Changelog

v0.2.1

The relayout pass (inferred FLIP and size animations) now skips elements far outside the viewport. It runs on every LiveView patch and measured every tracked element, so on a page with hundreds of animated elements a patch that changed three of them still cost tens of thousands of layout reads — twice, since the deferred exit removal triggers a second pass. Off-screen elements are now skipped, and the visibility observer reseeds their cached layout when they come back toward the viewport. The per-frame sibling remeasure during a size-collapse exit skips off-screen siblings the same way.

pin_exit attribute. On exit, if a staying sibling would move up into the leaving element's slot, Shift lifts the element out of flow (position: fixed) so the neighbours close the gap during the exit instead of snapping shut once the node is removed. Best for fade and scale exits. Off by default.

Enter and exit animations on large streamed lists no longer thrash layout. A filter that adds or removes hundreds of rows used to read and write layout once per row, forcing a reflow each time. Shift now batches the reads and the writes for the whole burst, so it forces layout once.
Elements far outside the viewport skip their enter and exit animation. On a long filtered list only the visible rows animate, and the rest appear or disappear at rest. Visibility is tracked with an IntersectionObserver, so deciding whether to skip reads no layout when a row enters or leaves.

live_redirect no longer waits for the outgoing page's exit animations before showing the new page. Shift now strips phx-remove off the outgoing animated nodes when the redirect starts, so LiveView swaps the page immediately.

package.json so the JS imports by name:

import { init as initShift } from "shift"

Exit animations no longer fire during a live_redirect. Mid-page interactions (clicks, form submits) still animate exits normally because their loading kind is "element", not "redirect".

Layout cache now seeds when an element transitions from hidden to visible. The v0.1.3 fix stopped caching a bogus (0, 0) for elements inside a display: none ancestor, but the cache stayed empty until the first DOM mutation while visible — and by that point the move had already happened, leaving FLIP without a pre-move position to animate from. An IntersectionObserver now watches every tracked element and seeds the cache the moment visibility changes.

Elements that mount inside a display: none ancestor no longer cache a bogus (0, 0) layout. The next time they appear and then change, FLIP would diff against the stale zero and fly the element in from the top-left of the page. measure now returns null when the element has no layout, and the cache stays empty until the element is actually visible.
Cross-parent moves where the element becomes the first child of its new parent now animate. The previous local-position FLIP gate saw localTop = 0 in both the old and new parent and skipped the animation entirely. Relayout now also FLIPs whenever the element's parent itself changes, using the body-relative delta for the transform amount.

Position FLIP is now gated by the element's position relative to its immediate parent, not its body-relative offset. Previously, any layout change that shrank content above a tracked list — a delete in one demo, for instance — would shift everything below it in body coordinates, and Shift would FLIP every unrelated element down the page back to its old absolute position. Now only elements whose position within their own parent changes get animated; the body- relative delta is still what the FLIP translates by, so bottom- anchored layouts (toast stacks) keep working.
Cached layouts now refresh on window resize. The MutationObserver doesn't fire on a resize, so previously every tracked element's __shiftLayout went stale and the next real layout change would FLIP against the pre-resize positions — animating the resize delta into whatever change came next. A debounced resize listener now remeasures every tracked element so the next FLIP starts from the current layout.

Sibling layout caches now refresh on every animation frame during a size-collapsing exit, and are nulled when the element is finally removed. Previously, the post-removal relayout would FLIP each neighbor by the full reflow distance, snapping them back to their pre-exit positions and animating up again.

Special-case collapse for <tr> exits. Because display: table-row derives its height from the tallest cell rather than its own CSS height, each cell's padding, font-size, and line-height are now animated to zero alongside the row's exit. The row's intrinsic height shrinks with the animation while the table layout stays intact.
fontSize and lineHeight added to PX_PROPS so the keyframe builder emits them with a px unit instead of as bare numbers (which WAAPI silently ignores).

Initial release.

<.animated> component — one component for enter, exit, layout (FLIP), and size animations.
Tween transitions with phase-aware easing defaults (ease-out on enter, ease-in-out on exit and layout).
Spring transitions backed by a numerical ODE solver — overshoot and damping behave physically.
Smart defaults: opacity fade by default, auto-resolved targets when only initial is given, padding/margin/border collapse on size animations.
Inferred mid-life animations — position and size changes animate automatically; opt out per element with disable: [:position, :size].
Server-driven exits via phx-remove, with cascading-order preservation and sliding-window stack handling out of the box.