The port of the block Slint repeats in 27 views (NavState.restore-scope /
scroll-restore / report-scroll). A .slint file cannot hand a component a
reference to a Flickable, which is why the reference inlines it; QML can, so
controls/ScrollMemory.qml exists once and 31 containers mount it.
Two divergences from the reference, both forced by the same fact — tabs are not
history entries in this port:
1. THE SCOPE IS NAMED BY THE VIEW, not derived from the entry by a scope_for
table. Slint can derive it because its entries carry the tab
(Favorites { tab }); here an entry is a bare route id, so a derived scope
would read "library" for all five Library tabs and pour the Albums grid's
offset into whatever tab mounted. Letting the reporter name its own scope
buys tab granularity for free, and the mismatch case degrades the right way:
an unmatched scope restores NOTHING instead of restoring the wrong thing.
2. THE RESTORE RE-ASSERTS instead of firing once. A Qt item view resets
contentY to 0 whenever its model is replaced, and several pages assign their
model from a binding whose inputs arrive over the network after the mount —
the album page rebuilds listCells from three deferred rails, so it hands its
ListView a new array up to four times in its first seconds and snaps back to
the top over a restore that already ran correctly. The offset is held and
re-applied until a 2.5 s deadline, or until the user takes over (a wheel, a
drag or a flick raises `moving`, and from then the position is theirs).
Diagnostics are off by default: QT_LOGGING_RULES="qbz.nav.scroll.info=true" for
the QML half, RUST_LOG=qbz=debug for the stamp/arm half.
cc
Both views were absent from the Qt frontend, not partial. This lands them
together with the core engine they need and the two entry points that reach
them.
- qbz-core gains scene discovery ("artists from the same place"): a
cancellable run with a phase for the progress label and a typed
SceneDiscoveryError, so a view can tell offline, all-upstreams-failed and
an honest empty result apart. CancelToken, ScenePhase and SceneDiscoveryError
are re-exported for frontends.
- qbz-integrations: MusicBrainz location resolution plus its cache layer.
- qbz-qt: ArtistSceneView with its three scene components, MusicianPageView
and MusicianModal, backed by artist_scene_qt.rs, musician_qt.rs and the two
bridges. The five-branch musician dispatcher is wired to all six of its
consumers. Both scene doors are live: the sidebar location link and the
overflow row that shipped grey with action: "stub".
- Translations: the new msgids in all eight locales.
Three defects fixed on the way, all with the same signature — a comment
asserting a mechanism that does not exist:
- Volume opened at 100 %. The comment claimed the poll loop mirrored it from
the engine; now_playing::set_volume has two callers and neither runs in a
local session.
- mbAvailable was documented as "MusicBrainz enabled AND resolved to an MBID"
while being assigned from the opt-in alone. Consumers now test the MBID.
- Session restore could not resume from a cold cursor ("cannot resume - no
audio data available") for want of a has_loaded_audio() guard. Investigation
in qbz-nix-docs/qt-frontend/2026-08-14-cold-cursor-resume.md.
Contract and evidence:
qbz-nix-docs/qt-frontend/2026-08-14-artist-scene-musician/00-CONTRACT.md,
which wins over specs 01..09 and records 20 deliberate divergences from the
reference in section 6.
cc
vicrodh