windowmanager dbus signal issue in Dab 4.0 RC1[m3ulcb]

We tried to add something in application dashboard at  “Dab 4.0 RC1” on m3ulcb, needs know if dashboard sceen is ontop or not. For example, change from dashboard to HomeScreen/Navigation.

First tried to find a method or siganal in windowmanager source, but got nothing.
And found something in 4.3.5 of this pdf, but don't know how to use it.

https://wiki.automotivelinux.org/_media/eg-ui-graphics/170606_agl_hmi-fw_arch_0_2_3.pdf

So we created by ourself like these. 

1) add a dbus signal in windowmanager named “appLayerVisibleChanged”, modified windowmanager.xml like this,

        <!--
        appLayerVisibleChanged:
        @pid: The pid of the app that changed.
        @visible: True, if the app layer is visible.
        This is emitted when the visible property of the app layer changes.
        -->
        <signal name="appLayerVisibleChanged">
        <arg name="pid" type="i"/>
        <arg name="visible" type="b"/>
        </signal>

2) changed windowmanager.hpp and windowmanager.cpp to send “appLayerVisibleChanged” signal

3) add receive signal code in dashboard like this,

        QDBusConnection::sessionBus().connect("org.agl.windowmanager",
        "/windowmanager",
        "org.agl.windowmanager",
        "appLayerVisibleChanged",
        this,
        SLOT(appLayerVisibleChangedSlot(int,bool)));

4) I test these on m3ulcb board,but dashboard application can not receive dbus signal.  Then I use dbus-monitor tool to track this signal , result like this,

        signal sender=:1.6 -> dest=(null destination) serial=7 path=/windowmanager; interface=org.agl.windowmanager; member=appLayerVisibleChanged
        int32 5271
        boolean true
        signal sender=:1.6 -> dest=(null destination) serial=8 path=/windowmanager; interface=org.agl.windowmanager; member=appLayerVisibleChanged
        int32 -1
        boolean false

   Windowmanager already sended “appLayerVisibleChanged” signal.   I thought may be dashboard application don’t have permission to receive this signal.   so I added a file named “windowmanager.conf” in /etc/dbus-1/session.d/ ,

        <?xml version="1.0"?> <!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN" "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd"<http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd>>
        <busconfig>
        <policy context="default">
                <allow receive_type="signal" receive_sender="org.agl.windowmanager" receive_interface="org.agl.windowmanager"/>
        </policy>
        </busconfig>

then reboot m3ulcb, swith to dashboard, dashboard application can receive this signal.

My question:

Q1: Does windowmanager had something can provide the application status?
       If not, may be windowmanager should provide IMO.

Q2: If Q1 is false. Does it correct that we add code like these.

Best Regards!