BREP_app 0.1.0

//! Scene panel — the engine-native **Scene tree** ("Scene Manager"), the second
//! sidebar tree in the design reference. Built on the SAME reusable [`tree`] node
//! helper (connector lines + `[+]`/`[-]` collapse boxes) the history panel uses,
//! so the two trees read as one system.
//!
//! # What it draws
//!
//! A file-tree of the engine's display scene:
//!   * `[-] Scene <☑>` — the root; its checkbox toggles ALL solids' visibility.
//!   * per solid `[-] <Name> <☑>` — the checkbox toggles that solid's visibility
//!     through the engine ([`EngineState::set_visible`]); expands to
//!   * `[+] Faces <☑>`, `[+] Edges <☑>`, `[+] Vertices <☑>` — each expands to the
//!     individual entities BY KERNEL NAME (vertices by index/position).
//!
//! # Selection sync (both ways)
//!
//! Clicking an entity row drives the engine's name-based SELECTION
//! ([`EngineState::select_by_name`] / [`select_vertex_by_position`]) so it
//! highlights (emphasis) in the viewport; and the engine's CURRENT selection
//! (`state.emphasis`) bolds the matching tree row — the same emphasis the
//! viewport reads, so a viewport pick lights up the tree and vice-versa.
//!
//! # This panel OWNS NO model state
//!
//! The scene + selection live in the engine ([`EngineState`], the single source
//! of truth). The panel holds only transient UI state: which nodes are expanded
//! and the per-frame `hits` map (widget screen rects) the headed verifier reads.
//! Each frame it snapshots the scene into owned rows FIRST, draws from that, and
//! applies at most one deferred engine mutation after the draw loop (so no borrow
//! of `state` is held across a `&mut` call — the history panel's pattern).
//!
//! # Two deliberate reshapes (functional-over-1:1, per the design doc)
//!
//! * The visibility checkbox is drawn in the row's RIGHT slot: the shared tree
//!   widget reserves the left columns for the collapse box + connector + glyph,
//!   and (per the constraints) it is reused verbatim, not modified. Functionally
//!   identical to the reference's left checkbox.
//! * **Per-entity visibility (live):** the engine now hides individual faces /
//!   edges / vertices and whole groups ([`EngineState::set_entity_visible`] /
//!   [`EngineState::set_group_visible`]). So each Faces/Edges/Vertices group
//!   checkbox is a live TRISTATE (all / some / none of that kind shown) and each
//!   entity leaf carries its own live checkbox — the render pass skips a hidden
//!   entity's triangles / segments / point. The whole-solid + whole-scene
//!   checkboxes still compose: a hidden solid draws nothing; re-showing it keeps
//!   any per-entity hides intact.

use crate::panels::tree::{self, TreeRow};
use brep_render::engine_state::EngineState;
use brep_render::visibility::{EntityKind as VisKind, GroupState};
use eframe::egui;
use std::collections::{HashMap, HashSet};

/// One entity leaf's identity — how a click maps to an engine selection call.
#[derive(Clone)]
enum EntityKind {
    /// Face, selected by kernel name (empty = unnamed → not selectable).
    Face(String),
    /// Edge, selected by kernel name (empty = unnamed → not selectable).
    Edge(String),
    /// Vertex, selected by owning-solid + world position (no kernel name).
    Vertex([f64; 3]),
}

/// One row under a Faces/Edges/Vertices group — a display label, its selection
/// identity, whether it is currently in the engine selection, and whether it is
/// currently VISIBLE in the engine (its live per-entity checkbox state).
#[derive(Clone)]
struct Entity {
    label: String,
    kind: EntityKind,
    selected: bool,
    visible: bool,
}

/// One solid's owned snapshot for the frame (decoupled from `state.scene` so the
/// draw loop can issue deferred `&mut state` mutations afterwards).
struct SolidRow {
    name: String,
    visible: bool,
    selected: bool,
    faces: Vec<Entity>,
    edges: Vec<Entity>,
    vertices: Vec<Entity>,
}

/// A deferred engine mutation, collected during the draw and applied once after
/// the loop (one per frame — the history panel's pattern).
enum Action {
    SetVisible(String, bool),
    SetAllVisible(bool),
    /// Hide/show one entity: `(solid, kind, index-in-kind-list, visible)`.
    SetEntityVisible(String, VisKind, usize, bool),
    /// Hide/show a whole group: `(solid, kind, visible)`.
    SetGroupVisible(String, VisKind, bool),
    Select(&'static str, String),
    SelectVertex(String, [f64; 3]),
    /// Show/hide a committed sketch's persistent overlay: `(feature-id, visible)`.
    SetSketchVisible(String, bool),
    /// Show/hide a construction datum/plane's plane: `(frame-name, visible)`.
    SetDatumVisible(String, bool),
    /// Select a construction datum/plane by frame NAME (a row click).
    SelectDatum(String),
}

/// The Scene tree panel's transient UI state (the scene + selection live in the
/// engine).
#[derive(Default)]
pub struct ScenePanel {
    /// Per-frame egui widget screen rects, published to JS for the headed
    /// verifier. Rebuilt every frame.
    hits: HashMap<String, egui::Rect>,
    /// The Scene ROOT is collapsed (absent/false = open — it defaults open).
    root_collapsed: bool,
    /// Solids explicitly COLLAPSED, by name (absent = open — solids default open,
    /// matching the reference showing a solid's Faces/Edges/Vertices).
    collapsed_solids: HashSet<String>,
    /// Faces/Edges/Vertices group nodes explicitly EXPANDED, keyed
    /// `"<solid>/<group>"` (absent = collapsed — groups default collapsed `[+]`).
    expanded_groups: HashSet<String>,
    /// The `Sketches` group node is collapsed (absent/false = open — it defaults
    /// open so committed sketches are visible in the tree).
    sketches_collapsed: bool,
    /// The `Planes & Datums` group node is collapsed (absent/false = open — it
    /// defaults open so construction datums are visible in the tree).
    datums_collapsed: bool,
}

impl ScenePanel {
    pub fn new() -> Self {
        Self::default()
    }

    /// Draw the Scene tree. Snapshots the scene + current selection into owned
    /// rows, draws them via the shared [`tree`] node helper, then applies at most
    /// one deferred engine mutation.
    pub fn show(&mut self, ui: &mut egui::Ui, state: &mut EngineState) {
        self.hits.clear();

        // --- snapshot scene + selection (owned) so we can mutate after drawing --
        let sel_solids = state.emphasis.selected_solids.clone();
        let sel_faces = state.emphasis.selected_faces.clone();
        let sel_edges = state.emphasis.selected_edges.clone();
        let sel_vertices = state.emphasis.selected_vertices.clone();
        let solids = snapshot(state, &sel_solids, &sel_faces, &sel_edges, &sel_vertices);
        // Committed sketches (id, visible) — listed under the solids in the tree.
        let sketches = state.committed_sketches();
        // Construction datums/planes (name, visible) + which are selected — listed as
        // the tree's LAST group.
        let sel_datums = state.emphasis.selected_datums.clone();
        let datums = state.construction_datums();

        // Tight, tree-like row spacing so connector verticals read continuously.
        ui.spacing_mut().item_spacing.y = 2.0;

        let mut action: Option<Action> = None;

        // --- ROOT: `[-] Scene  ☑` (visibility toggles every solid) ------------
        let root_open = !self.root_collapsed;
        let all_visible = !solids.is_empty() && solids.iter().all(|s| s.visible);
        let mut root_vis = all_visible;
        let mut root_vis_rect = egui::Rect::NOTHING;
        let mut root_vis_clicked = false;
        let root_resp = tree::node(
            ui,
            TreeRow {
                guides: &[],
                is_last: true,
                expandable: true,
                expanded: root_open,
                root: true,
                glyph: None,
                label: "Scene",
                selected: false,
                draggable: false,
            },
            |ui| {
                let cb = ui.add_enabled(!solids.is_empty(), egui::Checkbox::new(&mut root_vis, ""));
                root_vis_rect = cb.rect;
                root_vis_clicked = cb.clicked();
            },
        );
        self.hits.insert("box:__scene".into(), root_resp.box_rect);
        self.hits.insert("vis:__scene".into(), root_vis_rect);
        if root_vis_clicked {
            action = Some(Action::SetAllVisible(root_vis));
        }
        if root_resp.toggled || root_resp.label.clicked() {
            self.root_collapsed = !self.root_collapsed;
        }

        if solids.is_empty() && sketches.is_empty() && datums.is_empty() {
            let g = tree::child_guides(&[], true);
            tree::node(ui, TreeRow::leaf(&g, true, "(scene is empty)"), |_| {});
        }

        if root_open {
            // Group order under the root: solids, then `Sketches`, then
            // `Planes & Datums` (the last child), so nothing "below" is last while a
            // later group follows.
            let has_sketches = !sketches.is_empty();
            let has_datums = !datums.is_empty();
            let n = solids.len();
            for (si, solid) in solids.iter().enumerate() {
                let is_last = !has_sketches && !has_datums && si + 1 == n;
                self.render_solid(ui, solid, is_last, &mut action);
            }
            if has_sketches {
                self.render_sketches(ui, &sketches, &sel_solids, !has_datums, &mut action);
            }
            if has_datums {
                self.render_datums(ui, &datums, &sel_datums, &mut action);
            }
        }

        // --- apply the one deferred engine mutation ---------------------------
        match action {
            Some(Action::SetVisible(name, v)) => {
                state.set_visible(&name, v);
            }
            Some(Action::SetAllVisible(v)) => {
                for s in &solids {
                    state.set_visible(&s.name, v);
                }
            }
            Some(Action::SetEntityVisible(name, kind, index, v)) => {
                state.set_entity_visible(&name, kind, index, v);
            }
            Some(Action::SetGroupVisible(name, kind, v)) => {
                state.set_group_visible(&name, kind, v);
            }
            Some(Action::Select(kind, name)) => {
                state.select_by_name(kind, &name);
            }
            Some(Action::SelectVertex(solid, pos)) => {
                state.select_vertex_by_position(&solid, pos);
            }
            Some(Action::SetSketchVisible(id, v)) => {
                state.set_sketch_visible(&id, v);
            }
            Some(Action::SetDatumVisible(name, v)) => {
                state.set_datum_visible(&name, v);
            }
            Some(Action::SelectDatum(name)) => {
                state.select_datum(&name);
            }
            None => {}
        }

        // --- verifier hooks (wasm only): scene listing + widget hit-rects ------
        // Published from the panel (not the shared shell) so the headed verifier
        // can assert the tree contents / visibility and drive real clicks, without
        // touching `app.rs`'s shared publish block.
        #[cfg(target_arch = "wasm32")]
        {
            publish("__brepScene", &state.scene_entities_json());
            publish("__brepSketches", &state.sketch_entities_json());
            publish("__brepDatums", &state.datum_entities_json());
            publish("__brepSceneVis", &state.scene_visibility_json());
            publish("__brepSceneHit", &self.hits_json());
        }
    }

    /// The `Sketches` group node + (when open) one row per committed sketch, each
    /// with a visibility checkbox wired to
    /// [`EngineState::set_sketch_visible`](brep_render::engine_state::EngineState::set_sketch_visible)
    /// and a label that SELECTS the sketch's sheet solid on click (a committed
    /// sketch is a scene solid). Rendered under the solids (before the
    /// `Planes & Datums` group); `is_last` is set only when no datum group follows.
    fn render_sketches(
        &mut self,
        ui: &mut egui::Ui,
        sketches: &[(String, bool)],
        sel_solids: &HashSet<String>,
        is_last: bool,
        action: &mut Option<Action>,
    ) {
        let open = !self.sketches_collapsed;
        let resp = tree::node(
            ui,
            TreeRow::branch(&[], is_last, open, "Sketches"),
            |ui| {
                ui.add_space(6.0);
                ui.label(egui::RichText::new(format!("{}", sketches.len())).weak());
            },
        );
        self.hits.insert("box:__sketches".into(), resp.box_rect);
        if resp.toggled || resp.label.clicked() {
            self.sketches_collapsed = !self.sketches_collapsed;
        }
        if !open {
            return;
        }

        let base = tree::child_guides(&[], is_last);
        let m = sketches.len();
        for (i, (id, visible)) in sketches.iter().enumerate() {
            let last = i + 1 == m;
            let selected = sel_solids.contains(id);
            let mut vis = *visible;
            let mut vis_rect = egui::Rect::NOTHING;
            let mut vis_clicked = false;
            let resp = tree::node(
                ui,
                TreeRow::leaf(&base, last, id).selected(selected),
                |ui| {
                    let cb = ui.add(egui::Checkbox::new(&mut vis, ""));
                    vis_rect = cb.rect;
                    vis_clicked = cb.clicked();
                },
            );
            self.hits.insert(format!("vis:sketch/{id}"), vis_rect);
            self.hits.insert(format!("sel:sketch/{id}"), resp.label.rect);
            if vis_clicked {
                *action = Some(Action::SetSketchVisible(id.clone(), vis));
            } else if resp.label.clicked() {
                // A committed sketch is a scene solid — select it like any solid.
                *action = Some(Action::Select("solid", id.clone()));
            }
        }
    }

    /// The `Planes & Datums` group node + (when open) one row per construction
    /// datum/plane frame, each with a visibility checkbox wired to
    /// [`EngineState::set_datum_visible`](brep_render::engine_state::EngineState::set_datum_visible)
    /// and a label that selects the datum
    /// ([`EngineState::select_datum`](brep_render::engine_state::EngineState::select_datum))
    /// on click. Rendered as the Scene root's LAST child (only when there is at
    /// least one construction datum).
    fn render_datums(
        &mut self,
        ui: &mut egui::Ui,
        datums: &[(String, bool)],
        sel_datums: &HashSet<String>,
        action: &mut Option<Action>,
    ) {
        let open = !self.datums_collapsed;
        let resp = tree::node(
            ui,
            TreeRow::branch(&[], true, open, "Planes & Datums"),
            |ui| {
                ui.add_space(6.0);
                ui.label(egui::RichText::new(format!("{}", datums.len())).weak());
            },
        );
        self.hits.insert("box:__datums".into(), resp.box_rect);
        if resp.toggled || resp.label.clicked() {
            self.datums_collapsed = !self.datums_collapsed;
        }
        if !open {
            return;
        }

        let base = tree::child_guides(&[], true);
        let m = datums.len();
        for (i, (name, visible)) in datums.iter().enumerate() {
            let last = i + 1 == m;
            let selected = sel_datums.contains(name);
            let mut vis = *visible;
            let mut vis_rect = egui::Rect::NOTHING;
            let mut vis_clicked = false;
            let resp = tree::node(
                ui,
                TreeRow::leaf(&base, last, name).selected(selected),
                |ui| {
                    let cb = ui.add(egui::Checkbox::new(&mut vis, ""));
                    vis_rect = cb.rect;
                    vis_clicked = cb.clicked();
                },
            );
            self.hits.insert(format!("vis:datum/{name}"), vis_rect);
            self.hits.insert(format!("sel:datum/{name}"), resp.label.rect);
            if vis_clicked {
                *action = Some(Action::SetDatumVisible(name.clone(), vis));
            } else if resp.label.clicked() {
                *action = Some(Action::SelectDatum(name.clone()));
            }
        }
    }

    /// One solid node + (when open) its Faces / Edges / Vertices groups.
    fn render_solid(
        &mut self,
        ui: &mut egui::Ui,
        solid: &SolidRow,
        is_last: bool,
        action: &mut Option<Action>,
    ) {
        let name = &solid.name;
        let open = !self.collapsed_solids.contains(name);

        let mut vis = solid.visible;
        let mut vis_rect = egui::Rect::NOTHING;
        let mut vis_clicked = false;
        let resp = tree::node(
            ui,
            TreeRow::branch(&[], is_last, open, name).selected(solid.selected),
            |ui| {
                let cb = ui.add(egui::Checkbox::new(&mut vis, ""));
                vis_rect = cb.rect;
                vis_clicked = cb.clicked();
            },
        );
        self.hits.insert(format!("box:{name}"), resp.box_rect);
        self.hits.insert(format!("vis:{name}"), vis_rect);
        self.hits.insert(format!("sel:{name}"), resp.label.rect);

        if vis_clicked {
            *action = Some(Action::SetVisible(name.clone(), vis));
        }
        if resp.toggled {
            if open {
                self.collapsed_solids.insert(name.clone());
            } else {
                self.collapsed_solids.remove(name);
            }
        }
        if resp.label.clicked() {
            *action = Some(Action::Select("solid", name.clone()));
        }

        if open {
            let base = tree::child_guides(&[], is_last);
            self.render_group(ui, name, &base, false, "Faces", VisKind::Face, &solid.faces, action);
            self.render_group(ui, name, &base, false, "Edges", VisKind::Edge, &solid.edges, action);
            self.render_group(ui, name, &base, true, "Vertices", VisKind::Vertex, &solid.vertices, action);
        }
    }

    /// One Faces/Edges/Vertices group node + (when open) its entity leaves. The
    /// group checkbox is a live TRISTATE that hides/shows every entity of `kind`;
    /// each leaf carries its own live checkbox that hides just that entity.
    #[allow(clippy::too_many_arguments)]
    fn render_group(
        &mut self,
        ui: &mut egui::Ui,
        solid_name: &str,
        base: &[bool],
        is_last: bool,
        group: &str,
        kind: VisKind,
        entities: &[Entity],
        action: &mut Option<Action>,
    ) {
        let key = format!("{solid_name}/{group}");
        let open = self.expanded_groups.contains(&key);

        // Tristate over the group's entities (empty group reads All → checked).
        let state = group_state(entities);
        let mut checked = matches!(state, GroupState::All);
        let indeterminate = matches!(state, GroupState::Partial);
        let mut vis_rect = egui::Rect::NOTHING;
        let mut vis_clicked = false;
        let resp = tree::node(
            ui,
            TreeRow::branch(base, is_last, open, group),
            |ui| {
                // right-to-left: the tristate group checkbox (rightmost), then count.
                let cb = ui.add(
                    egui::Checkbox::new(&mut checked, "").indeterminate(indeterminate),
                );
                vis_rect = cb.rect;
                vis_clicked = cb.clicked();
                ui.add_space(6.0);
                ui.label(egui::RichText::new(format!("{}", entities.len())).weak());
            },
        );
        self.hits.insert(format!("box:{key}"), resp.box_rect);
        self.hits.insert(format!("vis:{key}"), vis_rect);
        if vis_clicked {
            // Standard tristate: All → hide all; None/Partial → show all.
            let want_visible = !matches!(state, GroupState::All);
            *action = Some(Action::SetGroupVisible(solid_name.to_string(), kind, want_visible));
        }
        if resp.toggled || resp.label.clicked() {
            if open {
                self.expanded_groups.remove(&key);
            } else {
                self.expanded_groups.insert(key.clone());
            }
        }

        if !open {
            return;
        }
        let gg = tree::child_guides(base, is_last);
        if entities.is_empty() {
            tree::node(ui, TreeRow::leaf(&gg, true, "(none)"), |_| {});
            return;
        }
        let m = entities.len();
        for (ei, e) in entities.iter().enumerate() {
            let last = ei + 1 == m;
            let mut vis = e.visible;
            let mut ev_rect = egui::Rect::NOTHING;
            let mut ev_clicked = false;
            let resp = tree::node(
                ui,
                TreeRow::leaf(&gg, last, &e.label).selected(e.selected),
                |ui| {
                    let cb = ui.add(egui::Checkbox::new(&mut vis, ""));
                    ev_rect = cb.rect;
                    ev_clicked = cb.clicked();
                },
            );
            self.hits.insert(format!("sel:{key}/{ei}"), resp.label.rect);
            self.hits.insert(format!("vis:{key}/{ei}"), ev_rect);
            if ev_clicked {
                *action = Some(Action::SetEntityVisible(solid_name.to_string(), kind, ei, vis));
            } else if resp.label.clicked() {
                *action = Some(match &e.kind {
                    EntityKind::Face(n) => Action::Select("face", n.clone()),
                    EntityKind::Edge(n) => Action::Select("edge", n.clone()),
                    EntityKind::Vertex(p) => Action::SelectVertex(solid_name.to_string(), *p),
                });
            }
        }
    }

    /// The published widget hit-rects (egui points) for the headed verifier.
    #[cfg(target_arch = "wasm32")]
    pub fn hits_json(&self) -> String {
        let map: serde_json::Map<String, serde_json::Value> = self
            .hits
            .iter()
            .map(|(k, r)| {
                (
                    k.clone(),
                    serde_json::json!([r.min.x, r.min.y, r.width(), r.height()]),
                )
            })
            .collect();
        serde_json::Value::Object(map).to_string()
    }
}

/// The tristate for a group of entity rows, computed from their live per-entity
/// `visible` flags (the same the engine would report). An empty group reads
/// [`GroupState::All`] — nothing to hide, so the checkbox shows checked.
fn group_state(entities: &[Entity]) -> GroupState {
    if entities.is_empty() {
        return GroupState::All;
    }
    let visible = entities.iter().filter(|e| e.visible).count();
    if visible == entities.len() {
        GroupState::All
    } else if visible == 0 {
        GroupState::None
    } else {
        GroupState::Partial
    }
}

/// Snapshot `state.scene` into owned rows, precomputing each entity's `selected`
/// flag against the current engine selection (cloned in by the caller) and its
/// live per-entity `visible` flag. Face / edge labels fall back to `Face i` /
/// `Edge i` when the kernel left them unnamed; unnamed entities are then not
/// name-selectable (the click is a no-op) but still hideable (by index).
fn snapshot(
    state: &EngineState,
    sel_solids: &HashSet<String>,
    sel_faces: &HashSet<String>,
    sel_edges: &HashSet<String>,
    sel_vertices: &[brep_render::style::VertexRef],
) -> Vec<SolidRow> {
    // Vertex positions are set exactly from the same source; a tiny tolerance
    // guards float round-trips.
    const TOL: f64 = 1e-6;
    state
        .scene
        .solids()
        .iter()
        .map(|s| {
            let faces = s
                .faces
                .iter()
                .enumerate()
                .map(|(i, f)| Entity {
                    label: if f.name.is_empty() {
                        format!("Face {i}")
                    } else {
                        f.name.clone()
                    },
                    selected: !f.name.is_empty() && sel_faces.contains(&f.name),
                    visible: s.visibility.is_face_visible(i),
                    kind: EntityKind::Face(f.name.clone()),
                })
                .collect();
            let edges = s
                .edges
                .iter()
                .enumerate()
                .map(|(i, e)| Entity {
                    label: if e.name.is_empty() {
                        format!("Edge {i}")
                    } else {
                        e.name.clone()
                    },
                    selected: !e.name.is_empty() && sel_edges.contains(&e.name),
                    visible: s.visibility.is_edge_visible(i),
                    kind: EntityKind::Edge(e.name.clone()),
                })
                .collect();
            let vertices = s
                .vertices
                .iter()
                .enumerate()
                .map(|(i, v)| Entity {
                    label: format!("Vertex {i}"),
                    selected: sel_vertices.iter().any(|r| {
                        r.solid == s.name
                            && (r.position[0] - v.position[0]).abs() <= TOL
                            && (r.position[1] - v.position[1]).abs() <= TOL
                            && (r.position[2] - v.position[2]).abs() <= TOL
                    }),
                    visible: s.visibility.is_vertex_visible(i),
                    kind: EntityKind::Vertex(v.position),
                })
                .collect();
            SolidRow {
                name: s.name.clone(),
                visible: s.visible,
                selected: sel_solids.contains(&s.name),
                faces,
                edges,
                vertices,
            }
        })
        .collect()
}

/// Mirror an engine JSON string to `window.<name>` (wasm/verification only).
#[cfg(target_arch = "wasm32")]
fn publish(name: &str, json: &str) {
    if let Some(win) = web_sys::window() {
        let _ = js_sys::Reflect::set(
            &win,
            &wasm_bindgen::JsValue::from_str(name),
            &wasm_bindgen::JsValue::from_str(json),
        );
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    /// A one-primitive cube history, name-parameterized — mirrors the fixture the
    /// engine-layer visibility tests use so the solid lands as `name` with 6 faces
    /// / 12 edges / 8 vertices.
    fn cube_history(name: &str) -> String {
        serde_json::json!({
            "expressions": "",
            "configurator": {},
            "features": [{
                "type": "P.CU",
                "inputParams": {
                    "id": name,
                    "sizeX": 10.0, "sizeY": 10.0, "sizeZ": 10.0,
                    "transform": {
                        "position": [0.0, 0.0, 0.0],
                        "rotationEuler": [0.0, 0.0, 0.0],
                        "scale": [1.0, 1.0, 1.0]
                    },
                    "boolean": { "targets": [], "operation": "NONE" }
                },
                "persistentData": {}
            }]
        })
        .to_string()
    }

    /// Run ONE egui frame of the Scene panel headlessly (no window / GPU), feeding
    /// `events` as this frame's input. Layout is deterministic, so widget rects are
    /// stable frame-to-frame and the `hits` map can be read back to drive a real
    /// pointer click at a checkbox's screen rect.
    fn run_frame(
        ctx: &egui::Context,
        panel: &mut ScenePanel,
        state: &mut EngineState,
        events: Vec<egui::Event>,
        scroll: bool,
    ) {
        let raw = egui::RawInput {
            screen_rect: Some(egui::Rect::from_min_size(
                egui::pos2(0.0, 0.0),
                egui::vec2(800.0, 600.0),
            )),
            events,
            ..Default::default()
        };
        let _ = ctx.run_ui(raw, |ui| {
            // `scroll` wraps the tree in the app's `ScrollArea::vertical()` so the
            // click-routing is exercised under the real sidebar geometry (tree.rs
            // warns right-slot content underlapping the scrollbar can be eaten as a
            // scroll drag), not just on a bare root Ui.
            if scroll {
                egui::ScrollArea::vertical().show(ui, |ui| panel.show(ui, state));
            } else {
                panel.show(ui, state);
            }
        });
    }

    /// Left-click at `pos` split across a press frame and a release frame (egui
    /// fires `clicked()` on release), re-running the panel each frame so the
    /// deferred visibility mutation is applied.
    fn click_at(
        ctx: &egui::Context,
        panel: &mut ScenePanel,
        state: &mut EngineState,
        pos: egui::Pos2,
        scroll: bool,
    ) {
        run_frame(
            ctx,
            panel,
            state,
            vec![
                egui::Event::PointerMoved(pos),
                egui::Event::PointerButton {
                    pos,
                    button: egui::PointerButton::Primary,
                    pressed: true,
                    modifiers: egui::Modifiers::default(),
                },
            ],
            scroll,
        );
        run_frame(
            ctx,
            panel,
            state,
            vec![egui::Event::PointerButton {
                pos,
                button: egui::PointerButton::Primary,
                pressed: false,
                modifiers: egui::Modifiers::default(),
            }],
            scroll,
        );
    }

    /// End-to-end through the real egui widget dispatch: clicking a group's
    /// tristate checkbox in the Scene tree must hide EVERY entity of that kind on
    /// the solid (the deferred `SetGroupVisible` action reaching
    /// `EngineState::set_group_visible`). Faces is the reported-broken case; Edges
    /// is the working control — both are driven so a face-specific regression shows
    /// up as an asymmetry, not a harness artifact.
    fn drive_group_checkbox(kind: VisKind, hit_key: &str, scroll: bool) {
        let ctx = egui::Context::default();
        let mut state = EngineState::new();
        state.set_history_json(&cube_history("Box")).unwrap();
        let mut panel = ScenePanel::new();

        // Frame 1: lay the tree out (no input) so `hits` holds the checkbox rects.
        run_frame(&ctx, &mut panel, &mut state, vec![], scroll);
        assert_eq!(
            state.group_visibility("Box", kind),
            Some(GroupState::All),
            "precondition: every {kind:?} starts visible"
        );
        let rect = *panel.hits.get(hit_key).unwrap_or_else(|| {
            panic!(
                "missing hit rect {hit_key}; have {:?}",
                panel.hits.keys().collect::<Vec<_>>()
            )
        });

        // Click the group checkbox → all of that kind hidden.
        click_at(&ctx, &mut panel, &mut state, rect.center(), scroll);
        assert_eq!(
            state.group_visibility("Box", kind),
            Some(GroupState::None),
            "clicking the {kind:?} group checkbox must hide the whole group"
        );

        // Click again → all shown (the tristate re-shows a fully-hidden group).
        run_frame(&ctx, &mut panel, &mut state, vec![], scroll);
        let rect = *panel.hits.get(hit_key).expect("checkbox rect after hide");
        click_at(&ctx, &mut panel, &mut state, rect.center(), scroll);
        assert_eq!(
            state.group_visibility("Box", kind),
            Some(GroupState::All),
            "re-clicking the {kind:?} group checkbox must re-show the whole group"
        );
    }

    #[test]
    fn scene_tree_faces_group_checkbox_hides_and_shows_through_egui() {
        drive_group_checkbox(VisKind::Face, "vis:Box/Faces", false);
    }

    #[test]
    fn scene_tree_edges_group_checkbox_hides_and_shows_through_egui() {
        drive_group_checkbox(VisKind::Edge, "vis:Box/Edges", false);
    }

    /// Same as the faces group test, but with the tree wrapped in the app's
    /// `ScrollArea::vertical()` — proves the checkbox click routes correctly under
    /// the real sidebar geometry (not eaten as a scroll drag).
    #[test]
    fn scene_tree_faces_group_checkbox_works_inside_scroll_area() {
        drive_group_checkbox(VisKind::Face, "vis:Box/Faces", true);
    }

    /// An INDIVIDUAL face leaf checkbox (group expanded first) hides just that one
    /// face — the deferred `SetEntityVisible` action reaching
    /// `EngineState::set_entity_visible`. The other reported-broken case alongside
    /// the group toggle.
    #[test]
    fn scene_tree_individual_face_checkbox_hides_one_face_through_egui() {
        let ctx = egui::Context::default();
        let mut state = EngineState::new();
        state.set_history_json(&cube_history("Box")).unwrap();
        let mut panel = ScenePanel::new();

        // Frame 1: layout → the Faces group's collapse box rect is published.
        run_frame(&ctx, &mut panel, &mut state, vec![], false);
        let box_rect = *panel.hits.get("box:Box/Faces").expect("faces group collapse box");

        // Expand the Faces group (a panel-local toggle) so its leaves render.
        click_at(&ctx, &mut panel, &mut state, box_rect.center(), false);
        run_frame(&ctx, &mut panel, &mut state, vec![], false);
        assert_eq!(
            state.entity_visible("Box", VisKind::Face, 0),
            Some(true),
            "face 0 starts visible"
        );
        let leaf = *panel.hits.get("vis:Box/Faces/0").unwrap_or_else(|| {
            panic!(
                "missing face-0 leaf checkbox; have {:?}",
                panel.hits.keys().collect::<Vec<_>>()
            )
        });

        // Click face 0's checkbox → only face 0 hidden.
        click_at(&ctx, &mut panel, &mut state, leaf.center(), false);
        assert_eq!(
            state.entity_visible("Box", VisKind::Face, 0),
            Some(false),
            "clicking face 0's checkbox must hide exactly face 0"
        );
        assert_eq!(
            state.entity_visible("Box", VisKind::Face, 1),
            Some(true),
            "sibling face 1 stays visible"
        );
        assert_eq!(
            state.group_visibility("Box", VisKind::Face),
            Some(GroupState::Partial),
            "one hidden face → group reads Partial"
        );
    }
}