DarkRoom/ui/dr-ui/ui/collections.slint

// The collections sidebar: a hierarchy of collections, and a drop target for
// images dragged out of the grid.
//
// TRACES: FR-CAT-7 | FR-UI-3 | FR-UI-5
//
// # Why the tree is flat here
//
// Slint has no recursive component instantiation, so a `for` cannot nest itself
// to arbitrary depth. The tree arrives from Rust already flattened, each row
// carrying its own `depth` — indentation is drawn from that integer. The
// ordering rules (siblings by name, children after their parent) live in
// `dr_catalog::collections::tree`, which is where the data model already is.
//
// # Drag and drop
//
// Each row is a `DropArea`, and the grid's cells are `DragArea`s. Slint owns the
// gesture: pointer capture, the threshold that separates a click from a drag,
// arbitration against the grid's `Flickable`, the image under the cursor, and
// delivery of the payload to whichever row the pointer is actually over.
//
// This replaced a hand-rolled version that tracked presses through `TouchArea`
// and is worth recording, because the failure was not obvious: an interactive
// `Flickable` claims any drag beginning inside it for scrolling and *cancels*
// the child TouchArea's press, so the gesture could never leave the grid. The
// hand-rolled version also had to decide the drop target from the last row
// hovered, since a captured pointer is invisible to everything else — which
// meant a tree rebuilt mid-drag could redirect the drop. `DropArea` hit-tests
// the release itself, so neither problem exists.
//
// `can-drop` runs while the cursor moves and decides whether this row will
// accept — a saved filter refuses there, so the cursor says no *before* the
// release rather than the drop being silently discarded after it.

import { Theme } from "theme.slint";
import { Button, Icon } from "widgets.slint";

// One row of the collection tree.
export struct CollectionRow {
    id: int,
    name: string,
    // 0 for a top-level collection. Indentation is drawn from this.
    depth: int,
    // Direct members. A parent shows this and its descendants' total
    // separately: an empty set of full children must not read as full.
    direct-count: int,
    // Distinct images including descendants'.
    deep-count: int,
    has-children: bool,
    expanded: bool,
    // A saved filter. Cannot be dropped onto — its membership is its selector.
    smart: bool,
    // TRACES: FR-NC-6a
    // Whether every photograph in here — and in its children — is pinned for
    // offline use. A collection holding nothing is never `pinned`: "all zero of
    // them are kept" is true and useless, and it would draw a full tray beside
    // an empty collection.
    pinned: bool,
    // Pinned in part: some of what is in here is kept, some is not. Distinct
    // from `pinned` because the two say different things to a user about to
    // board an aeroplane, and one bool could only say the more optimistic of
    // them.
    partly-pinned: bool,
}

// A collection row: disclosure arrow, name, count, and a drop highlight.
component TreeRow inherits Rectangle {
    in property <CollectionRow> entry;
    in property <bool> selected;
    /// Whether a drag hovering here could land. A saved filter's membership is
    /// computed from its selector, so it refuses — and says so on hover.
    in property <bool> drop-allowed: true;
    /// Whether this row is being renamed, in which case its name is drawn as an
    /// editable field rather than as text.
    in property <bool> renaming: false;

    callback clicked();
    callback toggle();
    /// The pointer is dwelling here mid-drag. What springs a collapsed parent
    /// open, so a child can be reached without ending the drag.
    callback drag-over(bool);
    /// Images were dropped on this row.
    callback dropped();
    callback context-menu();
    /// TRACES: FR-NC-6a
    /// Ask what should happen to this collection's local copies — keep them, or
    /// give the disk back. The question is asked rather than a toggle silently
    /// flipped, because both answers are expensive: one starts a download of
    /// gigabytes, the other deletes them.
    callback offline-menu();
    /// The row is being held, or has been let go. A long press is the touch
    /// route to [`offline-menu`], and the timer that decides how long is long
    /// lives in Rust — Slint has no long-press gesture, and a hand-rolled one
    /// here would need a `Timer` per row in the tree.
    callback press-changed(bool);
    /// Start renaming this row — a double-click on the name.
    callback rename-requested();
    /// The new name, committed with Enter or by clicking away.
    callback rename-committed(string);
    /// Renaming abandoned with Escape; the old name stands.
    callback rename-cancelled();

    height: Theme.row-height;

    // `drop.has-drag` is only true once `can-drop` has accepted, so a refused
    // row never lights up as though it would take the images.
    background: drop.has-drag
                ? Theme.selected
                : (root.selected ? Theme.surface-raised
                   : (touch.has-hover ? Theme.hover : transparent));
    border-radius: Theme.radius-sm;

    // A drop target is outlined as well as filled: on a dark ground a fill
    // change alone is easy to miss mid-drag, when the user is watching the
    // thumbnail under the cursor rather than the row.
    border-width: drop.has-drag ? 1px : 0px;
    border-color: Theme.selected-ring;

    // Behind the content, so the row's own TouchArea still gets ordinary
    // clicks. A DropArea only takes part in a drag; it does not block presses.
    drop := DropArea {
        width: 100%;
        height: 100%;

        can-drop(ev) => {
            // Refused here rather than after the release: the cursor shows
            // "no" while the user can still aim somewhere else.
            if (!root.drop-allowed) {
                return DragAction.none;
            }
            return DragAction.copy;
        }

        dropped(ev) => {
            root.dropped();
            return DragAction.copy;
        }

        // Dwelling over a collapsed parent springs it open. Reported rather
        // than acted on here, because the dwell timer and the collapse state
        // live in Rust with the rest of the tree.
        changed has-drag => { root.drag-over(self.has-drag); }
    }

    HorizontalLayout {
        // Indentation from depth. The guide rail below sits in this space.
        padding-left: Theme.gap-sm + root.entry.depth * Theme.indent;
        padding-right: Theme.gap-sm;
        spacing: Theme.gap-sm;

        // Disclosure arrow, or an equal blank so names stay aligned between
        // rows that have children and rows that do not.
        Rectangle {
            width: 14px;

            if root.entry.has-children: Icon {
                name: root.entry.expanded ? "chevron-down" : "chevron-right";
                ink: Theme.ink-faint;
                size: 10px;
                x: (parent.width - self.width) / 2;
                y: (parent.height - self.height) / 2;
            }

            // Its own hit area: toggling open must not also select, or every
            // expand reloads the grid.
            if root.entry.has-children: TouchArea {
                clicked => { root.toggle(); }
            }
        }

        // Smart collections read differently from manual ones — the icon is
        // the only cue that its contents are computed, and that dropping
        // images on it will be refused.
        Icon {
            name: root.entry.smart ? "collection-smart" : "collection";
            ink: root.entry.smart ? Theme.active-dim : Theme.ink-faint;
            size: 12px;
            y: (parent.height - self.height) / 2;
        }

        // The name, or the field that is replacing it while this row is being
        // renamed. Two branches of one `if` rather than a TextInput styled to
        // look like text at rest: a live TextInput would swallow the clicks
        // that select the collection and the presses that begin a drag.
        if !root.renaming: Text {
            text: root.entry.name;
            color: root.selected ? Theme.ink : Theme.ink-dim;
            font-size: Theme.text;
            font-weight: root.selected ? 600 : 400;
            vertical-alignment: center;
            overflow: elide;
            horizontal-stretch: 1;
        }

        if root.renaming: Rectangle {
            horizontal-stretch: 1;
            background: Theme.ground;
            border-radius: Theme.radius-sm;
            border-width: 1px;
            border-color: Theme.active;

            edit := TextInput {
                // Seeded once, when the field appears. Bound two-way to the
                // row's name it would rewrite the model on every keystroke,
                // and an edit abandoned with Escape could not be undone.
                text: root.entry.name;
                color: Theme.ink;
                font-size: Theme.text;
                vertical-alignment: center;
                single-line: true;
                // Inset by hand for the same reason `Field` does it: inside a
                // layout the input stops scrolling its own content once the
                // text outgrows the box.
                x: Theme.gap-sm;
                width: parent.width - 2 * Theme.gap-sm;
                height: 100%;

                // Focus and a full selection on appearance, so the placeholder
                // name a new collection arrives with is replaced by typing
                // rather than having to be cleared first.
                init => {
                    self.focus();
                    self.select-all();
                }

                accepted => { root.rename-committed(self.text); }

                key-pressed(event) => {
                    // Escape abandons. Handled here rather than on a
                    // surrounding FocusScope, which would never see the key —
                    // the input has focus and consumes it.
                    if (event.text == Key.Escape) {
                        root.rename-cancelled();
                        return accept;
                    }
                    return reject;
                }

                // Clicking away commits rather than discarding: the text is
                // visible on screen and the user typed it, so throwing it out
                // for want of an Enter is the surprising choice.
                changed has-focus => {
                    if (!self.has-focus) {
                        root.rename-committed(self.text);
                    }
                }
            }
        }

        // TRACES: FR-NC-6a | FR-NC-6c
        // Keep this collection on the device. Here rather than only in the
        // grid header because the header's version acts on whatever the grid
        // is *scoped* to: reaching it means selecting the collection, closing
        // the sidebar, opening the action row and finding the button — four
        // steps on a tablet to say "take this trip with me". This is one.
        //
        // Drawn only where there is something to keep, and on a row that is
        // already keeping something: an outline tray beside every collection
        // in the tree is chrome the eye has to filter past to read the names,
        // which is what the sidebar is actually for. A smart collection is
        // excluded for the same reason it refuses a drop — its membership is a
        // rule that has not been evaluated here.
        if !root.entry.smart
           && (root.entry.deep-count > 0 || root.entry.direct-count > 0)
           && (root.selected || root.entry.pinned || root.entry.partly-pinned
               || touch.has-hover): Rectangle {
            width: 18px;
            y: (parent.height - self.height) / 2;
            height: 18px;

            Icon {
                name: root.entry.pinned ? "offline-held" : "offline";
                // Held is the state worth colouring: it is a promise the app
                // has made about a gigabyte of transfer, and it should be
                // legible from across the room. A partial hold is dimmer than
                // a full one and brighter than an offer, which is the order
                // the three actually stand in.
                ink: root.entry.pinned ? Theme.active
                     : (root.entry.partly-pinned ? Theme.active-dim : Theme.ink-faint);
                size: 12px;
                x: (parent.width - self.width) / 2;
                y: (parent.height - self.height) / 2;
            }

            // Wider than it is drawn, and no taller. A 44px square here — the
            // touch minimum — would be 18px taller than the row it sits in and
            // would take presses aimed at the collections above and below it,
            // which is a worse failure than a small target: the user hits a
            // row and a different collection's download starts.
            TouchArea {
                width: 30px;
                height: parent.height;
                x: (parent.width - self.width) / 2;
                clicked => { root.offline-menu(); }
            }
        }

        // The count. A parent shows its deep total, since its own direct
        // membership is usually zero and "0" beside a full subtree reads as
        // broken. The distinction is spelled out in the tooltip-less way
        // available here: parentheses mean "including children".
        Text {
            text: root.entry.has-children && root.entry.deep-count != root.entry.direct-count
                  ? "(" + root.entry.deep-count + ")"
                  : (root.entry.direct-count > 0 ? root.entry.direct-count : "")
                    + "";
            color: Theme.ink-faint;
            font-size: Theme.text-sm;
            vertical-alignment: center;
        }
    }

    touch := TouchArea {
        // Disabled while the field is up, so a click landing on the row rather
        // than inside the input does not re-select the collection out from
        // under the edit in progress.
        enabled: !root.renaming;

        clicked => { root.clicked(); }
        // Double-click renames — the gesture a file manager or a Lightroom
        // panel uses for the same thing, so it needs no discovering.
        double-clicked => { root.rename-requested(); }
        pointer-event(ev) => {
            if (ev.kind == PointerEventKind.down
                && ev.button == PointerEventButton.right) {
                root.context-menu();
                return;
            }
            // The hold that opens the offline question. Reported both ways:
            // Rust starts a timer on the press and cancels it on the release,
            // so a tap that happens to be slow is still a tap.
            //
            // `cancel` matters as much as `up` here — the sidebar's Flickable
            // takes the pointer the moment the finger travels, and a press
            // that became a scroll must not fire a dialogue over the list the
            // user is scrolling.
            if (ev.kind == PointerEventKind.down) {
                root.press-changed(true);
            }
            if (ev.kind == PointerEventKind.up || ev.kind == PointerEventKind.cancel) {
                root.press-changed(false);
            }
        }
    }
}

export component CollectionsPanel inherits Rectangle {
    in property <[CollectionRow]> rows;
    // Which collection scopes the grid. 0 means the whole library.
    in property <int> selected-id: 0;
    in property <int> total-images: 0;
    in property <string> error: "";
    /// Whether a scan is running, which is when neither of the two actions at
    /// the foot of this panel can be honoured: pinning walks a collection the
    /// scan is still writing, and changing library pulls the catalog out from
    /// under it.
    in property <bool> scanning: false;

    // --- what to do with the collection this panel has scoped --------------
    //
    // TRACES: FR-NC-6a
    // These two used to be buttons in the library header, where they were the
    // only things in a row of library-wide actions that referred to *one
    // collection* — and where "Keep offline" could only ever mean the scoped
    // one while sitting nowhere near the tree that says which that is.
    //
    // Here they are under the tree, in the panel whose selection decides what
    // they act on, and in the same place and shape the trash already puts its
    // own two. The header keeps only what belongs to the whole library.
    /// TRACES: FR-NC-6a
    /// Whether the scoped collection is being kept on this device.
    in property <bool> scope-pinned: false;
    /// TRACES: FR-NC-6a
    /// Ask about the scoped collection's local copies — the same question the
    /// tray on a row and a held row open.
    callback toggle-pin-scope();
    /// Open a different library altogether.
    callback change-library();

    callback select(int);
    callback toggle(int);
    /// Images were dropped on a collection, by its id. Slint hit-tests the
    /// release itself, so this is the collection actually under the pointer —
    /// not the last one hovered.
    callback dropped-on(int);
    /// The payload for dragging a *collection*, so the tree can be rearranged.
    /// Built when the drag starts, and it is what tells `dropped-on` it is
    /// being handed a collection to reparent rather than photographs to file.
    pure callback collection-drag-payload(int) -> data-transfer;
    /// A drag is dwelling over a collection, or has left it. Drives the
    /// spring-loaded expansion, which is timed in Rust.
    callback drag-over(int, bool);
    callback new-collection();
    // Right-click on a row: rename, delete, new child.
    callback row-menu(int);
    /// TRACES: FR-NC-6a
    /// Ask about a collection's local copies, by id. Reached by tapping the
    /// tray on a row, or by holding the row itself.
    callback offline-menu(int);
    /// A row is being held, or was let go: its id, and which. The long-press
    /// timer is in Rust; see `TreeRow.press-changed`.
    callback row-press(int, bool);

    /// Which collection is being renamed, by id. 0 is none.
    ///
    /// Driven from Rust rather than held here, because a rename that fails —
    /// or one begun by *creating* a collection, which happens before this
    /// panel has the new row — has to be started and ended from that side.
    in property <int> renaming-id: 0;
    /// Renaming began on a row: its id.
    callback rename-start(int);
    /// A rename was committed: the id, and the new name.
    callback rename-commit(int, string);
    /// Renaming was abandoned.
    callback rename-cancel();

    // --- trash (FR-CAT-15) ---
    //
    // `selected-id == -1` is the trash being viewed. A sentinel rather than a
    // separate bool because the sidebar has exactly one selection, and two
    // flags could disagree about what the grid is showing.
    /// How many images are in the trash.
    in property <int> trash-count: 0;
    /// The count and the bytes it holds, already formatted — "12 · 340 MB".
    /// Formatted in Rust because Slint has no byte-size formatting and the
    /// arithmetic would be unreadable inline.
    in property <string> trash-label: "";

    /// How many grid cells are selected, so the trash view can offer to restore
    /// them. Read here as well as in the library panel because restoring is a
    /// selection action and the button has to say what it will act on.
    in property <int> selected-count: 0;

    /// Images were dropped on the trash: a soft delete.
    callback dropped-on-trash();
    /// Permanently delete everything in the trash.
    callback empty-trash();
    /// Put the selected images back where they came from.
    callback restore-selected();

    width: 232px;
    background: Theme.surface;

    VerticalLayout {
        padding: Theme.gap-sm;
        spacing: Theme.gap-sm;

        // --- header -------------------------------------------------------
        HorizontalLayout {
            height: 26px;
            spacing: Theme.gap-sm;

            Text {
                text: "COLLECTIONS";
                color: Theme.ink-faint;
                font-size: Theme.text-sm;
                font-weight: 700;
                letter-spacing: 1.2px;
                vertical-alignment: center;
                horizontal-stretch: 1;
            }

            // New collection. A mark rather than a word: the header is 232px
            // wide and the label would crowd out the title.
            Rectangle {
                width: 22px;
                height: 22px;
                y: (parent.height - self.height) / 2;
                background: add-touch.pressed ? Theme.pressed
                            : (add-touch.has-hover ? Theme.hover : transparent);
                border-radius: Theme.radius-sm;

                Icon {
                    name: "plus";
                    ink: Theme.ink-dim;
                    size: 12px;
                    x: (parent.width - self.width) / 2;
                    y: (parent.height - self.height) / 2;
                }
                add-touch := TouchArea {
                    clicked => { root.new-collection(); }
                }
            }
        }

        // --- the whole library --------------------------------------------
        //
        // Always first and never nested: it is how the user gets back to an
        // unscoped grid, and burying it inside the tree would make "show me
        // everything" a thing you have to find.
        Rectangle {
            height: Theme.row-height;
            background: root.selected-id == 0 ? Theme.surface-raised
                        : (all-touch.has-hover ? Theme.hover : transparent);
            border-radius: Theme.radius-sm;

            HorizontalLayout {
                padding-left: Theme.gap-sm;
                padding-right: Theme.gap-sm;
                spacing: Theme.gap-sm;

                Text {
                    text: "All photographs";
                    color: root.selected-id == 0 ? Theme.ink : Theme.ink-dim;
                    font-size: Theme.text;
                    font-weight: root.selected-id == 0 ? 600 : 400;
                    vertical-alignment: center;
                    horizontal-stretch: 1;
                }
                Text {
                    text: root.total-images > 0 ? root.total-images : "";
                    color: Theme.ink-faint;
                    font-size: Theme.text-sm;
                    vertical-alignment: center;
                }
            }
            all-touch := TouchArea {
                clicked => { root.select(0); }
                // Dropping onto "All photographs" would mean nothing — an
                // image is already in the library — so this reports no hover
                // during a drag and stays inert.
            }
        }

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

        // --- the tree -----------------------------------------------------
        Flickable {
            vertical-stretch: 1;
            viewport-height: root.rows.length * (Theme.row-height + 2px);

            // Wrapped rather than made draggable from the inside: the grid's
            // cells take the same shape, and a `DragArea` around the whole row
            // keeps the row's own TouchArea nested under it, which is what lets
            // a click still select while a drag reparents.
            for row[i] in root.rows: DragArea {
                y: i * (Theme.row-height + 2px);
                width: parent.width;
                height: Theme.row-height;

                // Move, not copy. A collection has one parent, so dragging it
                // somewhere takes it out of where it was — unlike a photograph,
                // which is filed in as many collections as you like.
                allow-move: true;
                data: root.collection-drag-payload(row.id);

                TreeRow {
                width: 100%;
                height: 100%;
                entry: row;
                selected: row.id == root.selected-id;
                // A saved filter's membership is computed, so a drop cannot
                // land there. Refused in `can-drop`, so the cursor says no
                // before the release rather than after.
                drop-allowed: !row.smart;
                renaming: row.id == root.renaming-id;

                clicked => { root.select(row.id); }
                toggle => { root.toggle(row.id); }
                context-menu => { root.row-menu(row.id); }
                offline-menu => { root.offline-menu(row.id); }
                press-changed(down) => { root.row-press(row.id, down); }
                dropped => { root.dropped-on(row.id); }
                drag-over(over) => { root.drag-over(row.id, over); }
                rename-requested => { root.rename-start(row.id); }
                rename-committed(name) => { root.rename-commit(row.id, name); }
                rename-cancelled => { root.rename-cancel(); }
                }
            }

            // Empty state. A blank panel gives no hint that collections exist
            // at all, let alone that images can be dragged into them.
            if root.rows.length == 0: VerticalLayout {
                alignment: center;
                spacing: Theme.gap-sm;
                padding: Theme.gap;

                Text {
                    text: "No collections yet";
                    color: Theme.ink-dim;
                    font-size: Theme.text-sm;
                    horizontal-alignment: center;
                }
                Text {
                    text: "Press + to make one, then drag photographs onto it.";
                    color: Theme.ink-faint;
                    font-size: Theme.text-sm;
                    horizontal-alignment: center;
                    wrap: word-wrap;
                }
            }
        }

        // TRACES: FR-NC-6a
        // Keep the scoped collection on this device.
        //
        // Only while one is scoped: "pin the whole library" is a different and
        // much more expensive request, and a button that meant either
        // depending on invisible state would be a trap. Ids at or below zero
        // are "All photographs" and the trash, neither of which is a
        // collection to pin.
        //
        // No tick on the kept label: `active` already inverts the button,
        // which says the same thing without a symbol inside a string.
        //
        // It opens the same question the tray on a row and a held row open,
        // rather than pinning outright — see the note on the callback in
        // `library_ui::wire`. This is the version with a word on it, for the
        // collection the grid is actually showing.
        if root.selected-id > 0: Button {
            text: root.scope-pinned ? "Kept offline" : "Keep offline";
            active: root.scope-pinned;
            enabled: !root.scanning;
            clicked => { root.toggle-pin-scope(); }
        }

        // --- trash --------------------------------------------------------
        //
        // TRACES: FR-CAT-15
        // Below the tree and separated from it, because it is not a collection:
        // dropping here *moves the file* into a trash folder on the server,
        // where every collection above merely references. A destination that
        // changes the library has no business sitting in the same list as ones
        // that do not.
        Rectangle {
            height: 1px;
            background: Theme.rule;
        }

        Rectangle {
            height: Theme.row-height;
            background: trash-drop.has-drag
                        ? Theme.selected
                        : (root.selected-id == -1 ? Theme.surface-raised
                           : (trash-touch.has-hover ? Theme.hover : transparent));
            border-radius: Theme.radius-sm;
            border-width: trash-drop.has-drag ? 1px : 0px;
            border-color: Theme.warn-ink;

            trash-drop := DropArea {
                width: 100%;
                height: 100%;
                // Deliberately `move`, where a collection drop is `copy`: this
                // one really does take the photograph out of the library, and
                // the cursor should say so.
                can-drop(ev) => { return DragAction.move; }
                dropped(ev) => {
                    root.dropped-on-trash();
                    return DragAction.move;
                }
            }

            HorizontalLayout {
                padding-left: Theme.gap-sm;
                padding-right: Theme.gap-sm;
                spacing: Theme.gap-sm;

                Icon {
                    name: "trash";
                    ink: root.trash-count > 0 ? Theme.warn-ink : Theme.ink-faint;
                    size: 12px;
                    y: (parent.height - self.height) / 2;
                }

                Text {
                    text: "Trash";
                    color: root.selected-id == -1 ? Theme.ink : Theme.ink-dim;
                    font-size: Theme.text;
                    font-weight: root.selected-id == -1 ? 600 : 400;
                    vertical-alignment: center;
                    horizontal-stretch: 1;
                }

                // The size, not just the count: "empty trash" is destructive and
                // what it frees is what tells the user whether they meant it.
                Text {
                    text: root.trash-count > 0 ? root.trash-label : "";
                    color: Theme.ink-faint;
                    font-size: Theme.text-sm;
                    vertical-alignment: center;
                }
            }

            trash-touch := TouchArea {
                clicked => { root.select(-1); }
            }
        }

        // Restore sits *above* Empty, and is the only one of the two that names
        // a number. The recoverable action should be the one the hand reaches
        // first, and the destructive one should not be what a user finds when
        // they open the trash looking for a way back.
        if root.selected-id == -1 && root.selected-count > 0: Button {
            text: root.selected-count == 1
                  ? "Restore 1 image"
                  : "Restore " + root.selected-count + " images";
            clicked => { root.restore-selected(); }
        }

        // Emptying is offered only while the trash is being *looked at*, so it
        // cannot be hit in passing. It is the one irreversible action in this
        // panel and it should take a deliberate visit to reach.
        if root.selected-id == -1 && root.trash-count > 0: Button {
            text: "Empty trash";
            clicked => { root.empty-trash(); }
        }

        // --- error --------------------------------------------------------
        //
        // A refused drop or a failed rename says so here rather than only in
        // the log: the gesture succeeded from the user's point of view, so
        // silence would read as data loss.
        if root.error != "": Text {
            text: root.error;
            color: Theme.warn-ink;
            font-size: Theme.text-sm;
            wrap: word-wrap;
        }

        // The foot of the panel, under everything the current library holds,
        // because it is the one control here that replaces all of it.
        //
        // It was in the library header, wedged between Sync and Rescan — two
        // buttons that act on the library you already have. Reading "Change
        // library" as one of that group is a way to lose a scan by aiming
        // badly. Down here it is the last thing in the panel and the only
        // thing below the tree it would replace.
        Rectangle { height: 1px; background: Theme.rule; }

        Button {
            text: "Change library";
            enabled: !root.scanning;
            clicked => { root.change-library(); }
        }
    }

    // Right edge, separating the panel from the grid.
    Rectangle {
        x: parent.width - 1px;
        width: 1px;
        background: Theme.rule;
    }
}

// TRACES: FR-NC-6a | FR-NC-6c | FR-UI-3
// What a held collection asks: keep these photographs on this device, or give
// the disk back.
//
// A question rather than a toggle, because the two answers are not symmetrical
// conveniences — one commits the device to downloading gigabytes over whatever
// connection it has, and the other deletes gigabytes it already holds. Neither
// is something to discover by having done it.
//
// The sizes are in the labels rather than in a second confirmation, the same
// way the grid's "Export 40" puts its count in the button: a number read before
// the tap is worth more than a dialogue asking the same question after it.
//
// Drawn over the whole window rather than inside the sidebar. The sidebar is
// 232px wide and collapses entirely in the compact layout — a dialogue that
// lived in there would be unreachable on the device this gesture exists for.
export component OfflinePrompt inherits Rectangle {
    /// The collection being asked about. Empty closes the prompt — a single
    /// source for "is this open", rather than a bool that can disagree with the
    /// name beside it.
    in property <string> title;
    /// What is in there and how much of it is already here, in one line.
    in property <string> detail;
    /// The affirmative label, with the transfer it commits to: Rust knows the
    /// count and the bytes, and this file should not be doing arithmetic on
    /// them.
    in property <string> keep-label;
    /// The destructive label, with the disk it frees.
    in property <string> release-label;
    /// Whether there is anything left to download, and anything held to delete.
    /// Both can be false — an empty collection — and the prompt then says only
    /// what it holds and offers the way out.
    in property <bool> can-keep: false;
    in property <bool> can-release: false;
    /// Whether a download is already running for this collection, so the
    /// affirmative reads as "already going" rather than inviting a second one.
    in property <bool> busy: false;

    callback keep();
    callback release();
    callback dismiss();

    visible: root.title != "";
    background: #000000CC;

    // Swallows everything that misses the card, and dismisses. Declared before
    // the card so the card's own controls sit above it.
    TouchArea {
        clicked => { root.dismiss(); }
    }

    Rectangle {
        width: min(420px, parent.width - 2 * Theme.gap-lg);
        height: card.preferred-height;
        x: (parent.width - self.width) / 2;
        y: (parent.height - self.height) / 2;
        background: Theme.surface;
        border-radius: Theme.radius;
        border-width: 1px;
        border-color: Theme.rule;

        // A press on the card must not reach the scrim behind it and close the
        // thing being read.
        TouchArea { }

        card := VerticalLayout {
            padding: Theme.gap-lg;
            spacing: Theme.gap;

            Text {
                text: "Keep offline";
                color: Theme.ink-faint;
                font-size: Theme.text-sm;
                font-weight: 700;
                letter-spacing: 1.2px;
            }

            Text {
                text: root.title;
                color: Theme.ink;
                font-size: Theme.text-lg;
                font-weight: 600;
                wrap: word-wrap;
            }

            Text {
                text: root.detail;
                color: Theme.ink-dim;
                font-size: Theme.text;
                wrap: word-wrap;
            }

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

            // Stacked rather than a row of three. At 420px on a tablet the
            // labels carry counts and byte sizes, and three of those side by
            // side elide to "Keep 128 pho…" — which loses exactly the number
            // the label exists to show.
            Button {
                text: root.busy ? "Downloading…" : root.keep-label;
                primary: true;
                enabled: root.can-keep && !root.busy;
                clicked => { root.keep(); }
            }

            if root.can-release: Button {
                text: root.release-label;
                clicked => { root.release(); }
            }

            Button {
                text: "Cancel";
                clicked => { root.dismiss(); }
            }
        }
    }
}