import { Theme } from "theme.slint";
import { AdjustPanel, GeometryPanel, GroupStrip, ParamRow, TransferPanel, ViewMode } from "adjust.slint";
import { CategoryRow, GradientHandle, GradientHandles, HandleRole, MaskPanel, MaskRow, SubjectRow } from "masks.slint";
import { SpotHandle, SpotHandles, SpotPanel, SpotRole } from "spots.slint";
import { CropOverlay } from "crop.slint";
import { HistoryPanel, HistoryRow } from "history.slint";
import { LaunchScreen } from "launch.slint";
import { IdentityScreen, IdentityPerson, IdentityFace } from "identity.slint";
import { LibraryGrid, LibraryCell, TimelineBar, PhotoRoll, KeywordRow, PersonChip } from "library.slint";
import { GestureRow } from "gestures.slint";
import { Button, PanelHeading, Label, Value, Caption, Panel, EmptyState, ProgressBar, ActivityRow } from "widgets.slint";
import { CollectionsPanel, CollectionRow, OfflinePrompt } from "collections.slint";
import { HistogramPanel, HistogramView } from "histogram.slint";
import { RecoveryPrompt } from "recovery.slint";
import { PresetSheet, ScopeChips, ScopeKind } from "presets.slint";
import { FocusMarks, FocusPanel } from "peaking.slint";
import { SettingsPage } from "settings.slint";
import { ImportPage } from "import.slint";
import { StatusBar, InfoPanel } from "develop.slint";
import { ToolRail } from "toolrail.slint";

export { LibraryCell, TimelineBar, CollectionRow, ActivityRow, HistogramView, PersonChip }
export { GestureRow }
export { ViewMode, GradientHandle, HandleRole, SpotHandle, SpotRole }

export component AppWindow inherits Window {
    title: "DarkRoom";
    // The one raster asset in the UI, and the exception that the header of
    // icons.slint does not cover: everything drawn *inside* the window is a
    // Path because a font might not have the glyph, but the window icon is
    // never drawn by us. It is handed to the window manager, which wants
    // pixels. Pre-shaped with rounded corners and transparent outside them,
    // because desktop window managers composite it as-is rather than masking
    // it the way Android does — the Android launcher icon is a separate,
    // maskable set under apps/darkroom-android/android/res.
    //
    // Where it actually shows up is narrower than it looks: X11 and Windows
    // read it, and Wayland ignores it outright in favour of matching app_id
    // against an installed .desktop file, which this repo does not install.
    // Android ignores it too — there is no title bar to put it in.
    icon: @image-url("app-icon.png");
    background: Theme.ground;
    preferred-width: 1100px;
    preferred-height: 720px;
    min-width: 360px;
    min-height: 320px;

    // Set from Rust each frame: the compute output, delivered as a texture.
    in property <image> canvas;
    in property <string> adapter: "detecting…";
    in property <string> backend: "—";
    in property <int> fps: 0;
    /// TRACES: FR-DSP-8
    /// The display showing the canvas and the colour transform it is getting.
    /// Shown under ABOUT in Settings; see `settings.slint` for why the second
    /// one is a sentence rather than a name.
    in property <string> display-name: "detecting…";
    in property <string> display-colour: "detecting…";
    in property <string> display-others: "";
    /// TRACES: FR-UI-2
    /// Set from `CARGO_PKG_VERSION`, so the About line cannot disagree with
    /// the binary it is part of.
    in property <string> app-version: "unknown";

    // Current image, for the status strip and empty state.
    in property <string> filename: "";
    in property <string> camera: "";
    in property <string> exposure: "";
    in property <string> dimensions: "";
    in property <int> index: 0;
    in property <int> total: 0;
    in property <string> load-error: "";

    /// TRACES: FR-DSP-7
    /// The counted frame. Set only when the render has settled — a histogram
    /// of a draft frame is a histogram of an image nobody is reading.
    in property <HistogramView> histogram;

    /// The same photograph counted in the raw domain — the demosaiced
    /// scene-linear texture, before white balance, the camera matrix or any
    /// curve, on an axis of stops below sensor saturation.
    ///
    /// Beside the display histogram rather than instead of it: the two answer
    /// different questions and the panel offers both. Unlike the one above it
    /// this is a property of the *file* and not of the render, so it survives
    /// a crop, a zoom and every slider — see `raw_histogram.rs`.
    in property <HistogramView> raw-histogram;

    /// TRACES: FR-CULL-3
    /// Focus peaking: the marks, whether they describe *this* frame, and the
    /// three things the photographer chose. All of them are Rust's, because
    /// the marks come from a compute pass — see `peaking.slint` for why
    /// `focus-overlay-ready` is a separate question from `peaking-on`.
    in property <image> focus-overlay;
    in property <bool> focus-overlay-ready: false;
    in property <bool> peaking-on: false;
    in property <bool> peaking-available: true;
    in property <int> peaking-sensitivity: 1;
    in property <int> peaking-colour: 0;

    callback peaking-toggled(bool);
    callback peaking-sensitivity-picked(int);
    callback peaking-colour-picked(int);

    // --- zoom, pan and crop (FR-DEV-4) ---
    //
    // Zoom is a *viewing* state, not an edit: it changes the resolution the
    // pipeline renders at, never what the file becomes. Rust owns the actual
    // rect; these carry only what the interface has to draw.
    in property <float> zoom: 1.0;
    in property <bool> zoomed: false;

    /// Whether one source pixel now covers more than one screen pixel.
    ///
    /// Drives the canvas's filtering, and nothing else. Rust decides it rather
    /// than the `zoom` property above, because the two are not the same
    /// question: whether the image is magnified depends on the source's
    /// resolution against the viewport's, which Slint does not know.
    in property <bool> magnified: false;

    /// TRACES: FR-UI-5
    /// What the develop view is currently doing (see `ViewMode`).
    ///
    /// One value rather than a flag per mode, so two modes cannot be on at
    /// once — which, with `crop-mode` a bare bool beside a masking panel that
    /// armed the canvas through two toggles of its own, they could be. Rust
    /// owns it: entering a mode has side effects on the session (crop drops
    /// the zoom, local clears nothing and leaving it clears the selection),
    /// and a property the interface could set directly would let the view
    /// change without them.
    ///
    /// In `crop` the canvas shows the *whole* frame — otherwise the area being
    /// cropped away would not be on screen to drag across — and the surround
    /// is greyed.
    in property <ViewMode> view-mode: ViewMode.photo;
    /// Shorthand for the two conditions half this file tests, so a mode
    /// comparison is written once rather than at each of a dozen call sites.
    property <bool> cropping: root.view-mode == ViewMode.crop;
    property <bool> local-mode: root.view-mode == ViewMode.local;
    /// TRACES: FR-DEV-8
    property <bool> repairing: root.view-mode == ViewMode.spots;

    /// The crop rect in fractions of the frame, mirrored from Rust so the
    /// overlay draws exactly what the pipeline holds.
    in-out property <float> crop-x: 0.0;
    in-out property <float> crop-y: 0.0;
    in-out property <float> crop-w: 1.0;
    in-out property <float> crop-h: 1.0;

    /// TRACES: FR-DEV-3
    /// The ratios the crop may be locked to, and which one is chosen.
    ///
    /// Named by Rust rather than listed here: the set is `CropAspect::CHOICES`
    /// and the labels come off it, so a ratio added there appears without this
    /// file changing.
    in property <[string]> crop-aspects;
    in property <int> crop-aspect: 0;
    /// Whether the chosen ratio is standing on its short edge.
    in property <bool> crop-portrait: false;
    /// Whether the chosen ratio has a portrait form at all — `Free` and the
    /// square do not, and the switch says so rather than vanishing.
    in property <bool> crop-aspect-turnable: false;

    /// Enter a mode, or `photo` to leave whichever one is current.
    callback mode-picked(ViewMode);
    /// A dragged crop rect in fractions of the frame, then the corner the drag
    /// is holding as a `0`/`1` pair — or `-1, -1` for a move, which keeps the
    /// shape it has. See `CropOverlay` in crop.slint for why the corner has to
    /// travel with the rect.
    callback crop-changed(float, float, float, float, float, float);
    /// Lock the crop to one of `crop-aspects`, by index.
    callback crop-aspect-picked(int);
    /// Stand the chosen ratio on its other edge.
    callback crop-portrait-toggled();

    // --- rotation, flips and straightening (FR-DEV-3) ---
    //
    // Mirrored from the session rather than held here, for the same reason the
    // crop rect is: Rust clamps and wraps these, so the panel must show what
    // was actually applied and not what the click asked for.
    in property <float> straighten: 0.0;
    /// The straighten slider's travel either way, from the descriptor.
    in property <float> max-straighten: 45.0;
    in property <bool> flip-h: false;
    in property <bool> flip-v: false;
    /// Any framing edit is in effect — what lights the section's dot and
    /// enables its reset. Distinct from the crop rect being non-full: a
    /// rotation or a flip is an edit with the crop still full.
    in property <bool> framing-modified: false;

    /// Quarter turns, positive clockwise.
    callback rotate-quarters(int);
    callback flip-h-toggled();
    callback flip-v-toggled();
    callback straighten-changed(float);
    /// TRACES: FR-DEV-3
    /// The straightening gesture is over and this is the angle to keep.
    ///
    /// Reported separately from the value because the auto-crop that follows a
    /// straighten has to happen once, at the end — see
    /// `DevelopSession::auto_crop_to_angle`.
    callback straighten-committed(float);
    /// Crop, angle, rotation and flips back to neutral, leaving colour alone.
    callback framing-reset();

    // --- undo and redo (FR-DEV-5) ---
    //
    // Rust owns whether there is anywhere to step, because "anywhere" is a
    // position in a stack of snapshots this side never sees. A whole drag is
    // one step; the coalescing that makes it so lives in `dr-pipeline`.
    in property <bool> can-undo: false;
    in property <bool> can-redo: false;
    callback undo();
    callback redo();

    /// Every step, newest first. Rust owns the order and stamps each row with
    /// its own position in the stack, so nothing here does arithmetic to turn
    /// a row back into a step.
    in property <[HistoryRow]> history-rows;
    /// What undo would take back, resolved. Empty when there is nowhere to go.
    in property <string> undo-label: "";
    /// A row's own `index`.
    callback history-picked(int);
    /// Scroll-to-zoom: factor, and the anchor in fractions of the visible area.
    callback zoom-at(float, float, float);
    callback pan-by(float, float);
    callback zoom-reset();

    // --- launch screen (FR-NC-1, FR-NC-4) ---
    //
    // The app opens here when no library is configured, and returns here to
    // sign out or switch account.
    in property <bool> show-launch: false;
    in property <bool> launch-signed-in: false;
    in property <string> launch-account: "";
    in property <string> launch-root: "";
    in property <string> launch-server: "";
    in property <string> launch-folder: "";
    in property <bool> launch-busy: false;
    in property <string> launch-status: "";
    in property <string> launch-error: "";
    in property <string> launch-login-url: "";
    in property <bool> launch-can-remember: true;
    in-out property <[string]> launch-format-labels;
    in-out property <[bool]> launch-format-checked;

    callback launch-sign-in(string);
    /// The path of a folder library — no account, no credential.
    callback launch-use-folder(string);
    /// server, username, app password
    callback launch-sign-in-direct(string, string, string);
    callback launch-sign-out();
    callback launch-choose-folder();
    callback launch-open-library();
    callback launch-format-toggled(int, bool);
    callback launch-copy-url();

    in property <bool> launch-browsing: false;
    in property <string> launch-browse-path: "";
    in property <bool> launch-browse-loading: false;
    in-out property <[string]> launch-browse-entries;

    callback launch-browse-into(string);
    callback launch-browse-up();
    callback launch-browse-confirm();
    callback launch-browse-cancel();

    // --- library grid (FR-CAT-4) ---
    //
    // Shown after a library is opened, before an image is chosen. Cells are a
    // window over the catalog, not the whole of it.
    in property <bool> show-library: false;
    in-out property <[LibraryCell]> library-cells;
    in property <int> library-total: 0;
    // --- background activity (FR-CAT-1, FR-NC-6c) ---
    //
    // Every background job in one register, filled by `activity.rs`. The
    // aggregate drives the bar across the top of the shell; the rows are the
    // list on the settings page, where a stalled transfer can be identified
    // rather than merely felt.
    in property <[ActivityRow]> activity-rows;
    /// Anything at all running. Drives the bar's visibility, so it is a
    /// property rather than `activity-rows.length > 0` — finished rows stay in
    /// the list for a while and must not keep the bar alight.
    in property <bool> activity-busy: false;
    /// Whether the running jobs, taken together, have a denominator. A scan
    /// alone does not; a scan beside a download does.
    in property <bool> activity-determinate: false;
    in property <float> activity-fraction: 0;
    in property <int> activity-running: 0;
    /// Jobs that stopped and are being kept: finished ones as a short history,
    /// failed ones until they are cleared.
    in property <int> activity-kept: 0;
    callback activity-clear-finished();

    in property <bool> library-scanning: false;
    in property <string> library-status: "";
    in property <string> library-error: "";

    // --- offline mode (FR-CAT-9) ---
    //
    // The library keeps working from local data when the server cannot be
    // reached: thumbnails come from the shards, and rating and sorting are
    // catalog operations that never needed the network. What stops is opening
    // an original that was never stored locally.
    //
    // `offline-reason` carries the transport's own message ("connection
    // refused", "dns error") because it is usually specific enough to act on,
    // where a bare "offline" leaves the user guessing whether it is their wifi
    // or the server.
    in property <bool> library-offline: false;
    in property <string> library-offline-reason: "";
    in property <string> library-offline-since: "";
    // Narrows the grid to images whose RAW is stored locally — the ones that
    // can actually be opened while offline. Off by default: the catalog is the
    // library, and hiding most of it the moment a connection drops would read
    // as data loss rather than as a filter.
    in-out property <bool> library-local-only: false;
    in property <int> library-local-count: 0;
    callback library-toggle-local-only();
    /// Whether the grid is narrowed to the timeline's visible span.
    in-out property <bool> library-range-active: false;
    callback library-toggle-date-range();
    /// TRACES: FR-CAT-5
    callback library-clear-selection();
    callback library-select-all();
    /// TRACES: FR-CAT-7
    /// Whether the grid is showing something with a manual order to change —
    /// a single manual collection, not a set and not a saved filter.
    in property <bool> library-reorderable: false;
    /// Move the selection beside the photograph at this row of the loaded
    /// window: after it where the drop landed on the cell's trailing half,
    /// before it otherwise.
    callback library-reorder-to(int, bool);
    callback library-collection-from-selection(string);
    /// TRACES: FR-CAT-6
    in property <string> library-range-from;
    in property <string> library-range-to;
    in property <bool> library-range-invalid: false;
    callback library-range-edited(string, string);
    /// The same range as a band on the capture-time axis, and the ends of it
    /// dragged. Fractions of the span the axis is drawn over — Rust owns the
    /// conversion both ways, so the band lands where the finger left it.
    in property <float> library-range-from-fraction: -1;
    in property <float> library-range-to-fraction: -1;
    callback library-timeline-range-changed(float, float);
    callback library-retry-connection();

    // --- pinning a collection offline (FR-NC-6a) ---
    in property <bool> library-scope-pinned: false;
    in property <int> library-pin-done: 0;
    in property <int> library-pin-total: 0;
    callback library-toggle-pin-scope();

    // The question a held collection asks: keep these on the device, or give
    // the disk back. Driven entirely from Rust — the counts and the byte sizes
    // in the labels are catalog reads, and an empty `title` is what closes it.
    in property <string> offline-prompt-title: "";
    in property <string> offline-prompt-detail: "";
    in property <string> offline-prompt-keep-label: "";
    in property <string> offline-prompt-release-label: "";
    in property <bool> offline-prompt-can-keep: false;
    in property <bool> offline-prompt-can-release: false;
    in property <bool> offline-prompt-busy: false;
    callback offline-prompt-keep();
    callback offline-prompt-release();
    callback offline-prompt-dismiss();

    // The question a damaged catalog asks. Same shape as the prompt above and
    // for the same reason: an empty title is what closes it, and every word in
    // it is composed in Rust, which is the only side that knows what SQLite
    // said and which backups exist.
    in property <string> recovery-title: "";
    in property <string> recovery-detail: "";
    in property <string> recovery-diagnosis: "";
    in property <string> recovery-restore-label: "";
    in property <bool> recovery-can-restore: false;
    in property <string> recovery-rebuild-label: "";
    in property <bool> recovery-busy: false;
    callback recovery-restore();
    callback recovery-rebuild();
    callback recovery-dismiss();

    in property <string> library-root-label: "";
    in-out property <[TimelineBar]> library-timeline;
    in property <string> library-timeline-label: "";
    in property <string> library-window-label: "";
    in property <int> library-offset: 0;

    in property <int> library-sweep-done: 0;
    in property <int> library-sweep-total: 0;

    in property <int> library-current-bucket: 0;
    in property <float> library-current-fraction: -1;
    in property <bool> library-timeline-anchored: false;

    callback library-scrub-fraction(float);
    callback library-timeline-pinch(float);
    callback library-timeline-pan(float);
    callback library-timeline-zoom(int);
    in-out property <int> library-columns: 1;
    in property <bool> library-syncing: false;
    /// TRACES: FR-CAT-3 | FR-NC-3
    /// The whole-library thumbnail pass, launched from the settings page.
    /// `library-open` gates the button on there being a library to sweep —
    /// the page is reachable from the launch screen too.
    in property <bool> library-thumbnailing: false;
    in property <bool> library-open: false;

    // --- people and faces (FR-CULL-8 … FR-CULL-12) ---
    //
    // A third top-level screen rather than a panel: naming a cluster and
    // pulling a stranger out of it are tasks with their own rhythm, and they
    // need the whole window. Gated the same way the other screens are, so
    // exactly one is ever up.
    in property <bool> show-identity: false;
    in property <[IdentityPerson]> identity-people;
    in property <[IdentityFace]> identity-faces;
    in property <int> identity-selected: -1;
    in property <string> identity-selected-name;
    in property <int> identity-unassigned: 0;
    in property <bool> identity-calibrated: false;
    in property <bool> identity-indexing: false;
    in property <string> identity-indexing-status;
    in property <bool> identity-model-missing: false;
    in property <string> identity-back-label: "‹ Library";
    in property <string> identity-coverage;
    in property <bool> identity-coverage-complete: false;
    in property <int> identity-picked: 0;
    /// The namesake merge the Identity screen is offering. See IdentityScreen.
    in property <string> identity-merge-offer-name;
    in property <int> identity-merge-offer-faces: 0;
    /// See IdentityScreen.name-revision.
    in property <int> identity-name-revision: 0;

    callback identity-open();
    callback identity-close();
    callback identity-person-picked(int);
    callback identity-rename(string);
    callback identity-merge-accept();
    callback identity-merge-decline();
    callback identity-name-edited(string);
    callback identity-confirm-face(int);
    callback identity-reject-face(int);
    callback identity-toggle-pick(int);
    callback identity-confirm-all();
    callback identity-split-picked();
    callback identity-recluster();
    in property <bool> identity-regrouping: false;
    in property <string> identity-regroup-status;
    // The grouping dials Regroup turns. Percent and a face count, both stored
    // in the device settings file beside the cache budgets.
    in property <float> identity-merge-probability: 80;
    in property <int> identity-min-group-size: 2;
    callback identity-merge-probability-changed(float);
    callback identity-min-group-size-changed(int);
    callback identity-preview-grouping();
    in property <bool> identity-previewing: false;
    in property <string> identity-grouping-preview;
    in property <int> identity-ignored-count: 0;
    in property <bool> identity-show-ignored: false;
    in property <bool> identity-selected-ignored: false;
    callback identity-toggle-show-ignored();
    callback identity-ignore-person(int, bool);
    callback identity-show-photos(int, bool);
    callback identity-index();
    callback identity-stop-indexing();
    callback identity-check-coverage();
    callback identity-delete-all();
    callback library-thumbnail-all();
    in-out property <length> library-cell-size: 180px;
    /// Whether this session is a touch one, which decides if the rating strip
    /// waits to be hovered or stands open. Seeded from the platform by Rust
    /// and latched by the grid on the first finger it sees.
    in-out property <bool> library-touched: false;
    callback library-zoom-cells(int);
    /// A pinch step on the grid: the ratio since the last update.
    callback library-pinch-cells(float);
    /// A pinch on the grid has begun, so the press that opened it was not one.
    callback library-pinch-started();
    in property <int> library-scroll-to: 0;
    in property <int> library-scroll-token: 0;
    /// Which row of the loaded window is the photograph currently open in
    /// develop, so the roll can mark it. `-1` when it is not in the window.
    in property <int> library-roll-current: -1;
    /// Whether the photo roll is out. Owned here rather than by the roll, so
    /// it survives the develop view being torn down and rebuilt.
    in-out property <bool> roll-open: false;
    /// A photograph was chosen from the roll: the row within the loaded
    /// window, which is what a cell click reports too.
    callback library-roll-pick(int);
    callback library-sync-now();
    callback library-columns-changed();
    callback library-scrolled(int);
    /// How many cells the grid's viewport shows at once. Rust sizes the
    /// loaded window from it — see `library_ui::window_move`.
    callback library-viewport-cells(int);
    callback library-cell-clicked(int);
    callback library-rescan();
    /// Grid → launch screen, to pick a different folder or account.
    callback library-change();
    /// Develop → grid.
    callback back-to-library();

    // --- collections (FR-CAT-7) ---
    //
    // The sidebar's tree, flattened in Rust: Slint cannot instantiate a
    // component recursively, so depth arrives as an integer per row.
    in-out property <[CollectionRow]> collection-rows;
    /// Which collection scopes the grid. 0 is the whole library.
    in property <int> collection-selected: 0;
    in property <string> collection-scope-label: "";
    in property <string> collection-error: "";
    /// Whether the sidebar is shown at all. Closed by default in the compact
    /// layout, where 232px of the window is most of the photograph (FR-UI-1),
    /// and openable from the grid header either way — see `panel-visible` for
    /// how a default and a user's answer to it are kept apart.
    in property <bool> collections-visible: true;

    /// Which collection is being renamed in the sidebar, by id. 0 is none.
    in property <int> collection-renaming: 0;

    callback collection-select(int);
    callback collection-toggle(int);
    callback collection-new();
    callback collection-menu(int);
    /// TRACES: FR-NC-6a
    /// Ask about a collection's local copies: the tray on a row, or a long
    /// press anywhere on it.
    callback collection-offline-menu(int);
    /// A row is held or released — the long press is timed in Rust.
    callback collection-row-press(int, bool);
    /// TRACES: FR-CAT-7 | FR-UI-4
    /// File the grid's selection in a collection without dragging it there:
    /// the target's id, and whether to take the images out of the collection
    /// currently being shown.
    callback library-file-in-collection(int, bool);
    /// TRACES: FR-CAT-5 | FR-CAT-6
    /// Keywording the grid's selection. The catalog has been searchable by
    /// keyword since it existed and there was nowhere to type one; this is it.
    ///
    /// The vocabulary arrives already answered against the selection — each row
    /// says how many of the selected photographs carry that word — because only
    /// Rust knows what is selected, and a `.slint` file counting it would need
    /// the selection as a second model that could disagree with the first.
    in property <[KeywordRow]> library-keywords;
    /// The sheet is opening: recompute the rows against the selection as it
    /// stands now. Pulled rather than pushed, because the selection changes on
    /// every arrow key and the sheet is shut for almost all of them.
    callback library-keywords-opened();
    /// Put a keyword on the selection, creating it if it is new. By name, so a
    /// word typed into the field and a word tapped in the list are one path.
    callback library-assign-keyword(string);
    /// Take a keyword off the selection. Never deletes the keyword itself —
    /// it stays in the vocabulary and on every other photograph that carries it.
    callback library-unassign-keyword(string);
    /// TRACES: FR-UI-2
    /// Whether a tap in the grid selects rather than opens, and the button
    /// that turns it on. The long press does the same thing without it.
    in property <bool> library-select-mode: false;
    callback library-toggle-select-mode();
    /// TRACES: FR-CAT-7 | FR-UI-4
    /// The row a press has held long enough to pick up, or `-1`.
    ///
    /// Set by the same hold that turns on selection mode and cleared by the
    /// grid when the press ends — `in-out` because both ends write it. See
    /// `held-row` in `library.slint` for what it draws and what it stops.
    in-out property <int> library-held-row: -1;
    /// A press on a cell ended, so the long-press timer can be cancelled.
    callback library-cell-press-ended();
    /// TRACES: FR-UI-2 | FR-UI-4
    /// Two taps on a cell: in selection mode, the far end of a range.
    /// Renaming started on a row, by id — a double-click, or `F2`.
    callback collection-rename-start(int);
    /// A rename was committed: the collection's id and the new name.
    callback collection-rename-commit(int, string);
    /// Renaming was abandoned with Escape.
    callback collection-rename-cancel();
    /// Row index and collection id under the pointer. The id is what the
    /// drop highlight follows: a spring expansion rebuilds the row model
    /// mid-drag, and an index would then point at a different collection.
    /// A drag is dwelling over a collection, or has left it: id, and whether
    /// it is over. Drives the spring-loaded expansion, timed in Rust.
    callback collection-drag-over(int, bool);
    /// Images were dropped on a collection, by id. Slint hit-tests the release,
    /// so this is the collection actually under the pointer.
    callback collection-dropped(int);
    /// Payload for dragging a collection onto another to reparent it.
    pure callback collection-drag-payload(int) -> data-transfer;

    // --- trash (FR-CAT-15) ---
    //
    // Not a collection: a drop here moves the file into a trash folder on the
    // server, where a collection drop only adds a reference.
    in property <int> trash-count: 0;
    in property <string> trash-label: "";
    /// A soft delete: move the dragged images to the trash folder.
    callback trash-dropped();
    /// A hard delete: permanently remove everything in the trash.
    callback trash-empty();
    /// Put the selected trashed images back where they came from.
    callback trash-restore();

    // --- drag and drop ---
    //
    // Slint's own `DragArea`/`DropArea` carry this: pointer capture, the
    // click-versus-drag threshold, arbitration against the grid's Flickable,
    // and the image drawn under the cursor. So there is no badge to position
    // and no hover state to mirror here — only the payload, which Rust builds
    // from the selection, and the count the header shows.
    /// The drag payload, built by Rust from the current selection.
    pure callback library-drag-payload() -> data-transfer;
    /// The bitmap that travels under the cursor: one thumbnail, or a fanned
    /// stack where several images are being dragged. Composited in Rust.
    in property <image> library-drag-image;
    /// A drag began on a cell, so an unselected one can be promoted before the
    /// payload is read.
    callback library-drag-started(int);
    callback library-drag-finished();
    in property <int> library-selected-count: 0;

    callback library-cell-pressed(int, bool, bool);
    callback library-remove-from-collection();

    // The keyboard cursor: where the arrows are in the library, as an image
    // ordinal. Rust owns it — clamping it needs the library's length, and
    // moving it may have to swap the loaded window underneath.
    in property <int> library-cursor: -1;
    callback library-move-cursor(int, bool);
    callback library-open-cursor();

    // --- ratings and flags (FR-CAT-5, FR-CULL-4) ---
    //
    // Stars and pick/reject, set from the grid and persisted to the catalog
    // and the sidecar. Every image enters unrated, which is a state of its
    // own rather than a zero score.
    /// A star was clicked on a cell: row, then the rating 0..5.
    callback library-cell-rated(int, int);
    /// The trash target was clicked on one cell, by row.
    callback library-cell-trashed(int);
    /// The burst mark was clicked on one cell, by row (FR-CULL-5).
    callback library-burst-toggled(int);
    /// Move the grid selection to the trash — the `Delete` key.
    callback library-trash-selection();
    /// A judgement key was pressed, applying to the whole selection. One of
    /// the two arguments is -1, saying which axis was *not* meant.
    callback library-judged(int, int);

    /// Whose photographs the grid is narrowed to, one entry each.
    in property <[PersonChip]> library-filter-people;
    /// Whether those people are an intersection rather than a union.
    in property <bool> library-filter-people-all: false;
    callback library-filter-person-cleared(int);
    callback library-filter-people-mode-toggled();
    /// Everyone the library knows, for the filter bar's people tray.
    /// TRACES: FR-UI-4
    /// The gesture reference's rows, read from the generated table.
    in property <[GestureRow]> library-gestures;
    in property <[PersonChip]> library-people;
    callback library-people-listed();
    callback library-filter-person-toggled(int);
    in property <int> library-filter-min-rating: 0;
    in property <bool> library-filter-unjudged: false;
    in property <int> library-filter-flag: 0;
    /// Images per star count, index 0 unrated, for the filter chips.
    in-out property <[int]> library-rating-counts;

    callback library-filter-min-rating-changed(int);
    callback library-filter-unjudged-changed(bool);
    callback library-filter-flag-changed(int);

    callback next-image();
    callback prev-image();

    // Adjustment controls, generated from what the pipeline reports it can
    // do. This window knows the *shape* of a control, never which operations
    // exist (FR-DEV-3a).
    in property <[ParamRow]> adjust-rows;
    // TRACES: FR-DEV-3f
    // The installed film stocks, "None" first, and which one this photograph
    // is on. Resolved names: the core publishes ids, and a stock's name is a
    // product name that does not translate.
    in property <[string]> film-stocks;
    in property <int> film-selected: 0;
    in property <bool> film-can-print: false;
    in property <bool> film-print: false;
    callback film-picked(int);
    callback film-print-toggled(bool);
    in property <[string]> adjust-tabs;
    in property <int> adjust-active-tab: -1;
    callback adjust-tab-picked(int);
    in property <bool> adjust-enabled: false;
    // The tone curve's sampled shape, evaluated by the core so the drawn
    // line and the applied one cannot disagree.
    in property <[float]> curve-samples;
    // The curves that widget can plot, named by the core, and which of them
    // `curve-samples` describes. Fewer than two means nothing to choose.
    in property <[string]> curve-channels;
    in property <int> curve-channel;
    callback param-changed(int, int, float);
    callback param-reset(int, int);
    callback curve-reset(int);
    callback curve-channel-picked(int);
    callback reset-all();

    // --- copying settings between photographs (FR-DEV-6) ---
    //
    // The clipboard is a window-lifetime thing rather than a view's, which is
    // why it lives here and not inside the develop column: a copy is taken in
    // develop and may be pasted onto a selection back in the library grid.
    /// Whether anything has been copied this session.
    in property <bool> settings-armed: false;
    /// What a paste would apply, at the current scope — "3 adjustments".
    in property <string> settings-summary;
    /// Whether the copy holds framing that the current setting is dropping.
    in property <bool> settings-framing-withheld: false;
    callback copy-settings();
    callback paste-settings();
    /// Apply the clipboard to every selected image in the grid.
    callback paste-settings-to-selection();

    // --- named presets (FR-DEV-6) ---
    //
    // The saved half of the same requirement. On the window rather than in a
    // view for the reason the clipboard is: a preset is saved in develop,
    // where there is an edit to capture, and applied most often in the grid,
    // where there is a selection to apply it to.
    in-out property <bool> presets-open: false;
    in property <[string]> preset-names;
    /// Whether there is an edit in hand to save, set by whichever view opened
    /// the sheet. `in-out` because that is where the answer is known.
    in-out property <bool> preset-can-save: false;
    /// What applying would act on: 0 is the open photograph, higher is that
    /// many selected. Set at open, and read back by Rust when one is picked —
    /// so the action matches the count the user read on the way in.
    in-out property <int> preset-apply-count: 0;
    /// What saving would capture, from the routine the clipboard summary uses.
    in property <string> preset-capture-summary;
    /// Why the last name was refused, cleared by the next keystroke.
    in property <string> preset-name-error;
    callback save-preset(string);
    callback apply-preset(string);
    callback rename-preset(string, string);
    callback delete-preset(string);
    callback preset-name-edited(string);
    /// Raised as the sheet opens over an open photograph, so Rust can say what
    /// saving would capture. A property refreshed on every slider drag would
    /// be recomputing a string nobody is looking at.
    callback presets-opened();

    /// TRACES: FR-DEV-6
    /// Which kinds of edit a copy, paste or preset carries.
    ///
    /// One set for all three, on the window because all three read it: the
    /// clipboard is pasted from develop and from the grid, and a preset is
    /// applied from both. A per-action set would be three answers to one
    /// question about how this photographer works.
    in property <[ScopeKind]> copy-scope-kinds;
    in property <bool> copy-scope-empty: false;
    callback copy-scope-toggled(string);

    /// TRACES: FR-DEV-6
    /// Reading Lightroom presets in, and what came of the last attempt.
    in property <string> preset-import-report;
    callback import-presets(string);

    // --- settings (FR-EXP-1, FR-EXP-3, FR-NC-6a) ---
    //
    // A page rather than an overlay, and the outermost of the view conditions
    // below: it is reachable from the library and from develop, so guarding it
    // with `!show-library` or `!show-launch` would make which one you came from
    // decide whether it appears.
    //
    // Every control saves on change (see `settings_ui.rs`), so there is no
    // dirty state here and nothing to confirm on the way out.
    in-out property <bool> show-settings: false;

    // --- import (FR-CAT-10, FR-CAT-11, FR-NC-7a) -------------------------
    //
    // A page like Settings, and outermost with it: an import is reachable from
    // the library, and it writes into the library, so it must not be nested
    // inside the view it is about to change under.
    //
    // Unlike Settings, this page holds a *decision* rather than a set of saved
    // preferences, which is why it carries `import-can-start` and a running
    // state: everything here exists to be committed or abandoned.
    in-out property <bool> show-import: false;
    /// Whether this platform can import at all — see `dr_plat::imports_supported`.
    in property <bool> import-supported: false;

    in property <[string]> import-volume-labels;
    in property <[string]> import-volume-details;
    in property <int> import-volume-selected: -1;
    in property <string> import-card-path: "";
    in property <bool> import-card-looks-right: false;
    in property <bool> import-surveying: false;
    in property <string> import-survey-summary: "";
    in property <string> import-upload-target: "";
    in property <string> import-folder-template: "";
    in property <string> import-template-preview: "";
    in property <[string]> import-mode-labels;
    in property <int> import-mode-selected: 0;
    in property <bool> import-mode-is-move: false;
    in property <[string]> import-duplicate-labels;
    in property <int> import-duplicate-selected: 0;
    in property <bool> import-verify: true;
    in property <bool> import-backup-on: false;
    in property <string> import-backup-path: "";
    in property <bool> import-running: false;
    in property <float> import-fraction: 0.0;
    in property <string> import-status: "";
    in property <string> import-error: "";
    in property <bool> import-can-start: false;

    callback import-open();
    callback import-close();
    callback import-volume-picked(int);
    callback import-card-path-changed(string);
    callback import-refresh-volumes();
    callback import-template-changed(string);
    callback import-mode-picked(int);
    callback import-duplicate-picked(int);
    callback import-verify-toggled(bool);
    callback import-backup-toggled(bool);
    callback import-backup-path-changed(string);
    callback import-start();
    callback import-stop();

    in property <string> settings-original-budget: "";
    in property <bool> settings-original-unlimited: false;
    in property <string> settings-thumbnail-budget: "";
    in property <bool> settings-thumbnail-unlimited: false;
    in property <bool> settings-keep-opened: true;
    in property <string> settings-cache-usage: "";

    callback settings-original-budget-changed(string);
    callback settings-original-unlimited-toggled(bool);
    callback settings-thumbnail-budget-changed(string);
    callback settings-thumbnail-unlimited-toggled(bool);
    callback settings-keep-opened-toggled(bool);
    /// TRACES: FR-CAT-6
    in property <[string]> settings-timeline-bar-labels;
    in property <int> settings-timeline-bars-selected: 0;
    callback settings-timeline-bars-picked(int);

    in property <[string]> settings-format-labels;
    in property <int> settings-format-selected: 0;
    in property <int> settings-quality: 90;
    in property <bool> settings-quality-enabled: true;
    in property <[string]> settings-colour-labels;
    in property <int> settings-colour-selected: 0;
    in property <[string]> settings-sizing-labels;
    in property <int> settings-sizing-selected: 0;
    in property <int> settings-sizing-value: 0;
    in property <bool> settings-sizing-has-value: false;
    in property <string> settings-sizing-unit: "px";
    in property <string> settings-sizing-value-label: "Size value";
    in property <int> settings-sizing-height: 0;
    in property <bool> settings-sizing-has-height: false;
    in property <[string]> settings-screen-labels;
    in property <int> settings-screen-selected: -1;
    in property <bool> settings-allow-upscaling: false;
    in property <[string]> settings-sharpening-labels;
    in property <int> settings-sharpening-selected: 0;
    in property <string> settings-filename-template: "";
    in property <[string]> settings-collision-labels;
    in property <int> settings-collision-selected: 0;
    in property <bool> settings-strip-location: true;
    in property <string> settings-destination: "";
    in property <string> settings-destination-hint;
    in property <bool> settings-browse-open: false;
    in property <string> settings-browse-path;
    in property <[string]> settings-browse-entries;
    in property <bool> settings-browse-loading: false;
    in property <bool> settings-browse-at-root: true;
    in property <bool> settings-browse-available: false;
    in property <[string]> settings-target-labels;
    in property <int> settings-target-selected: 0;
    in property <string> settings-error: "";

    callback settings-format-picked(int);
    callback settings-quality-changed(int);
    callback settings-colour-picked(int);
    callback settings-sizing-picked(int);
    callback settings-sizing-value-changed(string);
    callback settings-sizing-height-changed(string);
    callback settings-screen-picked(int);
    callback settings-upscaling-toggled(bool);
    callback settings-sharpening-picked(int);
    callback settings-template-changed(string);
    callback settings-collision-picked(int);
    callback settings-strip-location-toggled(bool);
    callback settings-destination-changed(string);
    callback settings-target-changed(int);
    callback settings-browse-open-picker();
    callback settings-browse-into(string);
    callback settings-browse-up();
    callback settings-browse-confirm();
    callback settings-browse-cancel();
    callback settings-reset();

    /// Show the settings page. Reads the file first, so a second instance's
    /// writes are picked up rather than overwritten.
    callback settings-open();
    callback settings-close();

    // FR-UI-1: layout class follows window width, not device type. A narrow
    // desktop window gets the compact layout, exactly as a tablet would.
    //
    // Set from Rust rather than derived from `root.width` here: a property
    // read inside the layout and also feeding it creates a binding loop,
    // which Slint warns about and which can panic at runtime.
    //
    // Nothing below reads `expanded` directly any more. It decides what the
    // two collapsible columns *default* to, and Rust applies that to
    // `panel-visible` and `collections-visible`; binding a column's width to
    // the class itself would mean a panel the user opened snapped shut again
    // on the next resize.
    in property <bool> expanded: true;
    in property <string> layout-class: "expanded";

    /// TRACES: FR-UI-2
    /// The most the develop column may take, in logical pixels.
    ///
    /// Set from Rust beside `layout-class` and for the same reason: the column
    /// sizes itself to its contents, and a ceiling read from `root.width`
    /// inside the layout that `root.width` depends on is the binding loop the
    /// note above describes.
    ///
    /// A ceiling and not a width. The column asks for what it needs and this
    /// only says when the answer has stopped being reasonable — a photograph
    /// with a third of a window left to show itself in is not a develop view.
    /// The default is generous because the first frame is drawn before any
    /// resize has been reported, and a column briefly too wide is a far
    /// smaller fault than one briefly clipped.
    in property <length> panel-max-width: 520px;

    // --- local adjustments (FR-DEV-3) ---------------------------------------

    /// The false-coloured region map, drawn over the photograph.
    ///
    /// An empty image when there is nothing to draw, which is also how the
    /// overlay is hidden — one source of truth rather than a flag that can
    /// disagree with the picture.
    in property <image> region-overlay;
    /// How strongly the overlay is composited. Not 1.0: the point of looking
    /// at it is to judge whether a boundary follows the *photograph*, and an
    /// opaque map hides the thing being judged.
    in property <float> overlay-strength: 0.55;
    in property <bool> overlay-on: false;
    /// TRACES: FR-DEV-3
    /// The photographer's switch for the same overlay, kept separate from
    /// `overlay-on` because the two answer different questions: `overlay-on`
    /// is "is there a mask to draw", which Rust decides, and this is "do I
    /// want to look at it right now", which only they can.
    ///
    /// Folding them into one property would mean the next recompute — any
    /// mask edit — silently switched the overlay back on under someone who had
    /// just turned it off to check their work against the photograph.
    in-out property <bool> overlay-hidden: false;
    /// Which part of the source-space overlay the view is showing, in overlay
    /// pixels. Without it the overlay stays frame-sized while the photograph
    /// moves under it.
    in property <int> overlay-clip-x;
    in property <int> overlay-clip-y;
    in property <int> overlay-clip-w;
    in property <int> overlay-clip-h;
    /// The straightening angle, so the overlay turns with the frame.
    in property <float> overlay-angle: 0.0;

    /// Whether a click on the canvas selects a region instead of panning.
    ///
    /// **Derived, not toggled.** It used to be a button in the masking panel,
    /// which meant local masking could be open with picking off — a mode
    /// entered and doing nothing. Arming a click is part of what local mode
    /// *is*, so it follows the mode and the existence of something to pick.
    property <bool> region-picking: root.local-mode && root.segmented;

    /// Whether shift is down, tracked by the develop key scope below.
    ///
    /// A `TouchArea`'s `clicked` carries no modifiers, so the state has to be
    /// held between the key event and the click. Private to the window because
    /// nothing outside it has any business setting it.
    property <bool> shift-held: false;

    in property <[MaskRow]> mask-rows;
    in property <[SubjectRow]> subject-rows;
    in property <[CategoryRow]> category-rows;
    in property <bool> segmented: false;
    in property <bool> segmenting: false;
    in property <bool> refining: false;
    /// The selected layer's name, already resolved, or "ADJUST" when the
    /// controls are global. Names the adjust panel's heading.
    in property <string> adjust-scope: "ADJUST";

    /// The selected gradient's handles, in fractions of the shown image.
    /// Empty unless a gradient layer is selected in local mode.
    in property <[GradientHandle]> gradient-handles;
    /// A handle dragged: which one, where the press was and where the pointer
    /// is now, both in fractions of the shown image.
    ///
    /// The press is carried rather than a running delta because the geometry
    /// is re-derived from the position it had when the drag began — which is
    /// what stops a drag accumulating rounding error along its length, the
    /// same reason the crop handles capture the rect they started from.
    callback gradient-handle-dragged(HandleRole, float, float, float, float);
    /// A drag finished, so the edit can be recorded as one history step
    /// rather than as one per frame of the gesture.
    callback gradient-handle-released();

    // --- repairs (FR-DEV-8) -------------------------------------------------

    /// Every repair on the photograph, as circles in fractions of the shown
    /// image. Rust maps them through the framing, so they follow a crop, a
    /// zoom, a pan and a rotation without anything here knowing about any of
    /// those.
    in property <[SpotHandle]> spot-handles;
    /// A click on the photograph in repair mode, in fractions of the shown
    /// image: cover what is here.
    callback spot-placed(float, float);
    /// A repair's circle dragged: which repair, which half of it, where the
    /// press landed and where the pointer is now.
    ///
    /// The press is carried rather than a running delta for the reason the
    /// gradient handles carry it — the geometry is re-derived from where it
    /// stood when the gesture began, so a drag cannot accumulate rounding
    /// error along its length.
    callback spot-handle-dragged(string, SpotRole, float, float, float, float);
    /// A drag finished, so it can be one history step rather than one a frame.
    callback spot-handle-released();
    /// A repair chosen, so the column describes it.
    callback spot-selected(string);
    /// Take the selected repair off the photograph.
    callback spot-removed(string);
    /// Which repair the column is describing, or "" for none.
    in-out property <string> selected-spot: "";
    /// The selected repair's settings, and how many repairs there are.
    ///
    /// Pushed as scalars rather than read off `spot-handles`, because the
    /// circles carry what is *drawn* — a radius already mapped through the
    /// framing into fractions of the shown image — and the panel edits what is
    /// *stored*. Deriving one from the other would mean a slider that moved
    /// differently at different zoom levels.
    in property <int> spot-count: 0;
    in property <float> spot-radius: 0.012;
    in property <float> spot-feather: 0.35;
    in property <float> spot-opacity: 1.0;
    /// 0 heal, 1 clone.
    in property <int> spot-mode: 0;

    callback spot-radius-changed(float);
    callback spot-feather-changed(float);
    callback spot-opacity-changed(float);
    callback spot-mode-picked(int);

    callback segment-image(bool);
    /// A click on the photograph, in fractions of the shown image, plus
    /// whether it should extend the selection rather than replace it.
    callback region-picked(float, float, bool);
    callback mask-selected(string, bool);
    callback mask-removed(string);
    callback mask-refined(string);
    callback mask-toggled(string, bool);
    callback mask-invert-toggled(string, bool);
    callback mask-opacity-changed(string, float);
    callback mask-feather-changed(string, float);
    callback mask-falloff-picked(string, int);
    callback mask-morphology-picked(string, int);
    callback mask-morph-radius-changed(string, float);
    callback add-gradient-mask(bool);
    callback add-subject-mask(int);
    callback add-category-mask(string);

    /// Whether the develop column — image info, geometry, adjust — is shown.
    ///
    /// Distinct from `expanded`, which is the *layout class* and only supplies
    /// this its default: a panel the user closed on a wide window stays closed,
    /// and one they opened on a narrow one stays open. Rust owns both for the
    /// reason given above — a property read inside the layout and also feeding
    /// it is a binding loop.
in property <bool> panel-visible: true;
    /// The export button's label and busy state, and the line it reports to.
    /// Rust owns all three: what an export is called depends on the format and
    /// on whether the destination is this device or the server, neither of
    /// which the toolbar can see.
    in property <string> export-label: "Export";
    in property <bool> export-busy: false;
    in property <string> export-status;
    /// TRACES: FR-EXP-7
    /// Whether an export would be queued for the server rather than written to
    /// this device. The grid says the same thing as the develop button, but it
    /// composes its own label around a selection count — so it is given the
    /// fact and not the sentence.
    in property <bool> export-to-server: false;
    /// Whether a batch is running. The grid's export button becomes its cancel
    /// button; there is nowhere else a long batch can be stopped from.
    in property <bool> library-exporting: false;
    /// Export the grid's selection in the background (FR-EXP-7).
    callback library-export-selection();
    /// TRACES: NFR-ARCH-3
    callback library-cancel-export();
    /// Show or hide the develop column.
    callback toggle-panel();
    /// Export the image on screen, using the settings as they stand.
    callback export-image();
    /// Show or hide the collections sidebar.
    callback toggle-collections();

    /// Android's back gesture, or Escape. Returns whether there was anywhere to
    /// go: `false` means this is the top of the stack, and the platform is left
    /// to close the application as it normally would.
    callback back-requested() -> bool;

    callback canvas-resized(int, int);
    callback window-resized(length);

    /// The width the interface actually has to lay out in.
    ///
    /// Not the window's: on Android the window spans the display and the
    /// left/right insets are given over to system furniture, so choosing the
    /// layout class from `width` would promise the layout space it cannot use.
    property <length> shell-width:
        root.width - root.safe-area-insets.left - root.safe-area-insets.right;

    // One-way: report width outward, never read layout back into it.
    changed shell-width => { root.window-resized(self.shell-width); }

    // Everything the interface draws lives inside this, for two reasons that
    // happen to want the same element.
    //
    // **The safe area.** From target SDK 35 Android draws applications behind
    // the status and navigation bars and offers no way out, so the window's
    // own coordinates include the strips those bars occupy — which is why the
    // develop status strip came out underneath the clock and the wifi icon.
    // `safe-area-insets` is what the platform reports as covered; the shell is
    // placed inside it and only the window background paints behind the bars.
    // Every inset is zero on the desktop, so nothing about that layout moves.
    //
    // **The back gesture.** Android's back button and back swipe arrive as
    // `Key.Back`, delivered to whatever holds focus and then bubbled up its
    // ancestors — so the one handler that answers for the whole application
    // has to be above all four views rather than beside them. Accepting the
    // key tells the platform we consumed it; rejecting it lets Android do what
    // it does by default and close the activity, which is exactly what should
    // happen at the top of the stack.
    shell := FocusScope {
        x: root.safe-area-insets.left;
        y: root.safe-area-insets.top;
        width: root.shell-width;
        height: root.height - root.safe-area-insets.top
                - root.safe-area-insets.bottom;

        // Deliberately does *not* focus itself.
        //
        // A key needs a focus item to bubble from, so each of the four views
        // below focuses a scope of its own on show — the grid's judgement keys,
        // develop's arrow keys, and a zero-sized holder on the two form pages
        // that would otherwise focus nothing. Claiming focus here as a fallback
        // would race with those: Slint does not promise whether a parent's
        // `init` runs before or after its children's, so on the wrong ordering
        // this would take focus back off the grid and silently break culling.

        key-pressed(event) => {
            // Escape alongside Back: the same "go up one" on a keyboard, and
            // the inner scopes that use it for something more specific — a
            // rename in the sidebar — see it first and accept it there.
            if (event.text == Key.Back || event.text == Key.Escape) {
                // A dialogue takes "go up one" first, and it is the *only*
                // thing that goes up. Without this, Android's Back button
                // would leave the library from behind an open question — the
                // view changing underneath a modal, which reads as the app
                // having lost its place.
                //
                // The recovery question is asked first because it is drawn
                // over everything, the offline prompt included: Back must
                // reach the thing the user can actually see.
                if (root.recovery-title != "") {
                    root.recovery-dismiss();
                    return accept;
                }
                if (root.offline-prompt-title != "") {
                    root.offline-prompt-dismiss();
                    return accept;
                }
                return root.back-requested() ? accept : reject;
            }
            return reject;
        }

        // Settings, over everything. First in the file and first in z-order so the
        // conditions below can be read as "and settings is not open".
        // Outermost with the settings page, and before it: both are reachable
        // from the library and from develop, so guarding either with
        // `!show-library` would make which view you came from decide whether
        // it appears.
        if root.show-import: ImportPage {
            width: 100%;
            height: 100%;

            volume-labels: root.import-volume-labels;
            volume-details: root.import-volume-details;
            volume-selected: root.import-volume-selected;
            card-path: root.import-card-path;
            card-looks-right: root.import-card-looks-right;
            surveying: root.import-surveying;
            survey-summary: root.import-survey-summary;
            upload-target: root.import-upload-target;
            folder-template: root.import-folder-template;
            template-preview: root.import-template-preview;
            mode-labels: root.import-mode-labels;
            mode-selected: root.import-mode-selected;
            mode-is-move: root.import-mode-is-move;
            duplicate-labels: root.import-duplicate-labels;
            duplicate-selected: root.import-duplicate-selected;
            verify: root.import-verify;
            backup-on: root.import-backup-on;
            backup-path: root.import-backup-path;
            running: root.import-running;
            fraction: root.import-fraction;
            status: root.import-status;
            error: root.import-error;
            can-start: root.import-can-start;

            volume-picked(i) => { root.import-volume-picked(i); }
            card-path-changed(t) => { root.import-card-path-changed(t); }
            refresh-volumes() => { root.import-refresh-volumes(); }
            template-changed(t) => { root.import-template-changed(t); }
            mode-picked(i) => { root.import-mode-picked(i); }
            duplicate-picked(i) => { root.import-duplicate-picked(i); }
            verify-toggled(on) => { root.import-verify-toggled(on); }
            backup-toggled(on) => { root.import-backup-toggled(on); }
            backup-path-changed(t) => { root.import-backup-path-changed(t); }
            begin() => { root.import-start(); }
            stop() => { root.import-stop(); }
            close() => { root.import-close(); }
        }

        if !root.show-import && root.show-settings: SettingsPage {
            width: 100%;
            height: 100%;

            adapter: root.adapter;
            backend: root.backend;
            fps: root.fps;
            layout-class: root.layout-class;
            app-version: root.app-version;
            display-name: root.display-name;
            display-colour: root.display-colour;
            display-others: root.display-others;

            original-budget: root.settings-original-budget;
            original-unlimited: root.settings-original-unlimited;
            thumbnail-budget: root.settings-thumbnail-budget;
            thumbnail-unlimited: root.settings-thumbnail-unlimited;
            keep-opened: root.settings-keep-opened;
            copy-scope-kinds: root.copy-scope-kinds;
            copy-scope-empty: root.copy-scope-empty;
            copy-scope-toggled(name) => { root.copy-scope-toggled(name); }
            timeline-bar-labels: root.settings-timeline-bar-labels;
            timeline-bars-selected: root.settings-timeline-bars-selected;
            timeline-bars-picked(i) => { root.settings-timeline-bars-picked(i); }
            cache-usage: root.settings-cache-usage;

            original-budget-changed(t) => { root.settings-original-budget-changed(t); }
            original-unlimited-toggled(on) => {
                root.settings-original-unlimited-toggled(on);
            }
            thumbnail-budget-changed(t) => { root.settings-thumbnail-budget-changed(t); }
            thumbnail-unlimited-toggled(on) => {
                root.settings-thumbnail-unlimited-toggled(on);
            }
            keep-opened-toggled(on) => { root.settings-keep-opened-toggled(on); }

            format-labels: root.settings-format-labels;
            format-selected: root.settings-format-selected;
            quality: root.settings-quality;
            quality-enabled: root.settings-quality-enabled;
            colour-labels: root.settings-colour-labels;
            colour-selected: root.settings-colour-selected;
            sizing-labels: root.settings-sizing-labels;
            sizing-selected: root.settings-sizing-selected;
            sizing-value: root.settings-sizing-value;
            sizing-has-value: root.settings-sizing-has-value;
            sizing-unit: root.settings-sizing-unit;
            sizing-value-label: root.settings-sizing-value-label;
            sizing-height: root.settings-sizing-height;
            sizing-has-height: root.settings-sizing-has-height;
            screen-labels: root.settings-screen-labels;
            screen-selected: root.settings-screen-selected;
            allow-upscaling: root.settings-allow-upscaling;
            sharpening-labels: root.settings-sharpening-labels;
            sharpening-selected: root.settings-sharpening-selected;
            filename-template: root.settings-filename-template;
            collision-labels: root.settings-collision-labels;
            collision-selected: root.settings-collision-selected;
            strip-location: root.settings-strip-location;
            destination: root.settings-destination;
            destination-hint: root.settings-destination-hint;
            browse-open: root.settings-browse-open;
            browse-path: root.settings-browse-path;
            browse-entries: root.settings-browse-entries;
            browse-loading: root.settings-browse-loading;
            browse-at-root: root.settings-browse-at-root;
            browse-available: root.settings-browse-available;
            target-labels: root.settings-target-labels;
            target-selected: root.settings-target-selected;
            error: root.settings-error;

            format-picked(i) => { root.settings-format-picked(i); }
            quality-changed(q) => { root.settings-quality-changed(q); }
            colour-picked(i) => { root.settings-colour-picked(i); }
            sizing-picked(i) => { root.settings-sizing-picked(i); }
            sizing-value-changed(t) => { root.settings-sizing-value-changed(t); }
            sizing-height-changed(t) => { root.settings-sizing-height-changed(t); }
            screen-picked(i) => { root.settings-screen-picked(i); }
            upscaling-toggled(on) => { root.settings-upscaling-toggled(on); }
            sharpening-picked(i) => { root.settings-sharpening-picked(i); }
            template-changed(t) => { root.settings-template-changed(t); }
            collision-picked(i) => { root.settings-collision-picked(i); }
            strip-location-toggled(on) => { root.settings-strip-location-toggled(on); }
            destination-changed(t) => { root.settings-destination-changed(t); }
            target-picked(i) => { root.settings-target-changed(i); }
            browse-open-picker() => { root.settings-browse-open-picker(); }
            browse-into(n) => { root.settings-browse-into(n); }
            browse-up() => { root.settings-browse-up(); }
            browse-confirm() => { root.settings-browse-confirm(); }
            browse-cancel() => { root.settings-browse-cancel(); }

            activity-rows: root.activity-rows;
            activity-running: root.activity-running;
            activity-kept: root.activity-kept;
            clear-finished() => { root.activity-clear-finished(); }
            thumbnailing: root.library-thumbnailing;
            // The face pass reuses the Identity Manager's own state rather
            // than duplicating it: one job, startable from either place, and
            // a button that cannot disagree with the screen about whether it
            // is running.
            face-indexing: root.identity-indexing;
            face-coverage: root.identity-coverage;
            face-model-missing: root.identity-model-missing;
            library-open: root.library-open;
            thumbnail-library() => { root.library-thumbnail-all(); }
            index-faces() => { root.identity-index(); }

            close() => { root.settings-close(); }
            reset-defaults() => { root.settings-reset(); }
        }

        // Like the launch screen, this replaces the window rather than
        // overlaying it — see `show-identity`.
        if !root.show-import && !root.show-settings && root.show-identity: IdentityScreen {
            width: 100%;
            height: 100%;
            people: root.identity-people;
            faces: root.identity-faces;
            selected-person: root.identity-selected;
            selected-name: root.identity-selected-name;
            unassigned: root.identity-unassigned;
            calibrated: root.identity-calibrated;
            indexing: root.identity-indexing;
            indexing-status: root.identity-indexing-status;
            model-missing: root.identity-model-missing;
            picked-count: root.identity-picked;
            back-label: root.identity-back-label;
            coverage: root.identity-coverage;
            coverage-complete: root.identity-coverage-complete;
            merge-offer-name: root.identity-merge-offer-name;
            merge-offer-faces: root.identity-merge-offer-faces;
            name-revision: root.identity-name-revision;

            person-picked(id) => { root.identity-person-picked(id); }
            rename(name) => { root.identity-rename(name); }
            merge-accept() => { root.identity-merge-accept(); }
            name-edited(t) => { root.identity-name-edited(t); }
            merge-decline() => { root.identity-merge-decline(); }
            confirm-face(id) => { root.identity-confirm-face(id); }
            reject-face(id) => { root.identity-reject-face(id); }
            toggle-pick(id) => { root.identity-toggle-pick(id); }
            confirm-all() => { root.identity-confirm-all(); }
            split-picked() => { root.identity-split-picked(); }
            compact: !root.expanded;
            photos-filtered: root.library-filter-people.length > 0;
            regrouping: root.identity-regrouping;
            regroup-status: root.identity-regroup-status;
            merge-probability: root.identity-merge-probability;
            min-group-size: root.identity-min-group-size;
            merge-probability-changed(v) => { root.identity-merge-probability-changed(v); }
            min-group-size-changed(n) => { root.identity-min-group-size-changed(n); }
            previewing: root.identity-previewing;
            grouping-preview: root.identity-grouping-preview;
            preview-grouping() => { root.identity-preview-grouping(); }
            ignored-count: root.identity-ignored-count;
            show-ignored: root.identity-show-ignored;
            selected-ignored: root.identity-selected-ignored;
            toggle-show-ignored() => { root.identity-toggle-show-ignored(); }
            ignore-person(id, on) => { root.identity-ignore-person(id, on); }
            show-photos(id, add) => { root.identity-show-photos(id, add); }
            recluster() => { root.identity-recluster(); }
            index-faces() => { root.identity-index(); }
            stop-indexing() => { root.identity-stop-indexing(); }
            check-coverage() => { root.identity-check-coverage(); }
            delete-all-face-data() => { root.identity-delete-all(); }
            close() => { root.identity-close(); }
        }

        // The launch screen replaces the whole window rather than overlaying it:
        // there is no library to look at until an account is configured.
        if !root.show-import && !root.show-settings && !root.show-identity && root.show-launch: LaunchScreen {
            width: 100%;
            height: 100%;
            signed-in: root.launch-signed-in;
            account: root.launch-account;
            library-root: root.launch-root;
            server-url: root.launch-server;
            folder-path: root.launch-folder;
            busy: root.launch-busy;
            status: root.launch-status;
            error: root.launch-error;
            login-url: root.launch-login-url;
            can-remember: root.launch-can-remember;
            format-labels: root.launch-format-labels;
            format-checked: root.launch-format-checked;

            sign-in(server) => { root.launch-sign-in(server); }
            use-folder(path) => { root.launch-use-folder(path); }
            sign-in-direct(server, user, pw) => {
                root.launch-sign-in-direct(server, user, pw);
            }
            sign-out() => { root.launch-sign-out(); }
            choose-folder() => { root.launch-choose-folder(); }
            open-library() => { root.launch-open-library(); }
            format-toggled(i, on) => { root.launch-format-toggled(i, on); }
            copy-login-url() => { root.launch-copy-url(); }

            browsing: root.launch-browsing;
            browse-path: root.launch-browse-path;
            browse-loading: root.launch-browse-loading;
            browse-entries: root.launch-browse-entries;

            browse-into(name) => { root.launch-browse-into(name); }
            browse-up() => { root.launch-browse-up(); }
            browse-confirm() => { root.launch-browse-confirm(); }
            browse-cancel() => { root.launch-browse-cancel(); }
        }

        // The library view sits between the launch screen and develop: a library
        // has been opened but no image chosen yet. The collections sidebar and the
        // grid are siblings here rather than the sidebar living inside the grid,
        // because the drag that connects them has to be owned above both.
        if !root.show-import && !root.show-settings && !root.show-identity && !root.show-launch && root.show-library: Rectangle {
            width: 100%;
            height: 100%;
            background: Theme.ground;

            HorizontalLayout {
                // Always instantiated, width collapsed to zero when hidden — the
                // same reasoning as the adjust panel below: an `if` here depends on
                // the layout class, which derives from the window width, which the
                // layout then influences. Slint flags that loop and it can panic.
                Rectangle {
                    width: root.collections-visible ? 232px : 0px;
                    visible: root.collections-visible;
                    horizontal-stretch: 0;

                    CollectionsPanel {
                        width: 100%;
                        height: 100%;
                        rows: root.collection-rows;
                        selected-id: root.collection-selected;
                        total-images: root.library-total;
                        error: root.collection-error;

                        // TRACES: FR-NC-6a
                        // The two actions that were in the library header and
                        // referred to the tree rather than to the library.
                        // They read the same window state the header did — one
                        // source per fact — and call the same handlers.
                        scanning: root.library-scanning;
                        scope-pinned: root.library-scope-pinned;
                        toggle-pin-scope() => { root.library-toggle-pin-scope(); }
                        change-library() => { root.library-change(); }

                        select(id) => { root.collection-select(id); }
                        toggle(id) => { root.collection-toggle(id); }
                        new-collection() => { root.collection-new(); }
                        row-menu(id) => { root.collection-menu(id); }
                        offline-menu(id) => { root.collection-offline-menu(id); }
                        row-press(id, down) => { root.collection-row-press(id, down); }

                        renaming-id: root.collection-renaming;
                        rename-start(id) => { root.collection-rename-start(id); }
                        rename-commit(id, name) => {
                            root.collection-rename-commit(id, name);
                        }
                        rename-cancel() => { root.collection-rename-cancel(); }
                        trash-count: root.trash-count;
                        trash-label: root.trash-label;
                        selected-count: root.library-selected-count;

                        dropped-on(id) => { root.collection-dropped(id); }
                        collection-drag-payload(id) => { return root.collection-drag-payload(id); }
                        dropped-on-trash() => { root.trash-dropped(); }
                        empty-trash() => { root.trash-empty(); }
                        restore-selected() => { root.trash-restore(); }
                        drag-over(id, over) => { root.collection-drag-over(id, over); }
                    }
                }

                LibraryGrid {
                    horizontal-stretch: 1;
                    // FR-UI-1: the header collapses its actions behind a
                    // disclosure below the breakpoint. A tablet in portrait is
                    // 768 logical pixels, which fits the title and the status
                    // line but not the library's buttons beside them.
                    expanded: root.expanded;
                    cells: root.library-cells;
                    total: root.library-total;
                    scanning: root.library-scanning;
                    scan-status: root.library-status;
                    scan-error: root.library-error;

                    offline: root.library-offline;
                    offline-reason: root.library-offline-reason;
                    offline-since: root.library-offline-since;
                    retry-connection() => { root.library-retry-connection(); }
                    local-only: root.library-local-only;
                    local-count: root.library-local-count;
                    toggle-local-only() => { root.library-toggle-local-only(); }
                    range-active: root.library-range-active;
                    toggle-date-range() => { root.library-toggle-date-range(); }
                    clear-selection() => { root.library-clear-selection(); }
                    select-all() => { root.library-select-all(); }
                    reorderable: root.library-reorderable;
                    reorder-to(row, after) => { root.library-reorder-to(row, after); }
                    collection-from-selection(name) => {
                        root.library-collection-from-selection(name);
                    }
                    range-from: root.library-range-from;
                    range-to: root.library-range-to;
                    range-invalid: root.library-range-invalid;
                    range-edited(a, b) => { root.library-range-edited(a, b); }
                    range-from-fraction: root.library-range-from-fraction;
                    range-to-fraction: root.library-range-to-fraction;
                    timeline-range-changed(a, b) => {
                        root.library-timeline-range-changed(a, b);
                    }

                    collections-visible: root.collections-visible;
                    toggle-collections() => { root.toggle-collections(); }

                    pin-done: root.library-pin-done;
                    pin-total: root.library-pin-total;
                    root-label: root.library-root-label;
                    timeline: root.library-timeline;
                    timeline-label: root.library-timeline-label;
                    window-label: root.library-window-label;
                    offset: root.library-offset;
                    selected-count: root.library-selected-count;
                    scope-label: root.collection-scope-label;
                    settings-armed: root.settings-armed;
                    paste-settings-to-selection => {
                        root.paste-settings-to-selection();
                    }
                    // TRACES: FR-DEV-6
                    // Opened with the selection's size, which is both what the
                    // sheet says it would act on and what the apply handler
                    // reads back to decide it means the batch.
                    open-presets => {
                        root.preset-apply-count = root.library-selected-count;
                        root.preset-can-save = false;
                        root.presets-open = true;
                    }

                    // TRACES: FR-EXP-7
                    exporting: root.library-exporting;
                    export-to-server: root.export-to-server;
                    export-selection => { root.library-export-selection(); }
                    cancel-export => { root.library-cancel-export(); }

                    sweep-done: root.library-sweep-done;
            sweep-total: root.library-sweep-total;

            current-bucket: root.library-current-bucket;
            current-bucket-fraction: root.library-current-fraction;
            timeline-anchored: root.library-timeline-anchored;

            scrub-fraction(f) => { root.library-scrub-fraction(f); }
            timeline-pinch(r) => { root.library-timeline-pinch(r); }
            timeline-pan(d) => { root.library-timeline-pan(d); }
            timeline-zoom(d) => { root.library-timeline-zoom(d); }
            syncing: root.library-syncing;
            requested-cell-size: root.library-cell-size;
            touched <=> root.library-touched;
            zoom-cells(d) => { root.library-zoom-cells(d); }
            pinch-cells(r) => { root.library-pinch-cells(r); }
            pinch-started() => { root.library-pinch-started(); }
            scroll-to: root.library-scroll-to;
            scroll-token: root.library-scroll-token;
            sync-now() => { root.library-sync-now(); }
            columns-changed(n) => {
                root.library-columns = n;
                // Which cell begins a row just changed, and month headings sit on
                // row-leading cells — so they must be recomputed, not just moved.
                root.library-columns-changed();
            }
            scrolled(i) => { root.library-scrolled(i); }
            viewport-cells-changed(n) => { root.library-viewport-cells(n); }
                    cell-clicked(i) => { root.library-cell-clicked(i); }
                    rescan() => { root.library-rescan(); }
                    can-import: root.import-supported;
                    open-import() => { root.import-open(); }
                    open-settings() => { root.settings-open(); }
                    open-people() => { root.identity-open(); }

                    cell-pressed(i, ctrl, shift) => {
                        root.library-cell-pressed(i, ctrl, shift);
                    }
                    cell-press-ended() => { root.library-cell-press-ended(); }
                    select-mode: root.library-select-mode;
                    toggle-select-mode() => { root.library-toggle-select-mode(); }
                    held-row <=> root.library-held-row;
                    // The sidebar's rows, not a second model: the sheet files
                    // into the same tree the sidebar draws.
                    collections: root.collection-rows;
                    file-in-collection(id, moves) => {
                        root.library-file-in-collection(id, moves);
                    }
                    keywords: root.library-keywords;
                    keywords-opened() => { root.library-keywords-opened(); }
                    assign-keyword(word) => { root.library-assign-keyword(word); }
                    unassign-keyword(word) => { root.library-unassign-keyword(word); }
                    cursor: root.library-cursor;
                    move-cursor(delta, extend) => {
                        root.library-move-cursor(delta, extend);
                    }
                    open-cursor() => { root.library-open-cursor(); }
                    drag-image: root.library-drag-image;
                    drag-payload() => { return root.library-drag-payload(); }
                    drag-started(i) => { root.library-drag-started(i); }
                    drag-finished() => { root.library-drag-finished(); }
                    remove-from-collection() => {
                        root.library-remove-from-collection();
                    }

                    filter-people: root.library-filter-people;
                    filter-people-all: root.library-filter-people-all;
                    people: root.library-people;
                    gestures: root.library-gestures;
                    filter-min-rating: root.library-filter-min-rating;
                    filter-unjudged: root.library-filter-unjudged;
                    filter-flag: root.library-filter-flag;
                    rating-counts: root.library-rating-counts;

                    cell-rated(i, n) => { root.library-cell-rated(i, n); }
                    cell-trashed(i) => { root.library-cell-trashed(i); }
                    burst-toggled(i) => { root.library-burst-toggled(i); }
                    trash-selection() => { root.library-trash-selection(); }
                    // Derived from the sidebar's own selection rather than
                    // mirrored in a second property: `-1` is already the sentinel
                    // for the trash row (see collections.slint), and two sources
                    // for one fact is how they come to disagree.
                    viewing-trash: root.collection-selected == -1;
                    judged(rating, flag) => { root.library-judged(rating, flag); }
                    // `F2` renames whatever the grid is scoped to. Answered from
                    // the sidebar's selection rather than a second property, for
                    // the same reason `viewing-trash` above is: one fact, one
                    // source. Ids at or below 0 are "all photographs" and the
                    // trash, neither of which has a name to change — Rust drops
                    // those rather than the binding trying to reason about it.
                    rename-scope() => {
                        root.collection-rename-start(root.collection-selected);
                    }
                    filter-min-rating-changed(n) => {
                        root.library-filter-min-rating-changed(n);
                    }
                    filter-unjudged-toggled(on) => {
                        root.library-filter-unjudged-changed(on);
                    }
                    filter-flag-changed(f) => { root.library-filter-flag-changed(f); }
                    filter-person-cleared(id) => { root.library-filter-person-cleared(id); }
                    filter-people-mode-toggled() => { root.library-filter-people-mode-toggled(); }
                    people-listed() => { root.library-people-listed(); }
                    filter-person-toggled(id) => { root.library-filter-person-toggled(id); }
                }
            }
        }

        if !root.show-import && !root.show-settings && !root.show-identity && !root.show-launch && !root.show-library: VerticalLayout {
            width: 100%;
            height: 100%;

            StatusBar {
                adapter: root.adapter;
                backend: root.backend;
                layout-class: root.layout-class;
                fps: root.fps;
                expanded: root.expanded;
                filename: root.filename;
                position: root.total > 0 ? root.index + 1 + " / " + root.total : "";
                // Only where a library was opened; command-line files have no
                // grid to return to.
                can-return-to-library: root.library-total > 0;
                panel-visible: root.panel-visible;
                export-label: root.export-label;
                export-busy: root.export-busy;
                export-status: root.export-status;
                can-undo: root.can-undo;
                can-redo: root.can-redo;
                back-to-library() => { root.back-to-library(); }
                open-people() => { root.identity-open(); }
                open-settings() => { root.settings-open(); }
                toggle-panel() => { root.toggle-panel(); }
                export-image() => { root.export-image(); }
                undo() => { root.undo(); }
                redo() => { root.redo(); }
            }

            HorizontalLayout {
                // **The tools, on the far side from their consequences.**
                //
                // A fixed rail rather than a row of chips inside the develop
                // column, which is where these three used to live. The column
                // can be put away — that is the whole point of the toggle in
                // the strip above — and putting the tools away with it meant
                // the way *out* of crop disappeared along with the way in.
                // Hence the "Done Cropping" button floating over the canvas
                // below: one control duplicated to paper over the other being
                // reachable only sometimes.
                //
                // The rail does not close, so a tool can always be put down
                // where it was picked up. `toolrail.slint` has the rest of the
                // reasoning and the table that generates it.
                //
                // Not conditioned on `total > 0` from out here: the rail
                // collapses itself on `enabled`, and an `if` in this layout is
                // the shape that has caused binding loops in this file before
                // (see the develop column below).
                ToolRail {
                    enabled: root.total > 0 && root.load-error == "";
                    mode: root.view-mode;
                    picked(m) => { root.mode-picked(m); }
                }

                // The canvas: compute output composited directly. No CPU
                // round-trip anywhere in this path (ARCH §6.1).
                canvas-area := Rectangle {
                    horizontal-stretch: 1;
                    background: Theme.ground;
                    clip: true;

                    canvas-image := Image {
                        width: 100%;
                        height: 100%;
                        source: root.canvas;
                        image-fit: contain;
                        // Past 1:1 there is no detail left to reconstruct, so
                        // smoothing only invents values between real pixels — and
                        // inspecting focus or noise is the whole reason to zoom in
                        // that far. Below 1:1 it stays smooth, where filtering is
                        // what keeps the image from aliasing.
                        //
                        // TRACES: FR-DSP-8
                        // The canvas is rendered at the *physical* pixel size of
                        // the box this image occupies, so `contain` presents it
                        // 1:1 and neither filter is reached at all until the
                        // photographer zooms. That is the point: on a fractionally
                        // scaled desktop the buffer used to be a logical-sized one
                        // that the compositor stretched, and no choice of filter
                        // recovers detail that was never rendered.
                        image-rendering: root.magnified
                            ? ImageRendering.pixelated
                            : ImageRendering.smooth;
                        visible: root.total > 0 && root.load-error == "";
                    }

                    // The region map, composited over the photograph at the
                    // same fitted rect.
                    //
                    // Drawn here rather than blended into the render because
                    // it is a diagnostic and not an edit: it must not reach
                    // the histogram, an export, or the texture the develop
                    // pass hands the compositor.
                    if root.overlay-on && !root.overlay-hidden && root.total > 0: Image {
                        x: parent.shown-x;
                        y: parent.shown-y;
                        width: parent.shown-w;
                        height: parent.shown-h;
                        source: root.region-overlay;
                        // The visible part of a source-space picture, which is
                        // what makes the overlay follow a zoom, a pan and a
                        // crop. The compositor does the crop and the scale;
                        // resampling on the CPU would mean rebuilding a
                        // megapixel image on every frame of a drag.
                        source-clip-x: root.overlay-clip-x;
                        source-clip-y: root.overlay-clip-y;
                        source-clip-width: root.overlay-clip-w;
                        source-clip-height: root.overlay-clip-h;
                        transform-rotation: -root.overlay-angle * 1deg;
                        image-fit: fill;
                        opacity: root.overlay-strength;
                        // Nearest-neighbour, always. The map is proxy-sized
                        // and its values are *names*: smoothing between region
                        // 4 and region 9 invents a colour belonging to
                        // neither, and draws a soft edge exactly where the
                        // point is to see a hard one.
                        image-rendering: ImageRendering.pixelated;
                    }

                    // TRACES: FR-CULL-3
                    // The focus marks, over the same fitted rect. See
                    // `peaking.slint` for why they are a layer over the canvas
                    // rather than a tint in it.
                    if root.focus-overlay-ready && root.total > 0: FocusMarks {
                        x: parent.shown-x;
                        y: parent.shown-y;
                        width: parent.shown-w;
                        height: parent.shown-h;
                        marks: root.focus-overlay;
                    }

                    // Where the photograph actually sits inside this box.
                    //
                    // `image-fit: contain` letterboxes, and Slint does not report
                    // the fitted rect, so it is derived from the source's aspect.
                    // The overlay is placed against *this*, not against the whole
                    // area — otherwise the crop rect drifts off the picture on any
                    // window whose shape differs from the image's.
                    property <float> src-w: root.canvas.width > 0 ? root.canvas.width : 1;
                    property <float> src-h: root.canvas.height > 0 ? root.canvas.height : 1;
                    property <float> box-w: self.width / 1px;
                    property <float> box-h: self.height / 1px;
                    property <float> fit-scale: min(self.box-w / self.src-w, self.box-h / self.src-h);
                    property <length> shown-w: self.src-w * self.fit-scale * 1px;
                    property <length> shown-h: self.src-h * self.fit-scale * 1px;
                    property <length> shown-x: (self.width - self.shown-w) / 2;
                    property <length> shown-y: (self.height - self.shown-h) / 2;

                    // Empty and error states say what happened rather than
                    // showing a blank canvas.
                    if root.total == 0 || root.load-error != "": EmptyState {
                        headline: root.load-error != "" ? "Could not load image" : "No images";
                        detail: root.load-error != "" ? root.load-error
                                : "Pass a folder or file on the command line.";
                    }

                    // --- zoom and pan ------------------------------------------
                    //
                    // Below the crop overlay in z-order so that, in crop mode, the
                    // handles take the drag instead. Scroll still zooms either way.

                    // TRACES: FR-UI-4
                    // Pinch to zoom. The wheel gesture below is the desktop's
                    // answer and there is no wheel on a tablet, so without this
                    // the only way to magnify a photograph on the device the
                    // panel was sized for is a control that does not exist.
                    //
                    // `scale` is cumulative from 1.0 across the whole gesture,
                    // so the ratio since the last update is what maps onto a
                    // zoom step — the same reasoning as the timeline's pinch,
                    // and for the same reason: applying the running total on
                    // every update squares it and shoots straight to the limit.
                    //
                    // Anchored on the midpoint between the fingers, which is
                    // what makes a pinch feel like it is moving the picture
                    // rather than the viewport.
                    if root.total > 0 && root.load-error == "": ScaleRotateGestureHandler {
                        x: 0; y: 0;
                        width: 100%;
                        height: 100%;
                        enabled: !root.cropping;

                        property <float> last-scale: 1.0;

                        started => { self.last-scale = 1.0; }
                        updated => {
                            root.zoom-at(
                                self.scale / max(0.01, self.last-scale),
                                (self.center.x - canvas-area.shown-x)
                                    / max(canvas-area.shown-w, 1px),
                                (self.center.y - canvas-area.shown-y)
                                    / max(canvas-area.shown-h, 1px),
                            );
                            self.last-scale = self.scale;
                        }
                        ended => { self.last-scale = 1.0; }
                        cancelled => { self.last-scale = 1.0; }
                    }

                    // Region picking, above the pan/zoom area so a click
                    // reaches it first. A separate area rather than a branch
                    // inside the one below: panning wants press-drag-release
                    // and picking wants a click, and interleaving the two in
                    // one handler is how a drag ends up selecting a region the
                    // user was only scrolling past.
                    if root.region-picking && root.total > 0 && root.load-error == "": pick := TouchArea {
                        x: parent.shown-x;
                        y: parent.shown-y;
                        width: parent.shown-w;
                        height: parent.shown-h;
                        mouse-cursor: MouseCursor.crosshair;
                        enabled: !root.cropping;

                        clicked => {
                            root.region-picked(
                                self.mouse-x / max(self.width, 1px),
                                self.mouse-y / max(self.height, 1px),
                                // Shift extends or removes, the modifier every
                                // selection tool uses for the same thing.
                                root.shift-held,
                            );
                        }
                    }

                    // TRACES: FR-DEV-8
                    // Placing a repair, beside the region picker and for the
                    // same reasons: a click and a pan want different handlers,
                    // and this one has to reach the click first.
                    //
                    // Below the circles declared further down, so a press that
                    // lands on an existing repair takes hold of it instead of
                    // making another one on top.
                    if root.repairing && root.total > 0 && root.load-error == "": TouchArea {
                        x: parent.shown-x;
                        y: parent.shown-y;
                        width: parent.shown-w;
                        height: parent.shown-h;
                        mouse-cursor: MouseCursor.crosshair;
                        enabled: !root.cropping;

                        clicked => {
                            root.spot-placed(
                                self.mouse-x / max(self.width, 1px),
                                self.mouse-y / max(self.height, 1px),
                            );
                        }
                    }

                    if root.total > 0 && root.load-error == "": TouchArea {
                        x: 0; y: 0;
                        width: 100%;
                        height: 100%;
                        // A pan is only meaningful once there is something outside
                        // the viewport to reach.
                        mouse-cursor: root.zoomed ? MouseCursor.grab : MouseCursor.default;
                        enabled: !root.cropping;

                        property <length> last-x;
                        property <length> last-y;

                        pointer-event(ev) => {
                            if (ev.kind == PointerEventKind.down) {
                                self.last-x = self.mouse-x;
                                self.last-y = self.mouse-y;
                            }
                        }

                        moved => {
                            if (self.pressed && root.zoomed) {
                                // Fractions of the *visible* area, which is what
                                // the session's pan expects. Negated: dragging
                                // right moves the image right, so the window onto
                                // it moves left.
                                root.pan-by(
                                    -(self.mouse-x - self.last-x) / max(parent.shown-w, 1px),
                                    -(self.mouse-y - self.last-y) / max(parent.shown-h, 1px),
                                );
                                self.last-x = self.mouse-x;
                                self.last-y = self.mouse-y;
                            }
                        }

                        scroll-event(ev) => {
                            if (ev.delta-y == 0) {
                                return reject;
                            }
                            // Anchored on the pointer, in fractions of the shown
                            // image, so whatever is under the cursor stays there.
                            root.zoom-at(
                                ev.delta-y > 0 ? 1.15 : 1.0 / 1.15,
                                (self.mouse-x - parent.shown-x) / max(parent.shown-w, 1px),
                                (self.mouse-y - parent.shown-y) / max(parent.shown-h, 1px),
                            );
                            return accept;
                        }

                        double-clicked => { root.zoom-reset(); }
                    }

                    // --- crop overlay ------------------------------------------
                    //
                    // Placed over the fitted image, so the fractions it draws are
                    // fractions of the picture. See `CropOverlay` in crop.slint.
                    if root.cropping && root.total > 0 && root.load-error == "": CropOverlay {
                        x: canvas-area.shown-x;
                        y: canvas-area.shown-y;
                        width: canvas-area.shown-w;
                        height: canvas-area.shown-h;

                        crop-x: root.crop-x;
                        crop-y: root.crop-y;
                        crop-w: root.crop-w;
                        crop-h: root.crop-h;

                        crop-changed(x, y, w, h, hx, hy) => {
                            root.crop-changed(x, y, w, h, hx, hy);
                        }
                    }

                    // --- gradient handles ---------------------------------------
                    //
                    // TRACES: FR-DEV-3 | FR-UI-3
                    // Handed the fitted image rect for the same reason the crop
                    // overlay and the repairs are: the photograph is letterboxed
                    // inside this box, Slint does not report the fitted rect, and
                    // anything that has to land *on* the picture is placed against
                    // the derived one. See `GradientHandles` in masks.slint.
                    GradientHandles {
                        x: canvas-area.shown-x;
                        y: canvas-area.shown-y;
                        width: canvas-area.shown-w;
                        height: canvas-area.shown-h;

                        handles: root.gradient-handles;

                        dragged(role, fx, fy, tx, ty) => {
                            root.gradient-handle-dragged(role, fx, fy, tx, ty);
                        }
                        released() => { root.gradient-handle-released(); }
                    }

                    // --- repairs (FR-DEV-8) -------------------------------------
                    //
                    // Every position in here is a fraction of the fitted image
                    // rect, which is why the overlay is handed that rect rather
                    // than the canvas box. See `SpotHandles` in spots.slint for
                    // what is drawn and why it is drawn at true size.
                    SpotHandles {
                        x: canvas-area.shown-x;
                        y: canvas-area.shown-y;
                        width: canvas-area.shown-w;
                        height: canvas-area.shown-h;

                        handles: root.spot-handles;

                        selected(id) => { root.spot-selected(id); }
                        dragged(id, role, fx, fy, tx, ty) => {
                            root.spot-handle-dragged(id, role, fx, fy, tx, ty);
                        }
                        released() => { root.spot-handle-released(); }
                    }

                    // Arrow keys and space step through the folder.
                    //
                    // Focused on show rather than waiting for a click, exactly
                    // as the grid's judgement scope is: without it the first
                    // keystroke after opening an image goes nowhere, and — now
                    // that the shell answers the back gesture by bubbling —
                    // there would be no focus item for `Key.Back` to bubble
                    // *from*, so back would close the application from develop
                    // instead of returning to the grid.
                    FocusScope {
                        init => { self.focus(); }

                        // Shift is state, not an event: the click that needs
                        // to know about it arrives through a `TouchArea`,
                        // which reports no modifiers of its own. Tracked on
                        // both edges so releasing it while the pointer is over
                        // the canvas is noticed.
                        key-released(event) => {
                            root.shift-held = event.modifiers.shift;
                            return reject;
                        }

                        key-pressed(event) => {
                            root.shift-held = event.modifiers.shift;
                            // Ctrl+Z and Ctrl+Shift+Z (FR-DEV-5). Both cases
                            // of the letter, because the logical key that
                            // reaches us carries the shift: holding it for
                            // redo turns "z" into "Z".
                            if (event.modifiers.control
                                && (event.text == "z" || event.text == "Z")) {
                                if (event.modifiers.shift) {
                                    root.redo();
                                } else {
                                    root.undo();
                                }
                                return accept;
                            }
                            // TRACES: FR-DEV-8
                            // Delete removes the selected repair, and only in
                            // repair mode: the same key in the grid judges
                            // photographs, and a key that means two things
                            // depending on a mode the user has forgotten they
                            // are in is how work disappears.
                            if (root.repairing && root.selected-spot != ""
                                && (event.text == Key.Delete
                                    || event.text == Key.Backspace)) {
                                root.spot-removed(root.selected-spot);
                                return accept;
                            }
                            if (event.text == Key.RightArrow || event.text == " ") {
                                root.next-image();
                                return accept;
                            }
                            if (event.text == Key.LeftArrow) {
                                root.prev-image();
                                return accept;
                            }
                            return reject;
                        }
                    }

                    // Zoom controls, floating over the canvas.
                    //
                    // Zoom stays here rather than moving to the sidebar with the
                    // crop: it is a property of *looking*, it is driven by the
                    // scroll wheel on the image itself, and its readout belongs
                    // beside what it is reporting on. Crop moved to the panel
                    // because it is an edit, and edits live with the other edits.
                    //
                    // **"Done" is no longer here because it has to be.** It was:
                    // the control that entered a mode was pinned inside the
                    // develop column, the column closes, and stranding someone
                    // in crop with no visible way out was worse than one
                    // duplicated control. The tool rail does not close, so that
                    // reason has gone.
                    //
                    // It stays because of where it is. Finishing a crop is a
                    // decision *about the photograph*, taken while looking at
                    // the photograph, and a confirmation the width of the
                    // window away from the thing being confirmed is a
                    // confirmation you take on trust. The rail is now the
                    // second way out rather than the first.
                    if root.total > 0 && root.load-error == "": HorizontalLayout {
                        x: 12px;
                        y: parent.height - self.preferred-height - 12px;
                        // Bounded, or the row takes the canvas's whole width
                        // and stretches its children across it. With one
                        // button that read as an odd-looking "Fit"; with two it
                        // reads as a toolbar laid over the photograph, which is
                        // the opposite of what a floating control should do.
                        width: self.preferred-width;
                        spacing: 6px;
                        alignment: start;

                        if root.view-mode != ViewMode.photo: Button {
                            // Names the mode being left rather than saying
                            // "Done", which was unambiguous while there was
                            // one mode and would not be with two.
                            text: root.cropping
                                ? "Done Cropping"
                                : (root.repairing ? "Done Repairing" : "Done Masking");
                            active: true;
                            clicked => { root.mode-picked(ViewMode.photo); }
                        }

                        // Zoom is a view state, so its readout doubles as the
                        // control that clears it.
                        Button {
                            text: root.zoomed
                                ? Math.round(root.zoom * 100) + "%"
                                : "Fit";
                            active: root.zoomed;
                            enabled: root.zoomed;
                            clicked => { root.zoom-reset(); }
                        }
                    }

                    // The photo roll, along the foot of the canvas.
                    //
                    // Only where a library was opened: with files named on the
                    // command line there is no window of photographs to roll
                    // through, which is the same condition the "‹ Library"
                    // button uses.
                    //
                    // Last in the canvas, so it draws over the photograph
                    // rather than under it.
                    if root.library-total > 0: PhotoRoll {
                        width: 100%;
                        height: 100%;
                        cells: root.library-cells;
                        current: root.library-roll-current;
                        open <=> root.roll-open;
                        pick(i) => { root.library-roll-pick(i); }
                    }

                    // Report size changes so the render target can be resized to
                    // match. Width and height are tracked separately because
                    // Slint has no single "geometry changed" hook.
                    property <int> px-w: Math.round(self.width / 1px);
                    property <int> px-h: Math.round(self.height / 1px);
                    changed px-w => { root.canvas-resized(self.px-w, self.px-h); }
                    changed px-h => { root.canvas-resized(self.px-w, self.px-h); }
                }

                // Always instantiated, width collapsed to zero when closed. A
                // conditional `if` here creates a binding loop — the layout
                // depends on `panel-visible`, which derives from the window
                // width, which the layout then influences. Slint flags it, and
                // it can panic at runtime.
                develop-column := Rectangle {
                    // TRACES: FR-UI-1
                    // **One width, stated once, and not measured.**
                    //
                    // This column used to size itself from its contents: every
                    // panel published a `content-width`, declared it as its own
                    // `min-width`, and the column took the largest. That was an
                    // answer to a real problem — before it, the width was two
                    // guessed constants (280px for a tablet, 380px for a
                    // desktop) and the generated chip row outgrew both, so a
                    // control ended up somewhere you had to pan to find.
                    //
                    // **It solved that by making the photograph pay.** The
                    // pixels a sidebar takes come out of the picture beside it,
                    // and a measured sidebar spends them on whatever happens to
                    // be widest: an axis label gaining a digit made the image
                    // smaller, and switching tools swapped one set of panels for
                    // another and shifted the image sideways under the eye
                    // that was judging it. In an application whose entire job is
                    // showing you a photograph accurately, the frame around it
                    // must not move because a caption changed.
                    //
                    // So the number is mandated: `panel-width`, in
                    // `style.yaml`, next to the reasoning and next to the rail
                    // on the other side, which is fixed for the same reason. A
                    // panel that wants more than that clips, and the Flickable
                    // below is what makes the rest of it reachable — the same
                    // fallback as before, now the first answer rather than the
                    // last. `AdjustPanel` is the panel the number was chosen
                    // against; its note says why.
                    //
                    // The generated row that started all this is not a problem
                    // any more either, because it is no longer in the column's
                    // way: the tools moved to `ToolRail` and what is left is
                    // group filters, which pan within their own strip without
                    // anything else having to move.
                    //
                    // `panel-max-width` survives, and it is the one thing here
                    // that is not a size: it is the policy that a column may
                    // not take the window from the photograph it exists to
                    // serve, and it bites only on a window narrow enough that
                    // 360px would. It comes from Rust rather than from
                    // `root.width` because reading the window width inside the
                    // layout that sets it is the binding loop the comment on
                    // `expanded` above describes; Rust already measures the
                    // window for `layout-class`, so this is one more thing said
                    // in the same breath.
                    width: root.panel-visible
                        ? min(root.panel-max-width, Theme.panel-width)
                        : 0px;
                    visible: root.panel-visible;
                    background: Theme.surface;
                    clip: true;

                    // **The whole column scrolls, histogram included.**
                    //
                    // Only the sliders used to. Everything above them — the
                    // capture metadata, the histogram, the geometry controls,
                    // copy and paste — was fixed, so on a 280px column in
                    // portrait they took the height the sliders needed and the
                    // histogram could not be moved out of the way. It is the
                    // instrument the sliders are judged against; being unable
                    // to scroll to it, or past it, is the worst of both.
                    //
                    // `interactive` stands down while a track has a gesture,
                    // the same arbitration `AdjustPanel` used to do for its own
                    // scroller — see the note on `SliderTrack`'s `claimed`.
                    // Without it every attempt to drag a slider would scroll
                    // the column instead.
                    // Pinned: the strip is how the column is navigated, so it
                    // cannot be somewhere you have to navigate to.
                    // A layout, because the parent is a Rectangle: two children of one
                    // would both sit at its origin and overlap. The strip is pinned by
                    // being outside the Flickable rather than by any coordinate.
                    VerticalLayout {
                        GroupStrip {
                            enabled: root.adjust-enabled;
                            tabs: root.adjust-tabs;
                            active-tab: root.adjust-active-tab;
                            picked(i) => { root.adjust-tab-picked(i); }
                        }

                        Flickable {
                            viewport-height: column.preferred-height;
                            // **And the width, or the column is drawn centred
                            // over its own edges.**
                            //
                            // Unset, a Flickable's viewport takes its content's
                            // preferred width, and a viewport wider than the
                            // Flickable is *centred* in it — the same rule the
                            // note on the seam's `x: 0` below records. So a
                            // column narrower than what it held did not clip
                            // the right-hand side and keep the left, it lost
                            // half of each: "HISTOGRAM" read "ISTOGRAM",
                            // "Straighten" read "aighten", and Paste ran off
                            // the far side. It looked like a rendering fault
                            // and it was an alignment one.
                            //
                            // **`min-width`, not `preferred-width`, and that is
                            // what makes a mandated column work at all.**
                            //
                            // With the preferred width here, the content laid
                            // itself out at whatever size it would have liked
                            // and the column clipped the difference: Paste came
                            // out sliced down the middle and the panel's reset
                            // was over the window's edge. That is the same
                            // fault as above wearing a different hat — the
                            // content was never told how much room it had, so
                            // it could not adapt to having less.
                            //
                            // The floor is the layout's *minimum* instead. A
                            // preferred width is what a panel would enjoy; a
                            // minimum is what it cannot go below, and between
                            // the two the layout does the work it exists to do
                            // — rows tighten, stretches give way — so the
                            // column fits because it was asked to rather than
                            // by luck.
                            //
                            // That does less here than it sounds like, and it
                            // is worth knowing why: this column's minimum and
                            // its preferred width are within a few pixels of
                            // each other, because a `Text` that does not elide
                            // reports the same for both and most of what is in
                            // here is text. So `panel-width` still has to be a
                            // number the contents actually fit in — see its
                            // note in `style.yaml` for the measurement. What
                            // this binding buys is that the clipping, when it
                            // comes, is of a panel that genuinely cannot
                            // shrink rather than of one that simply was not
                            // asked to, and that panning is then a real
                            // fallback rather than a permanent condition.
                            viewport-width: max(self.width, column.min-width);
                            interactive: !adjust.slider-dragging;

                            // **What the column holds is the mode's answer.**
                            //
                            // In local mode it is the mask stack and then the
                            // selected layer's adjustments, and nothing else:
                            // the capture metadata describes the file, copy and
                            // paste move a whole edit between photographs, and
                            // framing is a decision about the picture's shape —
                            // none of the three is a property of a region
                            // within it, so all three would be controls in
                            // scope of nothing.
                            //
                            // **Each child carries its own condition** rather
                            // than the three being grouped inside one `if`.
                            // A nested layout under-reports its height here and
                            // the panels below it get drawn on top of each
                            // other — invisible in this file and obvious on
                            // screen. `masks.slint` carries the same note for
                            // the same reason.
                            column := VerticalLayout {
                            if !root.local-mode && !root.repairing: InfoPanel {
                                camera: root.camera;
                                exposure: root.exposure;
                                dimensions: root.dimensions;
                            }

                            if !root.local-mode && !root.repairing: Rectangle {
                                height: 1px;
                                background: Theme.rule;
                            }

                            // Directly under the capture metadata and above every
                            // control, because it is the thing the controls are
                            // judged against: exposure, blacks and whites are all
                            // set by watching this move (FR-DSP-7). An instrument
                            // below the sliders it reports on would have the
                            // photographer looking away from it to use it.
                            //
                            // Kept in local mode, where it still reports the
                            // whole frame while the sliders edit a layer. That
                            // disagreement is real and is N3's to close; taking
                            // the instrument away instead would be a worse
                            // answer than an honest one that is not yet scoped.
                            HistogramPanel {
                                data: root.histogram;
                                raw-data: root.raw-histogram;
                            }

                            Rectangle {
                                height: 1px;
                                background: Theme.rule;
                            }

                            // TRACES: FR-CULL-3
                            // Under the histogram, because the two are the same
                            // kind of thing: instruments that report on the
                            // photograph rather than change it. Kept in every
                            // mode for the same reason the histogram is.
                            FocusPanel {
                                available: root.peaking-available;
                                showing: root.peaking-on;
                                sensitivity: root.peaking-sensitivity;
                                colour: root.peaking-colour;
                                toggled(v) => { root.peaking-toggled(v); }
                                sensitivity-picked(i) => { root.peaking-sensitivity-picked(i); }
                                colour-picked(i) => { root.peaking-colour-picked(i); }
                            }

                            Rectangle {
                                height: 1px;
                                background: Theme.rule;
                            }

                            // Framing above the colour work, matching how the edit is
                            // made rather than how it is applied: the frame is decided
                            // by eye first and the pipeline runs it last (see
                            // `dr_pipeline::framing` on the coordinate order).
                            if !root.local-mode && !root.repairing: GeometryPanel {
                                enabled: root.adjust-enabled;
                                angle: root.straighten;
                                max-straighten: root.max-straighten;
                                flip-h: root.flip-h;
                                flip-v: root.flip-v;
                                modified: root.framing-modified;

                                // The ratio chips belong to the crop tool, so
                                // they appear with it. Shown at all times they
                                // would be a control for a gesture that is not
                                // on screen; hidden behind a lid they would be
                                // a feature nobody finds.
                                cropping: root.cropping;
                                aspects: root.crop-aspects;
                                aspect: root.crop-aspect;
                                portrait: root.crop-portrait;
                                aspect-turnable: root.crop-aspect-turnable;
                                aspect-picked(i) => { root.crop-aspect-picked(i); }
                                portrait-toggled => { root.crop-portrait-toggled(); }

                                rotate(turns) => { root.rotate-quarters(turns); }
                                flip-h-toggled => { root.flip-h-toggled(); }
                                flip-v-toggled => { root.flip-v-toggled(); }
                                angle-changed(v) => { root.straighten-changed(v); }
                                angle-committed(v) => {
                                    root.straighten-committed(v);
                                }
                                angle-reset => { root.straighten-changed(0); }
                                reset => { root.framing-reset(); }
                            }

                            if !root.local-mode && !root.repairing: Rectangle {
                                height: 1px;
                                background: Theme.rule;
                            }

                            // Between the framing and the colour work, because it
                            // acts on both: a paste is about the whole edit, and
                            // burying it under thirty sliders would put the one
                            // control that operates on all of them below all of
                            // them.
                            if !root.local-mode && !root.repairing: TransferPanel {
                                enabled: root.adjust-enabled;
                                armed: root.settings-armed;
                                summary: root.settings-summary;
                                framing-withheld: root.settings-framing-withheld;
                                copy => { root.copy-settings(); }
                                paste => { root.paste-settings(); }
                                // Opened with no count, which is what tells
                                // the apply handler this means the open
                                // photograph rather than a selection.
                                open-presets => {
                                    root.preset-apply-count = 0;
                                    root.preset-can-save = root.adjust-enabled;
                                    root.presets-opened();
                                    root.presets-open = true;
                                }
                            }

                            Rectangle {
                                height: 1px;
                                background: Theme.rule;
                            }

                            // Above the adjust panel, because it decides what
                            // those sliders act on. Below it, the photographer
                            // would set an exposure and only then discover which
                            // scope it landed in.
                            //
                            // Only in local mode: it is no longer a panel among
                            // peers that silently re-points another panel, it is
                            // what that mode's column *is*. That also takes one
                            // panel out of a scrolling column that had six.
                            // TRACES: FR-DEV-8
                            // What the column *is* in repair mode, on the same
                            // terms as the mask panel: not a panel among peers
                            // that quietly re-points the sliders below it, but
                            // the whole of what this mode has to say.
                            if root.repairing: SpotPanel {
                                enabled: root.adjust-enabled;
                                has-selection: root.selected-spot != "";
                                count: root.spot-count;
                                radius: root.spot-radius;
                                feather: root.spot-feather;
                                spot-opacity: root.spot-opacity;
                                mode: root.spot-mode;

                                radius-changed(v) => { root.spot-radius-changed(v); }
                                feather-changed(v) => { root.spot-feather-changed(v); }
                                opacity-changed(v) => { root.spot-opacity-changed(v); }
                                mode-picked(i) => { root.spot-mode-picked(i); }
                                removed => { root.spot-removed(root.selected-spot); }
                            }

                            if root.repairing: Rectangle {
                                height: 1px;
                                background: Theme.rule;
                            }

                            if root.local-mode: MaskPanel {
                                enabled: root.adjust-enabled;
                                masks: root.mask-rows;
                                subjects: root.subject-rows;
                                categories: root.category-rows;
                                segmented: root.segmented;
                                segmenting: root.segmenting;
                                refining: root.refining;
                                // Two-way: the panel is where it is toggled and
                                // the canvas is what obeys it, so neither owns
                                // the value alone.
                                overlay-hidden <=> root.overlay-hidden;

                                segment(fine) => { root.segment-image(fine); }
                                mask-selected(id, extend) => { root.mask-selected(id, extend); }
                                mask-removed(id) => { root.mask-removed(id); }
                                mask-refined(id) => { root.mask-refined(id); }
                                mask-toggled(id, on) => { root.mask-toggled(id, on); }
                                mask-invert-toggled(id, on) => {
                                    root.mask-invert-toggled(id, on);
                                }
                                mask-opacity-changed(id, v) => {
                                    root.mask-opacity-changed(id, v);
                                }
                                mask-feather-changed(id, v) => {
                                    root.mask-feather-changed(id, v);
                                }
                                mask-falloff-picked(id, i) => {
                                    root.mask-falloff-picked(id, i);
                                }
                                mask-morphology-picked(id, i) => {
                                    root.mask-morphology-picked(id, i);
                                }
                                mask-morph-radius-changed(id, v) => {
                                    root.mask-morph-radius-changed(id, v);
                                }
                                add-gradient(radial) => { root.add-gradient-mask(radial); }
                                add-subject(i) => { root.add-subject-mask(i); }
                                add-category(n) => { root.add-category-mask(n); }
                            }

                            if root.local-mode: Rectangle {
                                height: 1px;
                                background: Theme.rule;
                            }

                            adjust := AdjustPanel {
                                rows: root.adjust-rows;
                                enabled: root.adjust-enabled;
                                scope: root.adjust-scope;
                                curve-samples: root.curve-samples;
                                curve-channels: root.curve-channels;
                                curve-channel: root.curve-channel;
                                curve-channel-picked(i) => {
                                    root.curve-channel-picked(i);
                                }
                                param-changed(op, param, value) => {
                                    root.param-changed(op, param, value);
                                }
                                param-reset(op, param) => {
                                    root.param-reset(op, param);
                                }
                                curve-reset(op) => { root.curve-reset(op); }
                                // A section's reset and a curve's reset are the same
                                // action — every parameter of one operation back to
                                // its default — so they share the one callback rather
                                // than duplicating a handler that would have to be
                                // kept in step with it.
                                op-reset(op) => { root.curve-reset(op); }
                                reset-all => { root.reset-all(); }
                                // TRACES: FR-DEV-3f
                                film-stocks: root.film-stocks;
                                film-selected: root.film-selected;
                                film-can-print: root.film-can-print;
                                film-print: root.film-print;
                                film-picked(i) => { root.film-picked(i); }
                                film-print-toggled(on) => { root.film-print-toggled(on); }
                            }

                            Rectangle {
                                height: 1px;
                                background: Theme.rule;
                            }

                            // Last in the column, and the length is why. The
                            // stack runs sixty-four deep, so anywhere else it
                            // would push the controls it is a record of below
                            // the fold. Its own rows run newest-first, which
                            // puts the steps worth reaching immediately under
                            // the heading rather than at the far end of them.
                            //
                            // Present in local mode as well. The mask work
                            // *is* history — adding a layer, moving a
                            // gradient and feathering an edge are all steps —
                            // and a list that emptied when the photographer
                            // entered the mode that produces the most steps
                            // would be a list they stopped trusting.
                            HistoryPanel {
                                rows: root.history-rows;
                                enabled: root.adjust-enabled;
                                can-undo: root.can-undo;
                                can-redo: root.can-redo;
                                undo-label: root.undo-label;
                                undo => { root.undo(); }
                                redo => { root.redo(); }
                                picked(i) => { root.history-picked(i); }
                            }
                            }
                        }
                    }

                    // The seam between the photograph and the column.
                    //
                    // **`x: 0` is load-bearing.** A child of a plain Rectangle
                    // that declares a size and no position is *centred* in it,
                    // so this hairline was being drawn straight down the middle
                    // of the develop column — over the histogram, the geometry
                    // controls and every slider below them. Invisible in the
                    // source and, at one pixel of `rule` grey, quiet enough on
                    // screen to be read as a divider that was meant to be
                    // there.
                    Rectangle {
                        x: 0;
                        width: 1px;
                        height: 100%;
                        background: Theme.rule;
                    }
                }
            }
        }

        // --- the load bar -------------------------------------------------
        //
        // Last in the file, so it is last in z-order and no view can cover it.
        //
        // At the top of the *shell* rather than inside a view, because that is
        // the only place that is true of every view: a pin download outlives
        // the grid it was started from, and until this existed it drew nothing
        // at all once the user opened an image. Three pixels, no text and no
        // hit area — it says only "something is running", and the settings
        // page says what (FR-CAT-1, FR-NC-6c).
        if root.activity-busy: ProgressBar {
            x: 0;
            y: 0;
            width: 100%;
            indeterminate: !root.activity-determinate;
            fraction: root.activity-fraction;
        }

        // TRACES: FR-NC-6a
        // The offline question, over the shell rather than inside the sidebar
        // that raises it. The sidebar is 232px wide and closes entirely in the
        // compact layout, so a dialogue living in there would be unreadable on
        // the device the gesture exists for — and the answer commits gigabytes
        // either way, which deserves the width to say so.
        //
        // Below the load bar, above everything else: a download started from
        // here shows its progress in that bar, and the bar must not be the
        // thing the dialogue covers.
        // TRACES: FR-DEV-6
        // Over the shell rather than inside a view, because both views open
        // it — and because the develop column is 360px wide, which is not
        // enough to list presets and rename one in.
        if root.presets-open: PresetSheet {
            width: 100%;
            height: 100%;
            names: root.preset-names;
            can-save: root.preset-can-save;
            apply-count: root.preset-apply-count;
            capture-summary: root.preset-capture-summary;
            name-error: root.preset-name-error;
            scope-kinds: root.copy-scope-kinds;
            scope-empty: root.copy-scope-empty;
            scope-toggled(name) => { root.copy-scope-toggled(name); }
            import-report: root.preset-import-report;
            import-presets(path) => { root.import-presets(path); }
            save(name) => { root.save-preset(name); }
            apply(name) => { root.apply-preset(name); }
            rename(from, to) => { root.rename-preset(from, to); }
            remove(name) => { root.delete-preset(name); }
            name-edited(text) => { root.preset-name-edited(text); }
            dismiss => { root.presets-open = false; }
        }

        OfflinePrompt {
            width: 100%;
            height: 100%;
            title: root.offline-prompt-title;
            detail: root.offline-prompt-detail;
            keep-label: root.offline-prompt-keep-label;
            release-label: root.offline-prompt-release-label;
            can-keep: root.offline-prompt-can-keep;
            can-release: root.offline-prompt-can-release;
            busy: root.offline-prompt-busy;
            keep() => { root.offline-prompt-keep(); }
            release() => { root.offline-prompt-release(); }
            dismiss() => { root.offline-prompt-dismiss(); }
        }

        // Last, and therefore over everything including the settings page and
        // the offline prompt. Not a preference about layering: this is asked
        // before the grid exists, and nothing else in the window is about a
        // library that can be read.
        RecoveryPrompt {
            width: 100%;
            height: 100%;
            title: root.recovery-title;
            detail: root.recovery-detail;
            diagnosis: root.recovery-diagnosis;
            restore-label: root.recovery-restore-label;
            can-restore: root.recovery-can-restore;
            rebuild-label: root.recovery-rebuild-label;
            busy: root.recovery-busy;
            restore() => { root.recovery-restore(); }
            rebuild() => { root.recovery-rebuild(); }
            dismiss() => { root.recovery-dismiss(); }
        }
    }
}