Implement all permutations of InputTransparent and CascadeInputTransparent

[mattleibow]

Description of Change

There are several input transparency issues and most of the fixes we have done fix some and potentially create new issues because of the way things are set up. My proposed fix is going to be similar to the changes for IsEnabled when the IsEnabled is controlled by 3 parts: IsEnabled, Parent.IsEnabled and ICommand.CanExecute.

The InputTransparent result value is controlled by a few parts:

• The InputTransparent property on the element
• The InputTransparent property on the PARENT but only iff the CascadeInputTransparent permits

I also assume that:

Setting the initial state X is the same as going from some arbitrary state into state X. For example, if the state is the layout being transparent and the control not transparent will result in the same final state even if the initial state was different.

However, this is semi-ambiguous as what happens when there are multiple nested layouts with different values? The table below tries to capture all the things in a truth table.

So far my observations are:

1. The control always overrides everything when set to transparent
2. The layout always overrides when set to transparent AND cascade
3. A nested layout cannot not un-set a parent-set transparency

Given the code:

new Layout {
    Tag = "Root",
    new Layout {
        Tag = "Nested"
        new Control {
            Tag = "Control"
        }
    }
}

✅ = True
❌ = False

Root.Tr	Root.Cas	Nested.Tr	Nested.Cas	Control.Tr	=	Nested.Tr	=	Control.Tr
✅	✅	✅	✅	✅		✅		✅
✅	✅	✅	✅	❌		✅		✅
✅	✅	✅	❌	✅		✅		✅
✅	✅	✅	❌	❌		✅		✅
✅	✅	❌	✅	✅		✅		✅
✅	✅	❌	✅	❌		✅		✅
✅	✅	❌	❌	✅		✅		✅
✅	✅	❌	❌	❌		✅		✅
✅	❌	✅	✅	✅		✅		✅
✅	❌	✅	✅	❌		✅		✅
✅	❌	✅	❌	✅		✅		✅
✅	❌	✅	❌	❌		✅		❌
✅	❌	❌	✅	✅		❌		✅
✅	❌	❌	✅	❌		❌		❌
✅	❌	❌	❌	✅		❌		✅
✅	❌	❌	❌	❌		❌		❌
❌	✅	✅	✅	✅		✅		✅
❌	✅	✅	✅	❌		✅		✅
❌	✅	✅	❌	✅		✅		✅
❌	✅	✅	❌	❌		✅		❌
❌	✅	❌	✅	✅		❌		✅
❌	✅	❌	✅	❌		❌		❌
❌	✅	❌	❌	✅		❌		✅
❌	✅	❌	❌	❌		❌		❌
❌	❌	✅	✅	✅		✅		✅
❌	❌	✅	✅	❌		✅		✅
❌	❌	✅	❌	✅		✅		✅
❌	❌	✅	❌	❌		✅		❌
❌	❌	❌	✅	✅		❌		✅
❌	❌	❌	✅	❌		❌		❌
❌	❌	❌	❌	✅		❌		✅
❌	❌	❌	❌	❌		❌		❌

Issues Fixed

• Fixes [Bug] InputTransparent = false does not work. #14828
• Fixes under iOS, "parent.InputTransparent = false" does not propagate to children as it should #10203
• Fixes InputTransparent with Opacity/IsVisible behaves differently with iOS/Mac vs Windows/Android #15608
• Fixes InputTransparent logic/intended behavior #7489
• Fixes CascadeInputTransparent="False" is not working on ContentView #10977

[jfversluis]

Probably also related: #9153

[mattleibow]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[jsuarezruiz]

Could you include inline comments here?