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Do not push a catalog over one we could not read

Browse Source 
`sync_catalog` is a read-modify-write over a file another device also
writes: take theirs, merge, push the union. It was shaped

    if let Ok(bytes) = backend.get(&RemoteId::Path(target), None).await {

which folds *every* failure into "there is no remote catalog" and carries
straight on to the upload. On a placeholder library the snapshot in
`.darkroom-derived/` is dehydrated like anything else, so the read failed
every time and each sync pushed our catalog over theirs unmerged —
taking the other device's collections and their members with it.

The same shape as the sidecar bug, and the same fix: a read that fails
for anything other than `NotFound` stops the upload and says why. An
unreadable or unopenable snapshot stops it too — "will not parse" is not
"is not there". This is what `NotFound` and `NotMaterialised` being
separate errors is *for*: one means ours is the whole truth, the other
means do not dare.

Shard downloads go through the same fetch-on-demand read. They logged
and skipped before, which on a library the client keeps dehydrated is
every shard, every pass, and a peer's thumbnails and faces silently
never arriving.

And `put` over a placeholder now replaces it rather than refusing.
Refusing was over-cautious of me: derived state lives inside the library
folder, so a folder the client had dehydrated could never be written to
again. An unconditional write replaces the whole file, so there is
nothing in the stub to keep — content first, then the placeholder, since
in a synced tree an absence is a deletion that propagates. `IfMatch`
still refuses, because a stub's validator describes the stub; `IfAbsent`
fails, because the file is there and only its content is not.
This commit is contained in:
dtourolle
2026-08-29 10:36:26 +02:00
parent 702d83c218
commit 4168d67cfa
5 changed files with 190 additions and 26 deletions
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docs/storage.md
+27 -3
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@@ -418,7 +418,9 @@ free of any client's protocol.
| `RemoteEntry::materialised` | `false` on a stub; the catalog maps it to `Availability::Offline` |
| `RemoteEntry::size` | `0` on a stub, meaning *unknown* — see below |
| `get` on a stub | `RemoteError::NotMaterialised`, **never** `NotFound` and never the stub's one byte |
| `put` over a stub | refused; writing a rival file hands the client a conflict to resolve arbitrarily |
| `put` over a stub, unconditional | **replaces it** — the whole file is being written, so there is nothing in the stub to keep, and the placeholder is removed after the content lands |
| `put` over a stub, `IfMatch` | `NotMaterialised` — a stub's validator describes the placeholder, so nothing here can satisfy the guard; the caller fetches and retries |
| `put` over a stub, `IfAbsent` | `PreconditionFailed` — the file *is* there, only its content is elsewhere |
| `move_to` a stub | moves the stub and keeps it a stub — culling without downloading is ordinary |
| `delete` a stub | deletes it; a photograph is deleted whether or not its bytes are here |
| `capabilities().materialisation` | `OnDemand` with a client, `Placeholders` without, `Always` on a plain folder |
@@ -480,7 +482,29 @@ keeps. A pass over all 100, borrowing and releasing as it goes:
The peak is the working set, not the library, and the release is selective.
### 6.4 Release means dehydrate, never delete
### 6.4 Derived state is dehydrated too
Shards and the catalog snapshot live in `.darkroom-derived/` **inside the
library folder**, so a sync client dehydrates them exactly as it dehydrates a
photograph. Unlike a photograph, none of them can be skipped: a shard that will
not open is a peer's thumbnails never merging, and a catalog snapshot that will
not open is their collections.
`derived_sync::read_derived` fetches on demand rather than giving up. More
important is what happens when it *cannot*:
The catalog sync is a read-modify-write over a file another device also writes.
It was shaped `if let Ok(bytes) = backend.get(..)`, which folded every failure
into "there is no remote catalog" and carried straight on to the upload — so a
dehydrated snapshot meant pushing ours over theirs unmerged, taking their
collections and members with it. The same shape as the sidecar bug in §6, and
the same fix: a read that fails for any reason other than `NotFound` **stops the
upload**.
That is why `NotFound` and `NotMaterialised` had to be separate errors. One
means "yours is the whole truth, write it"; the other means "do not dare".
### 6.5 Release means dehydrate, never delete
The single most dangerous thing in this feature. A synced folder is not a
cache: deleting a materialised file inside it propagates the deletion to the
@@ -492,7 +516,7 @@ This is also why the originals cache (`dr_catalog::cache`) cannot simply be
pointed at a VFS library: `Cache::release` deletes bytes, which is right for a
copy under `originals/` and catastrophic in place.
### 6.5 Which photographs stay downloaded
### 6.6 Which photographs stay downloaded
The user's half of the bargain: a pass borrows for a moment, but *some* of the
library should stay local — the trip you are about to take, the shoot you are
docs/traceability.md
+3 -3
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@@ -10,7 +10,7 @@ Denominators are parsed from [`requirements.md`](requirements.md) at run time, n
| Metric | Value |
|---|---|
| Source files scanned | 287 |
| TRACES tags found | 840 |
| TRACES tags found | 842 |
| Requirements defined | 179 |
| Requirements covered | 107 |
| **Coverage** | **59.8%** (107/179) |
@@ -96,12 +96,12 @@ _None._
| FR-NC-6 | [`ui/dr-ui/src/activity.rs:1`](../ui/dr-ui/src/activity.rs#L1) |
| FR-NC-6a | [`core/dr-catalog/src/cache.rs:1`](../core/dr-catalog/src/cache.rs#L1), [`core/dr-catalog/src/cache.rs:225`](../core/dr-catalog/src/cache.rs#L225), [`core/dr-catalog/src/schema.rs:1014`](../core/dr-catalog/src/schema.rs#L1014), [`core/dr-catalog/src/schema.rs:613`](../core/dr-catalog/src/schema.rs#L613), [`core/dr-sync-folder/src/borrow.rs:1`](../core/dr-sync-folder/src/borrow.rs#L1), [`core/dr-types/src/selector.rs:1`](../core/dr-types/src/selector.rs#L1), [`core/dr-types/src/settings.rs:1`](../core/dr-types/src/settings.rs#L1), [`ui/dr-ui/src/collections_ui.rs:3174`](../ui/dr-ui/src/collections_ui.rs#L3174), [`ui/dr-ui/src/collections_ui.rs:621`](../ui/dr-ui/src/collections_ui.rs#L621), [`ui/dr-ui/src/collections_ui.rs:683`](../ui/dr-ui/src/collections_ui.rs#L683), [`ui/dr-ui/src/lib.rs:1807`](../ui/dr-ui/src/lib.rs#L1807), [`ui/dr-ui/src/lib.rs:2698`](../ui/dr-ui/src/lib.rs#L2698), [`ui/dr-ui/src/library.rs:1449`](../ui/dr-ui/src/library.rs#L1449), [`ui/dr-ui/src/library.rs:1472`](../ui/dr-ui/src/library.rs#L1472), [`ui/dr-ui/src/library.rs:1747`](../ui/dr-ui/src/library.rs#L1747), [`ui/dr-ui/src/library_ui.rs:1065`](../ui/dr-ui/src/library_ui.rs#L1065), [`ui/dr-ui/src/library_ui.rs:1138`](../ui/dr-ui/src/library_ui.rs#L1138), [`ui/dr-ui/src/library_ui.rs:1239`](../ui/dr-ui/src/library_ui.rs#L1239), [`ui/dr-ui/src/library_ui.rs:1294`](../ui/dr-ui/src/library_ui.rs#L1294), [`ui/dr-ui/src/library_ui.rs:1429`](../ui/dr-ui/src/library_ui.rs#L1429), [`ui/dr-ui/src/library_ui.rs:1547`](../ui/dr-ui/src/library_ui.rs#L1547), [`ui/dr-ui/src/library_ui.rs:2074`](../ui/dr-ui/src/library_ui.rs#L2074), [`ui/dr-ui/src/library_ui.rs:273`](../ui/dr-ui/src/library_ui.rs#L273), [`ui/dr-ui/src/library_ui.rs:284`](../ui/dr-ui/src/library_ui.rs#L284), [`ui/dr-ui/src/library_ui.rs:292`](../ui/dr-ui/src/library_ui.rs#L292), [`ui/dr-ui/src/library_ui.rs:304`](../ui/dr-ui/src/library_ui.rs#L304), [`ui/dr-ui/src/library_ui.rs:313`](../ui/dr-ui/src/library_ui.rs#L313), [`ui/dr-ui/src/library_ui.rs:405`](../ui/dr-ui/src/library_ui.rs#L405), [`ui/dr-ui/src/library_ui.rs:415`](../ui/dr-ui/src/library_ui.rs#L415), [`ui/dr-ui/src/library_ui.rs:457`](../ui/dr-ui/src/library_ui.rs#L457), [`ui/dr-ui/src/library_ui.rs:520`](../ui/dr-ui/src/library_ui.rs#L520), [`ui/dr-ui/src/library_ui.rs:5318`](../ui/dr-ui/src/library_ui.rs#L5318), [`ui/dr-ui/src/library_ui.rs:5336`](../ui/dr-ui/src/library_ui.rs#L5336), [`ui/dr-ui/src/library_ui.rs:5348`](../ui/dr-ui/src/library_ui.rs#L5348), [`ui/dr-ui/src/library_ui.rs:551`](../ui/dr-ui/src/library_ui.rs#L551), [`ui/dr-ui/src/library_ui.rs:563`](../ui/dr-ui/src/library_ui.rs#L563), [`ui/dr-ui/src/settings_store.rs:1`](../ui/dr-ui/src/settings_store.rs#L1), [`ui/dr-ui/src/settings_ui.rs:1`](../ui/dr-ui/src/settings_ui.rs#L1), [`ui/dr-ui/ui/app.slint:2335`](../ui/dr-ui/ui/app.slint#L2335), [`ui/dr-ui/ui/app.slint:434`](../ui/dr-ui/ui/app.slint#L434), [`ui/dr-ui/ui/collections.slint:249`](../ui/dr-ui/ui/collections.slint#L249), [`ui/dr-ui/ui/collections.slint:369`](../ui/dr-ui/ui/collections.slint#L369), [`ui/dr-ui/ui/collections.slint:52`](../ui/dr-ui/ui/collections.slint#L52), [`ui/dr-ui/ui/collections.slint:682`](../ui/dr-ui/ui/collections.slint#L682), [`ui/dr-ui/ui/collections.slint:84`](../ui/dr-ui/ui/collections.slint#L84), [`ui/dr-ui/ui/icons.slint:260`](../ui/dr-ui/ui/icons.slint#L260), [`ui/dr-ui/ui/library.slint:980`](../ui/dr-ui/ui/library.slint#L980) |
| FR-NC-6b | [`ui/dr-ui/src/library_ui.rs:1294`](../ui/dr-ui/src/library_ui.rs#L1294) |
| FR-NC-6c | [`core/dr-catalog/src/cache.rs:225`](../core/dr-catalog/src/cache.rs#L225), [`core/dr-sync-folder/src/borrow.rs:1`](../core/dr-sync-folder/src/borrow.rs#L1), [`core/dr-sync-folder/src/lib.rs:197`](../core/dr-sync-folder/src/lib.rs#L197), [`core/dr-sync-folder/src/lib.rs:73`](../core/dr-sync-folder/src/lib.rs#L73), [`core/dr-sync-folder/src/lib.rs:770`](../core/dr-sync-folder/src/lib.rs#L770), [`core/dr-sync-folder/src/lib.rs:809`](../core/dr-sync-folder/src/lib.rs#L809), [`core/dr-sync-folder/src/vfs.rs:1`](../core/dr-sync-folder/src/vfs.rs#L1), [`core/dr-sync-nextcloud/src/desktop_client.rs:167`](../core/dr-sync-nextcloud/src/desktop_client.rs#L167), [`core/dr-sync-nextcloud/src/desktop_client.rs:30`](../core/dr-sync-nextcloud/src/desktop_client.rs#L30), [`core/dr-sync/src/capability.rs:41`](../core/dr-sync/src/capability.rs#L41), [`core/dr-sync/src/error.rs:39`](../core/dr-sync/src/error.rs#L39), [`core/dr-sync/src/lib.rs:158`](../core/dr-sync/src/lib.rs#L158), [`core/dr-sync/src/types.rs:101`](../core/dr-sync/src/types.rs#L101), [`core/dr-types/src/lib.rs:119`](../core/dr-types/src/lib.rs#L119), [`core/dr-types/src/lib.rs:201`](../core/dr-types/src/lib.rs#L201), [`ui/dr-ui/src/activity.rs:1`](../ui/dr-ui/src/activity.rs#L1), [`ui/dr-ui/src/collections_ui.rs:3174`](../ui/dr-ui/src/collections_ui.rs#L3174), [`ui/dr-ui/src/collections_ui.rs:621`](../ui/dr-ui/src/collections_ui.rs#L621), [`ui/dr-ui/src/collections_ui.rs:683`](../ui/dr-ui/src/collections_ui.rs#L683), [`ui/dr-ui/src/library.rs:1569`](../ui/dr-ui/src/library.rs#L1569), [`ui/dr-ui/src/library.rs:1659`](../ui/dr-ui/src/library.rs#L1659), [`ui/dr-ui/src/library.rs:3138`](../ui/dr-ui/src/library.rs#L3138), [`ui/dr-ui/src/library.rs:3476`](../ui/dr-ui/src/library.rs#L3476), [`ui/dr-ui/src/library.rs:948`](../ui/dr-ui/src/library.rs#L948), [`ui/dr-ui/src/library_ui.rs:1065`](../ui/dr-ui/src/library_ui.rs#L1065), [`ui/dr-ui/src/library_ui.rs:1138`](../ui/dr-ui/src/library_ui.rs#L1138), [`ui/dr-ui/src/library_ui.rs:1337`](../ui/dr-ui/src/library_ui.rs#L1337), [`ui/dr-ui/src/remote.rs:40`](../ui/dr-ui/src/remote.rs#L40), [`ui/dr-ui/ui/collections.slint:249`](../ui/dr-ui/ui/collections.slint#L249), [`ui/dr-ui/ui/collections.slint:682`](../ui/dr-ui/ui/collections.slint#L682), [`ui/dr-ui/ui/icons.slint:260`](../ui/dr-ui/ui/icons.slint#L260) |
| FR-NC-6c | [`core/dr-catalog/src/cache.rs:225`](../core/dr-catalog/src/cache.rs#L225), [`core/dr-sync-folder/src/borrow.rs:1`](../core/dr-sync-folder/src/borrow.rs#L1), [`core/dr-sync-folder/src/lib.rs:197`](../core/dr-sync-folder/src/lib.rs#L197), [`core/dr-sync-folder/src/lib.rs:73`](../core/dr-sync-folder/src/lib.rs#L73), [`core/dr-sync-folder/src/lib.rs:803`](../core/dr-sync-folder/src/lib.rs#L803), [`core/dr-sync-folder/src/lib.rs:842`](../core/dr-sync-folder/src/lib.rs#L842), [`core/dr-sync-folder/src/vfs.rs:1`](../core/dr-sync-folder/src/vfs.rs#L1), [`core/dr-sync-nextcloud/src/desktop_client.rs:167`](../core/dr-sync-nextcloud/src/desktop_client.rs#L167), [`core/dr-sync-nextcloud/src/desktop_client.rs:30`](../core/dr-sync-nextcloud/src/desktop_client.rs#L30), [`core/dr-sync/src/capability.rs:41`](../core/dr-sync/src/capability.rs#L41), [`core/dr-sync/src/error.rs:39`](../core/dr-sync/src/error.rs#L39), [`core/dr-sync/src/lib.rs:158`](../core/dr-sync/src/lib.rs#L158), [`core/dr-sync/src/types.rs:101`](../core/dr-sync/src/types.rs#L101), [`core/dr-types/src/lib.rs:119`](../core/dr-types/src/lib.rs#L119), [`core/dr-types/src/lib.rs:201`](../core/dr-types/src/lib.rs#L201), [`ui/dr-ui/src/activity.rs:1`](../ui/dr-ui/src/activity.rs#L1), [`ui/dr-ui/src/collections_ui.rs:3174`](../ui/dr-ui/src/collections_ui.rs#L3174), [`ui/dr-ui/src/collections_ui.rs:621`](../ui/dr-ui/src/collections_ui.rs#L621), [`ui/dr-ui/src/collections_ui.rs:683`](../ui/dr-ui/src/collections_ui.rs#L683), [`ui/dr-ui/src/derived_sync.rs:555`](../ui/dr-ui/src/derived_sync.rs#L555), [`ui/dr-ui/src/derived_sync.rs:627`](../ui/dr-ui/src/derived_sync.rs#L627), [`ui/dr-ui/src/library.rs:1569`](../ui/dr-ui/src/library.rs#L1569), [`ui/dr-ui/src/library.rs:1659`](../ui/dr-ui/src/library.rs#L1659), [`ui/dr-ui/src/library.rs:3138`](../ui/dr-ui/src/library.rs#L3138), [`ui/dr-ui/src/library.rs:3476`](../ui/dr-ui/src/library.rs#L3476), [`ui/dr-ui/src/library.rs:948`](../ui/dr-ui/src/library.rs#L948), [`ui/dr-ui/src/library_ui.rs:1065`](../ui/dr-ui/src/library_ui.rs#L1065), [`ui/dr-ui/src/library_ui.rs:1138`](../ui/dr-ui/src/library_ui.rs#L1138), [`ui/dr-ui/src/library_ui.rs:1337`](../ui/dr-ui/src/library_ui.rs#L1337), [`ui/dr-ui/src/remote.rs:40`](../ui/dr-ui/src/remote.rs#L40), [`ui/dr-ui/ui/collections.slint:249`](../ui/dr-ui/ui/collections.slint#L249), [`ui/dr-ui/ui/collections.slint:682`](../ui/dr-ui/ui/collections.slint#L682), [`ui/dr-ui/ui/icons.slint:260`](../ui/dr-ui/ui/icons.slint#L260) |
| FR-NC-7 | [`core/dr-catalog/src/face_shard.rs:1`](../core/dr-catalog/src/face_shard.rs#L1), [`core/dr-sync-nextcloud/src/lib.rs:104`](../core/dr-sync-nextcloud/src/lib.rs#L104), [`ui/dr-ui/src/derived_sync.rs:1`](../ui/dr-ui/src/derived_sync.rs#L1), [`ui/dr-ui/src/library.rs:3356`](../ui/dr-ui/src/library.rs#L3356), [`ui/dr-ui/src/library_ui.rs:3627`](../ui/dr-ui/src/library_ui.rs#L3627), [`ui/dr-ui/ui/settings.slint:372`](../ui/dr-ui/ui/settings.slint#L372) |
| FR-NC-7a | [`core/dr-ingest/src/layout.rs:1`](../core/dr-ingest/src/layout.rs#L1), [`core/dr-sync/src/upload.rs:1`](../core/dr-sync/src/upload.rs#L1), [`core/dr-sync/src/upload.rs:40`](../core/dr-sync/src/upload.rs#L40), [`core/dr-types/src/settings.rs:116`](../core/dr-types/src/settings.rs#L116), [`ui/dr-ui/src/import.rs:1`](../ui/dr-ui/src/import.rs#L1), [`ui/dr-ui/src/import.rs:97`](../ui/dr-ui/src/import.rs#L97), [`ui/dr-ui/src/import_ui.rs:1`](../ui/dr-ui/src/import_ui.rs#L1), [`ui/dr-ui/src/lib.rs:1123`](../ui/dr-ui/src/lib.rs#L1123), [`ui/dr-ui/ui/import.slint:5`](../ui/dr-ui/ui/import.slint#L5) |
| FR-NC-7b | [`core/dr-ingest/src/lib.rs:733`](../core/dr-ingest/src/lib.rs#L733), [`core/dr-sync/src/upload.rs:1`](../core/dr-sync/src/upload.rs#L1), [`ui/dr-ui/src/import.rs:122`](../ui/dr-ui/src/import.rs#L122), [`ui/dr-ui/src/import.rs:336`](../ui/dr-ui/src/import.rs#L336), [`ui/dr-ui/src/import.rs:584`](../ui/dr-ui/src/import.rs#L584), [`ui/dr-ui/src/import.rs:97`](../ui/dr-ui/src/import.rs#L97), [`ui/dr-ui/src/import_ui.rs:1`](../ui/dr-ui/src/import_ui.rs#L1), [`ui/dr-ui/src/lib.rs:1123`](../ui/dr-ui/src/lib.rs#L1123) |
| FR-NC-8 | [`core/dr-pipeline/src/sidecar.rs:118`](../core/dr-pipeline/src/sidecar.rs#L118), [`core/dr-pipeline/src/sidecar.rs:92`](../core/dr-pipeline/src/sidecar.rs#L92), [`ui/dr-ui/src/lib.rs:1777`](../ui/dr-ui/src/lib.rs#L1777), [`ui/dr-ui/src/library.rs:459`](../ui/dr-ui/src/library.rs#L459), [`ui/dr-ui/src/library_ui.rs:472`](../ui/dr-ui/src/library_ui.rs#L472) |
| FR-NC-9 | [`core/dr-catalog/src/merge.rs:1`](../core/dr-catalog/src/merge.rs#L1), [`core/dr-catalog/src/schema.rs:556`](../core/dr-catalog/src/schema.rs#L556), [`core/dr-catalog/src/sync.rs:1`](../core/dr-catalog/src/sync.rs#L1), [`core/dr-pipeline/src/sidecar.rs:156`](../core/dr-pipeline/src/sidecar.rs#L156), [`core/dr-pipeline/src/sidecar.rs:183`](../core/dr-pipeline/src/sidecar.rs#L183), [`core/dr-pipeline/src/sidecar.rs:2033`](../core/dr-pipeline/src/sidecar.rs#L2033), [`core/dr-pipeline/src/sidecar.rs:352`](../core/dr-pipeline/src/sidecar.rs#L352), [`core/dr-pipeline/src/sidecar.rs:450`](../core/dr-pipeline/src/sidecar.rs#L450), [`core/dr-pipeline/src/spot.rs:245`](../core/dr-pipeline/src/spot.rs#L245), [`core/dr-pipeline/tests/spot_sidecar.rs:1`](../core/dr-pipeline/tests/spot_sidecar.rs#L1), [`ui/dr-ui/src/library.rs:844`](../ui/dr-ui/src/library.rs#L844), [`ui/dr-ui/src/library.rs:998`](../ui/dr-ui/src/library.rs#L998) |
| FR-NC-9 | [`core/dr-catalog/src/merge.rs:1`](../core/dr-catalog/src/merge.rs#L1), [`core/dr-catalog/src/schema.rs:556`](../core/dr-catalog/src/schema.rs#L556), [`core/dr-catalog/src/sync.rs:1`](../core/dr-catalog/src/sync.rs#L1), [`core/dr-pipeline/src/sidecar.rs:156`](../core/dr-pipeline/src/sidecar.rs#L156), [`core/dr-pipeline/src/sidecar.rs:183`](../core/dr-pipeline/src/sidecar.rs#L183), [`core/dr-pipeline/src/sidecar.rs:2033`](../core/dr-pipeline/src/sidecar.rs#L2033), [`core/dr-pipeline/src/sidecar.rs:352`](../core/dr-pipeline/src/sidecar.rs#L352), [`core/dr-pipeline/src/sidecar.rs:450`](../core/dr-pipeline/src/sidecar.rs#L450), [`core/dr-pipeline/src/spot.rs:245`](../core/dr-pipeline/src/spot.rs#L245), [`core/dr-pipeline/tests/spot_sidecar.rs:1`](../core/dr-pipeline/tests/spot_sidecar.rs#L1), [`ui/dr-ui/src/derived_sync.rs:555`](../ui/dr-ui/src/derived_sync.rs#L555), [`ui/dr-ui/src/library.rs:844`](../ui/dr-ui/src/library.rs#L844), [`ui/dr-ui/src/library.rs:998`](../ui/dr-ui/src/library.rs#L998) |
| FR-PLAT-AND-1 | [`core/dr-types/src/lib.rs:53`](../core/dr-types/src/lib.rs#L53), [`platform/dr-plat/src/volumes.rs:62`](../platform/dr-plat/src/volumes.rs#L62) |
| FR-PLAT-AND-3 | [`core/dr-catalog/src/jobs.rs:1`](../core/dr-catalog/src/jobs.rs#L1) |
| FR-PLAT-LIN-1 | [`core/dr-types/src/settings.rs:1`](../core/dr-types/src/settings.rs#L1), [`platform/dr-plat/src/storage.rs:344`](../platform/dr-plat/src/storage.rs#L344), [`ui/dr-ui/src/lib.rs:866`](../ui/dr-ui/src/lib.rs#L866), [`ui/dr-ui/src/settings_store.rs:1`](../ui/dr-ui/src/settings_store.rs#L1) |