Key injection fails in QML test

The keyinput QML auto test fails in qtapplicationmanager in multi-process mode when a debug build is used with ASSERT: "nativeScanCode >= offset" in file qtwayland/src/compositor/compositor_api/qwaylandkeyboard.cpp (the test has been disabled for now). The problem was introduced with https://codereview.qt-project.org/c/qt/qtbase/+/454426. With this patch the injected key events by the TestCase type take a different code path (through QWindowSystemInterfacePrivate::eventHandler->sendEvent instead of QGuiApplicationPrivate::processWindowSystemEvent directly). Hence the key events don't got through QWaylandSeat::sendFullKeyEvent any more that would call keyToScanCode which calculates a proper scanCode.

This would fix the problem:

--- a/src/compositor/compositor_api/qwaylandcompositor.cpp
+++ b/src/compositor/compositor_api/qwaylandcompositor.cpp
@@ -101,6 +101,8 @@ public:
         ke->nativeScanCode += offset;
 #endif
         uint32_t code = ke->nativeScanCode;
+        if (code == 0)
+            code = seat->keyboard()->keyToScanCode(ke->key);
         bool isDown = ke->keyType == QEvent::KeyPress;
 
 #if QT_CONFIG(xkbcommon)

The issue can be reproduced more easily with qmltestrunner and the attached test (though might hang on Wayland desktops as a subsequent problem). The question is, how this should properly be solved.