* Add test_updateBackdropAlpha
* Fix backdrop alpha's flickers in Maps.app
This issue occurs when swinging down a panel with all one's might.
The trigger is here.
```
func floatingPanelWillEndDragging(_ vc: FloatingPanelController, withVelocity velocity: CGPoint, targetState: UnsafeMutablePointer<FloatingPanelState>) {
if targetState.pointee != .full {
owner.searchVC.hideHeader(animated: true)
}
if targetState.pointee == .tip {
>>> vc.contentMode = .static
}
}
```
However, any library users expect to affect the backdrop by this code.
And then I reconsidered the reason why the backdrop alpha changes in
activateLayout(for:forceLayout:) and it's because the animation using
CAAnimation on v1.
Therefore I decided to move the point to change the backdrop alpha into
the move animation's completion handler.
And also the responsibility of `setBackdropAlpha(of:)` was moved into
`Core` because `Core` takes on a role of changing the backdrop alpha.
* Support over 3 states in LayoutAdapter
* Allow to inherite FloatingPanelState
* Support a custome FloatingPanelState in ObjC
* Replace Menu enum with UseCase enum in Samples.app
* Rename UIExtensions to Extensions
* Add CustomState use case in Samples app
I applied `.defaultHigh` priority which might be safe to prevent
an ambiguous layout error. But that causes this issue, so I have to
use `.required` priority.
See more detail [#424
issue](https://github.com/SCENEE/FloatingPanel/issues/424).
* Prevent a possible memory leak at Core.move(from:to:animated:completion:)
* Replace ``self`` with `self`.
* Change `LayoutAdapter.vc` property to an unowned reference
* Prevent a crash at LayoutAdapter.surfaceLocation called in `NumericSpringAnimator.update` closure.
Because sometimes UIView.systemLayoutSizeFitting() returns a different
size between an onscreen and offscreen view which includes UIStackView.
This behavior depends on UIStackView behavior and the lib can not match
the difference.
Shin Yamamoto