import { Theme } from "theme.slint";
import { AdjustPanel, GeometryPanel, ModeStrip, ParamRow, TransferPanel, ViewMode } from "adjust.slint";
import { GradientHandle, HandleRole, MaskPanel, MaskRow, SubjectRow } from "masks.slint";
import { LaunchScreen } from "launch.slint";
import { LibraryGrid, LibraryCell, TimelineBar, PhotoRoll, KeywordRow } from "library.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 { SettingsPage } from "settings.slint";
import { ImportPage } from "import.slint";

export { LibraryCell, TimelineBar, CollectionRow, ActivityRow, HistogramView }
export { ViewMode, GradientHandle, HandleRole }

// Status strip — surfaces the GPU backend and adapter, which matters during
// v0.1 because assumption A1 is exactly "does this compositing path work on
// this hardware". Seeing the adapter at a glance makes vendor differences
// obvious during the S1/S2 spikes.
component StatusBar inherits Rectangle {
    in property <string> adapter;
    in property <string> backend;
    in property <string> layout-class;
    in property <int> fps;
    /// FR-UI-1: the layout class, so the instrumentation can stand down on a
    /// strip too narrow to carry both it and the controls.
    in property <bool> expanded: true;
    in property <string> filename;
    in property <string> position;
    /// Only offered where there is a library to go back to — with files named
    /// on the command line there is no grid behind this view.
    in property <bool> can-return-to-library: false;
    /// Whether the develop column is currently shown, for the toggle's label.
    in property <bool> panel-visible: true;
    /// What the export button says. Rust owns it because the answer depends
    /// on settings this component does not see — the format, and whether the
    /// destination is this device or the server.
    in property <string> export-label: "Export";
    in property <bool> export-busy: false;
    /// What the last export did. Sits beside the button rather than in a
    /// dialogue: an export that succeeded needs no acknowledging, and one
    /// that failed needs its reason where the retry is.
    in property <string> export-status;
    /// Whether the edit can be stepped either way (FR-DEV-5).
    in property <bool> can-undo: false;
    in property <bool> can-redo: false;

    callback back-to-library();
    callback open-settings();
    callback toggle-panel();
    callback export-image();
    callback undo();
    callback redo();

    // 44px and `surface`, the same bar the library and settings draw.
    //
    // It was 28px — the control height — which was a reasonable size for a
    // readout and the wrong size for the thing it actually is: this strip
    // carries the only way out of develop, and it was half the height of the
    // identical control on the two screens either side of it. Three screens
    // whose headers do not agree read as three applications, and the one place
    // the user needs to find a way back was the one drawn smallest.
    //
    // Controls keep their own 28px and are centred in it, exactly as the
    // library header centres the same buttons: a `Button` sets a fixed height,
    // which a HorizontalLayout parks at the top of the row rather than
    // centring for it.
    height: 44px;
    background: Theme.surface;

    // Scrolls rather than overflowing. A layout given less width than its
    // children need does not shrink them — it overruns the edge and reports
    // the oversized minimum to whatever contains it. Collapsing the
    // instrumentation below buys back about 200 logical pixels, which is
    // enough for a tablet; it is not enough for a phone, and nothing here
    // should be unreachable merely because the window is narrow.
    Flickable {
        width: 100%;
        height: 100%;
        viewport-height: self.height;
        viewport-width: max(self.width, strip.preferred-width);

    strip := HorizontalLayout {
        width: parent.viewport-width;
        height: parent.viewport-height;
        padding-left: Theme.gap;
        padding-right: Theme.gap;
        spacing: Theme.gap;
        alignment: start;

        // Kept instantiated with `visible` rather than wrapped in an `if`:
        // the strip is inside the layout that `expanded` feeds, and adding a
        // conditional child here is the shape that has already caused binding
        // loops in this file (see the panel below).
        Button {
            text: "‹ Library";
            y: (parent.height - self.height) / 2;
            visible: root.can-return-to-library;
            clicked => { root.back-to-library(); }
        }

        Value { text: root.filename; compact: true; overflow: elide; }

        Caption { text: root.position; }

        Rectangle { horizontal-stretch: 1; }

        // --- instrumentation lives in Settings now ------------------------
        //
        // The render backend, the layout class and the frame rate are
        // developer readouts. They cost about 200 logical pixels of a strip
        // that also carries the only way out of develop, the undo pair, the
        // panel toggle and the export button — and a `HorizontalLayout` given
        // less width than its children's minimums does not shrink them, it
        // runs off the end.
        //
        // A tablet in portrait is 768 logical pixels and was already below the
        // breakpoint that hid them, so it kept its header. Landscape is 1200
        // and is not, so the readouts came back and the header ran off the
        // right-hand edge there instead — a breakpoint that hides a problem at
        // one size and not another is a workaround, not a fix.
        //
        // The backend, the frame rate and the layout class used to live here.
        // They are diagnostics — read once when something looks wrong, and
        // never again — and as permanent furniture in a 44px strip they cost
        // three slots that the controls beside them actually needed. On a
        // tablet in landscape the header ran off the right-hand edge, and this
        // was a third of the reason.
        //
        // They are in Settings under ABOUT now, next to the version, which is
        // where someone goes when they have a bug to report rather than a
        // photograph to edit.

        // Undo and redo, in the strip rather than in the develop column: the
        // panel can be put away, and the one control that takes back a
        // mis-drag must not go away with it. Disabled rather than hidden, so
        // the pair keeps its place and the keyboard shortcut has something
        // visible to correspond to.
        Button {
            text: "Undo";
            enabled: root.can-undo;
            y: (parent.height - self.height) / 2;
            clicked => { root.undo(); }
        }

        Button {
            text: "Redo";
            enabled: root.can-redo;
            y: (parent.height - self.height) / 2;
            clicked => { root.redo(); }
        }

        // Show or hide the develop column. On a tablet the panel is 280px of a
        // screen that is mostly photograph, and the whole point of opening an
        // image is to look at it — so being able to put the instruments away
        // and bring them back is worth a control of its own. The glyph points
        // the way the panel will move.
        Button {
            text: root.panel-visible ? "Hide panel ›" : "‹ Panel";
            active: root.panel-visible;
            y: (parent.height - self.height) / 2;
            clicked => { root.toggle-panel(); }
        }

        Caption {
            text: root.export-status;
            vertical-alignment: center;
            overflow: elide;
        }

        // The export itself, beside the settings that shape it. This is the
        // screen where a photograph is finished, so it is the screen where
        // one is asked for — the grid can export a selection later, but a
        // single finished frame is exported from in front of it.
        Button {
            text: root.export-busy ? "Exporting…" : root.export-label;
            enabled: !root.export-busy;
            y: (parent.height - self.height) / 2;
            clicked => { root.export-image(); }
        }

        // Reachable from develop as well as from the grid: export defaults are
        // most likely to be wanted with a finished photograph on screen, which
        // is exactly where this bar is and the library header is not.
        Button {
            text: "Settings";
            y: (parent.height - self.height) / 2;
            clicked => { root.open-settings(); }
        }

    }
    }

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

// Capture metadata. Read-only; the adjustment controls live in AdjustPanel,
// which is generated from pipeline capabilities rather than written here.
//
// Flat, like everything else in this column. This was briefly a collapsible
// section so that every panel could be put away; the sidebar as a whole now
// closes from the status strip instead, which is the control that was actually
// wanted, and the per-group lids only stood between the user and the controls.
component InfoPanel inherits Rectangle {
    in property <string> camera;
    in property <string> exposure;
    in property <string> dimensions;

    background: transparent;
    height: panel.preferred-height;

    panel := Panel {
        // Flat: this abuts the adjust panel below it and the rule between
        // them is drawn by the column that stacks the two.
        flat: true;
        width: 100%;

        PanelHeading { text: "IMAGE"; }

        Value {
            text: root.camera == "" ? "—" : root.camera;
            placeholder: root.camera == "";
            wrap: word-wrap;
        }

        Label { text: root.exposure; }

        Caption { text: root.dimensions; }
    }
}

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-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;

    // --- 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;

    /// 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;

    /// Enter a mode, or `photo` to leave whichever one is current.
    callback mode-picked(ViewMode);
    /// A dragged crop rect, in fractions of the frame.
    callback crop-changed(float, float, float, float);

    // --- 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);
    /// 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();
    /// 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 <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);
    /// 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-collection-from-selection();
    /// 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();

    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;
    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();
    /// 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.
    callback library-cell-double-clicked(int);
    /// 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);
    /// 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);

    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();

    // --- 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 <bool> settings-copy-includes-framing: false;
    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);
    callback settings-copy-includes-framing-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 <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-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";

    // --- 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 <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();

    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);

    /// 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.
                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;

            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-includes-framing: root.settings-copy-includes-framing;
            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); }
            copy-includes-framing-toggled(on) => {
                root.settings-copy-includes-framing-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;
            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); }
            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;
            library-open: root.library-open;
            thumbnail-library() => { root.library-thumbnail-all(); }

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

        // 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-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;
            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); }
            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-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;

                        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
                    // readouts but not six 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(); }
                    collection-from-selection() => { root.library-collection-from-selection(); }
                    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(); }

                    scope-pinned: root.library-scope-pinned;
                    pin-done: root.library-pin-done;
                    pin-total: root.library-pin-total;
                    toggle-pin-scope() => { root.library-toggle-pin-scope(); }
                    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;
                    settings-summary: root.settings-summary;
                    paste-settings-to-selection => {
                        root.paste-settings-to-selection();
                    }

                    // 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(); }
                    change-library() => { root.library-change(); }
                    can-import: root.import-supported;
                    open-import() => { root.import-open(); }
                    open-settings() => { root.settings-open(); }

                    cell-pressed(i, ctrl, shift) => {
                        root.library-cell-pressed(i, ctrl, shift);
                    }
                    cell-press-ended() => { root.library-cell-press-ended(); }
                    cell-double-clicked(i) => { root.library-cell-double-clicked(i); }
                    select-mode: root.library-select-mode;
                    toggle-select-mode() => { root.library-toggle-select-mode(); }
                    // 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-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); }
                    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); }
                }
            }
        }

        if !root.show-import && !root.show-settings && !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-settings() => { root.settings-open(); }
                toggle-panel() => { root.toggle-panel(); }
                export-image() => { root.export-image(); }
                undo() => { root.undo(); }
                redo() => { root.redo(); }
            }

            HorizontalLayout {
                // 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.
                        //
                        // This matters even at moderate zoom on a HiDPI display:
                        // the canvas is rendered at *logical* size and Slint scales
                        // it up by the device pixel ratio, so the buffer is
                        // resampled on its way to the screen whatever the pipeline
                        // did.
                        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;
                    }

                    // 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,
                            );
                        }
                    }

                    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 ------------------------------------------
                    //
                    // Four dimmed, desaturated panels around the crop, then the
                    // rect itself with handles. Panels rather than one shape with
                    // a hole: Slint has no cut-out, and four rectangles are exact.
                    if root.cropping && root.total > 0 && root.load-error == "": crop-overlay := Rectangle {
                        x: parent.shown-x;
                        y: parent.shown-y;
                        width: parent.shown-w;
                        height: parent.shown-h;

                        property <length> rx: root.crop-x * self.width;
                        property <length> ry: root.crop-y * self.height;
                        property <length> rw: root.crop-w * self.width;
                        property <length> rh: root.crop-h * self.height;

                        // The surround: dimmed and drained of colour, so the crop
                        // reads as the photograph and everything else as context
                        // being discarded. Slint cannot desaturate a live image,
                        // so this is a heavy neutral wash over it — the dimming
                        // carries the separation and the neutrality kills the
                        // colour cue.
                        property <brush> veil: #20242aE0;

                        Rectangle {
                            x: 0;
                            y: 0;
                            width: parent.width;
                            height: crop-overlay.ry;
                            background: crop-overlay.veil;
                        }
                        Rectangle {
                            x: 0;
                            y: crop-overlay.ry + crop-overlay.rh;
                            width: parent.width;
                            height: parent.height - crop-overlay.ry - crop-overlay.rh;
                            background: crop-overlay.veil;
                        }
                        Rectangle {
                            x: 0;
                            y: crop-overlay.ry;
                            width: crop-overlay.rx;
                            height: crop-overlay.rh;
                            background: crop-overlay.veil;
                        }
                        Rectangle {
                            x: crop-overlay.rx + crop-overlay.rw;
                            y: crop-overlay.ry;
                            width: parent.width - crop-overlay.rx - crop-overlay.rw;
                            height: crop-overlay.rh;
                            background: crop-overlay.veil;
                        }

                        // The rect, its thirds, and the handles.
                        Rectangle {
                            x: parent.rx;
                            y: parent.ry;
                            width: parent.rw;
                            height: parent.rh;
                            border-width: 1px;
                            border-color: #ffffffCC;

                            // Rule of thirds, the reason a crop overlay is worth
                            // drawing at all rather than typing numbers.
                            Rectangle {
                                x: parent.width / 3;
                                y: 0; width: 1px; height: parent.height;
                                background: #ffffff44;
                            }
                            Rectangle {
                                x: parent.width * 2 / 3;
                                y: 0; width: 1px; height: parent.height;
                                background: #ffffff44;
                            }
                            Rectangle {
                                x: 0; y: parent.height / 3;
                                width: parent.width; height: 1px;
                                background: #ffffff44;
                            }
                            Rectangle {
                                x: 0; y: parent.height * 2 / 3;
                                width: parent.width; height: 1px;
                                background: #ffffff44;
                            }

                            // Drag the whole rect.
                            move-area := TouchArea {
                                width: 100%;
                                height: 100%;
                                mouse-cursor: MouseCursor.move;

                                property <float> start-x;
                                property <float> start-y;

                                pointer-event(ev) => {
                                    if (ev.kind == PointerEventKind.down) {
                                        self.start-x = root.crop-x;
                                        self.start-y = root.crop-y;
                                    }
                                }

                                moved => {
                                    if (self.pressed) {
                                        root.crop-changed(
                                            self.start-x
                                                + (self.mouse-x - self.pressed-x)
                                                    / max(crop-overlay.width, 1px),
                                            self.start-y
                                                + (self.mouse-y - self.pressed-y)
                                                    / max(crop-overlay.height, 1px),
                                            root.crop-w,
                                            root.crop-h,
                                        );
                                    }
                                }
                            }
                        }

                        // Corner handles. Each drags one corner while the opposite
                        // stays put, which is the only behaviour that lets a crop
                        // be shaped rather than merely moved.
                        for corner in [
                            { hx: 0.0, hy: 0.0 },
                            { hx: 1.0, hy: 0.0 },
                            { hx: 0.0, hy: 1.0 },
                            { hx: 1.0, hy: 1.0 },
                        ]: Rectangle {
                            property <length> size: 18px;
                            x: parent.rx + corner.hx * parent.rw - self.size / 2;
                            y: parent.ry + corner.hy * parent.rh - self.size / 2;
                            width: self.size;
                            height: self.size;

                            Rectangle {
                                width: 12px;
                                height: 12px;
                                background: #ffffff;
                                border-radius: 2px;
                            }

                            TouchArea {
                                width: 100%;
                                height: 100%;
                                mouse-cursor: (corner.hx == corner.hy)
                                    ? MouseCursor.nwse-resize
                                    : MouseCursor.nesw-resize;

                                property <float> ox;
                                property <float> oy;
                                property <float> ow;
                                property <float> oh;

                                pointer-event(ev) => {
                                    if (ev.kind == PointerEventKind.down) {
                                        self.ox = root.crop-x;
                                        self.oy = root.crop-y;
                                        self.ow = root.crop-w;
                                        self.oh = root.crop-h;
                                    }
                                }

                                // Movement as a fraction of the frame, live while
                                // the handle is held.
                                property <float> dx:
                                    (self.mouse-x - self.pressed-x) / max(crop-overlay.width, 1px);
                                property <float> dy:
                                    (self.mouse-y - self.pressed-y) / max(crop-overlay.height, 1px);

                                moved => {
                                    if (!self.pressed) {
                                        return;
                                    }
                                    // Dragging a left/top handle moves the origin
                                    // and shrinks the extent by the same amount;
                                    // a right/bottom handle moves only the extent.
                                    // Rust clamps the result, so an over-drag
                                    // slides rather than inverting.
                                    root.crop-changed(
                                        corner.hx == 0 ? self.ox + self.dx : self.ox,
                                        corner.hy == 0 ? self.oy + self.dy : self.oy,
                                        corner.hx == 0 ? self.ow - self.dx : self.ow + self.dx,
                                        corner.hy == 0 ? self.oh - self.dy : self.oh + self.dy,
                                    );
                                }
                            }
                        }
                    }

                    // --- gradient handles ---------------------------------------
                    //
                    // TRACES: FR-DEV-3 | FR-UI-3
                    // A linear or radial mask could be made and then never
                    // moved: there was nothing to grab, so a radial sat at the
                    // centre of the frame at its default size for ever.
                    //
                    // **Positioned against `shown-*`, like the crop overlay
                    // and the region picker.** The photograph is letterboxed
                    // inside this box and Slint does not report the fitted
                    // rect, so anything that has to land *on* the picture is
                    // placed against the derived one. Rust supplies the
                    // positions already mapped through the framing — the same
                    // map the shader applies — so a handle follows the mask
                    // through a zoom, a pan, a crop and a straightening rather
                    // than sitting where the mask used to be.
                    //
                    // **Drawn small, grabbed large.** The visible dot is 14px
                    // because a bigger one would hide the edge it is placed
                    // on, and the `TouchArea` is a full touch target, centred
                    // on it — `Button` establishes the same split. These are
                    // the first controls in the application meant to be
                    // dragged on the photograph, and a 12-inch tablet has no
                    // hover to reveal them with and no modifier to qualify
                    // them by, so what is drawn is all there is (FR-UI-7).
                    for handle in root.gradient-handles: Rectangle {
                        x: parent.shown-x + handle.x * parent.shown-w - self.width / 2;
                        y: parent.shown-y + handle.y * parent.shown-h - self.height / 2;
                        width: Theme.touch-target;
                        height: Theme.touch-target;

                        // The centre moves the whole mask, so it is filled;
                        // the others shape it and are rings. Shape rather than
                        // colour, because the handles sit on a photograph and
                        // any colour they carried would be read as part of it.
                        property <bool> solid: handle.role == HandleRole.centre;

                        Rectangle {
                            width: handle.role == HandleRole.rotate ? 12px : 14px;
                            height: self.width;
                            x: (parent.width - self.width) / 2;
                            y: (parent.height - self.height) / 2;
                            border-radius: self.width / 2;
                            border-width: 2px;
                            // White with a dark ring, so the handle is visible
                            // against a blown sky and against a black frame —
                            // one treatment, both extremes, no theme token
                            // because this is drawn over the image and not over
                            // the interface.
                            border-color: #00000099;
                            background: parent.solid ? #ffffff : #ffffff44;
                        }

                        drag := TouchArea {
                            width: 100%;
                            height: 100%;
                            mouse-cursor: parent.solid
                                ? MouseCursor.move
                                : MouseCursor.crosshair;

                            // Where the press landed, in the same fractions the
                            // callback reports in. Captured on the way down so
                            // the whole gesture is measured from one origin.
                            property <float> from-x;
                            property <float> from-y;

                            function fraction-x(local-x: length) -> float {
                                return (parent.x + local-x - canvas-area.shown-x)
                                    / max(canvas-area.shown-w, 1px);
                            }
                            function fraction-y(local-y: length) -> float {
                                return (parent.y + local-y - canvas-area.shown-y)
                                    / max(canvas-area.shown-h, 1px);
                            }

                            pointer-event(ev) => {
                                if (ev.kind == PointerEventKind.down) {
                                    self.from-x = self.fraction-x(self.pressed-x);
                                    self.from-y = self.fraction-y(self.pressed-y);
                                }
                                // One history step per gesture, not per frame.
                                if (ev.kind == PointerEventKind.up) {
                                    root.gradient-handle-released();
                                }
                            }

                            moved => {
                                if (self.pressed) {
                                    root.gradient-handle-dragged(
                                        handle.role,
                                        self.from-x,
                                        self.from-y,
                                        self.fraction-x(self.mouse-x),
                                        self.fraction-y(self.mouse-y),
                                    );
                                }
                            }
                        }
                    }

                    // 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;
                            }
                            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.
                    //
                    // A way out of whichever mode is on is still reachable from
                    // here — the develop column may be closed on a narrow
                    // window, and the strip that enters a mode is pinned inside
                    // it. Stranding the user in a mode with no visible way out
                    // is worse than one duplicated control, and it is worse
                    // still now that there are two modes to be stranded in.
                    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" : "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.
                Rectangle {
                    // TRACES: FR-UI-2
                    // 280px was chosen for a tablet, where the column is a
                    // large fraction of the screen and every pixel of it is
                    // taken from the photograph. On a desktop window it is
                    // simply too narrow: the mode strip alone is two modes,
                    // a separator, "All", and one chip per attribute the
                    // operation set declares, which is more words than 280px
                    // holds — so it scrolled sideways, and a control you have
                    // to pan to reach is one you do not know is there.
                    //
                    // Driven off `layout-class` rather than `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 classifies the window; this
                    // just spends the extra width where there is some.
                    width: root.panel-visible
                        ? (root.layout-class == "expanded" ? 380px : 280px)
                        : 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 {
                        ModeStrip {
                            enabled: root.adjust-enabled;
                            mode: root.view-mode;
                            tabs: root.adjust-tabs;
                            active-tab: root.adjust-active-tab;
                            picked(i) => { root.adjust-tab-picked(i); }
                            mode-picked(m) => { root.mode-picked(m); }
                        }

                        Flickable {
                            viewport-height: column.preferred-height;
                            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: InfoPanel {
                                camera: root.camera;
                                exposure: root.exposure;
                                dimensions: root.dimensions;
                            }

                            if !root.local-mode: 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;
                            }

                            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: 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;

                                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-reset => { root.straighten-changed(0); }
                                reset => { root.framing-reset(); }
                            }

                            if !root.local-mode: 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: 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(); }
                            }

                            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.
                            if root.local-mode: MaskPanel {
                                enabled: root.adjust-enabled;
                                masks: root.mask-rows;
                                subjects: root.subject-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); }
                            }

                            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); }
                            }
                            }
                        }
                    }

                    // 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.
        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(); }
        }
    }
}