Allow to create a custom event dispatcher for specific QThreads.

QAbstractEventDispatcher() does no longer install itself into the current
thread.  Instead the new methods QThread::setEventDispatcher() and
QCoreApplication::setEventDispatcher() allow to install a custom event
dispatcher into any QThread as long as there is no default event dispatcher
created yet.  That is, before the thread has been started with
QThread::start() or, in case of the main thread, before QCoreApplication has
been instantiated.

Change-Id: I7367e13d8d8aebed5a5651260bb69b8818eb1b90
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>

4 files changed, 45 insertions, 4 deletions

diff --git a/src/corelib/thread/qthread.cpp b/src/corelib/thread/qthread.cpp
index 6cc8a4875a..17b0f2cb94 100644
--- a/src/corelib/thread/qthread.cpp
+++ b/src/corelib/thread/qthread.cpp
@@ -757,4 +757,36 @@ QThread::QThread(QThreadPrivate &dd, QObject *parent)
 
 #endif // QT_NO_THREAD
 
+/*!
+    Returns a pointer to the event dispatcher object for the thread. If no event
+    dispatcher exists for the thread, this function returns 0.
+*/
+QAbstractEventDispatcher *QThread::eventDispatcher() const
+{
+    Q_D(const QThread);
+    return d->data->eventDispatcher;
+}
+
+/*!
+    Sets the event dispatcher for the thread to \a eventDispatcher. This is
+    only possible as long as there is no event dispatcher installed for the
+    thread yet. That is, before the thread has been started with start() or, in
+    case of the main thread, before QCoreApplication has been instantiated.
+    This method takes ownership of the object.
+*/
+void QThread::setEventDispatcher(QAbstractEventDispatcher *eventDispatcher)
+{
+    Q_D(QThread);
+    if (d->data->eventDispatcher != 0) {
+        qWarning("QThread::setEventDispatcher: An event dispatcher has already been created for this thread");
+    } else {
+        eventDispatcher->moveToThread(this);
+        if (eventDispatcher->thread() == this) // was the move successful?
+            d->data->eventDispatcher = eventDispatcher;
+        else
+            qWarning("QThread::setEventDispatcher: Could not move event dispatcher to target thread");
+    }
+}
+
+
 QT_END_NAMESPACE
diff --git a/src/corelib/thread/qthread.h b/src/corelib/thread/qthread.h
index 89a3ad8b1f..baad793969 100644
--- a/src/corelib/thread/qthread.h
+++ b/src/corelib/thread/qthread.h
@@ -54,6 +54,7 @@ QT_MODULE(Core)
 
 class QThreadData;
 class QThreadPrivate;
+class QAbstractEventDispatcher;
 
 #ifndef QT_NO_THREAD
 class Q_CORE_EXPORT QThread : public QObject
@@ -92,6 +93,9 @@ public:
 
     void exit(int retcode = 0);
 
+    QAbstractEventDispatcher *eventDispatcher() const;
+    void setEventDispatcher(QAbstractEventDispatcher *eventDispatcher);
+
 public Q_SLOTS:
     void start(Priority = InheritPriority);
     void terminate();
diff --git a/src/corelib/thread/qthread_unix.cpp b/src/corelib/thread/qthread_unix.cpp
index 46bc641d16..8c6fefcfd7 100644
--- a/src/corelib/thread/qthread_unix.cpp
+++ b/src/corelib/thread/qthread_unix.cpp
@@ -289,8 +289,10 @@ void *QThreadPrivate::start(void *arg)
         data->quitNow = thr->d_func()->exited;
     }
 
-    // ### TODO: allow the user to create a custom event dispatcher
-    createEventDispatcher(data);
+    if (data->eventDispatcher) // custom event dispatcher set?
+        data->eventDispatcher->startingUp();
+    else
+        createEventDispatcher(data);
 
     emit thr->started();
     pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
diff --git a/src/corelib/thread/qthread_win.cpp b/src/corelib/thread/qthread_win.cpp
index 80d7f3ff63..5b74bad7ef 100644
--- a/src/corelib/thread/qthread_win.cpp
+++ b/src/corelib/thread/qthread_win.cpp
@@ -315,8 +315,11 @@ unsigned int __stdcall QT_ENSURE_STACK_ALIGNED_FOR_SSE QThreadPrivate::start(voi
         QMutexLocker locker(&thr->d_func()->mutex);
         data->quitNow = thr->d_func()->exited;
     }
-    // ### TODO: allow the user to create a custom event dispatcher
-    createEventDispatcher(data);
+
+    if (data->eventDispatcher) // custom event dispatcher set?
+        data->eventDispatcher->startingUp();
+    else
+        createEventDispatcher(data);
 
 #if !defined(QT_NO_DEBUG) && defined(Q_CC_MSVC) && !defined(Q_OS_WINCE)
     // sets the name of the current thread.