anchored_list 0.1.1

Jump to any index in a lazy list in constant time, and hold your place when items arrive above it. One viewport anchored at the target, not two lists cross-fading.

0.1.1

Packaging only — no API or behaviour changes.

• The demo animations now ship inside the package, so they appear as screenshots on the pub.dev page rather than only in the README on GitHub.
• .pubignore excludes the raw recorder frames, so shipping them costs about 440 KB rather than the 11 MB the frame directory would have added.

0.1.0

Initial release.

Jumping

• AnchoredList.builder — a lazy list that jumps to any index in constant time, by re-anchoring a centre sliver rather than cross-fading two lists.
• AnchoredListController with jumpToIndex, animateToIndex and anchorIndex.
• One viewport and one set of children, so there is no transition artefact and nothing is built twice.

Holding position while the list changes

• itemsInsertedAbove and itemsRemovedAbove keep the viewport pixel-still when items arrive at or leave the top of the list. Because the anchor is an index, the correction is arithmetic on one integer and the scroll offset is never touched — nothing moves on screen, even mid-item.
• findChildIndexCallback locates items by key so their state survives insertions, translated across the two slivers for you.

Reaching the scroll position

• scrollController may be supplied, and AnchoredListController .scrollController returns whichever one is in use — enough for a Scrollbar, page-up/page-down, or linking two lists.
• Offsets are measured from the anchor, so zero is the anchored item and content above it is at negative offset.

Reporting

• itemPositions reports each built item's place as a fraction of the viewport, with isVisible, isFullyVisible and extent.

The rest of the ListView surface

• AnchoredList.separated and AnchoredList(children: [...]).
• padding, physics, reverse, scrollDirection, cacheExtent, semanticChildCount, dragStartBehavior, keyboardDismissBehavior, scrollBehavior, clipBehavior, restorationId and the three add* flags.
• padding is split between the two slivers rather than applied to both, which would double the inset at the anchor.
• Semantic indexes are translated, so items above the anchor announce their real list index instead of counting backwards from it.

Not supported: shrinkWrap, and this is not a sliver. Flutter asserts !shrinkWrap || center == null, so a centre-anchored viewport cannot size to its content — the parameter is absent rather than present and broken.