QDeclarativeTrace patch for a custom trace instance

Needed for the BB10 Cascades profiling. There are more reasons for
introducing this patch:

1) Cascades do not use QtGui library for QML rendering. It has its own
paint engine with client-server architecture. Profiler traces are sent
asynchronously from non Qt renderer thread to the Qt client.
The QPerformanceTimer has to be patched too, cause we need to know time
difference between tracing zero time and some time in past,
see: qint64 elapsedToAbsoluteTime(qint64 absoluteMonotonicTimeNs) const

2) Since we need more sophisticated trace engine in cascades, this patch
allows explicitly assign custom class derived from QDeclaraqtiveDebugtrace
to the trace framework.
If no custom instance is assigned, the default QDeclarativeDebugTrace
instance is created implicitly on first trace request.
Using custom trace instance which is not part of Qt
(it is part of libbbcascades) allows us to implement all Cascades trace
special needs in libbbcascades and not to carry Qt with the platform
specific code.

3) The NO_CUSTOM_DECLARATIVE_DEBUG_TRACE_INSTANCE macro is introduced to
allow custom trace engine only on the bleckberry platform,
see declarative.pro.
If this macro is defined Qt compiles from its original code.

4) Possibility of custom QDeclaraqtiveDebugTrace instance might be usable
for other projects which needs to extends somehow default Qt trace
functionality.

5) Patch is not intended to be applied to Qt Quick 2, since declarative
debugging infrastructure is changed there.

(cherry picked from commit f13b52f25c1e0bc26dcf3ea304b3495f7d5cd370)

Change-Id: I199211c1de66e930e252e8c033503d7f4940565f
Reviewed-by: Christiaan Janssen <christiaan.janssen@digia.com>

2 files changed, 78 insertions, 1 deletions

diff --git a/src/declarative/debugger/qdeclarativedebugtrace.cpp b/src/declarative/debugger/qdeclarativedebugtrace.cpp
index 1c2d440c50..d4ede07b5c 100644
--- a/src/declarative/debugger/qdeclarativedebugtrace.cpp
+++ b/src/declarative/debugger/qdeclarativedebugtrace.cpp
@@ -44,8 +44,68 @@
 #include <QtCore/qdatastream.h>
 #include <QtCore/qurl.h>
 #include <QtCore/qtimer.h>
+#include <QDebug>
+
+#ifdef CUSTOM_DECLARATIVE_DEBUG_TRACE_INSTANCE
+
+namespace {
+
+    class GlobalInstanceDeleter
+    {
+    private:
+        QBasicAtomicPointer<QDeclarativeDebugTrace> &m_pointer;
+    public:
+        GlobalInstanceDeleter(QBasicAtomicPointer<QDeclarativeDebugTrace> &p)
+        : m_pointer(p)
+        {}
+        ~GlobalInstanceDeleter()
+        {
+            delete m_pointer;
+            m_pointer = 0;
+        }
+    };
+
+    QBasicAtomicPointer<QDeclarativeDebugTrace> s_globalInstance = Q_BASIC_ATOMIC_INITIALIZER(0);
+}
+
+
+static QDeclarativeDebugTrace *traceInstance()
+{
+    return QDeclarativeDebugTrace::globalInstance();
+}
+
+QDeclarativeDebugTrace *QDeclarativeDebugTrace::globalInstance()
+{
+    if (!s_globalInstance) {
+        // create default QDeclarativeDebugTrace instance if it is not explicitly set by setGlobalInstance(QDeclarativeDebugTrace *instance)
+        // thread safe implementation
+        QDeclarativeDebugTrace *x = new QDeclarativeDebugTrace();
+        if (!s_globalInstance.testAndSetOrdered(0, x))
+            delete x;
+        else
+            static GlobalInstanceDeleter cleanup(s_globalInstance);
+    }
+    return s_globalInstance;
+}
+
+/*!
+ *  Set custom QDeclarativeDebugTrace instance \a custom_instance.
+ *  Function fails if QDeclarativeDebugTrace::globalInstance() was called before.
+ *  QDeclarativeDebugTrace framework takes ownership of the custom instance.
+ */
+void QDeclarativeDebugTrace::setGlobalInstance(QDeclarativeDebugTrace *custom_instance)
+{
+    if (!s_globalInstance.testAndSetOrdered(0, custom_instance)) {
+        qWarning() << "QDeclarativeDebugTrace::setGlobalInstance() - instance already set.";
+        delete custom_instance;
+    } else {
+        static GlobalInstanceDeleter cleanup(s_globalInstance);
+    }
+}
 
+#else // CUSTOM_DECLARATIVE_DEBUG_TRACE_INSTANCE
 Q_GLOBAL_STATIC(QDeclarativeDebugTrace, traceInstance);
+#endif
 
 // convert to a QByteArray that can be sent to the debug client
 // use of QDataStream can skew results if m_deferredSend == false
diff --git a/src/declarative/debugger/qdeclarativedebugtrace_p.h b/src/declarative/debugger/qdeclarativedebugtrace_p.h
index 5a077ac90b..ef5e618e68 100644
--- a/src/declarative/debugger/qdeclarativedebugtrace_p.h
+++ b/src/declarative/debugger/qdeclarativedebugtrace_p.h
@@ -44,6 +44,7 @@
 
 #include <private/qdeclarativedebugservice_p.h>
 #include <private/qperformancetimer_p.h>
+#include <QtCore/qglobal.h>
 
 QT_BEGIN_HEADER
 
@@ -63,7 +64,7 @@ struct QDeclarativeDebugData
 };
 
 class QUrl;
-class Q_AUTOTEST_EXPORT QDeclarativeDebugTrace : public QDeclarativeDebugService
+class Q_DECLARATIVE_EXPORT QDeclarativeDebugTrace : public QDeclarativeDebugService
 {
 public:
     enum Message {
@@ -105,6 +106,21 @@ public:
     static void endRange(RangeType);
 
     QDeclarativeDebugTrace();
+#ifdef CUSTOM_DECLARATIVE_DEBUG_TRACE_INSTANCE
+public:
+    static QDeclarativeDebugTrace* globalInstance();
+    static void setGlobalInstance(QDeclarativeDebugTrace *custom_instance);
+protected:
+    virtual void messageReceived(const QByteArray &);
+protected:
+    virtual void addEventImpl(EventType);
+    virtual void startRangeImpl(RangeType);
+    virtual void rangeDataImpl(RangeType, const QString &);
+    virtual void rangeDataImpl(RangeType, const QUrl &);
+    virtual void rangeLocationImpl(RangeType, const QString &, int);
+    virtual void rangeLocationImpl(RangeType, const QUrl &, int);
+    virtual void endRangeImpl(RangeType);
+#else
 protected:
     virtual void messageReceived(const QByteArray &);
 private:
@@ -115,6 +131,7 @@ private:
     void rangeLocationImpl(RangeType, const QString &, int);
     void rangeLocationImpl(RangeType, const QUrl &, int);
     void endRangeImpl(RangeType);
+#endif
     void processMessage(const QDeclarativeDebugData &);
     void sendMessages();
     QPerformanceTimer m_timer;