[UWP] [Shell] Make Navigation and Transition overridable for Shell

[GiampaoloGabba]

Description of Change

The ShellSectionRenderer for UWP doesn't expose any virtual method to override, closing a lot of possibilities expecially for plugin authors.

This PR comes after a conversation on Twitter with @PureWeen and adds a bunch of protected virtual methods to the navigation process (splitting up the NavigateToContent method in submethods).
Also i also made the GetTransitionInfo method virtual so we can change the animation transition between pages.

Please note that i also made virtual the NavigateToContent method, so we have the ability to to jump in the navigation process before the destination page has been created (or after with the new virtual methods).

API Changes

Added:

• protected void OnPopRequested(ShellNavigationSource source)
• protected void OnPopToRootRequested(ShellNavigationSource source)
• protected void OnPushRequested(ShellNavigationSource source)
• protected void OnInsertRequested(ShellNavigationSource source, Page page)
• protected void OnRemoveRequested(ShellNavigationSource source, Page page)
• protected void OnShellSectionChanged(ShellNavigationSource source)

Changed:

• protected virtual void NavigateToContent(ShellNavigationSource source, ShellContent shellContent, Page page, bool animate = true)
• protected virtual NavigationTransitionInfo GetTransitionInfo(ShellNavigationSource navSource)

Platforms Affected

• UWP

Behavioral/Visual Changes

None

Before/After Screenshots

Not applicable

Testing Procedure

I think the current tests are enough, i have just moved some code inside virtual methods, no need to special test cases.

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)

[pictos]

LGTM!

[PureWeen]

/azp run

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No pipelines are associated with this pull request.

[PureWeen]

Would these be more helpful if they included the full arg like iOS?

Xamarin.Forms/Xamarin.Forms.Platform.iOS/Renderers/ShellSectionRenderer.cs

Line 328 in a695fab

protected virtual async void OnPopRequested(NavigationRequestedEventArgs e)

[GiampaoloGabba]

yepp, is a good idea.
Do you think we should use the NavigationRequestedEventArgs in Xamarin.Forms.Core? Or just pass the Page and isAnimated properties in the virtual method?

I'm asking because the NavigationRequestedEventArgs has this property:
public Task<bool> Task { get; set; }
but in the shell renderer we dont have a navigation task

[PureWeen]

I think NavigationRequestedEventArgs makes sense

We use that property on the iOS renderers, it might be useful on UWP at some point

[GiampaoloGabba]

Sorry for the delay, i was really busy lately and didnt had time to finish the PR with the changes requested by @PureWeen

I had a conversation with pureween the other day and he is going to finish this, but.... Let me know if you are too busy, i can try to finish it!

[GiampaoloGabba]

@PureWeen definetely i love the new changes you made to the renderers and the NavigationRequestedEventArgs argument, thank you!

[PureWeen]

/azp run

[azure-pipelines]

No pipelines are associated with this pull request.

[PureWeen]

@GiampaoloGabba Awesome!!

I kicked off the UI Tests. Once those pass I'll merge

Thank you for all your work and focus on bringing better transitions to Forms. I'm really excited about what you are bringing to the ecosystem here!!!