generates a trace event containing the text.
+*/
+QScriptValue QScriptDebuggerBackend::traceFunction() const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (!engine())
+        return QScriptValue();
+    QScriptValue fun = engine()->newFunction(QScriptDebuggerBackendPrivate::trace);
+    fun.setData(qScriptValueFromValue(engine(), const_cast<QScriptDebuggerBackendPrivate*>(d)));
+    return fun;
+}
+
+QScriptValue QScriptDebuggerBackend::assertFunction() const
+{
+    if (!engine())
+        return QScriptValue();
+    QScriptValue fun = engine()->newFunction(QScriptDebuggerBackendPrivate::qsassert);
+    return fun;
+}
+
+QScriptValue QScriptDebuggerBackend::fileNameFunction() const
+{
+    if (!engine())
+        return QScriptValue();
+    QScriptValue fun = engine()->newFunction(QScriptDebuggerBackendPrivate::fileName);
+    return fun;
+}
+
+QScriptValue QScriptDebuggerBackend::lineNumberFunction() const
+{
+    if (!engine())
+        return QScriptValue();
+    QScriptValue fun = engine()->newFunction(QScriptDebuggerBackendPrivate::lineNumber);
+    return fun;
+}
+
+QScriptDebuggerCommandExecutor *QScriptDebuggerBackend::commandExecutor() const
+{
+    Q_D(const QScriptDebuggerBackend);
+    if (d->commandExecutor)
+        return d->commandExecutor;
+    QScriptDebuggerBackendPrivate *dd = const_cast<QScriptDebuggerBackendPrivate*>(d);
+    dd->commandExecutor = new QScriptDebuggerCommandExecutor();
+    return dd->commandExecutor;
+}
+
+void QScriptDebuggerBackend::setCommandExecutor(QScriptDebuggerCommandExecutor *executor)
+{
+    Q_D(QScriptDebuggerBackend);
+    d->commandExecutor = executor;
+}
+
+/*!
+  \fn void QScriptDebuggerBackend::resume()
+
+  This function is called when control should be returned back to the
+  back-end, i.e. when script evaluation should be resumed after an
+  event has been delivered.
+
+  Subclasses must reimplement this function to make event() return.
+
+  \sa event()
+*/
+
+/*!
+  \fn void QScriptDebuggerBackend::event(const QScriptDebuggerEvent &event)
+
+  This function is called when the back-end has generated the given \a event.
+
+  Subclasses must reimplement this function to handle the
+  event. Typically the event is forwarded to a
+  QScriptDebuggerFrontend, which will in turn forward it to its
+  QScriptDebuggerClient. The client may then query the front-end for
+  information about the execution state, and call e.g.
+  continueEvalution() to resume execution. This function should block
+  until resume() is called.
+
+  \sa resume()
+*/
+
+QT_END_NAMESPACE