PageControl Transition is not updated reactively

[Tapped]

Steps to reproduce

1. uno build -t=dotnetexe --run the following project PageControlTransition.zip
2. I'd expected no transition between the red and blue page.

Code

<App>
	<JavaScript>
		module.exports = {
			transistion: "None",
			alignment: "Center"
		}
	</JavaScript>
	<PageControl Transition="{transistion}">
		<Rectangle Color="Red">
			<Text Color="#fff" Alignment="{alignment}" Value="Red" />
		</Rectangle>
		<Rectangle Color="Blue">
			<Text Color="#fff" Alignment="{alignment}" Value="Blue" />
		</Rectangle>
	</PageControl>
</App>

[Tapped]

I suspect it's related to the following saying that it's only updated when rooted or unrooted https://github.com/fusetools/fuselibs-public/blob/master/Source/Fuse.Controls.Navigation/NavigationControl.uno#L84

[Tapped]

@mortoray Is this expected?

[mortoray]

Yes, several properties only have effect at rooting time. The complexity involved in gettiner everything supported post-rooting is too high. This means they can't be effectively bound to. We also have no way to mark them as being root-only for the docs.

Of course, if you have a high-level use-case for any property in particular we can debate changing it on a per-property basis.

[Tapped]

Then we have problems in preview, which expects all properties to support being changed at any time. Can we introduce an attribute for this? So that we can force reify in preview when a property decorated with that attribute changes, or give a warning to the user that the property he/she tried to set will need a reify to work properly.