[Interest] Disabling signal connections for an item and its children

[Elvis Stansvik]

2016-05-07 11:32 GMT+02:00 Elvis Stansvik <elvstone at gmail.com>:
> Hi all,
>
> In a fullscreen page-based embedded QML app (HMI), I find myself often
> wanting to disable all signal connections when the page is not active
> (on top of stack).
>
> I found this 5 year old bug:
>
>     https://bugreports.qt.io/browse/QTBUG-18245
>
> I think Daniel's analysis in the comments is very good.
>
> I just wanted to ask, since it's such an old bug and much may have
> happened: Is there any way to achieve this currently?
>
> In my case, many of my pages react to backend (hardware) events in
> various ways, and it's tedious and error prone to always have to make
> sure I set the `target` of my Connections to null when the page is not
> active, to avoid unwanted reactions to signals.

The best I've come up with right now is to give my Page an active property:

Page.qml:

    FocusScope {
        readonly property bool active: Stack.status === Stack.Active
        focus: active
        ...
    }

SomePage.qml:

    Page {
        id: page

        Connections {
            target: page.active ? backend : null
            onSomeSignal: doSomething();
        }
        ...
    }

But this just saves some typing. It's still error prone and repetitive
to have to check this property in my Connections.

Elvis

>
> The bug is also about the disabling of property bindings and
> animations, which I guess is also a valid point, though not so much
> for me at the moment.
>
> Cheers,
> Elvis