Handle signals in the registered object's thread

Do not call `sender()` from a different thread. As the API documentation
indicates, that is not supported and can lead to crashes as experienced
on the CI frequently.

Instead, we now have per-thread SignalHandlers and use those to get
notified about signals and metacall events.

Moving a registered object into a different thread isn't supported once
it was registered. But the object can be deregistered, moved, and then
re-registered.

[ChangeLog] Signals from objects living in a different thread than the
QWebChannel are now handled correctly.

Task-number: QTBUG-51366
Change-Id: I1edb0694b946a494b6c0d4a8a6dc6b452dcb2c7a
Reviewed-by: Arno Rehn <a.rehn@menlosystems.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/src/webchannel/qmetaobjectpublisher_p.h b/src/webchannel/qmetaobjectpublisher_p.h
index 5e57e8c..e87e4f0 100644
--- a/src/webchannel/qmetaobjectpublisher_p.h
+++ b/src/webchannel/qmetaobjectpublisher_p.h
@@ -60,6 +60,8 @@
 #include <QPointer>
 #include <QJsonObject>
 
+#include <unordered_map>
+
 #include "qwebchannelglobal.h"
 
 QT_BEGIN_NAMESPACE
@@ -275,7 +277,8 @@ private:
     friend class TestWebChannel;
 
     QWebChannel *webChannel;
-    SignalHandler<QMetaObjectPublisher> signalHandler;
+    std::unordered_map<const QThread*, SignalHandler<QMetaObjectPublisher>> signalHandlers;
+    SignalHandler<QMetaObjectPublisher> *signalHandlerFor(const QObject *object);
 
     // true when the client is idle, false otherwise
     bool clientIsIdle;