DarkRoom/ui/dr-ui/src/spots_ui.rs

//! TRACES: FR-DEV-8
//! Wiring the repair tool to the develop session.
//!
//! Translation only, exactly as [`crate::masks_ui`] is: circles out in one
//! direction, gestures in the other, and every decision in
//! [`crate::develop::DevelopSession`]. What this module does decide is when the
//! canvas is redrawn and when the panel is rebuilt, and those are the two
//! things that go wrong quietly here — see [`sync_handles`] for the one that
//! took a gesture out from under the finger.

use std::cell::RefCell;
use std::rc::Rc;

use slint::{ComponentHandle as _, Model as _, ModelRc, VecModel};

use crate::develop::DevelopSession;
use crate::{AppWindow, SpotHandle};

/// TRACES: FR-DEV-8 | FR-UI-3
/// Move the circles to where the repairs now are.
///
/// # Why this is not `set_spot_handles(VecModel::from(…))`
///
/// **A fresh model kills the gesture that is moving them.** The circles are a
/// repeater over this model, and handing Slint a new `ModelRc` makes it throw
/// the repeated items away and build new ones — the `TouchArea` holding the
/// pointer included. The drag then dies under the finger with the button still
/// down. `masks_ui::sync_handles` carries the same warning, and `develop.rs`
/// carries it about the parameter rows, where it broke slider drags: this is
/// the third place the same mistake is available, which is why it is written
/// down in all three.
///
/// So the model is kept and its rows are rewritten in place.
pub(crate) fn sync_handles(window: &AppWindow, session: &DevelopSession) {
    let next = session.spot_handles();
    let model = handle_model();

    while model.row_count() > next.len() {
        model.remove(model.row_count() - 1);
    }
    for (i, handle) in next.into_iter().enumerate() {
        if i < model.row_count() {
            // Only where it actually moved: an unchanged row written back is
            // still a change notification.
            if model.row_data(i).as_ref() != Some(&handle) {
                model.set_row_data(i, handle);
            }
        } else {
            model.push(handle);
        }
    }

    window.set_spot_handles(ModelRc::from(model));
    window.set_selected_spot(session.selected_spot_id().unwrap_or_default().into());
}

/// The circles' model, held for the life of the process — one shared identity,
/// for the reason [`sync_handles`] gives.
fn handle_model() -> Rc<VecModel<SpotHandle>> {
    thread_local! {
        static HANDLES: Rc<VecModel<SpotHandle>> = Rc::new(VecModel::default());
    }
    HANDLES.with(Clone::clone)
}

/// Take the repairs off the canvas between photographs.
///
/// Emptied rather than replaced, keeping the model's identity for the reason
/// [`sync_handles`] gives.
pub(crate) fn reset(window: &AppWindow) {
    let model = handle_model();
    while model.row_count() > 0 {
        model.remove(model.row_count() - 1);
    }
    window.set_spot_handles(ModelRc::from(model));
    window.set_selected_spot(Default::default());
    window.set_spot_count(0);
}

/// Install the repair tool's callbacks.
pub(crate) fn wire(
    window: &AppWindow,
    session: &Rc<RefCell<Option<DevelopSession>>>,
    redraw: Rc<dyn Fn(&AppWindow)>,
) {
    // --- placing ----------------------------------------------------------
    {
        let weak = window.as_weak();
        let session = session.clone();
        let redraw = redraw.clone();
        window.on_spot_placed(move |x, y| {
            let Some(w) = weak.upgrade() else { return };
            let placed = session
                .borrow_mut()
                .as_mut()
                .and_then(|s| s.place_spot(x, y));
            if placed.is_none() {
                // The letterbox margin, or a full set. Neither is an error and
                // neither should clear the selection: a near-miss that threw
                // away what the column was describing would read as hostile.
                return;
            }
            if let Some(s) = session.borrow().as_ref() {
                sync_handles(&w, s);
                sync_panel(&w, s);
            }
            sync_undo(&w, &session);
            redraw(&w);
        });
    }

    // --- dragging ---------------------------------------------------------
    //
    // The repair as it stood when the press landed, held for the gesture. A
    // drag is applied to *that* rather than accumulated frame by frame: the
    // clamps would otherwise compound, so a source dragged past its limit and
    // back would not return to where it started, and the result would depend on
    // how many pointer events the platform happened to deliver.
    let dragging: Rc<RefCell<Option<dr_pipeline::Spot>>> = Rc::new(RefCell::new(None));
    {
        let weak = window.as_weak();
        let session = session.clone();
        let redraw = redraw.clone();
        let dragging = dragging.clone();
        window.on_spot_handle_dragged(move |id, role, from_x, from_y, to_x, to_y| {
            let Some(w) = weak.upgrade() else { return };
            let origin = dragging.borrow().clone();
            let started = session.borrow_mut().as_mut().and_then(|s| {
                s.drag_spot(
                    id.as_str(),
                    role,
                    origin.as_ref(),
                    (from_x, from_y),
                    (to_x, to_y),
                )
            });
            if started.is_none() {
                return;
            }
            *dragging.borrow_mut() = started;
            // Only the circles. Rebuilding the panel on every frame of a drag
            // is work for no difference, and a full rebuild would take the
            // gesture out from under the finger — see `sync_handles`.
            if let Some(s) = session.borrow().as_ref() {
                sync_handles(&w, s);
            }
            redraw(&w);
        });
    }
    {
        let weak = window.as_weak();
        let session = session.clone();
        let dragging = dragging.clone();
        window.on_spot_handle_released(move || {
            // Forgotten on release, so the next gesture measures from wherever
            // this one left the repair.
            if dragging.borrow_mut().take().is_none() {
                // A press with no movement — a selection, not a drag. Recording
                // a step would put an identical snapshot on the undo stack.
                return;
            }
            if let Some(s) = session.borrow_mut().as_mut() {
                s.commit_spot_drag();
            }
            if let Some(w) = weak.upgrade() {
                sync_undo(&w, &session);
            }
        });
    }

    // --- the column's controls --------------------------------------------
    //
    // One closure shape, four callbacks: each hands the session a change to
    // make to whichever repair is selected, and the session decides whether
    // there is one. Reading the selection here instead would put the same
    // `Option` check in four places and let them disagree.
    macro_rules! control {
        ($install:ident, $apply:expr) => {{
            let weak = window.as_weak();
            let session = session.clone();
            let redraw = redraw.clone();
            window.$install(move |value| {
                let Some(w) = weak.upgrade() else { return };
                let changed = session
                    .borrow_mut()
                    .as_mut()
                    .is_some_and(|s| s.set_selected_spot(|spot| $apply(spot, value)));
                if !changed {
                    return;
                }
                if let Some(s) = session.borrow().as_ref() {
                    sync_handles(&w, s);
                    sync_panel(&w, s);
                }
                sync_undo(&w, &session);
                redraw(&w);
            });
        }};
    }

    control!(on_spot_radius_changed, |spot: &mut dr_pipeline::Spot, v| {
        spot.set_radius(v)
    });
    control!(
        on_spot_feather_changed,
        |spot: &mut dr_pipeline::Spot, v| { spot.set_feather(v) }
    );
    control!(
        on_spot_opacity_changed,
        |spot: &mut dr_pipeline::Spot, v| { spot.set_opacity(v) }
    );
    control!(on_spot_mode_picked, |spot: &mut dr_pipeline::Spot, i| {
        spot.mode = if i == 1 {
            dr_pipeline::SpotMode::Clone
        } else {
            dr_pipeline::SpotMode::Heal
        }
    });

    // --- selecting and removing -------------------------------------------
    {
        let weak = window.as_weak();
        let session = session.clone();
        let redraw = redraw.clone();
        window.on_spot_selected(move |id| {
            let Some(w) = weak.upgrade() else { return };
            if let Some(s) = session.borrow_mut().as_mut() {
                s.select_spot(Some(id.as_str()));
            }
            if let Some(s) = session.borrow().as_ref() {
                sync_handles(&w, s);
                sync_panel(&w, s);
            }
            // The canvas changes — the selected repair gains its source circle
            // — but no pixel does, so this is a repaint of the overlay rather
            // than of the photograph. `redraw` is the only hook there is, and
            // it is cheap enough: the render caches on the invalidation key,
            // which a selection does not move.
            redraw(&w);
        });
    }
    {
        let weak = window.as_weak();
        let session = session.clone();
        let redraw = redraw.clone();
        window.on_spot_removed(move |id| {
            let Some(w) = weak.upgrade() else { return };
            let removed = session
                .borrow_mut()
                .as_mut()
                .is_some_and(|s| s.remove_spot(id.as_str()));
            if !removed {
                return;
            }
            if let Some(s) = session.borrow().as_ref() {
                sync_handles(&w, s);
                sync_panel(&w, s);
            }
            sync_undo(&w, &session);
            redraw(&w);
        });
    }
}

/// TRACES: FR-DEV-8
/// Push the selected repair's settings into the column.
///
/// Separate from [`sync_handles`] because they answer different questions and
/// change at different times: the circles move on every frame of a drag and on
/// every pan, and these move when a repair is selected or a control is used.
pub(crate) fn sync_panel(window: &AppWindow, session: &DevelopSession) {
    window.set_spot_count(session.spot_count() as i32);
    if let Some(spot) = session.selected_spot() {
        window.set_spot_radius(spot.radius);
        window.set_spot_feather(spot.feather);
        window.set_spot_opacity(spot.opacity);
        window.set_spot_mode(match spot.mode {
            dr_pipeline::SpotMode::Heal => 0,
            dr_pipeline::SpotMode::Clone => 1,
        });
    }
}

/// Push whether undo and redo have anywhere to go.
///
/// Every repair is a history step, so every one of them moves these — and a
/// disabled undo button after an edit that *is* undoable is the kind of small
/// lie that stops people trusting the button at all.
fn sync_undo(window: &AppWindow, session: &Rc<RefCell<Option<DevelopSession>>>) {
    window.set_can_undo(session.borrow().as_ref().is_some_and(|s| s.can_undo()));
    window.set_can_redo(session.borrow().as_ref().is_some_and(|s| s.can_redo()));
}