cad-editor/src/app/update/viewport.rs

//! `viewport` arms and helpers, split out of the original `update.rs` (#mechanical decomposition).

#![allow(unused_imports)]
use super::util::*;
use super::{format_size, VIEWCUBE_HIT_SIZE};
use crate::app::helpers::{
    ortho_constrain, parse_coord, polar_constrain_near, ucs_rotate_vec, ucs_to_wcs, ucs_z_axis,
    CoordKind,
};
use crate::app::{Message, OpenCADStudio, POLY_START_DELAY_MS};
use crate::modules::ModuleEvent;
use crate::scene::pick::grip::{find_hit_grip, find_hit_grip_paper, find_hit_grip_rte, GripEdit};
use crate::scene::model::object::GripApply;
use crate::scene::{
    self, hover_id, CubeRegion, Scene, VIEWCUBE_DRAW_PX, VIEWCUBE_PAD, VIEWCUBE_PX,
};
use crate::ui::PropertiesPanel;
use acadrust::types::Color as AcadColor;
use acadrust::{EntityType as AcadEntityType, Handle};
use iced::time::Instant;
use iced::{mouse, Point, Task};

/// How long the right button must be held (ms) before a right-drag is treated
/// as an orbit. A press + release inside this window stays a click (context
/// menu / Enter), so quick right-clicks aren't lost to slight pointer jitter.
const RIGHT_HOLD_MS: u128 = 150;
/// Pixel radius for grabbing a UCS-icon grip (origin dot or an axis tip).
const UCS_GRIP_HIT_PX: f32 = 9.0;
/// Pixel reach for hovering/clicking the icon body (origin, tips, or an arm).
const UCS_ICON_PICK_PX: f32 = 10.0;
/// Pixel half-width for clicking an icon arm (line segment).
const UCS_ICON_ARM_PX: f32 = 6.0;

fn pt_pt_d2(a: Point, b: Point) -> f32 {
    (a.x - b.x).powi(2) + (a.y - b.y).powi(2)
}

/// Squared distance from `p` to the segment `a`–`b`.
fn pt_seg_d2(p: Point, a: Point, b: Point) -> f32 {
    let (vx, vy) = (b.x - a.x, b.y - a.y);
    let len2 = vx * vx + vy * vy;
    let t = if len2 > 1e-6 {
        (((p.x - a.x) * vx + (p.y - a.y) * vy) / len2).clamp(0.0, 1.0)
    } else {
        0.0
    };
    pt_pt_d2(p, Point::new(a.x + t * vx, a.y + t * vy))
}

/// Which UCS grip (if any) the cursor `p` is on.
fn ucs_grip_under(p: Point, h: &crate::ui::overlay::UcsIconHit) -> Option<crate::app::UcsGripKind> {
    let r2 = UCS_GRIP_HIT_PX * UCS_GRIP_HIT_PX;
    if pt_pt_d2(p, h.origin) <= r2 {
        Some(crate::app::UcsGripKind::Origin)
    } else if pt_pt_d2(p, h.tips[0]) <= r2 {
        Some(crate::app::UcsGripKind::XAxis)
    } else if pt_pt_d2(p, h.tips[1]) <= r2 {
        Some(crate::app::UcsGripKind::YAxis)
    } else {
        None
    }
}

/// True when `p` is over the icon body (origin, a tip, or an arm) — the pick
/// region for hover-highlight and select.
fn over_ucs_icon(p: Point, h: &crate::ui::overlay::UcsIconHit) -> bool {
    let pick2 = UCS_ICON_PICK_PX * UCS_ICON_PICK_PX;
    if pt_pt_d2(p, h.origin) <= pick2 || h.tips.iter().any(|t| pt_pt_d2(p, *t) <= pick2) {
        return true;
    }
    let arm2 = UCS_ICON_ARM_PX * UCS_ICON_ARM_PX;
    h.tips.iter().any(|t| pt_seg_d2(p, h.origin, *t) <= arm2)
}


impl OpenCADStudio {
    /// Write PDSIZE from the dialog buffer with the current relative/absolute
    /// sign. A relative size is stored negative; absolute positive. Switching to
    /// absolute with an empty/zero size seeds a positive value from the current
    /// on-screen size so the point stays representable (PDSIZE 0 always reads as
    /// relative, so absolute needs a non-zero magnitude).
    pub(in crate::app) fn apply_point_size(&mut self) {
        let i = self.active_tab;
        let mut mag = self
            .point_size_buf
            .trim()
            .parse::<f64>()
            .unwrap_or(0.0)
            .abs();
        if !self.point_size_relative && mag == 0.0 {
            let wpp = self.tabs[i].scene.world_per_pixel().unwrap_or(0.0);
            mag = if wpp > 0.0 {
                crate::entities::point::relative_world_size(0.0, wpp)
            } else {
                1.0
            };
            self.point_size_buf = format!("{mag:.4}");
        }
        let next = if self.point_size_relative { -mag } else { mag };
        self.push_undo_snapshot(i, "PDSIZE");
        self.tabs[i].scene.document.header.point_display_size = next;
        self.tabs[i].scene.bump_geometry();
        self.tabs[i].dirty = true;
    }

    /// Replace the `mask` bits of PDMODE with `value`, rebuild the point glyphs
    /// and mark the document dirty. Used by the Point Style (DDPTYPE) dialog.
    pub(in crate::app) fn set_point_mode_bits(&mut self, mask: i16, value: i16) {
        let i = self.active_tab;
        let cur = self.tabs[i].scene.document.header.point_display_mode;
        let next = (cur & !mask) | (value & mask);
        if next == cur {
            return;
        }
        self.push_undo_snapshot(i, "PDMODE");
        self.tabs[i].scene.document.header.point_display_mode = next;
        self.tabs[i].scene.bump_geometry();
        self.tabs[i].dirty = true;
    }

    /// Mirror the live grid display + grid-snap toggles onto tab `i`'s active
    /// model tile so a save writes them to that viewport's VPort entry (#121).
    pub(in crate::app) fn sync_vport_display(&mut self, i: usize) {
        let grid_on = self.show_grid;
        let snap_on = self.snapper.grid_snap();
        self.tabs[i].scene.set_active_tile_grid_snap(grid_on, snap_on);
    }

    /// Adopt the active viewport's grid *display* into the live toggle. Called
    /// on load and whenever the active tab or viewport changes, so the grid
    /// drawing follows the active viewport.
    ///
    /// Grid *snap* (`SnapType::Grid`) is deliberately NOT adopted here: it stays
    /// off by default everywhere and is controlled solely by the user's snap
    /// toggle, so it never silently leaks into object-snap when entering a
    /// viewport whose stored `snap_on` flag happens to be set.
    pub(in crate::app) fn adopt_view_display(&mut self, i: usize) {
        if let Some((grid_on, _snap_on)) = self.tabs[i].scene.active_tile_grid_snap() {
            self.show_grid = grid_on;
        }
    }

    pub(in crate::app) fn sync_render_mode_to_active_tile(&mut self, i: usize) {
        use acadrust::entities::ViewportRenderMode as M;
        if self.tabs[i].scene.current_layout != "Model" {
            return;
        }
        let mode = self.tabs[i].scene.active_model_tile_render_mode();
        if self.tabs[i].render_mode == mode {
            return;
        }
        let label = match mode {
            M::Wireframe2D => "Wireframe 2D",
            M::Wireframe3D => "Wireframe 3D",
            M::HiddenLine => "Hidden Line",
            M::FlatShaded => "Flat Shaded",
            M::GouraudShaded => "Gouraud Shaded",
            M::FlatShadedWithEdges => "Flat Shaded + Edges",
            M::GouraudShadedWithEdges => "Gouraud Shaded + Edges",
        };
        self.tabs[i].render_mode = mode;
        let wf = matches!(mode, M::Wireframe2D | M::Wireframe3D);
        self.tabs[i].wireframe = wf;
        self.ribbon.set_wireframe(wf);
        self.tabs[i].visual_style = label.into();
        self.tabs[i].scene.bump_geometry();
    }

    /// Project a pane-local cursor onto the active drawing plane and return a
    /// **model-space** point. Inside a floating viewport `edit_cam` is the
    /// viewport's own camera (a target-plane / UCS pick there already yields
    /// model coords); otherwise the paper camera projects onto the sheet and
    /// the result is mapped paper→model. Used by the readout, snap and click
    /// paths so all three agree on the cursor's model location.

    pub(in crate::app) fn cursor_model_point(
        &self,
        i: usize,
        edit_cam: &Option<crate::scene::view::camera::Camera>,
        p: iced::Point,
        bounds: iced::Rectangle,
    ) -> glam::DVec3 {
        // Constrain to the UCS plane only where the UCS applies (model space or
        // inside a viewport); plain paper space uses the target plane.
        let plane = self
            .tabs[i]
            .active_ucs
            .as_ref()
            .filter(|_| self.tabs[i].editing_model_space())
            .map(|ucs| {
                (
                    ucs_z_axis(ucs),
                    glam::DVec3::new(ucs.origin.x, ucs.origin.y, ucs.origin.z),
                )
            });
        let pick = |cam: &crate::scene::view::camera::Camera| match plane {
            Some((normal, origin)) => cam.pick_on_plane(p, bounds, normal, origin),
            None => cam.pick_on_target_plane(p, bounds),
        };
        match edit_cam {
            Some(cam) => pick(cam),
            None => {
                let paper = {
                    let c = self.tabs[i].scene.camera.borrow();
                    pick(&c)
                };
                self.tabs[i].scene.paper_to_model(paper)
            }
        }
    }

    /// Projection + hit-test wires for the active pane. Inside a floating
    /// viewport (`edit_cam` Some) it returns the viewport camera and the live
    /// **model** wires, so wire / hatch picking lands on the entity under the
    /// cursor exactly where the GPU draws it; otherwise the model/paper camera
    /// and the normal hit-test wires. `bounds` is the pane-local rectangle.

    pub(in crate::app) fn pick_view(
        &self,
        i: usize,
        edit_cam: &Option<crate::scene::view::camera::Camera>,
        bounds: iced::Rectangle,
    ) -> (glam::Mat4, glam::DVec3, std::sync::Arc<Vec<crate::scene::WireModel>>) {
        match edit_cam {
            Some(cam) => {
                let wires = match self.tabs[i].scene.active_viewport {
                    Some(h) => self.tabs[i].scene.model_wires_for_viewport_arc(h, bounds.height),
                    None => self.tabs[i].scene.hit_test_wires(),
                };
                (cam.view_proj_rte(bounds), cam.eye(), wires)
            }
            None => {
                let (view_rot, eye) = {
                    let c = self.tabs[i].scene.camera.borrow();
                    (c.view_proj_rte(bounds), c.eye())
                };
                (view_rot, eye, self.tabs[i].scene.hit_test_wires())
            }
        }
    }


    pub(in crate::app) fn update_grip_hover(&mut self, i: usize, p: iced::Point) {
        const HOVER_OPEN_MS: u128 = 600;
        const POPUP_DISMISS_PX: f32 = 80.0;
        if self.tabs[i].active_cmd.is_some()
            || self.tabs[i].active_grip.is_some()
            || self.tabs[i].selected_grips.is_empty()
        {
            self.grip_hover = None;
            self.grip_popup = None;
            return;
        }
        let Some(handle) = self.tabs[i].selected_handle else {
            self.grip_hover = None;
            self.grip_popup = None;
            return;
        };
        let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
        let bounds = iced::Rectangle {
            x: 0.0,
            y: 0.0,
            width: vw,
            height: vh,
        };
        let is_paper = self.tabs[i].scene.current_layout != "Model";
        // In-viewport grips are model-space — project with the viewport camera
        // at the viewport's own rect; the cursor is mapped into that rect.
        let edit_frame = self.tabs[i].scene.viewport_edit_frame((vw, vh));
        let hit = if let Some((cam, full)) = &edit_frame {
            let local = iced::Rectangle {
                x: 0.0,
                y: 0.0,
                width: full.width,
                height: full.height,
            };
            let p_local = iced::Point::new(p.x - full.x, p.y - full.y);
            find_hit_grip_rte(
                p_local,
                &self.tabs[i].selected_grips,
                cam.view_proj_rte(local),
                cam.eye(),
                local,
            )
        } else if is_paper {
            let cam = self.tabs[i].scene.camera.borrow();
            let aspect = if vh > 0.0 { vw / vh } else { 1.0 };
            let half_h = cam.ortho_size();
            let half_w = half_h * aspect;
            let tx = cam.target.x as f32;
            let ty = cam.target.y as f32;
            drop(cam);
            find_hit_grip_paper(
                p,
                &self.tabs[i].selected_grips,
                tx,
                ty,
                half_w,
                half_h,
                bounds,
            )
        } else {
            let cam = self.tabs[i].scene.camera.borrow();
            find_hit_grip(p, &self.tabs[i].selected_grips, &cam, bounds)
        };
        match hit {
            Some((grip_id, _, _)) => {
                let same = self
                    .grip_hover
                    .as_ref()
                    .map_or(false, |h| h.handle == handle && h.grip_id == grip_id);
                if !same {
                    self.grip_hover = Some(crate::app::GripHover {
                        handle,
                        grip_id,
                        screen: p,
                        started: iced::time::Instant::now(),
                    });
                    self.grip_popup = None;
                } else if let Some(h) = self.grip_hover.as_mut() {
                    h.screen = p;
                }
                // Open popup once dwell crosses the threshold. The visibility
                // grip has its own click-to-open dropdown, so it gets no
                // hover grip-menu.
                if self.grip_popup.is_none()
                    && grip_id != crate::app::visibility::VIS_GRIP_ID
                    && self
                        .grip_hover
                        .as_ref()
                        .map_or(false, |h| h.started.elapsed().as_millis() >= HOVER_OPEN_MS)
                {
                    let entity_opt = self.tabs[i].scene.document.get_entity(handle);
                    if let Some(e) = entity_opt {
                        use crate::entities::traits::EntityTypeOps;
                        let items = e.grip_menu(grip_id);
                        if !items.is_empty() {
                            self.grip_popup = Some(crate::app::GripPopup {
                                handle,
                                grip_id,
                                anchor: p,
                                items,
                                selected: 0,
                            });
                        }
                    }
                }
            }
            None => {
                self.grip_hover = None;
                if let Some(popup) = &self.grip_popup {
                    let dx = p.x - popup.anchor.x;
                    let dy = p.y - popup.anchor.y;
                    if (dx * dx + dy * dy).sqrt() > POPUP_DISMISS_PX {
                        self.grip_popup = None;
                    }
                }
            }
        }
    }

pub(super) fn on_tick(&mut self, t: Instant) -> Task<Message> {
                let i = self.active_tab;
                self.tabs[i].scene.update(t - self.start);

                // If the camera moved since we last synced, write it back to
                // the document and mark the file dirty.
                let gen = self.tabs[i].scene.camera_generation;
                if gen != self.tabs[i].last_synced_camera_gen {
                    self.tabs[i].last_synced_camera_gen = gen;
                    if self.tabs[i].scene.sync_camera_to_document() {
                        self.tabs[i].dirty = true;
                    }
                }

                // Surface any plugin-guard panic messages that piled up since
                // the last tick (the host singleton isn't reachable from inside
                // the plugin hooks, so they queue and we flush here). (#145)
                #[cfg(not(target_arch = "wasm32"))]
                for msg in crate::plugin::drain_errors() {
                    self.command_line.push_error(&msg);
                }

                Task::none()
    }

    pub(super) fn on_set_render_mode(&mut self, mode: acadrust::entities::ViewportRenderMode) -> Task<Message> {
                use acadrust::entities::ViewportRenderMode as M;
                let i = self.active_tab;
                let label = match mode {
                    M::Wireframe2D => "Wireframe 2D",
                    M::Wireframe3D => "Wireframe 3D",
                    M::HiddenLine => "Hidden Line",
                    M::FlatShaded => "Flat Shaded",
                    M::GouraudShaded => "Gouraud Shaded",
                    M::FlatShadedWithEdges => "Flat Shaded + Edges",
                    M::GouraudShadedWithEdges => "Gouraud Shaded + Edges",
                };
                // In a paper layout with an active (double-clicked)
                // viewport, the picker drives that viewport entity's own
                // render mode; the model-layout tab style is untouched.
                if self.tabs[i].scene.set_active_viewport_render_mode(mode) {
                    self.tabs[i].scene.bump_geometry();
                    self.command_line
                        .push_output(&format!("Viewport visual style: {label}"));
                    return Task::none();
                }
                self.tabs[i].render_mode = mode;
                // Write the style onto the active Model tile alone so it
                // sticks when that tile loses focus and the other tiles keep
                // their own styles.
                self.tabs[i].scene.set_active_model_tile_render_mode(mode);
                // Keep the legacy `wireframe` bool synced — both wireframe
                // modes set it, everything else clears it.
                let wf = matches!(mode, M::Wireframe2D | M::Wireframe3D);
                self.tabs[i].wireframe = wf;
                self.ribbon.set_wireframe(wf);
                self.tabs[i].visual_style = label.into();
                // Re-upload face3d fills on the next frame — the render
                // pipeline keys its upload cache off `geometry_epoch`.
                self.tabs[i].scene.bump_geometry();
                self.command_line
                    .push_output(&format!("Visual style: {label}"));
                Task::none()
    }

    pub(super) fn on_cursor_moved(&mut self, p: Point) -> Task<Message> {
                // `p` is relative to the ViewCube hit area's top-left. Map
                // it back to full-canvas coordinates so ViewportClick's
                // hit-test lines up. The hit area sits in the top-right of
                // the full canvas in model space, or of the active
                // viewport's screen rectangle in a paper layout.
                let i = self.active_tab;
                let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
                let (ox, oy) = match self.tabs[i]
                    .scene
                    .active_viewport
                    .and_then(|h| self.tabs[i].scene.viewport_screen_rect(h, (vw, vh)))
                {
                    Some(rect) => (
                        rect.x + rect.width - VIEWCUBE_PAD - VIEWCUBE_HIT_SIZE,
                        rect.y + VIEWCUBE_PAD,
                    ),
                    None => {
                        // Model layout: the cube sits in the active tile's
                        // top-right corner.
                        let tb = self.tabs[i].scene.active_model_tile_bounds(vw, vh);
                        (
                            tb.x + tb.width - VIEWCUBE_PAD - VIEWCUBE_HIT_SIZE,
                            tb.y + VIEWCUBE_PAD,
                        )
                    }
                };
                self.cursor_pos = iced::Point::new(ox + p.x, oy + p.y);

                // Drive the ViewCube hover highlight directly from this
                // message — it fires whenever the cube's hit-area overlay
                // sees motion, so we don't depend on the shader widget's
                // `Program::update` receiving the same event (overlays sit
                // above the shader and can mask it). Map the cursor into
                // the active viewport's local box and use that box's size,
                // since that's where the cube is actually drawn.
                let tile = match self.tabs[i]
                    .scene
                    .active_viewport
                    .and_then(|h| self.tabs[i].scene.viewport_screen_rect(h, (vw, vh)))
                {
                    Some(rect) => rect,
                    None => self.tabs[i].scene.active_model_tile_bounds(vw, vh),
                };
                let cam_rot = self.tabs[i].scene.active_view_rotation_mat();
                let hover = hover_id(
                    self.cursor_pos.x - tile.x,
                    self.cursor_pos.y - tile.y,
                    tile.width,
                    tile.height,
                    cam_rot,
                    VIEWCUBE_PX,
                );
                self.tabs[i].scene.viewcube_hover.set(hover);
                Task::none()
    }

    pub(super) fn on_viewport_move(&mut self, p: Point) -> Task<Message> {
                let i = self.active_tab;

                // UCS icon grip drag: map the cursor onto the UCS plane and
                // slide the origin / rotate the axis. Short-circuits pan & snap.
                if let Some(kind) = self.ucs_grip_drag {
                    self.drag_ucs_grip(i, kind, p);
                    self.tabs[i].scene.selection.borrow_mut().last_move_pos = Some(p);
                    return Task::none();
                }

                // Keep the ViewCube hover in sync as the cursor leaves the
                // hit-area overlay and moves over the rest of the viewport.
                // `hover_id` returns None outside the cube box, which clears
                // any stale highlight from the previous `CursorMoved`.
                let (svw, svh) = self.tabs[i].scene.selection.borrow().vp_size;
                let cube_tile = match self.tabs[i]
                    .scene
                    .active_viewport
                    .and_then(|h| self.tabs[i].scene.viewport_screen_rect(h, (svw, svh)))
                {
                    Some(rect) => rect,
                    None => self.tabs[i].scene.active_model_tile_bounds(svw, svh),
                };
                let cam_rot = self.tabs[i].scene.active_view_rotation_mat();
                self.tabs[i].scene.viewcube_hover.set(hover_id(
                    p.x - cube_tile.x,
                    p.y - cube_tile.y,
                    cube_tile.width,
                    cube_tile.height,
                    cam_rot,
                    VIEWCUBE_PX,
                ));

                // Multi-functional grip hover: detect cursor sitting on a
                // selected entity's grip and, after a dwell, open the
                // popup menu. See scene::model::object::GripMenuItem.
                self.update_grip_hover(i, p);

                // UCS icon hover highlight (suppressed mid grip-drag).
                self.ucs_icon_hover = self.ucs_grip_drag.is_none()
                    && self
                        .ucs_icon_hit_info(i, svw, svh)
                        .map(|h| over_ucs_icon(p, &h))
                        .unwrap_or(false);

                let mut sel = self.tabs[i].scene.selection.borrow_mut();
                sel.last_move_pos = Some(p);

                if sel.left_down {
                    let press = sel.left_press_pos.unwrap_or(p);
                    let dx = p.x - press.x;
                    let dy = p.y - press.y;
                    let dist2 = dx * dx + dy * dy;
                    let elapsed_ms = sel
                        .left_press_time
                        .map(|t| Instant::now().duration_since(t).as_millis())
                        .unwrap_or(u128::MAX);
                    if !sel.left_dragging && elapsed_ms >= POLY_START_DELAY_MS && dist2 > 9.0 {
                        sel.left_dragging = true;
                        sel.poly_active = true;
                        sel.poly_crossing = p.x < press.x;
                        sel.poly_points.clear();
                        sel.poly_points.push(press);
                        sel.poly_points.push(p);
                    } else if sel.left_dragging && sel.poly_active {
                        if sel.poly_points.last().map_or(true, |lp| {
                            let ddx = p.x - lp.x;
                            let ddy = p.y - lp.y;
                            ddx * ddx + ddy * ddy > 16.0
                        }) {
                            sel.poly_points.push(p);
                        }
                    }
                } else if sel.box_anchor.is_some() {
                    sel.box_current = Some(p);
                    if let Some(a) = sel.box_anchor {
                        sel.box_crossing = p.x < a.x;
                    }
                }

                if sel.right_down {
                    // Time-based click-vs-orbit split: a quick right-click
                    // (press + release within RIGHT_HOLD_MS) is always a click —
                    // it opens the context menu / fires Enter on release, even if
                    // the pointer drifted a little. Orbit only engages once the
                    // button has been *held* past the threshold and the pointer
                    // is actually moving, so hand jitter during a click never
                    // promotes it to an orbit drag.
                    if !sel.right_dragging {
                        let held = sel
                            .right_press_time
                            .map(|t| t.elapsed().as_millis() >= RIGHT_HOLD_MS)
                            .unwrap_or(false);
                        let moved = sel
                            .right_press_pos
                            .map(|press| {
                                let (dx, dy) = (p.x - press.x, p.y - press.y);
                                dx * dx + dy * dy > 4.0
                            })
                            .unwrap_or(false);
                        if held && moved {
                            sel.right_dragging = true;
                            sel.context_menu = None;
                            // An orbit restarts the right-click cycle.
                            sel.right_click_entered = false;
                            // Start the orbit from the current position so the
                            // view doesn't jump by the pre-threshold movement.
                            sel.right_last_pos = Some(p);
                        }
                    }
                    if sel.right_dragging {
                        if let Some(last) = sel.right_last_pos {
                            let (dx, dy) = (p.x - last.x, p.y - last.y);
                            if self.tabs[i].scene.active_viewport.is_some() {
                                // Update position before dropping the borrow.
                                sel.right_last_pos = Some(p);
                                drop(sel);
                                self.tabs[i].scene.orbit_active_viewport(dx, dy);
                                // Bump so the GPU re-uploads the viewport's
                                // re-culled wire set after the view rotates.
                                self.tabs[i].scene.camera_generation += 1;
                                return Task::none();
                            } else if self.tabs[i].scene.current_layout == "Model" {
                                sel.right_last_pos = Some(p);
                                drop(sel);
                                self.tabs[i].scene.camera.borrow_mut().orbit(dx, dy);
                                self.tabs[i].scene.camera_generation += 1;
                                return Task::none();
                            } else {
                                // Paper sheet is top-locked: right-drag never
                                // orbits it (orbiting would corrupt the camera
                                // frame and skew subsequent pans).
                                sel.right_last_pos = Some(p);
                                return Task::none();
                            }
                        } else {
                            sel.right_last_pos = Some(p);
                        }
                    }
                }

                let (mid_down, mid_last, vp_size) =
                    (sel.middle_down, sel.middle_last_pos, sel.vp_size);
                if mid_down {
                    if let Some(last) = mid_last {
                        let (dx, dy) = (p.x - last.x, p.y - last.y);
                        // Pan scale uses the active tile's size (ortho size
                        // is relative to viewport height), so a tiled pane
                        // pans at the correct rate.
                        let bounds = self.tabs[i]
                            .scene
                            .active_model_tile_bounds(vp_size.0, vp_size.1);
                        // Drop `sel` before calling mutable scene methods.
                        drop(sel);
                        if self.tabs[i].scene.active_viewport.is_some() {
                            self.tabs[i].scene.pan_active_viewport(dx, dy, bounds);
                            // Bump so the GPU re-uploads the viewport's re-culled
                            // wire set — otherwise newly-revealed lines stay
                            // invisible until MSPACE is exited.
                            self.tabs[i].scene.camera_generation += 1;
                        } else {
                            // `bounds` is the active tile; pan by its height so
                            // the point under the cursor tracks correctly.
                            self.tabs[i].scene.camera.borrow_mut().pan_screen(
                                dx,
                                dy,
                                bounds.height,
                            );
                            self.tabs[i].scene.camera_generation += 1;
                        }
                        self.tabs[i].scene.selection.borrow_mut().middle_last_pos = Some(p);
                        return Task::none();
                    }
                    sel.middle_last_pos = Some(p);
                }

                let dragging = sel.left_down || sel.right_down || sel.middle_down;
                let vp_size = sel.vp_size;
                drop(sel);

                // The active pane already follows the cursor (each pane's own
                // mouse_area focuses it via `PaneMove` → `focus_model_pane`), so
                // the camera + tile bounds used for picking below are already the
                // pane the cursor is in.

                // Tile-relative picking: shadow `p` with the cursor mapped
                // into the active Model tile and `vp_size` with the tile's
                // size, so every pick / snap / view_proj below operates in
                // the active pane. `p_full` keeps the canvas-space cursor
                // for screen overlays (cursor marker, snap glyph).
                let p_full = p;
                // Inside a floating viewport (MSPACE) the active "pane" is the
                // viewport's own screen rectangle and its own camera — the very
                // camera the GPU draws the content with. Routing picking / snap
                // / projection through it makes in-viewport editing behave like
                // the main model view (model coords, no paper round-trip) and
                // track the viewport's pan / zoom / twist exactly.
                let edit_frame = self.tabs[i].scene.viewport_edit_frame(vp_size);
                let tile_b = match &edit_frame {
                    Some((_, full)) => *full,
                    None => self.tabs[i]
                        .scene
                        .active_model_tile_bounds(vp_size.0, vp_size.1),
                };
                let edit_cam = edit_frame.map(|(cam, _)| cam);
                let p = iced::Point {
                    x: p_full.x - tile_b.x,
                    y: p_full.y - tile_b.y,
                };
                let vp_size = (tile_b.width, tile_b.height);

                // ── Grip drag ─────────────────────────────────────────────
                if let Some(grip) = self.tabs[i].active_grip.clone() {
                    let (vw, vh) = vp_size;
                    let bounds = iced::Rectangle {
                        x: 0.0,
                        y: 0.0,
                        width: vw,
                        height: vh,
                    };
                    // In a viewport, pick the cursor's model point with the
                    // viewport camera directly; otherwise project on the paper
                    // sheet and map to model. Either way `raw` is model space.
                    let raw = match &edit_cam {
                        Some(cam) => cam.pick_on_target_plane(p, bounds),
                        None => {
                            let paper = self
                                .tabs[i]
                                .scene
                                .camera
                                .borrow()
                                .pick_on_target_plane(p, bounds);
                            self.tabs[i].scene.paper_to_model(paper)
                        }
                    };
                    let (view_rot, eye) = match &edit_cam {
                        Some(cam) => (cam.view_proj_rte(bounds), cam.eye()),
                        None => {
                            let cam = self.tabs[i].scene.camera.borrow();
                            (cam.view_proj_rte(bounds), cam.eye())
                        }
                    };

                    // First move of this drag: hide the edited entity from the
                    // base tessellation (one re-tess) so subsequent moves only
                    // refresh a cheap overlay preview instead of re-tessellating
                    // the whole model on every move.
                    if self.grip_preview_handle != Some(grip.handle) {
                        if let Some(prev) = self.grip_preview_handle.take() {
                            self.tabs[i].scene.hidden.remove(&prev);
                        }
                        // Back up the original geometry so Esc can cancel the drag.
                        self.grip_original =
                            self.tabs[i].scene.document.get_entity(grip.handle).cloned();
                        self.tabs[i].scene.hidden.insert(grip.handle);
                        // Grip drag never changes a block definition — keep the
                        // block cache so the hide doesn't re-tessellate blocks.
                        self.tabs[i].scene.bump_geometry_no_blocks();
                        self.grip_preview_handle = Some(grip.handle);
                    }

                    // The edited entity is hidden, so it's already absent from
                    // `hit_test_wires` — snap against the set directly, no clone
                    // and no self-snap.
                    let all_wires = if let (Some(_), Some(h)) =
                        (&edit_cam, self.tabs[i].scene.active_viewport)
                    {
                        self.tabs[i].scene.model_wires_for_viewport_arc(h, bounds.height)
                    } else {
                        self.tabs[i].scene.hit_test_wires()
                    };
                    // Grip drag has no single rubber-band origin for a perp foot.
                    self.snapper.from_point = None;
                    let (go, gr) = self.tabs[i].ucs_grid_basis();
                    // `raw` is already model space (viewport camera or paper→model),
                    // and the wires are model space, so the snap result is model.
                    let snap_hit = self
                        .snapper
                        .snap(raw, p, &all_wires[..], view_rot, eye, bounds, go, gr);
                    let mut snapped = snap_hit.map(|s| s.world).unwrap_or(raw);
                    self.tabs[i].snap_result = snap_hit;
                    if let Some(s) = self.tabs[i].snap_result.as_mut() {
                        s.screen.x += tile_b.x;
                        s.screen.y += tile_b.y;
                    }

                    if snap_hit.is_none() {
                        let base = grip.origin_world.as_vec3();
                        let ucs_xf = self.tabs[i].ucs_xform();
                        if self.ortho_mode {
                            snapped = ortho_constrain(snapped.as_vec3(), base, &ucs_xf).as_dvec3();
                        } else if self.polar_mode {
                            snapped = polar_constrain_near(
                                snapped.as_vec3(),
                                base,
                                self.polar_increment_deg,
                                view_rot,
                                eye,
                                bounds,
                                self.snapper.osnap_radius_px,
                                &ucs_xf,
                            )
                            .as_dvec3();
                        }
                    }

                    let apply = if grip.is_translate {
                        GripApply::Translate(snapped - grip.last_world)
                    } else {
                        GripApply::Absolute(snapped)
                    };
                    self.tabs[i]
                        .scene
                        .apply_grip(grip.handle, grip.grip_id, apply);
                    self.tabs[i].dirty = true;
                    self.tabs[i].active_grip.as_mut().unwrap().last_world = snapped;
                    // Overlay the moved entity (hidden from the base) — no base
                    // re-tessellation, just a one-entity preview tessellation.
                    let preview = self.tabs[i].scene.wire_models_for(&[grip.handle]);
                    self.tabs[i].scene.set_preview_wires(preview);
                    self.refresh_selected_grips();
                    self.refresh_properties();
                    return Task::none();
                }

                // Keep the coordinate readout live on every move, even with no
                // active command. When a command is running the snap path below
                // overwrites this with the snapped point.
                {
                    let bounds = iced::Rectangle {
                        x: 0.0,
                        y: 0.0,
                        width: vp_size.0,
                        height: vp_size.1,
                    };
                    let world = self.cursor_model_point(i, &edit_cam, p, bounds);
                    self.tabs[i].last_cursor_world = world.as_vec3();
                }

                // Rollover highlight: when idle (no active command, no
                // drag), defer the pick until the cursor stops. The full
                // pick (wires + hatches + block hatches + shaded meshes) is
                // O(N) per frame and stalls the cursor on large drawings,
                // so each move clears the current highlight and resets the
                // dwell timer — `HoverDwellTick` runs the hit-test only
                // once the cursor has been still for `HOVER_DWELL_MS`.
                if !dragging && self.tabs[i].active_cmd.is_none() {
                    self.tabs[i].scene.set_hover_highlight(None);
                    self.hover_dwell = Some(crate::app::HoverDwell {
                        last_move_at: Instant::now(),
                        point: p,
                        tile_size: vp_size,
                        tab: i,
                    });
                } else {
                    // Suppress the rollover during a command or a drag.
                    self.tabs[i].scene.set_hover_highlight(None);
                    self.hover_dwell = None;
                }

                if self.tabs[i].active_cmd.is_some() {
                    let (vw, vh) = vp_size;
                    let bounds = iced::Rectangle {
                        x: 0.0,
                        y: 0.0,
                        width: vw,
                        height: vh,
                    };
                    // Inside a floating viewport the cursor, camera and wires are
                    // all model-space (the viewport's own camera draws the
                    // content), so snap / hit-test / preview run exactly like the
                    // main model view — no paper projection, tracks pan/zoom/twist.
                    let cursor_world = self.cursor_model_point(i, &edit_cam, p, bounds);
                    let (view_rot, eye) = match &edit_cam {
                        Some(cam) => (cam.view_proj_rte(bounds), cam.eye()),
                        None => {
                            let cam = self.tabs[i].scene.camera.borrow();
                            (cam.view_proj_rte(bounds), cam.eye())
                        }
                    };
                    // Sync grid-snap spacing to the adaptive spacing of the visible grid.
                    self.snapper.grid_spacing =
                        crate::ui::overlay::compute_grid_step(view_rot, bounds);
                    // Cursor and wires are model-space; the snap result is model.
                    let snap_cursor = cursor_world;

                    let all_wires = if let (Some(_), Some(h)) =
                        (&edit_cam, self.tabs[i].scene.active_viewport)
                    {
                        self.tabs[i].scene.model_wires_for_viewport_arc(h, bounds.height)
                    } else {
                        self.tabs[i].scene.hit_test_wires()
                    };
                    let needs_entity = self.tabs[i]
                        .active_cmd
                        .as_ref()
                        .map(|c| c.needs_entity_pick())
                        .unwrap_or(false);
                    let needs_structure = self.tabs[i]
                        .active_cmd
                        .as_ref()
                        .map(|c| c.needs_structure_point_pick())
                        .unwrap_or(false);
                    let is_gathering = self.tabs[i]
                        .active_cmd
                        .as_ref()
                        .map(|c| c.is_selection_gathering())
                        .unwrap_or(false);
                    let needs_tan = self.tabs[i]
                        .active_cmd
                        .as_ref()
                        .map(|c| c.needs_tangent_pick())
                        .unwrap_or(false);
                    self.tabs[i].snap_result = if needs_entity || is_gathering || needs_structure {
                        None
                    } else if needs_tan {
                        self.snapper.snap_tangent_only(
                            snap_cursor.as_vec3(),
                            p,
                            &all_wires[..],
                            view_rot,
                            eye,
                            bounds,
                        )
                    } else {
                        let (go, gr) = self.tabs[i].ucs_grid_basis();
                        self.snapper.from_point = self.last_point;
                        self.snapper
                            .snap(snap_cursor, p, &all_wires[..], view_rot, eye, bounds, go, gr)
                    };

                    // Object Snap Tracking: update dwell, then align the cursor
                    // to a tracking ray (and store the alignment so a typed
                    // distance can place a point along it — issue #69).
                    let otrack_hit = {
                        let snap_world = self.tabs[i].snap_result.map(|s| s.world.as_vec3());
                        self.snapper.update_otrack_dwell(
                            snap_world,
                            view_rot,
                            eye,
                            bounds,
                            Instant::now(),
                        );
                        if self.tabs[i].snap_result.is_none() {
                            let step = if self.polar_mode {
                                Some(self.polar_increment_deg)
                            } else {
                                None
                            };
                            let ucs = self.tabs[i].scene.viewcube_ucs_mat();
                            self.snapper.otrack_snap(
                                cursor_world.as_vec3(),
                                view_rot,
                                eye,
                                bounds,
                                step,
                                self.last_point,
                                ucs,
                            )
                        } else {
                            None
                        }
                    };
                    self.otrack_active = otrack_hit.map(|h| (h.base, h.dir));

                    let effective = {
                        let mut pt: glam::DVec3 = if let Some(h) = otrack_hit {
                            // Tracking alignment wins over the free cursor;
                            // ortho/polar don't re-constrain it.
                            h.aligned.as_dvec3()
                        } else {
                            // Snap runs in model space (viewport camera or the
                            // model/paper view), so the result is already model.
                            let mut pt = self.tabs[i]
                                .snap_result
                                .map(|s| s.world)
                                .unwrap_or(cursor_world);
                            // Object snap wins over ortho/polar: a snapped point
                            // is taken as-is so it isn't pulled onto the ortho
                            // axis. Grid snap is positional, not an object snap,
                            // so it still combines with ortho/polar. (#132)
                            let osnap_locked = self.tabs[i]
                                .snap_result
                                .is_some_and(|s| s.snap_type != crate::snap::SnapType::Grid);
                            if !osnap_locked {
                                if let Some(base) = self.last_point {
                                    let ucs_xf = self.tabs[i].ucs_xform();
                                    if self.ortho_mode {
                                        pt = ortho_constrain(pt.as_vec3(), base, &ucs_xf)
                                            .as_dvec3();
                                    } else if self.polar_mode {
                                        pt = polar_constrain_near(
                                            pt.as_vec3(),
                                            base,
                                            self.polar_increment_deg,
                                            view_rot,
                                            eye,
                                            bounds,
                                            self.snapper.osnap_radius_px,
                                            &ucs_xf,
                                        )
                                        .as_dvec3();
                                    }
                                }
                            }
                            pt
                        };
                        // Clamp to world XY only when no UCS is active; with a
                        // UCS the point already lies on the UCS XY plane.
                        if self.tabs[i].active_cmd.is_some() && self.tabs[i].active_ucs.is_none() {
                            pt.z = 0.0;
                        }
                        pt
                    };
                    self.tabs[i].last_cursor_world = effective.as_vec3();
                    self.tabs[i].last_cursor_screen = p_full;
                    // Project the step anchor (an explicit `dyn_anchor` or the
                    // last point) so the dynamic-input overlay can place its
                    // guide geometry and labels.
                    // `proj` returns a pane-local pixel; shift by the active pane
                    // origin (`tile_b`, the viewport rect inside a viewport) so
                    // the DYN guide/labels share the canvas frame with
                    // `last_cursor_screen` (= p_full, canvas space).
                    let proj = |bp: glam::Vec3| {
                        let ndc = view_rot.project_point3((bp.as_dvec3() - eye).as_vec3());
                        iced::Point::new(
                            (ndc.x + 1.0) * 0.5 * bounds.width + tile_b.x,
                            (1.0 - ndc.y) * 0.5 * bounds.height + tile_b.y,
                        )
                    };
                    // Anchors are stored in model coords and `proj` (view_rot /
                    // eye) is the model→screen view — the viewport camera inside
                    // a viewport, the model/paper camera otherwise — so feed them
                    // straight through; no paper mapping needed.
                    let anchor = self.tabs[i].dyn_anchor.or(self.last_point);
                    let dyn_ref = self.tabs[i].dyn_ref;
                    let lps = anchor.map(|a| proj(a));
                    let drs = dyn_ref.map(|r| proj(r));
                    self.tabs[i].last_point_screen = lps;
                    self.tabs[i].dyn_ref_screen = drs;

                    // Entity-pick previews (TRIM/EXTEND/FILLET…) compare the
                    // cursor against WCS document entities and return WCS wires.
                    // `effective` is offset-relative, so build a WCS copy for
                    // the click and shift the returned wires back to the
                    // offset-relative frame the renderer expects (model space
                    // only; paper-space entities use sheet coordinates).
                    let wo_local = if self.tabs[i].scene.current_layout == "Model" {
                        [0.0_f64; 3]
                    } else {
                        [0.0; 3]
                    };
                    let wo_f = glam::DVec3::new(wo_local[0], wo_local[1], wo_local[2]);
                    let effective_wcs = effective + wo_f;

                    // Orange object snap (plugin commands implement resolve_object_pick).
                    if needs_structure {
                        use crate::snap::{SnapResult, SnapType};
                        let pick = self.tabs[i].active_cmd.as_ref().and_then(|c| {
                            c.resolve_object_pick(
                                &self.tabs[i].scene,
                                effective.x as f64,
                                effective.y as f64,
                            )
                        });
                        if let Some(pick) = pick {
                            let world = glam::DVec3::new(pick.x, pick.y, effective.z);
                            let ndc = view_rot.project_point3((world - eye).as_vec3());
                            let screen = iced::Point::new(
                                (ndc.x + 1.0) * 0.5 * bounds.width,
                                (1.0 - ndc.y) * 0.5 * bounds.height,
                            );
                            self.tabs[i].snap_result = Some(SnapResult {
                                world,
                                screen,
                                snap_type: SnapType::ObjectPick,
                                tangent_obj: None,
                            });
                            if let Some(cmd) = self.tabs[i].active_cmd.as_mut() {
                                cmd.set_acquisition_hint(Some(pick.label));
                            }
                        } else if let Some(cmd) = self.tabs[i].active_cmd.as_mut() {
                            cmd.set_acquisition_hint(None);
                        }
                    }

                    // Snap glyph is positioned in canvas space; shift the
                    // tile-local snap screen point back to the full canvas.
                    if let Some(s) = self.tabs[i].snap_result.as_mut() {
                        s.screen.x += tile_b.x;
                        s.screen.y += tile_b.y;
                    }

                    // Give the command the current UCS before it builds its
                    // rubber-band preview (and, by persistence, its commit).
                    self.push_ucs_to_cmd(i);
                    let mut previews = if needs_structure {
                        let mut p = self.tabs[i]
                            .active_cmd
                            .as_ref()
                            .map(|c| c.object_pick_hover_previews(&self.tabs[i].scene, effective))
                            .unwrap_or_default();
                        if let Some(cmd) = self.tabs[i].active_cmd.as_mut() {
                            p.extend(cmd.on_preview_wires(effective));
                        }
                        p
                    } else if needs_entity {
                        let hover_handle =
                            scene::pick::hit_test::click_hit(p, &all_wires[..], view_rot, eye, bounds)
                                .and_then(|s| Scene::handle_from_wire_name(s))
                                .unwrap_or(acadrust::Handle::NULL);
                        let mut p = self.tabs[i]
                            .active_cmd
                            .as_mut()
                            .map(|c| c.on_hover_entity(hover_handle, effective_wcs))
                            .unwrap_or_default();
                        // on_hover_entity returns WCS wires; shift to the
                        // offset-relative frame so the preview lands on the
                        // geometry on large-coordinate drawings.
                        if wo_f != glam::DVec3::ZERO {
                            for w in p.iter_mut() {
                                for pt in w.points.iter_mut() {
                                    pt[0] -= wo_f.x as f32;
                                    pt[1] -= wo_f.y as f32;
                                    pt[2] -= wo_f.z as f32;
                                }
                            }
                        }
                        if !hover_handle.is_null() {
                            if let Some(cmd) = self.tabs[i].active_cmd.as_ref() {
                                p.extend(cmd.entity_pick_acquire_previews(
                                    &self.tabs[i].scene,
                                    hover_handle,
                                ));
                            }
                            if let Some(cmd) = self.tabs[i].active_cmd.as_mut() {
                                if let Some(hint) = cmd.entity_pick_acquire_hint(hover_handle) {
                                    cmd.set_acquisition_hint(Some(hint));
                                }
                            }
                        }
                        p
                    } else {
                        self.tabs[i]
                            .active_cmd
                            .as_mut()
                            .map(|c| c.on_preview_wires(effective))
                            .unwrap_or_default()
                    };
                    // Polar tracking guide line: dotted line from last_point along
                    // the snapped angle direction, extending across the drawing.
                    if self.polar_mode && !needs_entity {
                        if let Some(base) = self.last_point {
                            let effective = effective.as_vec3();
                            let dx = effective.x - base.x;
                            let dy = effective.y - base.y;
                            // Only show the guide while POLAR is actually engaged
                            // — i.e. the point is snapped onto a polar ray, not
                            // floating free near no angle (issue #70).
                            let step = self.polar_increment_deg.to_radians();
                            let angle = dy.atan2(dx);
                            let snapped =
                                step > 1e-6 && ((angle / step).round() * step - angle).abs() < 1e-3;
                            if snapped && (dx * dx + dy * dy).sqrt() > 1e-4 {
                                let far = 1e5_f32;
                                let dir = glam::Vec3::new(dx, dy, 0.0).normalize();
                                let far_pos = base + dir * far;
                                let far_neg = base - dir * far;
                                let guide = crate::scene::WireModel {
                                    name: "__polar_guide__".into(),
                                    points: vec![
                                        [far_neg.x, far_neg.y, far_neg.z],
                                        [far_pos.x, far_pos.y, far_pos.z],
                                    ],
                                    points_low: Vec::new(),
                                    color: [0.2, 0.7, 0.9, 0.6],
                                    selected: false,
                                    aci: 0,
                                    pattern_length: 0.8,
                                    pattern: [0.5, -0.3, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0],
                                    line_weight_px: 1.0,
                                    snap_pts: vec![],
                                    tangent_geoms: vec![],
                                    key_vertices: vec![],
                                    aabb: crate::scene::WireModel::UNBOUNDED_AABB,
                                    plinegen: true,
                                    vp_scissor: None,
                                    fill_tris: vec![],
                                    fill_tris_low: Vec::new(),
                                };
                                previews.push(guide);
                            }
                        }
                    }
                    // OTRACK alignment guide: dashed ray through the tracking
                    // point along the aligned direction (issue #69).
                    if let Some(h) = otrack_hit {
                        if !needs_entity {
                            let far = 1e5_f32;
                            let far_pos = h.base + h.dir * far;
                            let far_neg = h.base - h.dir * far;
                            previews.push(crate::scene::WireModel {
                                name: "__otrack_guide__".into(),
                                points: vec![
                                    [far_neg.x, far_neg.y, far_neg.z],
                                    [far_pos.x, far_pos.y, far_pos.z],
                                ],
                                points_low: Vec::new(),
                                color: [0.2, 0.9, 0.5, 0.6],
                                selected: false,
                                aci: 0,
                                pattern_length: 0.8,
                                pattern: [0.5, -0.3, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0],
                                line_weight_px: 1.0,
                                snap_pts: vec![],
                                tangent_geoms: vec![],
                                key_vertices: vec![],
                                aabb: crate::scene::WireModel::UNBOUNDED_AABB,
                                plinegen: true,
                                vp_scissor: None,
                                fill_tris: vec![],
                                fill_tris_low: Vec::new(),
                            });
                        }
                    }
                    self.tabs[i].scene.set_preview_wires(previews);
                } else {
                    self.tabs[i].snap_result = None;
                }

                self.sync_dyn_fields();
                Task::none()
    }

    pub(super) fn on_viewport_exit(&mut self) -> Task<Message> {
                let i = self.active_tab;
                let mut sel = self.tabs[i].scene.selection.borrow_mut();
                sel.left_down = false;
                sel.left_press_pos = None;
                sel.left_press_time = None;
                sel.left_dragging = false;
                sel.right_down = false;
                sel.right_press_pos = None;
                sel.right_press_time = None;
                sel.right_last_pos = None;
                sel.right_dragging = false;
                sel.right_click_entered = false;
                sel.middle_down = false;
                sel.middle_last_pos = None;
                sel.box_anchor = None;
                sel.box_current = None;
                sel.box_crossing = false;
                sel.poly_active = false;
                sel.poly_points.clear();
                sel.poly_crossing = false;
                drop(sel);
                // Clear the rollover highlight when the cursor leaves the
                // viewport so it doesn't stick while the mouse is over the
                // ribbon / panels.
                self.tabs[i].scene.set_hover_highlight(None);
                // Don't touch `context_menu` here. ViewportExit also fires
                // when an upper overlay (the right-click menu panel) takes
                // the cursor, so clearing the menu state on every exit
                // would close the menu the moment it opens. Outside-click
                // dismiss is handled in `ViewportLeftPress`.
                Task::none()
    }

    /// Screen positions of the UCS-icon grips (origin + axis tips, absolute px)
    /// for the active pane, or `None` when the icon is not shown / not anchored
    /// at its on-screen origin / a command is active. The single source of truth
    /// for both hover and grip hit-testing, so they match what is drawn.
    fn ucs_icon_hit_info(&self, i: usize, vw: f32, vh: f32) -> Option<crate::ui::overlay::UcsIconHit> {
        if !self.show_ucs_icon || self.tabs[i].active_cmd.is_some() {
            return None;
        }
        let tab = &self.tabs[i];
        let (_, ux, uy, uz) = tab.ucs_xform().axes();
        // Project through whichever pane owns the icon — a floating viewport's
        // own camera, else the active model tile. Bare paper space shows none.
        let (cam, bounds) = if let Some((c, full)) = tab.scene.viewport_edit_frame((vw, vh)) {
            (c, full)
        } else if tab.scene.current_layout == "Model" {
            (
                tab.scene.camera.borrow().clone(),
                tab.scene.active_model_tile_bounds(vw, vh),
            )
        } else {
            return None;
        };
        // Mirror the draw: anchor at the projected origin only when ORigin mode
        // is on AND the origin is on-screen; otherwise `None` parks it in the
        // corner — still selectable/draggable there.
        let os = if self.ucs_icon_at_origin {
            cam.project(tab.ucs_origin_world(), bounds)
                .map(|q| Point::new(bounds.x + q.x, bounds.y + q.y))
        } else {
            None
        };
        crate::ui::overlay::ucs_icon_hit(cam.view_proj_rte(bounds), bounds, (ux, uy, uz), os)
    }

    /// Apply one frame of a UCS-icon grip drag: map the cursor onto the active
    /// UCS plane (so the move stays in-plane) and either slide the origin there
    /// or rotate the chosen axis to point at it, keeping a right-handed frame
    /// with Z fixed. Live — the commit (persist) happens on release.
    fn drag_ucs_grip(&mut self, i: usize, kind: crate::app::UcsGripKind, p_full: Point) {
        let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
        if vw <= 1.0 || vh <= 1.0 {
            return;
        }
        // Same pane framing as the rest of the move handler: pane-local cursor
        // and origin-zero bounds, with the floating-viewport camera when inside
        // one. `cursor_model_point` handles the paper→model round-trip.
        let edit_frame = self.tabs[i].scene.viewport_edit_frame((vw, vh));
        let tile_b = match &edit_frame {
            Some((_, full)) => *full,
            None => self.tabs[i].scene.active_model_tile_bounds(vw, vh),
        };
        let edit_cam = edit_frame.map(|(cam, _)| cam);
        let p = Point::new(p_full.x - tile_b.x, p_full.y - tile_b.y);
        let bounds = iced::Rectangle {
            x: 0.0,
            y: 0.0,
            width: tile_b.width,
            height: tile_b.height,
        };
        let raw = self.cursor_model_point(i, &edit_cam, p, bounds);

        // Object/grid snap, same path as an entity grip or command drag: the
        // dragged UCS point sticks to endpoints/midpoints/grid under the cursor,
        // and the snap marker is published via `snap_result`.
        let (view_rot, eye) = match &edit_cam {
            Some(cam) => (cam.view_proj_rte(bounds), cam.eye()),
            None => {
                let cam = self.tabs[i].scene.camera.borrow();
                (cam.view_proj_rte(bounds), cam.eye())
            }
        };
        let all_wires = if let (Some(_), Some(h)) =
            (&edit_cam, self.tabs[i].scene.active_viewport)
        {
            self.tabs[i].scene.model_wires_for_viewport_arc(h, bounds.height)
        } else {
            self.tabs[i].scene.hit_test_wires()
        };
        self.snapper.grid_spacing = crate::ui::overlay::compute_grid_step(view_rot, bounds);
        // No rubber-band origin (perp/extension feet don't apply to a free drag).
        self.snapper.from_point = None;
        let (go, gr) = self.tabs[i].ucs_grid_basis();
        let snap_hit = self
            .snapper
            .snap(raw, p, &all_wires[..], view_rot, eye, bounds, go, gr);
        let world = snap_hit.map(|s| s.world).unwrap_or(raw);
        self.tabs[i].snap_result = snap_hit;
        if let Some(s) = self.tabs[i].snap_result.as_mut() {
            // Snap marker is pane-local; lift it to absolute canvas px.
            s.screen.x += tile_b.x;
            s.screen.y += tile_b.y;
        }

        use acadrust::types::Vector3;
        let v3 = |d: glam::DVec3| Vector3::new(d.x, d.y, d.z);
        {
            let ucs = self.tabs[i]
                .active_ucs
                .get_or_insert_with(|| acadrust::tables::Ucs::new("*ACTIVE*"));
            match kind {
                crate::app::UcsGripKind::Origin => {
                    ucs.origin = v3(world);
                }
                crate::app::UcsGripKind::XAxis | crate::app::UcsGripKind::YAxis => {
                    let o = glam::dvec3(ucs.origin.x, ucs.origin.y, ucs.origin.z);
                    let x = glam::dvec3(ucs.x_axis.x, ucs.x_axis.y, ucs.x_axis.z);
                    let y = glam::dvec3(ucs.y_axis.x, ucs.y_axis.y, ucs.y_axis.z);
                    let z = x.cross(y).normalize_or(glam::DVec3::Z);
                    // Direction from origin to cursor, flattened into the UCS
                    // plane; bail on a degenerate (cursor on the origin).
                    let dir = world - o;
                    let d = dir - z * dir.dot(z);
                    if d.length_squared() < 1e-12 {
                        return;
                    }
                    let d = d.normalize();
                    // Z fixed; the dragged axis = d, the other = right-handed
                    // completion (z×x = y, y×z = x).
                    let (nx, ny) = match kind {
                        crate::app::UcsGripKind::XAxis => (d, z.cross(d)),
                        _ => (d.cross(z), d),
                    };
                    ucs.x_axis = v3(nx);
                    ucs.y_axis = v3(ny);
                }
            }
        }
        self.tabs[i].sync_ucs_to_scene();
        self.tabs[i].dirty = true;
        self.tabs[i].scene.camera_generation += 1;
    }

    // ── Per-pane Model viewport (pane_grid) ───────────────────────────────

    /// Focus Model pane `idx` (cursor entered it): swap in its camera, sync the
    /// render-mode / grid display. No-op if already active.
    pub(super) fn focus_model_pane(&mut self, idx: usize) {
        let i = self.active_tab;
        if self.tabs[i].scene.set_active_model_tile(idx) {
            self.tabs[i].scene.camera_generation += 1;
            self.sync_render_mode_to_active_tile(i);
            self.adopt_view_display(i);
        }
    }

    /// Convert a pane-local cursor point (from the pane's `mouse_area`) to the
    /// canvas-relative point the viewport handlers expect.
    pub(super) fn pane_canvas_point(&self, idx: usize, local: Point) -> Point {
        let i = self.active_tab;
        let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
        let o = self.tabs[i].scene.pane_origin_px(idx, vw, vh);
        Point::new(o.x + local.x, o.y + local.y)
    }

    pub(super) fn on_pane_resized(
        &mut self,
        ev: iced::widget::pane_grid::ResizeEvent,
    ) -> Task<Message> {
        let i = self.active_tab;
        self.tabs[i].scene.model_panes.resize(ev.split, ev.ratio);
        let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
        self.tabs[i].scene.sync_tiles_from_panes(vw, vh);
        self.tabs[i].scene.camera_generation += 1;
        Task::none()
    }

    pub(super) fn on_pane_clicked(
        &mut self,
        pane: iced::widget::pane_grid::Pane,
    ) -> Task<Message> {
        let i = self.active_tab;
        if let Some(&idx) = self.tabs[i].scene.model_panes.get(pane) {
            self.focus_model_pane(idx);
        }
        Task::none()
    }

    pub(super) fn on_pane_dragged(
        &mut self,
        ev: iced::widget::pane_grid::DragEvent,
    ) -> Task<Message> {
        if let iced::widget::pane_grid::DragEvent::Dropped { pane, target } = ev {
            let i = self.active_tab;
            self.tabs[i].scene.model_panes.drop(pane, target);
            let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
            self.tabs[i].scene.sync_tiles_from_panes(vw, vh);
            self.tabs[i].scene.camera_generation += 1;
        }
        Task::none()
    }

    pub(super) fn on_viewport_left_press(&mut self) -> Task<Message> {
                let i = self.active_tab;
                // A left-click during a command resets the right-click cycle, so
                // the next right-click acts as Enter again rather than opening
                // the context menu.
                self.tabs[i].scene.selection.borrow_mut().right_click_entered = false;
                // A click in the viewport dismisses any open ribbon dropdown
                // (e.g. the annotation style combo), which has no backdrop of
                // its own to catch outside clicks.
                self.ribbon.close_dropdown();
                // Likewise dismiss the Properties color dropdowns — a viewport
                // press starts a box selection, so without this they'd only
                // close on the second click (issue #104).
                self.tabs[i].properties.color_picker_open = false;
                self.tabs[i].properties.color_palette_open = false;
                // Click anywhere outside the popup dismisses it. The
                // menu's own buttons live above this mouse_area, so a
                // press that reaches here means the cursor is not on
                // any menu item.
                if self.grip_popup.take().is_some() {
                    self.grip_hover = None;
                    return Task::none();
                }
                // Outside-click dismiss for the visibility-state dropdown
                // (its buttons sit above this mouse_area).
                if self.visibility_popup.take().is_some() {
                    return Task::none();
                }
                // Same dismiss-on-outside-click for the right-click
                // context menu: its panel is opaque, so a press that
                // reaches here is outside the menu.
                {
                    let mut sel = self.tabs[i].scene.selection.borrow_mut();
                    if sel.context_menu.take().is_some() {
                        return Task::none();
                    }
                }
                let (p, vp_size) = {
                    let sel = self.tabs[i].scene.selection.borrow();
                    let p = match sel.last_move_pos {
                        Some(p) => p,
                        None => return Task::none(),
                    };
                    (p, sel.vp_size)
                };
                let (vw, vh) = vp_size;

                // PAN mode: a left press begins a pan drag. Reuse the middle-
                // button pan path (the move handler pans whenever `middle_down`),
                // so no selection/pick logic runs while panning.
                if self.tabs[i].pan_mode {
                    let mut sel = self.tabs[i].scene.selection.borrow_mut();
                    sel.middle_down = true;
                    sel.middle_last_pos = Some(p);
                    return Task::none();
                }

                if vw > 1.0 && vh > 1.0 {
                    let rot = self.tabs[i].scene.active_view_rotation_mat();
                    // Map the cursor into whichever area owns the cube (active
                    // viewport rect in paper, active tile in model) so the
                    // consume-check lines up with the gizmo — same framing as
                    // ViewportClick's snap hit-test.
                    let (cx, cy, w, h) = match self.tabs[i]
                        .scene
                        .active_viewport
                        .and_then(|hndl| self.tabs[i].scene.viewport_screen_rect(hndl, (vw, vh)))
                    {
                        Some(rect) => (p.x - rect.x, p.y - rect.y, rect.width, rect.height),
                        None => {
                            let tb = self.tabs[i].scene.active_model_tile_bounds(vw, vh);
                            (p.x - tb.x, p.y - tb.y, tb.width, tb.height)
                        }
                    };
                    if scene::hit_test(cx, cy, w, h, rot, VIEWCUBE_PX).is_some() {
                        return Task::none();
                    }
                }

                // UCS icon: click to select (grips appear), then drag a grip to
                // move/rotate. A click off the icon clears the selection. Works
                // in the corner too (parked icon), not just at the origin.
                if self.show_ucs_icon && self.tabs[i].active_cmd.is_none() {
                    if let Some(hit) = self.ucs_icon_hit_info(i, vw, vh) {
                        // Already selected → a press on a grip starts the drag.
                        if self.ucs_icon_selected {
                            if let Some(kind) = ucs_grip_under(p, &hit) {
                                self.ucs_grip_drag = Some(kind);
                                return Task::none();
                            }
                        }
                        // Press on the icon body selects it (and shows grips).
                        if over_ucs_icon(p, &hit) {
                            self.ucs_icon_selected = true;
                            self.ucs_icon_hover = true;
                            return Task::none();
                        }
                    }
                    // Press elsewhere drops the selection, then falls through to
                    // the normal pick / box-select so the click still lands.
                    self.ucs_icon_selected = false;
                }

                // Divider resize is handled natively by the input pane_grid
                // (`on_resize`); the active pane already follows the cursor via
                // `focus_model_pane`. So a press here goes straight to picking.

                // From here the click targets the active tile: map the
                // cursor into it and use the tile's size for picking, so
                // grip / selection hit-tests land in the right pane.
                let p_full = p;
                // Inside a floating viewport the pane is the viewport's own rect
                // + camera (matches the GPU); otherwise the active model tile.
                let edit_frame = self.tabs[i].scene.viewport_edit_frame((vw, vh));
                let tile_b = match &edit_frame {
                    Some((_, full)) => *full,
                    None => self.tabs[i].scene.active_model_tile_bounds(vw, vh),
                };
                let edit_cam = edit_frame.map(|(cam, _)| cam);
                let p = iced::Point {
                    x: p_full.x - tile_b.x,
                    y: p_full.y - tile_b.y,
                };
                let (vw, vh) = (tile_b.width, tile_b.height);
                let bounds = iced::Rectangle {
                    x: 0.0,
                    y: 0.0,
                    width: vw,
                    height: vh,
                };

                if self.tabs[i].active_cmd.is_none()
                    && self.tabs[i].active_grip.is_none()
                    && !self.tabs[i].selected_grips.is_empty()
                {
                    if let Some(handle) = self.tabs[i].selected_handle {
                        let is_paper = self.tabs[i].scene.current_layout != "Model";
                        // In-viewport grips are model-space; project them with the
                        // viewport camera so they hit-test where the GPU draws
                        // them. Paper-space entities use the 2-D paper transform;
                        // the model tab uses the model camera.
                        let grip_hit = if let Some(cam) = &edit_cam {
                            find_hit_grip_rte(
                                p,
                                &self.tabs[i].selected_grips,
                                cam.view_proj_rte(bounds),
                                cam.eye(),
                                bounds,
                            )
                        } else if is_paper {
                            let cam = self.tabs[i].scene.camera.borrow();
                            let aspect = if vh > 0.0 { vw / vh } else { 1.0 };
                            let half_h = cam.ortho_size();
                            let half_w = half_h * aspect;
                            let tx = cam.target.x as f32;
                            let ty = cam.target.y as f32;
                            drop(cam);
                            find_hit_grip_paper(
                                p,
                                &self.tabs[i].selected_grips,
                                tx,
                                ty,
                                half_w,
                                half_h,
                                bounds,
                            )
                        } else {
                            let cam = self.tabs[i].scene.camera.borrow();
                            find_hit_grip(p, &self.tabs[i].selected_grips, &cam, bounds)
                        };
                        if let Some((grip_id, is_translate, world)) = grip_hit {
                            // The visibility (lookup) grip opens a state
                            // dropdown instead of starting a stretch drag.
                            if grip_id == crate::app::visibility::VIS_GRIP_ID {
                                self.open_visibility_popup(p);
                                self.grip_hover = None;
                                self.grip_popup = None;
                                return Task::none();
                            }
                            self.tabs[i].active_grip = Some(GripEdit {
                                handle,
                                grip_id,
                                is_translate,
                                origin_world: world,
                                last_world: world,
                            });
                            self.grip_hover = None;
                            self.grip_popup = None;
                            return Task::none();
                        }
                    }
                }

                let mut sel = self.tabs[i].scene.selection.borrow_mut();
                sel.left_down = true;
                // Stored in full-canvas space (like ViewportMove's cursor and
                // the overlay box / lasso drawing); release maps it into the
                // active tile. Tile-local here would double-offset the anchor.
                sel.left_press_pos = Some(p_full);
                sel.left_press_time = Some(Instant::now());
                sel.left_dragging = false;
                Task::none()
    }

    pub(super) fn on_viewport_left_release(&mut self) -> Task<Message> {
                let i = self.active_tab;

                // PAN mode: end the pan drag but stay in pan mode for the next
                // drag (exit is Esc / another command). Mirror of the press.
                if self.tabs[i].pan_mode {
                    let mut sel = self.tabs[i].scene.selection.borrow_mut();
                    sel.middle_down = false;
                    sel.middle_last_pos = None;
                    return Task::none();
                }

                // Commit a UCS icon grip drag: persist the new UCS so it
                // round-trips, and clear the lingering press state.
                if self.ucs_grip_drag.take().is_some() {
                    self.tabs[i].persist_active_ucs();
                    self.tabs[i].snap_result = None;
                    self.snapper.from_point = None;
                    let mut sel = self.tabs[i].scene.selection.borrow_mut();
                    sel.left_down = false;
                    sel.left_press_pos = None;
                    sel.left_dragging = false;
                    return Task::none();
                }

                let (p, is_click, is_down) = {
                    let sel = self.tabs[i].scene.selection.borrow();
                    let p = match sel.last_move_pos {
                        Some(p) => p,
                        None => return Task::none(),
                    };
                    (p, !sel.left_dragging, sel.left_down)
                };

                // Grip editing: click-move-click (plus legacy press-drag).
                // The grip engages on press (active_grip set). This release
                // commits only if the grip has actually moved, or if it was a
                // press-drag. A bare engaging click (no movement yet) keeps the
                // grip hot so the user can move the cursor and click again to
                // place it. Escape cancels (handled elsewhere).
                if let Some(grip) = self.tabs[i].active_grip.clone() {
                    // Reset mouse state so the lingering press from the engaging
                    // click doesn't read as an in-progress drag on later moves.
                    {
                        let mut sel = self.tabs[i].scene.selection.borrow_mut();
                        sel.left_down = false;
                        sel.left_press_pos = None;
                        sel.left_press_time = None;
                        sel.left_dragging = false;
                    }
                    let moved = grip.last_world != grip.origin_world;
                    if is_click && !moved {
                        // Engaging click — stay hot, wait for the placement click.
                        return Task::none();
                    }
                    self.tabs[i].active_grip = None;
                    // Commit the grip drag: keep the doc's dragged geometry
                    // (drop the cancel backup), un-hide the edited entity and
                    // re-tessellate the base once, dropping the overlay preview.
                    if let Some(h) = self.grip_preview_handle.take() {
                        self.grip_original = None;
                        self.tabs[i].scene.hidden.remove(&h);
                        self.tabs[i].scene.clear_preview_wire();
                        // Only the dragged entity changed — re-tessellate just it.
                        self.tabs[i].scene.mark_entity_dirty(h);
                        self.tabs[i].scene.bump_geometry_no_blocks();
                    }
                    // Placement confirmed — keep the just-added leader.
                    self.grip_add_provisional = None;
                    self.tabs[i].snap_result = None;
                    self.refresh_properties();
                    return Task::none();
                }

                // Map the release point into the active Model tile so the
                // click's pick / on_point / selection use the active pane's
                // camera + bounds. `p_full` keeps the canvas point for the
                // box/poly selection rectangle (drawn in canvas space).
                let p_full = p;
                // Inside a floating viewport the pane is the viewport's own rect
                // and camera (see the MoveCursor path); pick / snap then run in
                // model space exactly where the GPU draws the content.
                let canvas_sz = self.tabs[i].scene.selection.borrow().vp_size;
                let edit_frame = self.tabs[i].scene.viewport_edit_frame(canvas_sz);
                let (tile_vw, tile_vh, tile_off) = match &edit_frame {
                    Some((_, full)) => (full.width, full.height, iced::Point::new(full.x, full.y)),
                    None => {
                        let tb = self
                            .tabs[i]
                            .scene
                            .active_model_tile_bounds(canvas_sz.0, canvas_sz.1);
                        (tb.width, tb.height, iced::Point::new(tb.x, tb.y))
                    }
                };
                let edit_cam = edit_frame.map(|(cam, _)| cam);
                let p = iced::Point {
                    x: p_full.x - tile_off.x,
                    y: p_full.y - tile_off.y,
                };

                let is_gathering = self.tabs[i]
                    .active_cmd
                    .as_ref()
                    .map(|c| c.is_selection_gathering())
                    .unwrap_or(false);

                if is_down && is_click && self.tabs[i].active_cmd.is_some() && !is_gathering {
                    let (vw, vh) = (tile_vw, tile_vh);
                    let bounds = iced::Rectangle {
                        x: 0.0,
                        y: 0.0,
                        width: vw,
                        height: vh,
                    };

                    let snap_taken = self.tabs[i].snap_result.take();
                    let tangent_obj_at_click = snap_taken.and_then(|s| s.tangent_obj);

                    let world_pt = {
                        // Cursor → model point (viewport camera inside a viewport,
                        // else paper sheet → model). Model space throughout.
                        let raw = self.cursor_model_point(i, &edit_cam, p, bounds);
                        let (view_rot, eye) = match &edit_cam {
                            Some(cam) => (cam.view_proj_rte(bounds), cam.eye()),
                            None => {
                                let c = self.tabs[i].scene.camera.borrow();
                                (c.view_proj_rte(bounds), c.eye())
                            }
                        };
                        let snap_cursor = raw;
                        let all_wires = if let (Some(_), Some(h)) =
                            (&edit_cam, self.tabs[i].scene.active_viewport)
                        {
                            self.tabs[i].scene.model_wires_for_viewport_arc(h, bounds.height)
                        } else {
                            self.tabs[i].scene.hit_test_wires()
                        };
                        let needs_tan = self.tabs[i]
                            .active_cmd
                            .as_ref()
                            .map(|c| c.needs_tangent_pick())
                            .unwrap_or(false);
                        let needs_entity_click = self.tabs[i]
                            .active_cmd
                            .as_ref()
                            .map(|c| c.needs_entity_pick())
                            .unwrap_or(false);
                        let snap_hit = if needs_entity_click {
                            None
                        } else if needs_tan {
                            self.snapper
                                .snap_tangent_only(snap_cursor.as_vec3(), p, &all_wires[..], view_rot, eye, bounds)
                        } else {
                            let (go, gr) = self.tabs[i].ucs_grid_basis();
                            self.snapper.from_point = self.last_point;
                            self.snapper.snap(snap_cursor, p, &all_wires[..], view_rot, eye, bounds, go, gr)
                        };
                        // Snap runs in model space; the result is already model.
                        let mut pt = snap_hit.map(|s| s.world).unwrap_or(raw);
                        // When no UCS is active clamp to world XY; with a UCS the point is
                        // already constrained to that plane by the ray–plane intersection.
                        if self.tabs[i].active_ucs.is_none() {
                            pt.z = 0.0;
                        }
                        // OTRACK alignment wins over ortho/polar; otherwise apply
                        // ortho/polar relative to the last point.
                        let otrack = if snap_hit.is_none() {
                            let step = if self.polar_mode {
                                Some(self.polar_increment_deg)
                            } else {
                                None
                            };
                            let ucs = self.tabs[i].scene.viewcube_ucs_mat();
                            self.snapper
                                .otrack_snap(raw.as_vec3(), view_rot, eye, bounds, step, self.last_point, ucs)
                        } else {
                            None
                        };
                        if let Some(h) = otrack {
                            pt = h.aligned.as_dvec3();
                            if self.tabs[i].active_ucs.is_none() {
                                pt.z = 0.0;
                            }
                        } else if !snap_hit
                            .is_some_and(|s| s.snap_type != crate::snap::SnapType::Grid)
                        {
                            // Object snap wins over ortho/polar — a snapped point
                            // commits as-is. Grid snap still combines. (#132)
                            if let Some(base) = self.last_point {
                                let ucs_xf = self.tabs[i].ucs_xform();
                                if self.ortho_mode {
                                    pt = ortho_constrain(pt.as_vec3(), base, &ucs_xf).as_dvec3();
                                } else if self.polar_mode {
                                    pt = polar_constrain_near(
                                        pt.as_vec3(),
                                        base,
                                        self.polar_increment_deg,
                                        view_rot,
                                        eye,
                                        bounds,
                                        self.snapper.osnap_radius_px,
                                        &ucs_xf,
                                    )
                                    .as_dvec3();
                                }
                            }
                        }
                        pt
                    };

                    // `world_pt` is in offset-relative (local) space, matching
                    // the camera and the point-creation commands. Entity-pick /
                    // tangent / structure-pick commands instead compare the
                    // click against WCS document entities, so they need the
                    // world_offset added back (model space only — paper-space
                    // entities are already in sheet coordinates). Without this,
                    // TRIM/EXTEND/FILLET pick the wrong side on UTM-scale files.
                    let pick_wcs = {
                        let wo = if self.tabs[i].scene.current_layout == "Model" {
                            [0.0_f64; 3]
                        } else {
                            [0.0; 3]
                        };
                        world_pt + glam::DVec3::new(wo[0], wo[1], wo[2])
                    };

                    let result = if self.tabs[i]
                        .active_cmd
                        .as_ref()
                        .map(|c| c.needs_structure_point_pick())
                        .unwrap_or(false)
                    {
                        let pick = self.tabs[i].active_cmd.as_ref().and_then(|c| {
                            c.resolve_object_pick(
                                &self.tabs[i].scene,
                                pick_wcs.x as f64,
                                pick_wcs.y as f64,
                            )
                        });
                        if let Some(pick) = pick {
                            let center = glam::DVec3::new(pick.x, pick.y, pick_wcs.z);
                            let result = self.tabs[i]
                                .active_cmd
                                .as_mut()
                                .map(|c| c.on_structure_pick(pick.handle, center));
                            self.command_line
                                .push_info(&format!("{} acquired.", pick.label));
                            result
                        } else {
                            let msg = self.tabs[i]
                                .active_cmd
                                .as_ref()
                                .map(|c| c.object_pick_miss_message())
                                .unwrap_or("No object near click.");
                            self.command_line.push_error(msg);
                            None
                        }
                    } else if self.tabs[i]
                        .active_cmd
                        .as_ref()
                        .map(|c| c.needs_entity_pick())
                        .unwrap_or(false)
                    {
                        let (view_rot2, eye2, all_wires2) = self.pick_view(i, &edit_cam, bounds);
                        let hit = scene::pick::hit_test::click_hit(p, &all_wires2[..], view_rot2, eye2, bounds)
                            .and_then(|s| Scene::handle_from_wire_name(s));
                        if let Some(handle) = hit {
                            // Some commands (e.g. SS_CATCHMENT) need the entity
                            // body before `on_entity_pick` can advance.
                            let inject_first = self.tabs[i]
                                .active_cmd
                                .as_ref()
                                .map(|c| c.inject_before_entity_pick())
                                .unwrap_or(false);
                            if inject_first {
                                if let Some(entity) =
                                    self.tabs[i].scene.document.get_entity(handle).cloned()
                                {
                                    if let Some(cmd) = self.tabs[i].active_cmd.as_mut() {
                                        cmd.inject_picked_entity(entity);
                                    }
                                }
                            }

                            let result = self.tabs[i]
                                .active_cmd
                                .as_mut()
                                .map(|c| c.on_entity_pick(handle, pick_wcs));
                            // HATCHEDIT: after pick, inject hatch model data into the command.
                            if self.tabs[i]
                                .active_cmd
                                .as_ref()
                                .map(|c| c.name() == "HATCHEDIT")
                                .unwrap_or(false)
                            {
                                if let Some(model) =
                                    self.tabs[i].scene.hatches.get(&handle).cloned()
                                {
                                    use crate::command::CadCommand;
                                    use crate::modules::draw::draw::hatchedit::HatcheditCommand;
                                    let cmd: Box<dyn CadCommand> =
                                        Box::new(HatcheditCommand::with_handle(
                                            handle,
                                            model.name.clone(),
                                            model.scale,
                                            model.angle_offset,
                                        ));
                                    self.command_line.push_info(&cmd.prompt());
                                    self.tabs[i].active_cmd = Some(cmd);
                                } else {
                                    self.command_line
                                        .push_error("HATCHEDIT: not a hatch entity.");
                                    self.tabs[i].active_cmd = None;
                                }
                            }
                            // DIMTEDIT / MLEADERADD / MLEADERREMOVE: inject cloned entity via trait.
                            {
                                let needs_inject = self.tabs[i]
                                    .active_cmd
                                    .as_ref()
                                    .map(|c| {
                                        matches!(
                                            c.name(),
                                            "DIMTEDIT" | "MLEADERADD" | "MLEADERREMOVE"
                                        )
                                    })
                                    .unwrap_or(false);
                                if needs_inject {
                                    if let Some(entity) =
                                        self.tabs[i].scene.document.get_entity(handle).cloned()
                                    {
                                        if let Some(cmd) = self.tabs[i].active_cmd.as_mut() {
                                            cmd.inject_picked_entity(entity);
                                            let prompt = cmd.prompt();
                                            self.command_line.push_info(&prompt);
                                        }
                                    }
                                }
                            }
                            result
                        } else {
                            self.command_line.push_info("Nothing found at that point.");
                            None
                        }
                    } else if self.tabs[i]
                        .active_cmd
                        .as_ref()
                        .map(|c| c.needs_tangent_pick())
                        .unwrap_or(false)
                    {
                        if let Some(obj) = tangent_obj_at_click {
                            self.tabs[i]
                                .active_cmd
                                .as_mut()
                                .map(|c| c.on_tangent_point(obj, pick_wcs))
                        } else {
                            self.command_line.push_info("Select a tangent object.");
                            None
                        }
                    } else {
                        // A scalar typed into the dynamic-input box but not
                        // yet confirmed with Enter is applied before the
                        // point pick — e.g. an OFFSET distance typed and then
                        // clicked takes effect rather than being discarded.
                        let wants_text = self.tabs[i]
                            .active_cmd
                            .as_ref()
                            .map(|c| c.wants_text_input())
                            .unwrap_or(false);
                        if wants_text {
                            if let Some(text) = self.tabs[i]
                                .dyn_fields
                                .iter()
                                .find_map(|f| f.buffer.clone())
                            {
                                let text = crate::app::expr_eval::eval_to_string(text.trim());
                                if let Some(c) = self.tabs[i].active_cmd.as_mut() {
                                    c.on_text_input(&text);
                                }
                                for f in self.tabs[i].dyn_fields.iter_mut() {
                                    f.buffer = None;
                                }
                                self.tabs[i].dyn_active = 0;
                            }
                        }
                        self.last_point = Some(world_pt.as_vec3());
                        self.dyn_user_reshaped = false;
                        self.sync_dyn_fields();
                        self.reset_tracking_after_point();
                        self.tabs[i]
                            .active_cmd
                            .as_mut()
                            .map(|c| c.on_point(world_pt))
                    };

                    if let Some(r) = result {
                        let task = self.apply_cmd_result(r);
                        let mut sel = self.tabs[i].scene.selection.borrow_mut();
                        sel.left_down = false;
                        sel.left_press_pos = None;
                        sel.left_press_time = None;
                        sel.left_dragging = false;
                        return task;
                    }
                    let mut sel = self.tabs[i].scene.selection.borrow_mut();
                    sel.left_down = false;
                    sel.left_press_pos = None;
                    sel.left_press_time = None;
                    sel.left_dragging = false;
                    return Task::none();
                }

                let (is_down2, is_dragging, box_anchor, box_crossing, _vp_size, elapsed_ms) = {
                    let sel = self.tabs[i].scene.selection.borrow();
                    let elapsed = sel
                        .left_press_time
                        .map(|t| Instant::now().duration_since(t).as_millis())
                        .unwrap_or(u128::MAX);
                    (
                        sel.left_down,
                        sel.left_dragging,
                        sel.box_anchor,
                        sel.box_crossing,
                        sel.vp_size,
                        elapsed,
                    )
                };

                let mut selection_just_completed = false;

                // Active-tile-local selection: tile-sized bounds and the box
                // anchor mapped into the tile, so box / crossing selection
                // matches the active pane (p is already tile-local).
                let vp_size = (tile_vw, tile_vh);
                let box_anchor = box_anchor.map(|a| iced::Point {
                    x: a.x - tile_off.x,
                    y: a.y - tile_off.y,
                });

                if is_down2 {
                    let bounds = iced::Rectangle {
                        x: 0.0,
                        y: 0.0,
                        width: vp_size.0,
                        height: vp_size.1,
                    };

                    if is_dragging {
                        if elapsed_ms < POLY_START_DELAY_MS {
                            if let Some(a) = box_anchor {
                                let crossing = box_crossing;
                                let (view_rot, eye, all_wires) = self.pick_view(i, &edit_cam, bounds);
                                let mut handles: Vec<Handle> = scene::pick::hit_test::box_hit(
                                    a,
                                    p,
                                    crossing,
                                    &all_wires[..],
                                    view_rot,
                                    eye,
                                    bounds,
                                )
                                .into_iter()
                                .filter_map(|s| Scene::handle_from_wire_name(s))
                                .collect();
                                handles.extend(scene::pick::hit_test::box_hit_hatch(
                                    a,
                                    p,
                                    crossing,
                                    &self.tabs[i].scene.visible_hatches_for_click(),
                                    view_rot,
                                    eye,
                                    bounds,
                                ));
                                handles.extend(
                                    self.tabs[i].scene.mesh_box_hit(a, p, crossing, view_rot, eye, bounds),
                                );
                                handles.extend(self.tabs[i].scene.block_mesh_box_hit(
                                    a, p, crossing, view_rot, eye, bounds,
                                ));
                                // Box/lasso accumulates like individual picks
                                // (issue #83): a plain box adds to the current
                                // selection, Shift+box removes the boxed
                                // entities. Esc / empty-space click still clears.
                                if self.shift_down {
                                    for h in &handles {
                                        self.tabs[i].scene.deselect_entity(*h);
                                    }
                                } else {
                                    for h in &handles {
                                        self.tabs[i].scene.select_entity(*h, false);
                                    }
                                    self.tabs[i].scene.expand_selection_for_groups(&handles);
                                }
                                self.refresh_properties();
                                selection_just_completed = true;
                            }
                        } else {
                            let (poly_pts, crossing) = {
                                let sel = self.tabs[i].scene.selection.borrow();
                                // Map lasso points into the active tile.
                                let pts: Vec<iced::Point> = sel
                                    .poly_points
                                    .iter()
                                    .map(|pp| iced::Point {
                                        x: pp.x - tile_off.x,
                                        y: pp.y - tile_off.y,
                                    })
                                    .collect();
                                (pts, sel.poly_crossing)
                            };
                            self.tabs[i].scene.selection.borrow_mut().poly_last_crossing = crossing;
                            let (view_rot, eye, all_wires) = self.pick_view(i, &edit_cam, bounds);
                            let mut handles: Vec<Handle> = scene::pick::hit_test::poly_hit(
                                &poly_pts,
                                crossing,
                                &all_wires[..],
                                view_rot,
                                eye,
                                bounds,
                            )
                            .into_iter()
                            .filter_map(|s| Scene::handle_from_wire_name(s))
                            .collect();
                            handles.extend(scene::pick::hit_test::poly_hit_hatch(
                                &poly_pts,
                                crossing,
                                &self.tabs[i].scene.visible_hatches_for_click(),
                                view_rot,
                                eye,
                                bounds,
                            ));
                            handles.extend(
                                self.tabs[i].scene.mesh_poly_hit(&poly_pts, crossing, view_rot, eye, bounds),
                            );
                            handles.extend(self.tabs[i].scene.block_mesh_poly_hit(
                                &poly_pts, crossing, view_rot, eye, bounds,
                            ));
                            // Selection filter: keep only allowed types.
                            handles.retain(|&h| self.tabs[i].scene.passes_selection_filter(h));
                            // Accumulate like the box path (issue #83): plain
                            // lasso adds, Shift+lasso removes. An empty lasso
                            // leaves the current selection untouched so a stray
                            // drag never discards hard-won picks.
                            if self.shift_down {
                                for h in &handles {
                                    self.tabs[i].scene.deselect_entity(*h);
                                }
                            } else {
                                for h in &handles {
                                    self.tabs[i].scene.select_entity(*h, false);
                                }
                                self.tabs[i].scene.expand_selection_for_groups(&handles);
                            }
                            self.refresh_properties();
                            selection_just_completed = true;
                        }
                        let mut sel = self.tabs[i].scene.selection.borrow_mut();
                        sel.poly_active = false;
                        sel.poly_points.clear();
                        sel.poly_crossing = false;
                        sel.box_anchor = None;
                        sel.box_current = None;
                    } else {
                        if box_anchor.is_none() {
                            let (view_rot, eye, all_wires) =
                                self.pick_view(i, &edit_cam, bounds);

                            // Selection cycling: where two or more objects
                            // overlap, open a list box to pick which one; a
                            // single object falls through to the normal click.
                            // Gated behind the toggle, so default picking is
                            // unchanged when off.
                            let mut handled_by_cycling = false;
                            if self.selection_cycling {
                                let cands: Vec<Handle> = scene::pick::hit_test::click_hits_all(
                                    p,
                                    &all_wires[..],
                                    view_rot,
                                    eye,
                                    bounds,
                                )
                                .into_iter()
                                .filter_map(|s| Scene::handle_from_wire_name(s))
                                .filter(|&h| self.tabs[i].scene.passes_selection_filter(h))
                                .collect();
                                if cands.len() >= 2 {
                                    // Overlap: open the list box at the cursor.
                                    self.cycle_candidates = Some((p_full, cands));
                                    handled_by_cycling = true;
                                }
                            }

                            if !handled_by_cycling {
                                let hit =
                                    scene::pick::hit_test::click_hit(p, &all_wires[..], view_rot, eye, bounds)
                                        .and_then(|s| Scene::handle_from_wire_name(s))
                                        .or_else(|| {
                                            scene::pick::hit_test::click_hit_hatch(
                                                p,
                                                &self.tabs[i].scene.visible_hatches_for_click(),
                                                view_rot,
                                                eye,
                                                bounds,
                                            )
                                        })
                                        .or_else(|| {
                                            // Block-internal hatch: resolve to the
                                            // parent Insert (AutoCAD behaviour).
                                            scene::pick::hit_test::click_hit_insert_hatch(
                                                p,
                                                &self.tabs[i].scene.insert_hatches_for_click(),
                                                view_rot,
                                                eye,
                                                bounds,
                                            )
                                        })
                                        .or_else(|| {
                                            // 3D solids: click anywhere on the shaded
                                            // body — top-level solids and block-internal
                                            // ones together, front-most wins (a block in
                                            // front of a solid resolves to the block).
                                            self.tabs[i].scene.solid_click_hit(p, view_rot, eye, bounds)
                                        });
                                // Selection filter: drop a pick whose type is excluded.
                                let hit =
                                    hit.filter(|&h| self.tabs[i].scene.passes_selection_filter(h));
                                if let Some(handle) = hit {
                                    // Individual picks accumulate (issue #47):
                                    // each plain click adds to the selection,
                                    // Shift+click removes the picked entity.
                                    // Esc / empty-space click clears.
                                    if self.shift_down {
                                        self.tabs[i].scene.deselect_entity(handle);
                                    } else {
                                        self.tabs[i].scene.select_entity(handle, false);
                                        self.tabs[i].scene.expand_selection_for_groups(&[handle]);
                                    }
                                    self.refresh_properties();
                                    selection_just_completed = true;
                                } else {
                                    // Empty-space click only ARMS a box here; it
                                    // no longer clears the selection, so a box can
                                    // add to it (issue #83). The box completion
                                    // (or Esc) decides what happens to the
                                    // selection.
                                    let mut sel = self.tabs[i].scene.selection.borrow_mut();
                                    // Full-canvas space: ViewportMove updates
                                    // box_current in canvas coords and the overlay
                                    // draws there; release maps back into the tile.
                                    sel.box_anchor = Some(p_full);
                                    sel.box_current = Some(p_full);
                                    sel.box_crossing = false;
                                }
                            }
                        } else {
                            let a = box_anchor.unwrap();
                            let crossing = box_crossing;
                            let (view_rot, eye, all_wires) = self.pick_view(i, &edit_cam, bounds);
                            let mut handles: Vec<Handle> = scene::pick::hit_test::box_hit(
                                a,
                                p,
                                crossing,
                                &all_wires[..],
                                view_rot,
                                eye,
                                bounds,
                            )
                            .into_iter()
                            .filter_map(|s| Scene::handle_from_wire_name(s))
                            .collect();
                            handles.extend(scene::pick::hit_test::box_hit_hatch(
                                a,
                                p,
                                crossing,
                                &self.tabs[i].scene.visible_hatches_for_click(),
                                view_rot,
                                eye,
                                bounds,
                            ));
                            handles.extend(
                                self.tabs[i].scene.mesh_box_hit(a, p, crossing, view_rot, eye, bounds),
                            );
                            handles.extend(self.tabs[i].scene.block_mesh_box_hit(
                                a, p, crossing, view_rot, eye, bounds,
                            ));
                            // Selection filter: keep only allowed types.
                            handles.retain(|&h| self.tabs[i].scene.passes_selection_filter(h));
                            // Accumulate (issue #83): a plain box adds to the
                            // current selection, Shift+box removes the boxed
                            // entities. An empty box leaves the selection alone
                            // so an accidental empty drag never discards it.
                            if self.shift_down {
                                for h in &handles {
                                    self.tabs[i].scene.deselect_entity(*h);
                                }
                            } else {
                                for h in &handles {
                                    self.tabs[i].scene.select_entity(*h, false);
                                }
                                self.tabs[i].scene.expand_selection_for_groups(&handles);
                            }
                            self.refresh_properties();
                            let mut sel = self.tabs[i].scene.selection.borrow_mut();
                            sel.box_last = Some((a, p));
                            sel.box_last_crossing = crossing;
                            sel.box_anchor = None;
                            sel.box_current = None;
                            sel.box_crossing = false;
                            selection_just_completed = true;
                        }
                    }

                    let mut sel = self.tabs[i].scene.selection.borrow_mut();
                    sel.left_down = false;
                    sel.left_press_pos = None;
                    sel.left_press_time = None;
                    sel.left_dragging = false;
                }

                if is_gathering && selection_just_completed {
                    let handles: Vec<Handle> = self.tabs[i]
                        .scene
                        .selected_entities()
                        .into_iter()
                        .map(|(h, _)| h)
                        .collect();
                    if let Some(cmd) = self.tabs[i].active_cmd.as_mut() {
                        let result = cmd.on_selection_complete(handles);
                        return self.apply_cmd_result(result);
                    }
                }

                // ── Double-click in Model Space: DDEDIT for Text/MText ────
                if is_click
                    && is_down
                    && self.tabs[i].active_cmd.is_none()
                    && self.tabs[i].scene.current_layout == "Model"
                {
                    let now = Instant::now();
                    let is_double_model = self
                        .last_vp_click_time
                        .map(|t| {
                            let dt = now.duration_since(t).as_millis();
                            let last = self.last_vp_click_pos.unwrap_or(p);
                            let d = (p.x - last.x).hypot(p.y - last.y);
                            dt < 400 && d < 8.0
                        })
                        .unwrap_or(false);

                    self.last_vp_click_time = Some(now);
                    self.last_vp_click_pos = Some(p);

                    if is_double_model {
                        let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
                        let bounds = iced::Rectangle {
                            x: 0.0,
                            y: 0.0,
                            width: vw,
                            height: vh,
                        };
                        let (view_rot, eye) = { let c = self.tabs[i].scene.camera.borrow(); (c.view_proj_rte(bounds), c.eye()) };
                        let all_wires = self.tabs[i].scene.hit_test_wires();
                        // Resolve the double-clicked object — its wire, or (for a
                        // block/solid with no wire under the cursor) its shaded
                        // body, which maps to the parent INSERT.
                        let hit = scene::pick::hit_test::click_hit(p, &all_wires[..], view_rot, eye, bounds)
                            .and_then(|s| Scene::handle_from_wire_name(s))
                            .or_else(|| self.tabs[i].scene.solid_click_hit(p, view_rot, eye, bounds));
                        if let Some(handle) = hit {
                            // Any text-bearing entity opens its in-place editor
                            // (plain box or rich MText editor, per type). A
                            // Leader resolves to the entity it annotates.
                            let is_editable_text = self.tabs[i]
                                .scene
                                .document
                                .get_entity(handle)
                                .is_some_and(|e| {
                                    crate::app::text_inline::read_text_field(e).is_some()
                                        || matches!(e, AcadEntityType::Leader(_))
                                });
                            if is_editable_text {
                                return self.begin_text_edit(handle);
                            }
                            // Double-clicking a block reference enters in-place
                            // block edit (REFEDIT), so its geometry can be edited
                            // and the change reflects in every instance. (#136)
                            let is_insert = matches!(
                                self.tabs[i].scene.document.get_entity(handle),
                                Some(AcadEntityType::Insert(_))
                            );
                            if is_insert && self.tabs[i].refedit_session.is_none() {
                                return Task::done(Message::Command(format!(
                                    "REFEDIT_BEGIN:{}",
                                    handle.value()
                                )));
                            }
                        }
                    }
                }

                // ── Double-click: enter/exit MSPACE ───────────────────────
                // Only when no command is running, no drag, and we're in paper space.
                if is_click
                    && is_down   // ensures there was a matching left-press
                    && self.tabs[i].active_cmd.is_none()
                    && self.tabs[i].scene.current_layout != "Model"
                {
                    let now = Instant::now();
                    let is_double = self
                        .last_vp_click_time
                        .map(|t| {
                            let dt = now.duration_since(t).as_millis();
                            let last = self.last_vp_click_pos.unwrap_or(p);
                            let d = (p.x - last.x).hypot(p.y - last.y);
                            dt < 400 && d < 8.0
                        })
                        .unwrap_or(false);

                    self.last_vp_click_time = Some(now);
                    self.last_vp_click_pos = Some(p);

                    if is_double {
                        let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
                        let bounds = iced::Rectangle {
                            x: 0.0,
                            y: 0.0,
                            width: vw,
                            height: vh,
                        };

                        // 1) Try direct wire hit — works when the border is clicked.
                        let wire_hit: Option<acadrust::Handle> = {
                            let (view_rot, eye) = { let c = self.tabs[i].scene.camera.borrow(); (c.view_proj_rte(bounds), c.eye()) };
                            let all_wires = self.tabs[i].scene.hit_test_wires();
                            scene::pick::hit_test::click_hit(p, &all_wires[..], view_rot, eye, bounds)
                                .and_then(|s| Scene::handle_from_wire_name(s))
                                .and_then(|h| {
                                    if let Some(AcadEntityType::Viewport(vp)) =
                                        self.tabs[i].scene.document.get_entity(h)
                                    {
                                        if Scene::is_content_viewport(vp) {
                                            Some(h)
                                        } else {
                                            None
                                        }
                                    } else {
                                        None
                                    }
                                })
                        };

                        // 2) Decide which viewport (if any) the click enters,
                        //    keyed on the *visible* on-screen rectangle. Screen-space
                        //    (not the full paper rect) so a click on the empty area
                        //    beside an off-screen viewport doesn't match its
                        //    partly-off-canvas rect and switch to it by mistake.
                        //    The wire hit only refines *which* visible viewport
                        //    (border precision / overlap), and only when the click
                        //    actually lands inside THAT viewport's visible rect —
                        //    otherwise its border-wire pick tolerance could match a
                        //    far viewport whose edge merely passes near the cursor
                        //    (e.g. clicking the overlap of two viewports while a
                        //    third's border runs nearby) and enter the wrong one.
                        let screen_hit = self
                            .tabs[i]
                            .scene
                            .viewport_at_screen_point(p.x, p.y, (vw, vh));
                        let wire_in_visible = wire_hit.filter(|&h| {
                            self.tabs[i]
                                .scene
                                .viewport_screen_rect(h, (vw, vh))
                                .is_some_and(|r| {
                                    let x0 = r.x.max(0.0);
                                    let y0 = r.y.max(0.0);
                                    let x1 = (r.x + r.width).min(vw);
                                    let y1 = (r.y + r.height).min(vh);
                                    p.x >= x0 && p.x <= x1 && p.y >= y0 && p.y <= y1
                                })
                        });
                        let hit_vp = wire_in_visible.or(screen_hit);

                        if let Some(handle) = hit_vp {
                            return Task::done(Message::EnterViewport(handle));
                        } else if self.tabs[i].scene.active_viewport.is_some() {
                            // Double-clicked outside all viewports while in MSPACE → exit.
                            return Task::done(Message::ExitViewport);
                        }
                    }
                }

                Task::none()
    }

    pub(super) fn on_viewport_middle_press(&mut self) -> Task<Message> {
                let i = self.active_tab;
                self.ribbon.close_dropdown();
                let now = Instant::now();
                let is_double = {
                    let sel = self.tabs[i].scene.selection.borrow();
                    sel.middle_last_press_time
                        .map(|t| now.duration_since(t).as_millis() < 300)
                        .unwrap_or(false)
                };
                {
                    let mut sel = self.tabs[i].scene.selection.borrow_mut();
                    let Some(p) = sel.last_move_pos else {
                        return Task::none();
                    };
                    sel.middle_down = true;
                    sel.middle_last_pos = Some(p);
                    sel.middle_last_press_time = Some(now);
                }
                if is_double {
                    self.tabs[i].scene.fit_all();
                    self.command_line.push_output("Zoom Extents");
                }
                Task::none()
    }

    pub(super) fn on_viewport_scroll(&mut self, delta: mouse::ScrollDelta) -> Task<Message> {
                let s = match delta {
                    mouse::ScrollDelta::Lines { y, .. } => y,
                    mouse::ScrollDelta::Pixels { y, .. } => y * 0.01,
                };
                let i = self.active_tab;
                let cursor = self.tabs[i].scene.selection.borrow().last_move_pos;
                let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
                let bounds = iced::Rectangle {
                    x: 0.0,
                    y: 0.0,
                    width: vw,
                    height: vh,
                };
                if self.tabs[i].scene.active_viewport.is_some() {
                    // In MSPACE: zoom the active viewport's model-space view,
                    // keeping the model point under the cursor stationary.
                    let cursor_paper = cursor.map(|cp| {
                        let pt = self.tabs[i]
                            .scene
                            .camera
                            .borrow()
                            .pick_on_target_plane(cp, bounds);
                        glam::Vec2::new(pt.x as f32, pt.y as f32)
                    });
                    self.tabs[i].scene.zoom_active_viewport(s, cursor_paper);
                    // Bump so the GPU re-uploads the viewport's re-culled wire
                    // set after zooming inside it.
                    self.tabs[i].scene.camera_generation += 1;
                } else {
                    // Model space: zoom about the cursor within the active
                    // tile so the point under it stays put in that pane.
                    let tile_b = self.tabs[i].scene.active_model_tile_bounds(vw, vh);
                    let mut cam = self.tabs[i].scene.camera.borrow_mut();
                    if let Some(cursor) = cursor {
                        let local = iced::Point {
                            x: cursor.x - tile_b.x,
                            y: cursor.y - tile_b.y,
                        };
                        let tb = iced::Rectangle {
                            x: 0.0,
                            y: 0.0,
                            width: tile_b.width,
                            height: tile_b.height,
                        };
                        cam.zoom_about_point(local, tb, s);
                    } else {
                        cam.zoom(s);
                    }
                    drop(cam);
                    self.tabs[i].scene.camera_generation += 1;
                }
                Task::none()
    }

    pub(super) fn on_viewport_click(&mut self) -> Task<Message> {
                let i = self.active_tab;
                let rot = self.tabs[i].scene.active_view_rotation_mat();
                let (vw, vh) = self.tabs[i].scene.selection.borrow().vp_size;
                // The ViewCube draws in the top-right of whichever area
                // owns it: the full canvas in model space, or the active
                // viewport's screen rectangle in a paper layout. Map the
                // cursor into that area before hit-testing so paper-space
                // picks line up with the gizmo.
                let (cx, cy, w, h) = match self.tabs[i]
                    .scene
                    .active_viewport
                    .and_then(|hndl| self.tabs[i].scene.viewport_screen_rect(hndl, (vw, vh)))
                {
                    Some(rect) => (
                        self.cursor_pos.x - rect.x,
                        self.cursor_pos.y - rect.y,
                        rect.width,
                        rect.height,
                    ),
                    None => {
                        // Model layout: hit-test within the active tile.
                        let tb = self.tabs[i].scene.active_model_tile_bounds(vw, vh);
                        (
                            self.cursor_pos.x - tb.x,
                            self.cursor_pos.y - tb.y,
                            tb.width,
                            tb.height,
                        )
                    }
                };
                // Prefer the currently-highlighted region: hover is recomputed
                // on every move straight from the cube's own overlay, so it is
                // immune to `cursor_pos` being overwritten by the viewport's
                // move handler between the last move and this press.
                if let Some(id) = self.tabs[i].scene.viewcube_hover.get() {
                    let region = if id < 6 {
                        scene::CubeRegion::Face(id)
                    } else if id < 18 {
                        scene::CubeRegion::Edge(id)
                    } else {
                        scene::CubeRegion::Corner(id)
                    };
                    return Task::done(Message::ViewCubeSnap(region));
                }
                if let Some(region) = scene::hit_test(cx, cy, w, h, rot, VIEWCUBE_PX) {
                    return Task::done(Message::ViewCubeSnap(region));
                }
                // Compass cardinals are world-fixed: hit-test through the camera-
                // only rotation (strip the UCS) so the target matches the drawn
                // N/E/S/W, and snap in world frame.
                let rot_world = rot * self.tabs[i].scene.viewcube_ucs_mat().inverse();
                if let Some(card) = scene::hit_test_cardinal(cx, cy, w, h, rot_world, VIEWCUBE_PX) {
                    return Task::done(Message::ViewCubeSnapWorld(card.face_region()));
                }
                Task::none()
    }

    pub(super) fn on_view_cube_snap(&mut self, region: CubeRegion) -> Task<Message> {
                // The cube is oriented in the active UCS, so snap in the UCS frame.
                let r_ucs = self.tabs[self.active_tab].scene.viewcube_ucs_mat();
                self.snap_view_region(region, r_ucs)
    }

    /// Compass cardinals are world-fixed, so they snap in the world frame
    /// (no UCS composition).
    pub(super) fn on_view_cube_snap_world(&mut self, region: CubeRegion) -> Task<Message> {
                self.snap_view_region(region, glam::Mat4::IDENTITY)
    }

    fn snap_view_region(&mut self, region: CubeRegion, r_ucs: glam::Mat4) -> Task<Message> {
                let i = self.active_tab;
                let mut region = region;
                // "Already there → flip to opposite" check: compare the
                // current gaze direction with the region's target gaze.
                let target_dir = r_ucs.transform_vector3(region.snap_direction());
                let cur_dir = self.tabs[i].scene.active_gaze_dir();
                if cur_dir.dot(target_dir) > 0.9999 {
                    region = region.opposite();
                }
                let eye_dir = r_ucs.transform_vector3(region.snap_direction());

                // Faces snap to a canonical upright orientation (never upside
                // down); edges/corners keep the current up-sense so they spin
                // smoothly around the clicked feature.
                let is_face = matches!(region, scene::CubeRegion::Face(_));
                if self.tabs[i].scene.active_viewport.is_some() {
                    if is_face {
                        self.tabs[i]
                            .scene
                            .mutate_active_viewport_camera(|c| c.snap_to_face(eye_dir, r_ucs));
                    } else {
                        self.tabs[i]
                            .scene
                            .snap_active_viewport_to_direction(eye_dir, r_ucs);
                    }
                } else {
                    let mut cam = self.tabs[i].scene.camera.borrow_mut();
                    if is_face {
                        cam.snap_to_face(eye_dir, r_ucs);
                    } else {
                        cam.snap_to_direction(eye_dir, r_ucs);
                    }
                }
                self.tabs[i].scene.camera_generation += 1;
                self.command_line
                    .push_output(&format!("View: {}", region.label()));
                Task::none()
    }

    pub(super) fn on_hover_dwell_tick(&mut self) -> Task<Message> {
                let Some(dwell) = self.hover_dwell.clone() else {
                    return Task::none();
                };
                if Instant::now()
                    .duration_since(dwell.last_move_at)
                    .as_millis()
                    < crate::app::HOVER_DWELL_MS
                {
                    return Task::none();
                }
                let i = dwell.tab;
                // Re-check the gate — drag / command may have started
                // between the move that armed the dwell and this tick.
                if i >= self.tabs.len() || self.tabs[i].active_cmd.is_some() {
                    self.hover_dwell = None;
                    return Task::none();
                }
                let bounds = iced::Rectangle {
                    x: 0.0,
                    y: 0.0,
                    width: dwell.tile_size.0,
                    height: dwell.tile_size.1,
                };
                let p = dwell.point;
                // Inside a viewport, hover-pick through the viewport camera +
                // model wires so the rollover highlights the entity under the
                // cursor (dwell.point / dwell.tile_size are already pane-local).
                let canvas_sz = self.tabs[i].scene.selection.borrow().vp_size;
                let edit_cam = self
                    .tabs[i]
                    .scene
                    .viewport_edit_frame(canvas_sz)
                    .map(|(cam, _)| cam);
                let (view_rot, eye, all_wires) = self.pick_view(i, &edit_cam, bounds);
                // Mirror the click-selection pick order so the rollover
                // highlights every selectable object: wire → hatch →
                // block-internal hatch → shaded 3D solid body.
                let hovered = scene::pick::hit_test::click_hit(p, &all_wires[..], view_rot, eye, bounds)
                    .and_then(|s| Scene::handle_from_wire_name(s))
                    .or_else(|| {
                        scene::pick::hit_test::click_hit_hatch(
                            p,
                            &self.tabs[i].scene.visible_hatches_for_click(),
                            view_rot,
                            eye,
                            bounds,
                        )
                    })
                    .or_else(|| {
                        scene::pick::hit_test::click_hit_insert_hatch(
                            p,
                            &self.tabs[i].scene.insert_hatches_for_click(),
                            view_rot,
                            eye,
                            bounds,
                        )
                    })
                    .or_else(|| self.tabs[i].scene.solid_click_hit(p, view_rot, eye, bounds));
                self.tabs[i].scene.set_hover_highlight(hovered);
                self.hover_dwell = None;
                Task::none()
    }

    pub(super) fn on_layout_switch(&mut self, name: String) -> Task<Message> {
                let i = self.active_tab;
                let going_to_paper = name != "Model";
                // Persist the camera of the layout we're leaving BEFORE switching
                // so returning to it restores where the user left off (the
                // periodic sync only fires on a tick, which may not have run
                // since the last pan/zoom).
                self.tabs[i].scene.sync_camera_to_document();
                self.tabs[i].last_synced_camera_gen = self.tabs[i].scene.camera_generation;
                // Cancel any pending rename/context-menu and active viewport when switching.
                self.layout_rename_state = None;
                self.layout_context_menu = None;
                self.tabs[i].scene.active_viewport = None;
                self.tabs[i].scene.set_current_layout(name);
                self.tabs[i].scene.deselect_all();
                // UCS follows the pane: model header UCS in the Model tab, none
                // in plain paper space (a viewport's UCS is adopted on entry).
                self.tabs[i].refresh_active_ucs();
                self.tabs[i].scene.restore_saved_camera();
                self.tabs[i].last_synced_camera_gen = self.tabs[i].scene.camera_generation;
                // Grid/snap are per-view: load the layout we just entered (its
                // sheet viewport in paper space, the model tile in model space)
                // so model and each layout keep independent grid state.
                self.adopt_view_display(i);
                // Paper-space tools live in the right-edge side toolbar now, so
                // entering/leaving a layout no longer hijacks the ribbon tab.
                let _ = going_to_paper;
                // Refresh VP freeze columns for the new layout.
                let doc_layers = self.tabs[i].scene.document.layers.clone();
                let vp_info = self.tabs[i].scene.viewport_list();
                self.tabs[i]
                    .layers
                    .sync_with_viewports(&doc_layers, vp_info);
                Task::none()
    }

    pub(super) fn on_layout_create(&mut self) -> Task<Message> {
                let i = self.active_tab;
                // Find a unique name (e.g. Layout2, Layout3, ...).
                let existing = self.tabs[i].scene.layout_names();
                let mut idx = existing.len();
                let new_name = loop {
                    let candidate = format!("Layout{}", idx);
                    if !existing.contains(&candidate) {
                        break candidate;
                    }
                    idx += 1;
                };
                self.push_undo_snapshot(i, "LAYOUT");
                match self.tabs[i].scene.document.add_layout(&new_name) {
                    Ok(_) => {
                        // Override the acadrust default limits (12×9 imperial) with A4 landscape.
                        for obj in self.tabs[i].scene.document.objects.values_mut() {
                            if let acadrust::objects::ObjectType::Layout(l) = obj {
                                if l.name == new_name {
                                    l.min_limits = (0.0, 0.0);
                                    l.max_limits = (297.0, 210.0);
                                    l.min_extents = (0.0, 0.0, 0.0);
                                    l.max_extents = (297.0, 210.0, 0.0);
                                    break;
                                }
                            }
                        }
                        self.tabs[i].scene.current_layout = new_name.clone();
                        // Safety net — `add_layout` already creates the overall
                        // sheet viewport; this covers any path that doesn't.
                        self.tabs[i].scene.ensure_sheet_viewport(&new_name);
                        self.tabs[i].scene.deselect_all();
                        self.tabs[i].scene.fit_all();
                        self.command_line.push_output(&format!(
                            "Layout \"{new_name}\" created — use MVIEW to add a viewport"
                        ));
                        self.tabs[i].dirty = true;
                    }
                    Err(e) => self
                        .command_line
                        .push_error(&format!("Failed to create layout: {e}")),
                }
                Task::none()
    }

    pub(super) fn on_layout_rename_commit(&mut self) -> Task<Message> {
                if let Some((orig, new_name)) = self.layout_rename_state.take() {
                    let new_name = new_name.trim().to_string();
                    if !new_name.is_empty() && new_name != orig {
                        let i = self.active_tab;
                        let exists = self.tabs[i]
                            .scene
                            .layout_names()
                            .iter()
                            .any(|n| *n == new_name);
                        if exists {
                            self.command_line
                                .push_error(&format!("\"{}\" name already in use", new_name));
                        } else {
                            self.push_undo_snapshot(i, "LAYOUT RENAME");
                            self.tabs[i].scene.rename_layout(&orig, &new_name);
                            if self.tabs[i].scene.current_layout == orig {
                                self.tabs[i].scene.current_layout = new_name.clone();
                            }
                            self.tabs[i].dirty = true;
                            self.command_line
                                .push_output(&format!("Layout \"{orig}\" → \"{new_name}\""));
                        }
                    }
                }
                Task::none()
    }
}