AppLinkEntry Support

[edgarfgp]

Implementation of fabulous-dev/Fabulous.XamarinForms#21

In order to support Deep linking a Indexing we need to:

• Create a Fabulous CustomApplication so we can override the relevant method and expose a Event so we can add a method extension.

type CustomApplication() =
    inherit Application()

    let linkRequestReceived = Event<EventHandler<LinkRequestReceivedEventArgs>, _>()

    [<CLIEvent>]
    member _.LinkRequestReceived = linkRequestReceived.Publish

    override this.OnAppLinkRequestReceived(uri : Uri)=
        linkRequestReceived.Trigger(this, LinkRequestReceivedEventArgs(uri))
        base.OnAppLinkRequestReceived(uri)

• Adds and extension method fore the event :

  
  let LinkRequestReceived =
  Attributes.defineEvent<LinkRequestReceivedEventArgs>
  "Application_LinkRequestReceived"
  (fun target -> (target :?> CustomApplication).LinkRequestReceived)

[] static member inline onLinkReceived(this: WidgetBuilder<'msg, #IApplication>, fn: LinkRequestReceivedEventArgs -> 'msg) = this.AddScalar(Application.LinkRequestReceived.WithValue(fn >> box))

## Limitation

- The initial idea was to have a DSL like : 
```fsharp
Application(...)
    .onAppLinkReceived(NavigateDeepInAppMsg)
        .appLinks {
            AppLink(...)
            AppLink(...)
        }

BUT AppLinks is not a List of AppLink is just and Intercase AppLinks . So can not use a widget collection.

Workaround

• Use ViewRef to to get access to the Register and DeRegister methods

  
  let applicationRef = ViewRef<Application>()
  let createLink =
   let pageLink = new Xamarin.Forms.AppLinkEntry()
   pageLink.Title <- "Im a deep link"
   pageLink.Description <- "Counter App"
   pageLink.AppLinkUri <- Uri("https://www.xamarin.com/platform")
   pageLink.IsLinkActive <- true
  
   pageLink.KeyValues.Add("contentType", "TodoItemPage");
   pageLink.KeyValues.Add("appName", "");
   pageLink.KeyValues.Add("companyName", "Xamarin");
  
   pageLink

match applicationRef.TryValue with | Some target -> target.AppLinks.RegisterLink(createLink) | None -> failwith "No application ref")

[edgarfgp]

@twop After some investigation this how the feature could be implemented. and detailed some of the limitation . Not sure if there is a way to fix the limitation I found. @TimLariviere and yourself know the internals better that I do . So any feedback is appreciated

[TimLariviere]

Maybe you can add a AppLinks collection to CustomApplication to be able to use widget collection?

[TimLariviere]

Hmm, actually you can do it without adding a new property to CustomApplication. You can create a fake "AppLinks" collection attribute that would direct update Application.AppLinks.Register/Deregister (see NavigationPage.Pages for example)