Mitigate private header problems in QtCreator by adding semi-private API

Add a semi-private API to get QScriptEngine for a QDeclarativeEngine. So far the qmljsdebugger lib in QtCreator
accessed the script engine via QDeclarativeEnginePrivate. Replace this by a minimal API that is still in a
private header, where we nevertheless can make some BC checks/guarantees.

Aaron Kennedy agreed with the idea.

Task-number: QTCREATORBUG-2179
(cherry picked from commit 63c4c0449361ced03838e51d18e1113740f27fa9)

4 files changed, 42 insertions, 3 deletions

diff --git a/src/declarative/debugger/debugger.pri b/src/declarative/debugger/debugger.pri
index 33d0843..25f7687 100644
--- a/src/declarative/debugger/debugger.pri
+++ b/src/declarative/debugger/debugger.pri
@@ -6,7 +6,8 @@ SOURCES += \
     $$PWD/qdeclarativedebugservice.cpp \
     $$PWD/qdeclarativedebugclient.cpp \
     $$PWD/qdeclarativedebug.cpp \
-    $$PWD/qdeclarativedebugtrace.cpp
+    $$PWD/qdeclarativedebugtrace.cpp \
+    $$PWD/qdeclarativedebughelper.cpp
 
 HEADERS += \
     $$PWD/qdeclarativedebuggerstatus_p.h \
@@ -14,4 +15,5 @@ HEADERS += \
     $$PWD/qdeclarativedebugservice_p.h \
     $$PWD/qdeclarativedebugclient_p.h \
     $$PWD/qdeclarativedebug_p.h \
-    $$PWD/qdeclarativedebugtrace_p.h
+    $$PWD/qdeclarativedebugtrace_p.h \
+    $$PWD/qdeclarativedebughelper_p.h
diff --git a/src/declarative/debugger/qdeclarativedebug_p.h b/src/declarative/debugger/qdeclarativedebug_p.h
index f0fc488..2b1a115 100644
--- a/src/declarative/debugger/qdeclarativedebug_p.h
+++ b/src/declarative/debugger/qdeclarativedebug_p.h
@@ -365,7 +365,6 @@ private:
     int m_queryId;
     QVariant m_expr;
     QVariant m_result;
-
 };
 
 QT_END_NAMESPACE
diff --git a/src/declarative/debugger/qdeclarativedebughelper.cpp b/src/declarative/debugger/qdeclarativedebughelper.cpp
new file mode 100644
index 0000000..99feff4
--- /dev/null
+++ b/src/declarative/debugger/qdeclarativedebughelper.cpp
@@ -0,0 +1,13 @@
+#include "private/qdeclarativedebughelper_p.h"
+#include "private/qdeclarativeengine_p.h"
+
+#include <QtScript/QScriptEngine>
+
+QT_BEGIN_NAMESPACE
+
+QScriptEngine *QDeclarativeDebugHelper::getScriptEngine(QDeclarativeEngine *engine)
+{
+    return QDeclarativeEnginePrivate::getScriptEngine(engine);
+}
+
+QT_END_NAMESPACE
diff --git a/src/declarative/debugger/qdeclarativedebughelper_p.h b/src/declarative/debugger/qdeclarativedebughelper_p.h
new file mode 100644
index 0000000..a403c45
--- /dev/null
+++ b/src/declarative/debugger/qdeclarativedebughelper_p.h
@@ -0,0 +1,25 @@
+#ifndef QDECLARATIVEDEBUGHELPER_P_H
+#define QDECLARATIVEDEBUGHELPER_P_H
+
+#include <QtCore/qglobal.h>
+
+QT_BEGIN_HEADER
+
+QT_BEGIN_NAMESPACE
+
+class QScriptEngine;
+class QDeclarativeEngine;
+
+// Helper methods to access private API through a stable interface
+// This is used in the qmljsdebugger library of QtCreator.
+class Q_DECLARATIVE_EXPORT QDeclarativeDebugHelper
+{
+public:
+    static QScriptEngine *getScriptEngine(QDeclarativeEngine *engine);
+};
+
+QT_END_NAMESPACE
+
+QT_END_HEADER
+
+#endif // QDECLARATIVEDEBUGHELPER_P_H