sliver_tree/animation_style library

Value types configuring animation timing and easing for the sliver tree stack.

TreeAnimationSpec is one (duration, curve) pair. TreeAnimationStyle carries one spec per animation family:

• TreeAnimationStyle.expandCollapse: expand/collapse operation groups, bulk expandAll/collapseAll, and the scroll orchestrator's animated-concurrent mode gate.
• TreeAnimationStyle.enterExit: node enter/exit rows for insert and remove. Inherits expandCollapse when unset.
• TreeAnimationStyle.reorderSlide: FLIP reorder slides (moveNode, reorderRoots/reorderChildren, animateSlideFromOffsets, the drag-commit baseline).
• TreeAnimationStyle.makeRoom: the drag make-room preview, meaning gap open, re-target and release. Inherits reorderSlide when unset.
• TreeAnimationStyle.dropSettle: the drag proxy settle glides, for the commit handoff and the cancel return. Inherits reorderSlide when unset.

A family whose resolved spec has Duration.zero duration is OFF: it snaps instead of animating, and that kill switch dominates explicit per-call durations. TreeAnimationStyle.disabled turns every family off, the canonical synchronous-test configuration. Every family gates on its OWN resolved zero: in particular, dropSettle glides run even when reorderSlide is zeroed (the drop commits instantly and the card settles into its new slot).

The zero rule splits two meanings cleanly: a zero family CREATES no motion (installs are refused; other families' in-flight animations are untouched and re-base seamlessly across concurrent structural changes), while DISABLING, meaning restyling reorderSlide to zero at runtime, STOPS in-flight slide motion at the transition.

Classes

TreeAnimationSpec

A (duration, curve) pair for one animation family.

TreeAnimationStyle

Timing/easing for every animation family in the sliver tree stack.