Propagate events to hidden widgets in Either

[andrewhickman]

Fixes #1350

The should_propagate_to_hidden methods are taken from the tabs widget. I made them public since they seem useful for external widget implementors.

[jneem]

Makes sense to me.

[andrewhickman]

This currently has an issue when using a Spinner (or other animated widget). Either doesn't lay out its hidden child, so there is a warning when it gets AnimFrame events

WARN  druid::core] Widget 'druid::widget::spinner::Spinner' received an event (AnimFrame(167854600)) without having been laid out. This likely indicates a missed call to set_layout_rect.

I'm not sure whether it should lay out both children (as Tabs does) or not send AnimFrame events to the child

[andrewhickman]

I've changed the warning to only be emitted for events that have should_propagate_to_hidden() == false. @cmyr does that sound reasonable? It means Event::Command and Event::AnimFrame will no longer generate the warning.

[luleyleo]

This should have a changlog entry (probably multiple)

[luleyleo]

Thanks!

[andrewhickman]

CI had a spurious error but that seems to have resolved itself now

[luleyleo]

@andrewhickman this looks good to me, should we merge it?

[andrewhickman]

Yep, its ready to merge 👍