The Listen list and the sidebar queue now reach their views through
QbzKeyedModel. In the Listen list a removed track fades out while the
rows below slide up, "play next" slides the queue open, a history row
trimmed above the window leaves the rows on screen where they are, and a
committed drag lands the row where it was dropped while its neighbours
slide (the chevrons keep the animated swap). Identity is the track
(source + id, repeats by occurrence); phase, section and phaseIndex are
data, so a track ending updates rows in place and moves nothing. The
follow-playing position and the cover window now run after the model
holds the new rows. A search is a different list and is replaced at once.
The sidebar's Up Next and Recently played are Repeaters in Columns, which
have no remove transition: a leaving row disappears and the rows below
slide up, a joining row fades in, and a page or search change is laid out
synchronously without animation. Drop slots count the Repeater's own
items.
tst_keyed_model gains the Repeater-in-a-Column case (silent first page and
page change, sliding rows that keep their items, fading insert).
cc
Handing an item view a new JS array is a model swap: every delegate is
thrown away, the scroll offset resets and the page is built again.
QbzKeyedModel takes the same arrays and reconciles them by key into
removes, inserts, moves and in-place updates, so a view keeps its
delegates, its offset and its artwork, and a leaving row can fade out
while its neighbours slide into the gap.
Each model row carries only `rowKey` and `rowRev`; a delegate looks the
row up by key, so it reads the host's own JS object (no copy into a
ListModel map) and a rev bump hands it a changed row. New objects for an
existing key are compared field by field, so a republished document with
the same data touches no delegate. A reorder keeps the longest in-order
run steady and moves only the rest; past a cap, and on any scope change
(tab, sort, search), the rows are replaced without animation, laid out
synchronously and started from the top, like the swap they replace.
Three shared transitions (add, remove, displaced) give every adopter the
same motion. The remove transition restores opacity and scale as its last
step: the view pools a delegate the moment the transition ends and hands
it back as it was left, which measured 76 invisible rows after three
removals and a scroll.
tst_keyed_model covers order and identity under 400 random edits, the
one-move reorder, silent resets, a removal that keeps the viewport and
creates at most two delegates, the fade that keeps its content, and the
pooled rows; it runs in the runtime gate.
cc
vicrodh