AUTO_FOCUS on App should apply to screen

[willmcgugan]

If you don't define a screen, there is no way to set AUTO_FOCUS. We should make AUTO_FOCUS on App apply to the default screen.

[rodrigogiraoserrao]

I tought about that but I concluded that if you want a non-default auto focus, you should create your own screen.
The default screen has limitations and is just a convenience, right?

If you still want App.AUTO_FOCUS, isn't there a possibility for people to think that App.AUTO_FOCUS should apply to all screens in the app?
In other words, I think it is weird to have App.AUTO_FOCUS to be special-cased.
“Special cases aren't special enough to break the rules.”

I suggest:

• App.AUTO_FOCUS = "*" by default;
• Screen.AUTO_FOCUS = None by default;

The auto focus is then taken from the app's and the screen's, with the screen's taking precedence if it is not None.

[rodrigogiraoserrao]

@willmcgugan pinging you explicitly to ask for your feedback on this ^

[willmcgugan]

How then would you disable AUTO_FOCUS on a screen? Set it to empty string?

[rodrigogiraoserrao]

After some discussion, we're going with this:

• App.AUTO_FOCUS defaults to "*";
• Screen.AUTO_FOCUS defaults to None;
• Setting AUTO_FOCUS to "" explicitly disables it; and
• Setting AUTO_FOCUS to None (on a screen) means we “inherit” the value of AUTO_FOCUS from the app.

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