Handling key events in Wayland compositor (IviApplication)

Horatio

I am working on this IviApplication example on Ubuntu 22.04 desktop. I am using Qt5.15.2.
https://doc.qt.io/qt-6.5/qtwaylandcompositor-ivi-compositor-example.html
Example source code:
https://code.qt.io/cgit/qt/qtwayland.git/tree/examples/wayland/ivi-compositor?h=5.15

I successfully run it. I can see two programs running on the left and right area.

By adding onFocusChanged and Keys.onReleased signal handlers to the ShellSurfaceItem, I can see the program getting focus when I mouse-click on its area and the program getting key events when I press keyboard.

My question is how to move focus from one program to another by using keyboard? It is essential on a device without touch screen.
I tried the WaylandSeat but always got error no matter where I put it. The QML engine cannot create it.

Thank you for your help.

Horatio

Answering my own question...

Pass WaylandCompositor's property - defaultSeat into C++ as QWaylandSeat*.
https://doc.qt.io/archives/qt-5.15/qml-qtwayland-compositor-waylandcompositor.html#defaultSeat-prop

WaylandCompositor
{
    id: iCompositor
    Component.onCompleted:
    {
        CppHelper.setDefaultWaylandSeat( iCompositor.defaultSeat );
    }
}

Use QWaylandSeat's setKeyboardFocus(), which takes QWaylandSurface*.
https://doc.qt.io/archives/qt-5.15/qwaylandseat.html#setKeyboardFocus
QWaylandSurface* can be found in the onIviSurfaceCreated() as iviSurface. You can pass it into C++.

IviApplication 
{
    onIviSurfaceCreated:
    {
        var surfaceArea = iviSurface.iviId === 1337 ? leftArea : rightArea;
        var item = chromeComponent.createObject(surfaceArea, { "shellSurface": iviSurface } );
        item.handleResized();
        // Pass QWaylandSurface* into C++.
        CppHelper.registerIviSurface( iviSurface );
    }
}

The signal keyboardFocusChanged can be used to observe the change.
https://doc.qt.io/archives/qt-5.15/qwaylandseat.html#keyboardFocusChanged

However, setKeyboardFocus() doesn't work very well. I do get the signal keyboard focus changed, but the focus jump back to the original window if I actually press a keyboard key.