[X] GetValueSource

[StephaneDelcroix]

Description of Change

Add an internal API for tooling. This is a first pass, to test the API and the utility. The values returned might need to be refined, depending on actual testing.

@chabiss

Issues Fixed

Fixes #17223

[japarson]

I'm seeing that Shell.NavBarHasShadow defined in Styles.xaml is being classified as a Local property:

Through debugging, I'm seeing that the property is set to Local due to the following condition being met in your implementation of GetValueSource():

Is this expected behavior?

[japarson]

I'm seeing that we are picking up certain properties that are not "bindable" as in there is a null BindableProperty and we cannot call GetValueSource on them:

The values above are from a normal Button

These properties also have values that are different from their default values.

Few questions:

1. Why are these properties not bindable?
2. What is setting their values to be different from the default?
3. What ValueSource should these properties be considered. In WPF, we would set these properties to be Local, but that doesn't seem right here.

[StephaneDelcroix]

just like in WPF where GetValueSource works only on DependencyProperty.ies, this only works on BindableProperty.ies. Dis or BPs can not be assigned by styes, triggers, bindings, dynamic resources, ... anyway, and the source is most certainly 'Local'

[StephaneDelcroix]

@japarson 'Why are these properties not bindable?' which one ? anyway, that's out of the scope of this

[PureWeen]

/rebase

[PureWeen]

Test failure unrelated