Unfocus children in Group#clearChildren()

[petoncle]

Group.removeActor(Actor child, boolean unfocus) gives the option to unfocus the removed child.
Group.removeActor(Actor child) unfocuses the removed child (calls removeActor(child, true)).

For some reason, Group.clearChildren() currently does not unfocus the children. This looks wrong.
This PR adds a clearChildren(boolean unfocus) method.

Now the question is: do you want clearChildren() (no arguments) to unfocus like removeActor(child) does, or do you want clearChildren() to not unfocus to avoid potentially breaking apps which may rely on the fact that clearChildren() never unfocused until now? I'm all for breaking apps, but 🤷.

[petoncle]

After thinking about it some more, I believe not making clearChildren() (no arguments) unfocus its children is not good for me personally as I'll have to change all my clearChildren() calls to clearChildren(true), and most of the times I don't even call clearChildren() but clear().

[NathanSweet]

Good find. I think clearChildren without specifying unfocus should match removeActor without specifying unfocus: it should unfocus. As @petoncle mentioned, this makes it a breaking change but the API consistency is likely worth it.

Some notes: Having removed actors retain focus can cause errors and surprises. We don't always remove focus though, because sometimes removal is temporary and keeping the focus is desired. Adding an unfocus boolean to a bunch of methods isn't great, but gives the flexibility needed and helps people consider the issue.

[NathanSweet]

I wonder, should we have a Group clear(boolean unfocus)?

[petoncle]

I wonder, should we have a Group clear(boolean unfocus)?

We might as well for consistency with the clearChildren and removeActor methods.

[petoncle]

@NathanSweet I've added a Group#clear(boolean unfocus) method if you're interested. I think you'll have to re-open the PR to be able to merge it in.

[NathanSweet]

No worries, I've made the change.