1.20.0

What's Changed

• ObserverController
  • Add observeIntervalForScrolling to set the minimum amount of time to wait for firing observe callback during scrolling.
• ObserverUtils
  • Improve the logic of isDisplayingSliverInViewport method.
• ScrollViewOnceObserveNotificationResult
  • Add observeViewportResultModel.
• ChatScrollObserver
  • Add ChatScrollObserverRefIndexType.
  • Add refIndexType to specify the role of refItemIndex and refItemIndexAfterUpdate.
• Slivers
  • Add SliverObserveContext.
• ObserveDisplayingChildModelMixin
  • Add visibleFraction and visibleMainAxisSize.

Above features are implemented by @LinXunFeng.

Full Changelog: 1.19.1...1.20.0