Fade callEnd button when call is ended

[Melr0k]

Checklist

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Feature description

Fade the callEnd button when the phone call is ended. Why not fade the others as they should not be enabled too…

Why do you want this feature?

When a phone call ends I don't really understand why it stays there for a bit before the call activity closes. And in this moment I always doubt if the phone call is really ended or not, and it took some time to see the text "Call ended". I think it's more clear to fade/dim the buttons to reassures that the phone call is ended. And it's easy to do.

Additional information

I tried binding.callEnd.setAlpha(0.5f) in the method endCall from CallActivity (line 759, just before the if statement) and I like it. It probably should be in its own function so we can visually disable all the buttons we decide to fade.