OverviewFelgo 2 Support (Qt 5) › [Feedback] Documentation of lazy-loaded components

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  • #12343


    The documentation does not seem to state that the v-play navigation infrastructure will lazy-load pages. This is rather surprising for someone who’s used to standard QML, which will construct all components defined in the QML source at startup, unless they are wrapped in a Component{}. This leads to unexpected behavior such as getting a “ReferenceError: listPage is not defined” error from something like this:

    App {
      Component.onCompleted: console.log(listPage.x)
      Navigation {
        NavigationItem {
          id: widgetsItem
          title: "Widgets"
          icon: IconType.calculator
          WidgetsPage { title: widgetsItem.title }
        NavigationItem {
          title: "Simple List"
          icon: IconType.list
          NavigationStack { //this tab/navigation item uses stack-based sub-navigation
            SimpleListPage { id: listPage }


    This behavior should be documented in the Navigation and NavigationItem detailed description sections.


    Felgo Team

    Hi Nathan,
    thank you for your feedback!
    We will add it to the documentation. 😉

    Our current implementation uses the Qt Quick TabView internally, which automatically comes with this lazy-loading mechanism.
    Besides the Navigation, this also affects the TabControl component.





    Ahh, that makes sense. I also note that NavigationItem inherits Tab, which could have been a hint (since Qt’s Tab documentation emphasizes that Tabs are lazy-loaded), but I didn’t follow that link. It’s probably worth emphasizing on NavigationItem that it is lazy-loaded, and referencing the Tab docs for more info.

    It appears that NavigationStack also lazy-loads its children, though, since in my original example (which was just a tweak from the example on the Navigation doc) I still can’t access listPage from an onSelected handler on its containing NavigationItem. I believe this is also the behavior of Qt Quick Controls’ StackView, if that’s what’s being used behind the scenes.


    Felgo Team

    You guessed right, we use the StackView internally.
    Besides the Navigation/TabControl and the NavigationStack there aren’t any more items that lazy-load their content. So if you keep in mind that these types do you should be good to go.


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