Merge pull request #2555 from dotCooCoo/feat/simplify-slider

Simplify: Object › Path › Simplify opens a slider with Auto-Simplify and More Options

crates/engine/src/cmd/pathops.rs

@@ -130,7 +130,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Simplify…",
             ["Object", "Path"],
             None,
-            "{tolerance?: pt (1), cornerAngle?: deg (30), straightLines?: bool} → {ids, before, after} anchor counts",
+            "{tolerance?: pt (1), level?: 0..100 (the Simplify slider, in place of tolerance: 0 fewest anchor points, 50 is 1 pt, every 10 levels halves or doubles it), auto?: bool (Auto-Simplify: the lowest level whose tolerance is at most 1/400 of the selection's longer side, or 100 when that side is under 12.5 pt), cornerAngle?: deg (30), straightLines?: bool} → {ids, before, after} anchor counts, and the level used with level or auto",
             has_selection,
             simplify
         ),
@@ -800,13 +800,29 @@ fn edit_paths(s: &mut Session, label: &str, f: impl Fn(&PathData) -> PathData) -
 }
 
 fn simplify(s: &mut Session, p: &Value) -> Result<Value> {
+    // With auto, the slider's level is Auto-Simplify's for the selection's size; otherwise it is the level given.
+    let level = if bool_or(p, "auto", false) {
+        let roots = selected_roots(s)?;
+        let size = s.doc()?.doc.bounds_of(&roots, false).map_or(0.0, |b| b.width().max(b.height()));
+        Some(po::auto_simplify_level(size))
+    } else {
+        num_param(p, "level").map(|l| if l.is_finite() { l.round().clamp(0.0, 100.0) } else { po::SIMPLIFY_LEVEL })
+    };
+    let tolerance = match level {
+        Some(l) => po::simplify_level_tolerance(l),
+        None => len_param(p, "tolerance").unwrap_or(1.0),
+    };
     let opts = po::SimplifyOptions {
-        tolerance: len_param(p, "tolerance").unwrap_or(1.0).clamp(1e-4, 1e4),
+        tolerance: tolerance.clamp(1e-4, 1e4),
         corner_angle_deg: num_param(p, "cornerAngle").unwrap_or(30.0).clamp(0.0, 180.0),
         straight_lines: bool_or(p, "straightLines", false),
     };
     let (ids, before, after) = edit_paths(s, "Simplify", |path| po::simplify_with(path, &opts))?;
-    Ok(json!({ "ids": ids.iter().map(|i| i.0).collect::<Vec<_>>(), "before": before, "after": after }))
+    let mut out = json!({ "ids": ids.iter().map(|i| i.0).collect::<Vec<_>>(), "before": before, "after": after });
+    if let Some(l) = level {
+        out["level"] = json!(l);
+    }
+    Ok(out)
 }
 
 fn add_anchor_points(s: &mut Session, _: &Value) -> Result<Value> {

crates/engine/src/lib.rs

@@ -36,6 +36,7 @@ pub use journal::Journal;
 pub use tooling::{UiRequest, ViewInfo};
 pub use vectorcraft_doc as doc;
 pub use vectorcraft_doc::cancel;
+pub use vectorcraft_pathops::{SIMPLIFY_LEVEL, simplify_level_tolerance};
 pub use vectorcraft_tools as tools;
 
 #[derive(Debug, thiserror::Error)]

crates/engine/src/tests_pathops.rs

@@ -448,6 +448,58 @@ fn simplify_dense_polyline() {
     assert!(close(bounds(&s, id), Rect::new(0.0, 60.0, 300.0, 140.0), 2.0));
 }
 
+/// A sine wave with an anchor every point over `width` pt, `amplitude` pt high and a wavelength of
+/// `2π × period` pt, its anchors `jag` pt above and below it in turn, selected: (the session, the
+/// path's id).
+fn dense_wave(width: u32, amplitude: f64, period: f64, jag: f64) -> (Session, NodeId) {
+    let mut s = session();
+    let y = |i: u32| 100.0 + amplitude * (f64::from(i) / period).sin() + if i.is_multiple_of(2) { jag } else { -jag };
+    let anchors: Vec<Value> = (0..=width).map(|i| json!({"x": f64::from(i), "y": y(i)})).collect();
+    let r = s.execute("path.create", &json!({"anchors": anchors})).unwrap();
+    (s, NodeId(r["id"].as_u64().unwrap()))
+}
+
+/// The Simplify slider: moving its level from 0 to 100 never lowers the anchor count, level 0
+/// leaves fewer anchors than level 100, and level 50 gives the 1 pt result.
+#[test]
+fn simplify_level_moves_the_anchor_count_monotonically() {
+    let (mut s, id) = dense_wave(300, 40.0, 25.0, 0.0);
+    let mut counts = vec![];
+    for level in (0..=100).step_by(10) {
+        let out = s.execute("object.path.simplify", &json!({ "level": level })).unwrap();
+        assert_eq!(out["level"], json!(f64::from(level)));
+        counts.push(path_of(&s, id).0.anchor_count());
+        s.execute("edit.undo", &json!({})).unwrap();
+    }
+    assert!(counts.windows(2).all(|w| w[0] <= w[1]), "{counts:?}");
+    assert!(counts[0] < counts[10], "{counts:?}");
+    s.execute("object.path.simplify", &json!({"tolerance": 1})).unwrap();
+    assert_eq!(path_of(&s, id).0.anchor_count(), counts[5], "level 50 is 1 pt");
+}
+
+/// Auto-Simplify picks the lowest level whose tolerance is at most 1/400 of the selection's longer
+/// side, and 11 sampled points on each segment of the original path stay that close to the result.
+#[test]
+fn auto_simplify_keeps_the_shape_within_a_400th_of_its_size() {
+    let (mut s, id) = dense_wave(100, 15.0, 8.0, 0.2);
+    let original = path_of(&s, id).0.clone();
+    let out = s.execute("object.path.simplify", &json!({"auto": true})).unwrap();
+    // 100 pt across: 0.25 pt at most, level 70 (0.25 pt).
+    assert_eq!(out["level"], json!(70.0));
+    let result = path_of(&s, id).0.clone();
+    assert!(result.anchor_count() < original.anchor_count() / 2, "{}", result.anchor_count());
+    // How far each point along the original lies from the nearest point of the result.
+    use vectorcraft_geom::ParamCurve;
+    use vectorcraft_geom::kurbo::ParamCurveNearest;
+    let fitted = &result.subpaths[0];
+    let off = |p: vectorcraft_geom::Point| {
+        (0..fitted.segment_count()).map(|i| fitted.segment(i).nearest(p, 1e-9).distance_sq.sqrt()).fold(f64::INFINITY, f64::min)
+    };
+    let sp = &original.subpaths[0];
+    let worst = (0..sp.segment_count()).flat_map(|i| (0..=10).map(move |k| sp.segment(i).eval(f64::from(k) / 10.0))).map(off).fold(0.0, f64::max);
+    assert!(worst <= 100.0 / 400.0, "{worst}");
+}
+
 /// How many steps there are to undo and to redo, and whether the document has unsaved changes.
 fn history(s: &Session) -> (usize, usize, bool) {
     let st = s.doc().unwrap();

crates/engine/tests/command_sweep.rs

@@ -355,6 +355,9 @@ fn structured_junk() {
         ("object.path.offsetPath", json!({"offset": 1e308})),
         ("object.path.offsetPath", json!({"offset": -1e308})),
         ("object.path.simplify", json!({"tolerance": -1, "cornerAngle": 1e308})),
+        ("object.path.simplify", json!({"level": 1e308, "tolerance": "x"})),
+        ("object.path.simplify", json!({"level": -1e308, "auto": "yes"})),
+        ("object.path.simplify", json!({"auto": true, "level": [1]})),
         (
             "shape.rectangularGrid",
             json!({"x": 0, "y": 0, "width": 1e308, "height": -1e308, "rows": 999, "columns": u64::MAX, "rowSkew": 1e308, "columnSkew": -1e308, "frame": false, "fill": true}),

crates/pathops/src/edit.rs

@@ -29,6 +29,30 @@ pub fn simplify(path: &PathData, tolerance: f64) -> PathData {
     simplify_with(path, &SimplifyOptions { tolerance, ..Default::default() })
 }
 
+/// The Simplify slider's level for a tolerance of 1 pt, where the slider opens.
+pub const SIMPLIFY_LEVEL: f64 = 50.0;
+
+/// The tolerance (points) of Simplify slider level `level`, from 0 (the fewest anchor points) to
+/// 100 (the closest to the original): 1 pt at [`SIMPLIFY_LEVEL`], doubled for every 10 levels below
+/// it and halved for every 10 above, so level 0 is 32 pt and level 100 is 1/32 pt. A level outside
+/// 0..=100 counts as the nearer end, and one that is not a number counts as [`SIMPLIFY_LEVEL`].
+pub fn simplify_level_tolerance(level: f64) -> f64 {
+    let level = if level.is_finite() { level.clamp(0.0, 100.0) } else { SIMPLIFY_LEVEL };
+    ((SIMPLIFY_LEVEL - level) / 10.0).exp2()
+}
+
+/// Auto-Simplify's level for paths whose bounds are `size` points on their longer side: the lowest
+/// whole level whose tolerance ([`simplify_level_tolerance`]) is at most 1/400 of `size`. It returns
+/// level 100 for a size of 0 or one that is not a number, and for a size under 12.5 pt, where no
+/// level is that close.
+pub fn auto_simplify_level(size: f64) -> f64 {
+    let target = size / 400.0;
+    if !(target.is_finite() && target > 0.0) {
+        return 100.0;
+    }
+    (SIMPLIFY_LEVEL - 10.0 * target.log2()).ceil().clamp(0.0, 100.0)
+}
+
 /// Simplify never adds anchors: keep whichever subpath is smaller.
 fn no_worse(original: &SubPath, fitted: SubPath) -> SubPath {
     if fitted.anchors.len() > original.anchors.len() { original.clone() } else { fitted }

crates/pathops/src/lib.rs

@@ -15,8 +15,8 @@ mod planar;
 
 pub use boolean::{BoolOp, DEFAULT_PRECISION, area, boolean, boolean_n, normalize, try_boolean, try_normalize, unite_all};
 pub use edit::{
-    AverageAxis, SimplifyOptions, add_anchor_points, average, join, remove_anchor, remove_redundant_points, simplify, simplify_with, smooth,
-    split_into_grid,
+    AverageAxis, SIMPLIFY_LEVEL, SimplifyOptions, add_anchor_points, auto_simplify_level, average, join, remove_anchor, remove_redundant_points,
+    simplify, simplify_level_tolerance, simplify_with, smooth, split_into_grid,
 };
 pub use offset::{Cap, Join, offset_path, outline_stroke, stroke_region};
 pub use pathfinder::{FaceMerger, PathfinderOp, Region, Shape, merge_regions, pathfinder, region_at, regions};

crates/pathops/tests/ops.rs

@@ -343,6 +343,20 @@ fn simplify_straight_lines_option() {
     assert!(max_deviation(&c, &s) <= 1.0 + 1e-6);
 }
 
+/// The Simplify slider's levels: 1 pt at 50, doubled for every 10 levels down and halved for every
+/// 10 up; Auto-Simplify takes the lowest level whose tolerance is at most 1/400 of the size, and
+/// level 100 for a size under 12.5 pt.
+#[test]
+fn simplify_levels_and_auto_simplify() {
+    assert_eq!(simplify_level_tolerance(SIMPLIFY_LEVEL), 1.0);
+    assert_eq!((simplify_level_tolerance(0.0), simplify_level_tolerance(100.0)), (32.0, 1.0 / 32.0));
+    assert_eq!((simplify_level_tolerance(-5.0), simplify_level_tolerance(500.0), simplify_level_tolerance(f64::NAN)), (32.0, 1.0 / 32.0, 1.0));
+    assert_eq!((auto_simplify_level(400.0), auto_simplify_level(100.0), auto_simplify_level(300.0)), (50.0, 70.0, 55.0));
+    assert!(simplify_level_tolerance(auto_simplify_level(300.0)) <= 300.0 / 400.0);
+    assert_eq!((auto_simplify_level(12.5), auto_simplify_level(10.0)), (100.0, 100.0));
+    assert_eq!((auto_simplify_level(0.0), auto_simplify_level(f64::INFINITY), auto_simplify_level(1e9)), (100.0, 100.0, 0.0));
+}
+
 #[test]
 fn smooth_rounds_corners() {
     let s = smooth(&rect(0.0, 0.0, 10.0, 10.0), 1.0);

crates/ui-egui/src/canvas.rs

@@ -552,7 +552,8 @@ pub fn show(app: &mut VectorcraftApp, ui: &mut Ui) {
         }
         rulers(ui, full, &xf, app.hover_doc, app.session.general_unit(), origin_preview.unwrap_or_else(|| app.ruler_origin()), &t);
     }
-    if app.ui.task_bar && !revolve_edit && !app.session.tool_busy() && app.ui.screen_mode < 3 {
+    // The task bar is not drawn while the Simplify slider shows.
+    if app.ui.task_bar && !revolve_edit && !app.session.tool_busy() && app.ui.screen_mode < 3 && !crate::dialogs::simplify_slider::showing(app) {
         task_bar(app, ui, &xf);
     }
     if app.ui.screen_mode < 3 {

crates/ui-egui/src/dialogs/form.rs

@@ -611,14 +611,21 @@ pub(super) fn preview_result(
         }
         return None;
     }
+    preview_now(app, d, label, cmd, params)
+}
+
+/// The preview of [`preview_result`] without its checkbox: `params` run again on the interaction's
+/// snapshot when they differ from the last preview. Returns the command's result only when a new
+/// preview succeeds.
+pub(super) fn preview_now(app: &mut crate::VectorcraftApp, d: &mut Dialog, label: &str, cmd: &str, params: Value) -> Option<Value> {
     let mut result = None;
-    if d.fields.get(LAST) != Some(&params) || !app.session.in_interaction() {
+    if d.fields.get(PREVIEWED) != Some(&params) || !app.session.in_interaction() {
         let _ = app.session.begin_interaction(label);
         match app.session.preview(cmd, &params) {
             Ok(r) => result = Some(r),
             Err(e) => app.status(e.to_string()),
         }
-        d.fields.insert(LAST.into(), params);
+        d.fields.insert(PREVIEWED.into(), params);
     }
     result
 }

crates/ui-egui/src/dialogs/mod.rs

@@ -89,6 +89,7 @@ pub mod save_swatch_library;
 pub mod script_check;
 mod shapes;
 pub mod shortcut_import;
+pub(crate) mod simplify_slider;
 pub mod slices;
 pub mod spot_colors;
 pub(crate) mod svg_options;
@@ -325,6 +326,7 @@ registry! {
     Plugin: [plugin::KIND] => plugin::SPEC,
     ScriptCheck: [script_check::KIND] => script_check::SPEC,
     VectorHalftone: [halftone::KIND] => halftone::SPEC,
+    SimplifySlider: [simplify_slider::KIND] => simplify_slider::SPEC,
     PerspectiveGrid: [perspective_grid::KIND] => perspective_grid::SPEC,
     Envelope: [envelope::WARP, envelope::MESH, envelope::OPTIONS] => envelope::SPEC,
     LiquifyOptions: [liquify::KIND] => liquify::SPEC,

crates/ui-egui/src/dialogs/path_ops.rs

@@ -101,9 +101,18 @@ fn split_grid(ui: &mut egui::Ui, d: &mut Dialog, unit: Unit) {
     form::check(ui, d, "addGuides", tl!("Add Guides"));
 }
 
+/// The fields the Simplify dialog opens with at `tolerance` (points): the slider's tolerance when
+/// its More Options opens the dialog.
+pub(crate) fn simplify_dialog(tolerance: f64) -> Value {
+    json!({"tolerance": tolerance, "angleThreshold": ANGLE_THRESHOLD, "straightLines": false, "showOriginal": false, "retain": false, "preview": true})
+}
+
+/// The fields the Simplify dialog keeps when OK confirms it with `retain` ticked.
+const SIMPLIFY_KEPT: [&str; 6] = ["tolerance", "angleThreshold", "straightLines", "showOriginal", "retain", "preview"];
+
 /// Simplify's fields: Tolerance, Corner Point Angle Threshold (its label above a slider from 0° on
-/// the left, the smoothest, to 180°, the sharpest), Convert to Straight Lines and Show Original
-/// Path.
+/// the left, the smoothest, to 180°, the sharpest), Convert to Straight Lines, Show Original Path
+/// and Open this dialog with these settings next time.
 fn simplify_fields(ui: &mut egui::Ui, d: &mut Dialog, unit: Unit) {
     let rail = Tokens::get(ui.ctx()).input_border;
     egui::Grid::new("dlg").num_columns(2).spacing([10.0, 8.0]).show(ui, |ui| {
@@ -115,6 +124,7 @@ fn simplify_fields(ui: &mut egui::Ui, d: &mut Dialog, unit: Unit) {
     ui.add_space(8.0);
     form::check(ui, d, "straightLines", tl!("Convert to Straight Lines"));
     form::check(ui, d, "showOriginal", tl!("Show Original Path"));
+    form::check(ui, d, "retain", tl!("Open this dialog with these settings next time"));
 }
 
 /// Simplify's Show Original Path: while the dialog previews with it on, every path the preview ran
@@ -175,6 +185,12 @@ fn confirm(app: &mut VectorcraftApp, d: &Dialog) -> Result<Value, String> {
         return run_and_close(app, id, params);
     }
     let r = form::commit_preview(app, id, params)?;
+    // Simplify: with retain ticked, the menu item opens this dialog on these fields next time; with it
+    // unticked, the menu item opens the slider.
+    if d.kind == "simplify" {
+        let kept = SIMPLIFY_KEPT.into_iter().filter_map(|k| Some((k.to_string(), d.fields.get(k)?.clone())));
+        app.ui.simplify = if d.bool("retain") { Value::Object(kept.collect()) } else { Value::Null };
+    }
     // The fields as the dialog held them, so they show as typed when it opens again.
     if d.kind == "offsetPath" {
         let kept = ["offset", "joins", "miterLimit"].into_iter().filter_map(|k| Some((k.to_string(), d.fields.get(k)?.clone())));

crates/ui-egui/src/dialogs/simplify_slider.rs

@@ -0,0 +1,165 @@
+//! Object › Path › Simplify's slider: a strip under the selection with Auto-Simplify, a slider from
+//! the fewest anchor points (left) to the closest fit to the original (right), and More Options,
+//! which opens the Simplify dialog at the slider's tolerance. While the strip is open, the canvas
+//! previews `object.path.simplify {level}`; Enter or a click outside the strip keeps the result as
+//! one undo step, and Escape puts the paths back. The slider opens at level 50, a tolerance of
+//! 1 pt (`vectorcraft_pathops::simplify_level_tolerance` maps levels to tolerances).
+//!
+//! Fields: `level` (0..=100, the command's parameter).
+
+use egui::{Color32, CornerRadius, Order, Pos2, Sense, Stroke, vec2};
+use serde_json::{Value, json};
+use vectorcraft_engine::{SIMPLIFY_LEVEL, simplify_level_tolerance};
+use vectorcraft_geom::Rect;
+
+use super::{DialogResult, DialogSpec, form, modal};
+use crate::state::Dialog;
+use crate::theme::Tokens;
+use crate::{VectorcraftApp, widgets};
+
+/// The dialog kind of the Simplify slider.
+pub(crate) const KIND: &str = "simplifySlider";
+
+pub(super) const SPEC: DialogSpec = DialogSpec { window: Some(show), confirm, preview: true, ..DialogSpec::FORM };
+
+/// The command the slider previews, and its undo label.
+const CMD: &str = "object.path.simplify";
+const LABEL: &str = "Simplify";
+
+/// The fields the slider opens with.
+pub(crate) fn fields() -> Value {
+    json!({ "level": SIMPLIFY_LEVEL })
+}
+
+/// Whether the Simplify slider is open.
+pub(crate) fn showing(app: &VectorcraftApp) -> bool {
+    app.ui.dialog.as_ref().is_some_and(|d| d.kind == KIND)
+}
+
+/// The slider's level, a whole number from 0 to 100.
+fn level(d: &Dialog) -> f64 {
+    let l = d.f64("level", SIMPLIFY_LEVEL);
+    if l.is_finite() { l.round().clamp(0.0, 100.0) } else { SIMPLIFY_LEVEL }
+}
+
+fn params(d: &Dialog) -> Value {
+    json!({ "level": level(d) })
+}
+
+fn confirm(app: &mut VectorcraftApp, d: &Dialog) -> DialogResult {
+    form::commit_preview(app, CMD, params(d))
+}
+
+/// The open slider, or an error when it isn't open.
+fn open_slider(app: &VectorcraftApp) -> Result<Dialog, String> {
+    app.ui.dialog.clone().filter(|d| d.kind == KIND).ok_or_else(|| "the Simplify slider is not open".to_string())
+}
+
+/// Auto-Simplify (`ui.simplifyAuto`): the open slider moves to the level `object.path.simplify
+/// {auto: true}` picks for the selection, and the canvas previews it → {level}.
+pub(crate) fn auto(app: &mut VectorcraftApp) -> Result<Value, String> {
+    let mut d = open_slider(app)?;
+    let _ = app.session.begin_interaction(LABEL);
+    let r = app.session.preview(CMD, &json!({ "auto": true })).map_err(|e| e.to_string())?;
+    let level = r["level"].as_f64().unwrap_or(SIMPLIFY_LEVEL);
+    d.fields.insert("level".into(), json!(level));
+    d.fields.insert(form::PREVIEWED.into(), params(&d));
+    app.ui.dialog = Some(d);
+    Ok(json!({ "level": level }))
+}
+
+/// More Options (`ui.simplifyMoreOptions`): the Simplify dialog takes the slider's place, at the
+/// slider's tolerance → {tolerance}.
+pub(crate) fn more_options(app: &mut VectorcraftApp) -> Result<Value, String> {
+    let d = open_slider(app)?;
+    let tolerance = simplify_level_tolerance(level(&d));
+    app.ui.dialog = Some(Dialog::new("simplify", super::path_ops::simplify_dialog(tolerance)));
+    Ok(json!({ "tolerance": tolerance }))
+}
+
+/// The private field that holds the selection's bounds before the preview, `[x0, y0, x1, y1]`.
+const BOUNDS: &str = "__bounds";
+
+/// The selection's bounds before the preview: the interaction's snapshot when a preview runs, read
+/// once and kept in `d`, so the strip stays where it opened while the preview changes the paths.
+fn bounds(app: &mut VectorcraftApp, d: &mut Dialog) -> Option<Rect> {
+    if let Some([x0, y0, x1, y1]) = d.fields.get(BOUNDS).and_then(|v| serde_json::from_value::<[f64; 4]>(v.clone()).ok()) {
+        return Some(Rect::new(x0, y0, x1, y1));
+    }
+    let b = match app.session.active().and_then(|st| st.interaction.as_ref()) {
+        Some(it) => it.doc.bounds_of(&it.selection.objects, true),
+        None => app.selection_bounds(),
+    }?;
+    d.fields.insert(BOUNDS.into(), json!([b.x0, b.y0, b.x1, b.y1]));
+    Some(b)
+}
+
+/// Where the strip goes: under the lowest corner on screen of `bounds` (the selection's, before the
+/// preview), centered on them, kept on the canvas.
+fn place(app: &mut VectorcraftApp, ctx: &egui::Context, id: egui::Id, bounds: Option<Rect>) -> Pos2 {
+    let size = egui::AreaState::load(ctx, id).and_then(|s| s.size).unwrap_or(vec2(270.0, 42.0));
+    let screen = ctx.content_rect();
+    let Some((rect, view)) = app.canvas_rect.zip(app.view().copied()) else { return screen.center() - size / 2.0 };
+    let xf = crate::canvas::Xf::new(rect, &view);
+    let under = match bounds {
+        Some(b) => {
+            let lowest = xf.quad(b).iter().map(|c| c.y).fold(f32::NEG_INFINITY, f32::max);
+            Pos2::new(xf.to_screen(b.center()).x - size.x / 2.0, lowest + 28.0)
+        }
+        None => rect.center() - size / 2.0,
+    };
+    let bounds = rect.shrink(8.0);
+    under.clamp(bounds.min, (bounds.max - size).max(bounds.min))
+}
+
+/// What a button of the strip asked for.
+enum Action {
+    Auto,
+    MoreOptions,
+}
+
+fn show(app: &mut VectorcraftApp, ctx: &egui::Context) {
+    let Some(mut d) = app.ui.dialog.clone() else { return };
+    let t = Tokens::get(ctx);
+    let id = egui::Id::new(("dialog", KIND));
+    let b = bounds(app, &mut d);
+    let pos = place(app, ctx, id, b);
+    // A click anywhere else keeps the result, and the rest of the app doesn't take it.
+    let dim = modal::backdrop();
+    let outside =
+        egui::Area::new(dim.id).order(dim.order).fixed_pos(Pos2::ZERO).show(ctx, |ui| ui.allocate_rect(ctx.content_rect(), Sense::click())).inner;
+    let mut action = None;
+    egui::Area::new(id).order(Order::Foreground).fixed_pos(pos).show(ctx, |ui| {
+        egui::Frame::NONE
+            .fill(t.panel)
+            .stroke(Stroke::new(1.0, t.tool_active))
+            .corner_radius(CornerRadius::same(5))
+            .inner_margin(egui::Margin::symmetric(8, 6))
+            .shadow(egui::epaint::Shadow { offset: [0, 3], blur: 10, spread: 0, color: Color32::from_black_alpha(70) })
+            .show(ui, |ui| {
+                ui.horizontal(|ui| {
+                    ui.spacing_mut().item_spacing.x = 6.0;
+                    if widgets::icon_button(ui, "wand-sparkles", tl!("Auto-Simplify"), false, 28.0).clicked() {
+                        action = Some(Action::Auto);
+                    }
+                    let rail = t.input_border;
+                    form::slider_rail_named(ui, &mut d, "level", tl!("Simplify"), 0.0..=100.0, &|_| rail);
+                    if widgets::icon_button(ui, "ellipsis", tl!("More Options"), false, 28.0).clicked() {
+                        action = Some(Action::MoreOptions);
+                    }
+                });
+            });
+    });
+    let p = params(&d);
+    let _ = form::preview_now(app, &mut d, LABEL, CMD, p);
+    app.ui.dialog = Some(d);
+    let r = match action {
+        Some(Action::Auto) => auto(app),
+        Some(Action::MoreOptions) => more_options(app),
+        None if outside.clicked() || ctx.input(|i| i.key_pressed(egui::Key::Enter)) => super::confirm(app),
+        None => Ok(Value::Null),
+    };
+    if let Err(e) = r {
+        app.status(e);
+    }
+}

crates/ui-egui/src/dialogs/tests.rs

@@ -474,6 +474,10 @@ fn menu_parameter_dialogs_are_compact() {
         app.run("shape.rectangle", json!({"x": 10, "y": 10, "width": 50, "height": 50})).unwrap();
         app.run("select.all", json!({})).unwrap();
         crate::menus::invoke(&mut app, id, json!({}));
+        // Simplify opens its slider; More Options opens the dialog.
+        if id == "object.path.simplify" {
+            app.run("ui.simplifyMoreOptions", json!({})).unwrap();
+        }
         assert!(app.ui.dialog.is_some(), "{id} opened no dialog");
         let wide = dialog_rect(&mut app, 1600.0);
         eprintln!("{id}: {:.0} × {:.0} in a 1600-point window", wide.width(), wide.height());

crates/ui-egui/src/dialogs/tests_modal.rs

@@ -292,13 +292,181 @@ fn app_with_dense_path() -> VectorcraftApp {
     app
 }
 
+/// Object › Path › Simplify, then the slider's More Options: the Simplify dialog.
+fn open_simplify_dialog(app: &mut VectorcraftApp) {
+    crate::menus::invoke(app, "object.path.simplify", json!({}));
+    app.run("ui.simplifyMoreOptions", json!({})).unwrap();
+}
+
+/// The anchors of the paths in `app`'s document.
+fn anchor_count(app: &VectorcraftApp) -> usize {
+    let mut n = 0;
+    app.session.doc().unwrap().doc.walk(|node| {
+        if let vectorcraft_doc::NodeKind::Path { path, .. } = &node.kind {
+            n += path.anchor_count();
+        }
+    });
+    n
+}
+
+/// The parameters of the Simplify preview on the canvas.
+fn simplify_preview(app: &VectorcraftApp) -> serde_json::Value {
+    app.session.doc().unwrap().interaction.as_ref().and_then(|it| it.preview.clone()).expect("a preview").1
+}
+
+/// The Simplify slider's strip, and the centers of its Auto-Simplify button, its rail and its More
+/// Options button.
+fn slider_strip(ctx: &egui::Context) -> (Rect, Pos2, Pos2, Pos2) {
+    let r = rect_of(ctx, egui::Id::new(("dialog", simplify_slider::KIND)));
+    let y = r.center().y;
+    (r, Pos2::new(r.left() + 8.0 + 14.0, y), Pos2::new(r.left() + 8.0 + 28.0 + 6.0 + 90.0, y), Pos2::new(r.right() - 8.0 - 14.0, y))
+}
+
+/// Object › Path › Simplify opens a slider under the selection that previews the 1 pt result.
+/// Dragging it to the right previews more anchor points and to the left fewer, and Enter keeps the
+/// result as one undo step.
+#[test]
+fn simplify_opens_a_slider_whose_drag_previews_fewer_or_more_points() {
+    let (ctx, mut app) = (ctx(), app_with_dense_path());
+    let undo_len = app.session.doc().unwrap().history.undo.len();
+    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    assert_eq!(app.ui.dialog.as_ref().map(|d| d.kind.as_str()), Some(simplify_slider::KIND));
+    settle(&ctx, &mut app);
+    assert_eq!(simplify_preview(&app), json!({"level": 50.0}));
+    assert_eq!(anchor_count(&app), 2, "the 1 pt result");
+    let (_, _, rail, _) = slider_strip(&ctx);
+    drag(&ctx, &mut app, rail, vec2(100.0, 0.0));
+    assert_eq!(simplify_preview(&app), json!({"level": 100.0}));
+    let most = anchor_count(&app);
+    assert!(most > 2, "{most}");
+    let (_, _, rail, _) = slider_strip(&ctx);
+    drag(&ctx, &mut app, rail + vec2(90.0, 0.0), vec2(-190.0, 0.0));
+    assert_eq!(simplify_preview(&app), json!({"level": 0.0}));
+    assert_eq!(anchor_count(&app), 2);
+    frame(
+        &ctx,
+        &mut app,
+        vec![Event::Key { key: egui::Key::Enter, physical_key: None, pressed: true, repeat: false, modifiers: Default::default() }],
+    );
+    assert!(app.ui.dialog.is_none() && !app.session.in_interaction());
+    assert_eq!(app.session.doc().unwrap().history.undo.len(), undo_len + 1);
+    assert_eq!(anchor_count(&app), 2);
+}
+
+/// Escape, taken by the app's key handling before the dialog layer draws, closes the Simplify
+/// slider and puts the paths back as they were, with no undo step.
+#[test]
+fn simplify_slider_escape_puts_the_paths_back() {
+    let (ctx, mut app) = (ctx(), app_with_dense_path());
+    let before = app.session.doc().unwrap().doc.clone();
+    let undo_len = app.session.doc().unwrap().history.undo.len();
+    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    settle(&ctx, &mut app);
+    let (_, _, rail, _) = slider_strip(&ctx);
+    drag(&ctx, &mut app, rail, vec2(100.0, 0.0));
+    assert_eq!(simplify_preview(&app), json!({"level": 100.0}));
+    assert_ne!(app.session.doc().unwrap().doc, before, "the preview changes the path");
+    let escape = Event::Key { key: egui::Key::Escape, physical_key: None, pressed: true, repeat: false, modifiers: Default::default() };
+    let input = egui::RawInput { screen_rect: Some(Rect::from_min_size(Pos2::ZERO, SCREEN)), events: vec![escape], ..Default::default() };
+    let mut out = ctx.run_ui(input, |ui| {
+        crate::shortcuts::handle(&mut app, ui.ctx());
+        show(&mut app, ui.ctx());
+    });
+    out.textures_delta.clear();
+    assert!(app.ui.dialog.is_none() && !app.session.in_interaction());
+    assert_eq!(app.session.doc().unwrap().doc, before);
+    assert_eq!(app.session.doc().unwrap().history.undo.len(), undo_len);
+    assert_eq!(anchor_count(&app), 20);
+}
+
+/// The Simplify slider stays where it opened, under the paths as they were, while the preview
+/// changes their bounds, so a drag doesn't move the rail under the pointer.
+#[test]
+fn simplify_slider_stays_where_it_opened_while_the_preview_changes_the_bounds() {
+    let ctx = ctx();
+    let mut app = VectorcraftApp::new(Session::new(), Default::default());
+    app.run("file.new", json!({"width": 400, "height": 300})).unwrap();
+    app.canvas_rect = Some(Rect::from_min_size(Pos2::ZERO, SCREEN));
+    // A hump 20 pt high, which level 0 (32 pt) fits with a lower curve, seen at 400%.
+    let anchors: Vec<_> = (0..20).map(|i| json!({"x": 30 + i * 15, "y": 100.0 + 20.0 * (std::f64::consts::PI * i as f64 / 19.0).sin()})).collect();
+    app.run("path.create", json!({"anchors": anchors})).unwrap();
+    app.run("view.setZoom", json!({"zoom": 400})).unwrap();
+    app.view_mut().unwrap().center = vectorcraft_geom::Point::new(172.5, 60.0);
+    let before = app.selection_bounds().unwrap();
+    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    settle(&ctx, &mut app);
+    let opened = rect_of(&ctx, egui::Id::new(("dialog", simplify_slider::KIND)));
+    app.ui.dialog.as_mut().unwrap().fields.insert("level".into(), json!(0));
+    settle(&ctx, &mut app);
+    assert_eq!(simplify_preview(&app), json!({"level": 0.0}));
+    let after = app.selection_bounds().unwrap();
+    assert!(after.height() < before.height() - 0.5, "the preview changes the bounds: {before:?} → {after:?}");
+    assert_eq!(rect_of(&ctx, egui::Id::new(("dialog", simplify_slider::KIND))), opened);
+}
+
+/// Auto-Simplify moves the slider to the level that keeps the path within 1/400 of its size, and a
+/// click outside the strip keeps the result as one undo step.
+#[test]
+fn simplify_slider_auto_simplify_and_a_click_outside_keep_the_result() {
+    let (ctx, mut app) = (ctx(), app_with_dense_path());
+    let before = app.session.doc().unwrap().doc.clone();
+    let undo_len = app.session.doc().unwrap().history.undo.len();
+    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    settle(&ctx, &mut app);
+    let (_, auto, ..) = slider_strip(&ctx);
+    click(&ctx, &mut app, auto);
+    // The path is 285 pt wide: 0.7125 pt at most, level 55.
+    assert_eq!(app.ui.dialog.as_ref().unwrap().f64("level", 0.0), 55.0);
+    assert_eq!(app.session.doc().unwrap().interaction.as_ref().and_then(|it| it.preview.clone()).unwrap().1, json!({"auto": true}));
+    frame(&ctx, &mut app, vec![]);
+    assert_eq!(anchor_count(&app), 2);
+    assert!(app.session.in_interaction(), "the result waits for a click outside");
+    click(&ctx, &mut app, Pos2::new(20.0, 20.0));
+    assert!(app.ui.dialog.is_none() && !app.session.in_interaction());
+    assert_eq!(app.session.doc().unwrap().history.undo.len(), undo_len + 1);
+    assert_ne!(app.session.doc().unwrap().doc, before);
+}
+
+/// More Options opens the Simplify dialog at the slider's tolerance. With "Open this dialog with
+/// these settings next time" ticked, OK makes the menu item open the dialog on its settings; with
+/// it unticked, the slider again.
+#[test]
+fn simplify_slider_more_options_and_the_dialog_that_opens_directly() {
+    let (ctx, mut app) = (ctx(), app_with_dense_path());
+    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    app.ui.dialog.as_mut().unwrap().fields.insert("level".into(), json!(60));
+    settle(&ctx, &mut app);
+    assert_eq!(simplify_preview(&app), json!({"level": 60.0}));
+    let (_, _, _, more) = slider_strip(&ctx);
+    click(&ctx, &mut app, more);
+    let d = app.ui.dialog.as_ref().unwrap();
+    assert_eq!((d.kind.as_str(), d.f64("tolerance", 0.0), d.bool("retain")), ("simplify", 0.5, false));
+    settle(&ctx, &mut app);
+    assert_eq!(simplify_preview(&app)["tolerance"], json!(0.5));
+    let texts = frame(&ctx, &mut app, vec![]);
+    let retain = texts.iter().find(|(t, _)| t == "Open this dialog with these settings next time").map(|(_, r)| *r).expect("the checkbox");
+    click(&ctx, &mut app, retain.center());
+    app.ui.dialog.as_mut().unwrap().fields.insert("straightLines".into(), json!(true));
+    confirm(&mut app).unwrap();
+    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    let d = app.ui.dialog.clone().unwrap();
+    assert_eq!((d.kind.as_str(), d.f64("tolerance", 0.0), d.bool("straightLines"), d.bool("retain")), ("simplify", 0.5, true, true));
+    app.ui.dialog.as_mut().unwrap().fields.insert("retain".into(), json!(false));
+    confirm(&mut app).unwrap();
+    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    assert_eq!(app.ui.dialog.as_ref().map(|d| d.kind.as_str()), Some(simplify_slider::KIND));
+    assert!(app.run("ui.simplifyAuto", json!({})).is_ok());
+    cancel(&mut app);
+    assert!(app.run("ui.simplifyMoreOptions", json!({})).is_err(), "the slider is not open");
+}
+
 #[test]
 fn simplify_dialog_preview_counts_and_cancel_restore_the_original() {
     let (ctx, mut app) = (ctx(), app_with_dense_path());
     let before = app.session.doc().unwrap().doc.clone();
     let selection = app.session.doc().unwrap().selection.clone();
     let undo_len = app.session.doc().unwrap().history.undo.len();
-    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    open_simplify_dialog(&mut app);
     settle(&ctx, &mut app);
     let texts = frame(&ctx, &mut app, vec![]);
     let preview = texts.iter().find(|(t, _)| t == "Preview").map(|(_, r)| *r).expect("a Preview checkbox");
@@ -337,7 +505,7 @@ fn simplify_dialog_ok_keeps_exactly_one_undo_with_or_without_preview() {
         let before = app.session.doc().unwrap().doc.clone();
         let selection = app.session.doc().unwrap().selection.clone();
         let undo_len = app.session.doc().unwrap().history.undo.len();
-        crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+        open_simplify_dialog(&mut app);
         app.ui.dialog.as_mut().unwrap().fields.insert("preview".into(), json!(on));
         settle(&ctx, &mut app);
         if on {
@@ -381,7 +549,7 @@ fn only_straight_segments(app: &VectorcraftApp) -> bool {
 fn simplify_dialog_sends_corner_angle_and_straight_lines() {
     let (ctx, mut app) = (ctx(), app_with_selection());
     app.run("shape.ellipse", json!({"x": 100, "y": 200, "width": 160, "height": 90})).unwrap();
-    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    open_simplify_dialog(&mut app);
     settle(&ctx, &mut app);
     let texts = frame(&ctx, &mut app, vec![]);
     assert!(texts.iter().any(|(t, _)| t == "Corner Point Angle Threshold:"), "{texts:?}");
@@ -407,7 +575,7 @@ fn simplify_dialog_corner_point_angle_threshold_keeps_or_smooths_corners() {
     let (ctx, mut app) = (ctx(), app_with_selection());
     app.run("edit.clear", json!({})).unwrap();
     app.run("shape.polygon", json!({"cx": 200, "cy": 200, "radius": 100, "sides": 8})).unwrap();
-    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    open_simplify_dialog(&mut app);
     app.ui.dialog.as_mut().unwrap().fields.insert("tolerance".into(), json!("10 pt"));
     settle(&ctx, &mut app);
     assert!(only_straight_segments(&app), "the corners stay and the sides stay straight");
@@ -426,7 +594,7 @@ fn simplify_dialog_show_original_path_outlines_the_paths_before_the_preview() {
         Some((id, vectorcraft_doc::NodeKind::Path { path, .. })) => (id, path.clone()),
         _ => panic!("a path is selected"),
     };
-    crate::menus::invoke(&mut app, "object.path.simplify", json!({}));
+    open_simplify_dialog(&mut app);
     settle(&ctx, &mut app);
     let texts = frame(&ctx, &mut app, vec![]);
     assert!(super::path_ops::original_paths(&app).is_empty(), "Show Original Path is off as the dialog opens");

crates/ui-egui/src/i18n/bg.tsv

@@ -2868,6 +2868,8 @@
 	Show Note	Показване на бележка
 	Show Options	Показване на опциите
 	Show Original Path	Показване на оригиналния път
+	Open this dialog with these settings next time	Отваряне на този прозорец с тези настройки следващия път
+	Auto-Simplify	Автоматично опростяване
 	Show Package	Показване на пакет
 	Show Panel	Показване на панел
 	Show Pattern Swatches	Показване на образци за мостра

crates/ui-egui/src/i18n/cs.tsv

@@ -1712,6 +1712,8 @@ lighting	Light	Světlo
 	Corner Point Angle Threshold:	Prahový úhel rohových bodů:
 	Convert to Straight Lines	Převést na přímé čáry
 	Show Original Path	Zobrazit původní cestu
+	Open this dialog with these settings next time	Příště otevřít toto dialogové okno s tímto nastavením
+	Auto-Simplify	Automaticky zjednodušit
 	Transparency Options	Možnosti průhlednosti
 	Color Mixer (Shift-click the chip)	Míchání barev (Shift+kliknutí na políčko)
 	Fill: click for swatches, Shift-click for the color mixer	Výplň: kliknutím otevřete vzorník, Shift+kliknutím míchání barev
@@ -4173,6 +4175,7 @@ imageTrace	Outline	Obrys
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	pozadí {other}: transparent, white, black nebo barva jako "#ff8800"
 @msg	bad color {v}	chybná barva {v}
 @msg	the Color Picker is not open	Výběr barvy není otevřený
+@msg	the Simplify slider is not open	Posuvník Zjednodušit není otevřený
 @msg	the screen color sampler is already open	nástroj pro nabírání barvy z obrazovky už je otevřený
 @msg	this system has no screen color sampler	tento systém nemá nástroj pro nabírání barvy z obrazovky
 @msg	bad colour `{hex}` (#rrggbb)	chybná barva `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/da.tsv

@@ -5052,6 +5052,8 @@ swatch	Bright Violet	Kraftig violet
 	Outline Object	Objekt til kontur
 	Update Selection	Opdater markering
 	Show Original Path	Vis oprindelig kurve
+	Open this dialog with these settings next time	Åbn denne dialogboks med disse indstillinger næste gang
+	Auto-Simplify	Forenkl automatisk
 @msg	check a layer to export	markér et lag, der skal eksporteres
 @msg	select the art to export first	markér først grafikken, der skal eksporteres
 @msg	no saved selection recalled	ingen gemt markering hentet

crates/ui-egui/src/i18n/de.tsv

@@ -2907,6 +2907,8 @@ mark-style	Japanese	Japanisch
 	Show Note	Notiz einblenden
 	Show Options	Optionen einblenden
 	Show Original Path	Originalpfad einblenden
+	Open this dialog with these settings next time	Dieses Dialogfeld nächstes Mal mit diesen Einstellungen öffnen
+	Auto-Simplify	Automatisch vereinfachen
 	Color Panel Options	Optionen für das Farbbedienfeld
 	Show Package	Paket anzeigen
 	Show Panel	Bedienfeld einblenden
@@ -3808,6 +3810,7 @@ theme	Appearance	Erscheinungsbild
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	background {other}: transparent, white, black oder eine Farbe wie "#ff8800"
 @msg	bad color {v}	ungültige Farbe {v}
 @msg	the Color Picker is not open	der Farbwähler ist nicht geöffnet
+@msg	the Simplify slider is not open	der Regler „Vereinfachen“ ist nicht geöffnet
 @msg	the screen color sampler is already open	die Farbaufnahme vom Bildschirm ist bereits geöffnet
 @msg	this system has no screen color sampler	dieses System hat keine Farbaufnahme vom Bildschirm
 @msg	bad colour `{hex}` (#rrggbb)	ungültige Farbe `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/el.tsv

@@ -3325,6 +3325,8 @@ theme	Appearance	Εμφάνιση
 	Show Note	Εμφάνιση σημείωσης
 	Show Options	Εμφάνιση επιλογών
 	Show Original Path	Εμφάνιση αρχικής διαδρομής
+	Open this dialog with these settings next time	Άνοιγμα αυτού του παραθύρου με αυτές τις ρυθμίσεις την επόμενη φορά
+	Auto-Simplify	Αυτόματη απλοποίηση
 	Show Package	Εμφάνιση συσκευασίας
 	Show Panel	Εμφάνιση πίνακα
 	Show Pattern Swatches	Εμφάνιση δειγμάτων μοτίβου
@@ -5113,6 +5115,7 @@ effect	Points	Σημεία
 @msg	span: "selection" places a linear or radial gradient, not a freeform one	span: το "selection" τοποθετεί γραμμικό ή ακτινικό ντεγκραντέ, όχι ελεύθερης μορφής
 @msg	span: "selection" places the gradient itself: leave out `start` and `end` (they already place it in document coordinates)	span: το "selection" τοποθετεί το ίδιο το ντεγκραντέ: παραλείψτε τα `start` και `end` (το τοποθετούν ήδη σε συντεταγμένες εγγράφου)
 @msg	the Color Picker is not open	ο επιλογέας χρώματος δεν είναι ανοιχτός
+@msg	the Simplify slider is not open	ο ρυθμιστής Απλοποίησης δεν είναι ανοιχτός
 @msg	the action has no steps	η ενέργεια δεν έχει βήματα
 @msg	the file's layers weren't read ({_1}): it comes in as its page, in one layer	τα επίπεδα του αρχείου δεν διαβάστηκαν ({_1}): εισάγεται ως η σελίδα του, σε ένα επίπεδο
 @msg	the file's layers weren't read from its editing data ({_1}): they come from its PDF part	τα επίπεδα του αρχείου δεν διαβάστηκαν από τα δεδομένα επεξεργασίας του ({_1}): προέρχονται από το τμήμα PDF του

crates/ui-egui/src/i18n/es.tsv

@@ -2925,6 +2925,8 @@
 	Show Note	Mostrar nota
 	Show Options	Mostrar opciones
 	Show Original Path	Mostrar trazado original
+	Open this dialog with these settings next time	Abrir este cuadro de diálogo con estos ajustes la próxima vez
+	Auto-Simplify	Simplificar automáticamente
 	Color Panel Options	Opciones del panel Color
 	Show Package	Mostrar paquete
 	Show Panel	Mostrar panel
@@ -3871,6 +3873,7 @@ axis	Both	Ambos
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	fondo {other}: transparent, white, black o un color como "#ff8800"
 @msg	bad color {v}	color no válido {v}
 @msg	the Color Picker is not open	el Selector de color no está abierto
+@msg	the Simplify slider is not open	el regulador de Simplificar no está abierto
 @msg	the screen color sampler is already open	el muestreador de color de la pantalla ya está abierto
 @msg	this system has no screen color sampler	este sistema no tiene muestreador de color de la pantalla
 @msg	bad colour `{hex}` (#rrggbb)	color no válido `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/fi.tsv

@@ -1675,6 +1675,8 @@ lighting	Light	Valo
 	Corner Point Angle Threshold:	Kulmapisteiden kulmakynnys:
 	Convert to Straight Lines	Muunna suoriksi viivoiksi
 	Show Original Path	Näytä alkuperäinen polku
+	Open this dialog with these settings next time	Avaa tämä valintaikkuna näillä asetuksilla ensi kerralla
+	Auto-Simplify	Yksinkertaista automaattisesti
 	Transparency Options	Läpinäkyvyysasetukset
 	Color Mixer (Shift-click the chip)	Värisekoitin (Vaihto-napsauta värilaattaa)
 	Fill: click for swatches, Shift-click for the color mixer	Täyttö: napsauta avataksesi värimallit, Vaihto-napsauta avataksesi värisekoittimen
@@ -5125,6 +5127,7 @@ mark-style	Japanese	Japanilainen
 @msg	span: "selection" places a linear or radial gradient, not a freeform one	span: "selection" sijoittaa lineaarisen tai säteittäisen liukuvärin, ei vapaamuotoista
 @msg	span: "selection" places the gradient itself: leave out `start` and `end` (they already place it in document coordinates)	span: "selection" sijoittaa itse liukuvärin: jätä pois `start` ja `end` (ne sijoittavat sen jo asiakirjan koordinaatteihin)
 @msg	the Color Picker is not open	värinvalitsin ei ole auki
+@msg	the Simplify slider is not open	Yksinkertaista-liukusäädin ei ole auki
 @msg	the action has no steps	toiminnossa ei ole vaiheita
 @msg	the file's layers weren't read ({_1}): it comes in as its page, in one layer	tiedoston tasoja ei luettu ({_1}): se tuodaan sivunaan yhdelle tasolle
 @msg	the file's layers weren't read from its editing data ({_1}): they come from its PDF part	tiedoston tasoja ei luettu sen muokkaustiedoista ({_1}): ne tulevat sen PDF-osasta

crates/ui-egui/src/i18n/fr.tsv

@@ -2922,6 +2922,8 @@
 	Show Note	Afficher la note
 	Show Options	Afficher les options
 	Show Original Path	Afficher le tracé d’origine
+	Open this dialog with these settings next time	Ouvrir cette boîte de dialogue avec ces réglages la prochaine fois
+	Auto-Simplify	Simplifier automatiquement
 	Color Panel Options	Options du panneau Couleur
 	Show Package	Afficher le dossier d’assemblage
 	Show Panel	Afficher le panneau
@@ -3868,6 +3870,7 @@ axis	Both	Les deux
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	arrière-plan {other} : transparent, white, black ou une couleur comme "#ff8800"
 @msg	bad color {v}	couleur non valide {v}
 @msg	the Color Picker is not open	le Sélecteur de couleurs n’est pas ouvert
+@msg	the Simplify slider is not open	le curseur Simplifier n’est pas ouvert
 @msg	the screen color sampler is already open	l’outil de prélèvement de couleur à l’écran est déjà ouvert
 @msg	this system has no screen color sampler	ce système n’a pas d’outil de prélèvement de couleur à l’écran
 @msg	bad colour `{hex}` (#rrggbb)	couleur non valide `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/hu.tsv

@@ -3543,6 +3543,8 @@ mark-style	Japanese	Japán
 	Show Note	Megjegyzés megjelenítése
 	Show Options	Beállítások megjelenítése
 	Show Original Path	Eredeti útvonal megjelenítése
+	Open this dialog with these settings next time	Legközelebb ez a párbeszédablak nyíljon meg ezekkel a beállításokkal
+	Auto-Simplify	Automatikus egyszerűsítés
 	Color Panel Options	Szín panel beállításai
 	Show Package	Csomag megjelenítése
 	Show Panel	Panel megjelenítése
@@ -4414,6 +4416,7 @@ imageTrace	Outline	Körvonal
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	background {other}: transparent, white, black vagy egy szín, például "#ff8800"
 @msg	bad color {v}	hibás szín: {v}
 @msg	the Color Picker is not open	a Színválasztó nincs megnyitva
+@msg	the Simplify slider is not open	az Egyszerűsítés csúszka nincs megnyitva
 @msg	the screen color sampler is already open	a képernyős színmintavevő már nyitva van
 @msg	this system has no screen color sampler	ezen a rendszeren nincs képernyős színmintavevő
 @msg	bad colour `{hex}` (#rrggbb)	hibás szín: `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/id.tsv

@@ -5052,6 +5052,8 @@ swatch	Bright Violet	Violet cerah
 	Outline Object	Kerangka objek
 	Update Selection	Perbarui seleksi
 	Show Original Path	Tampilkan jalur asli
+	Open this dialog with these settings next time	Buka dialog ini dengan pengaturan ini lain kali
+	Auto-Simplify	Sederhanakan otomatis
 @msg	check a layer to export	centang lapisan yang akan diekspor
 @msg	select the art to export first	pilih dulu karya yang akan diekspor
 @msg	no saved selection recalled	tidak ada seleksi tersimpan yang dipanggil

crates/ui-egui/src/i18n/it.tsv

@@ -2958,6 +2958,8 @@ mark-style	Japanese	Giapponese
 	Show Note	Mostra nota
 	Show Options	Mostra opzioni
 	Show Original Path	Mostra tracciato originale
+	Open this dialog with these settings next time	Apri questa finestra di dialogo con queste impostazioni la prossima volta
+	Auto-Simplify	Semplifica automaticamente
 	Color Panel Options	Opzioni pannello Colore
 	Show Package	Mostra pacchetto
 	Show Panel	Mostra pannello
@@ -3910,6 +3912,7 @@ axis	Both	Entrambi
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	sfondo {other}: transparent, white, black o un colore come "#ff8800"
 @msg	bad color {v}	colore non valido {v}
 @msg	the Color Picker is not open	il Selettore colore non è aperto
+@msg	the Simplify slider is not open	il cursore Semplifica non è aperto
 @msg	the screen color sampler is already open	il campionatore di colore dello schermo è già aperto
 @msg	this system has no screen color sampler	questo sistema non ha un campionatore di colore dello schermo
 @msg	bad colour `{hex}` (#rrggbb)	colore non valido `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/ja.tsv

@@ -2766,6 +2766,8 @@ mark-style	Japanese	日本式
 	Show Note	メモを表示
 	Show Options	オプションを表示
 	Show Original Path	元のパスを表示
+	Open this dialog with these settings next time	次回はこの設定でこのダイアログを開く
+	Auto-Simplify	自動単純化
 	Color Panel Options	カラーパネルオプション
 	Show Package	パッケージを表示
 	Show Panel	パネルを表示
@@ -4225,6 +4227,7 @@ swatch	Bright Violet	ビビッドバイオレット
 @msg	no blend options	ブレンドオプションがありません
 @msg	bad color {v}	カラー {v} が正しくありません
 @msg	the Color Picker is not open	カラーピッカーが開いていません
+@msg	the Simplify slider is not open	単純化スライダーが開いていません
 @msg	the screen color sampler is already open	画面のカラーサンプラーはすでに開いています
 @msg	this system has no screen color sampler	このシステムには画面のカラーサンプラーがありません
 @msg	Corners edits the corners of a path	「コーナー」で編集できるのはパスの角だけです

crates/ui-egui/src/i18n/ka.tsv

@@ -4756,6 +4756,7 @@ imageTrace	Outline	კონტური
 @msg	the file's layers weren't read ({_1}): it comes in as its page, in one layer	ფაილის შრეები ვერ წაიკითხა ({_1}): ის გაიხსნება როგორც მისი გვერდი, ერთ შრეში
 @msg	the file's layers weren't read from its editing data ({_1}): they come from its PDF part	ფაილის შრეები რედაქტირების მონაცემებიდან ვერ წაიკითხა ({_1}): ისინი მისი PDF ნაწილიდან აიღება
 @msg	the Color Picker is not open	ფერის ამრჩევი გახსნილი არ არის
+@msg	the Simplify slider is not open	გამარტივების სლაიდერი გახსნილი არ არის
 @msg	the screen color sampler is already open	ეკრანიდან ფერის აღება უკვე გახსნილია
 @msg	this system has no screen color sampler	ამ სისტემას ეკრანიდან ფერის აღების საშუალება არ აქვს
 # Dimension tool and Object › Dimensions. A drafting dimension is ზომა (ზომის დასმა), like a dimension on a technical drawing.
@@ -4899,6 +4900,8 @@ imageTrace	Outline	კონტური
 	Rotate View to Selection	ხედის შემობრუნება მონიშნულის მიხედვით
 	Update Selection	მონიშნულის განახლება
 	Show Original Path	საწყისი ტრაექტორიის ჩვენება
+	Open this dialog with these settings next time	შემდეგ ჯერზე ამ დიალოგის ამ პარამეტრებით გახსნა
+	Auto-Simplify	ავტომატური გამარტივება
 	Texture Image	ტექსტურის გამოსახულება
 @msg	check a layer to export	მონიშნეთ საექსპორტო შრე
 @msg	select the art to export first	ჯერ მონიშნეთ საექსპორტო ნახატი

crates/ui-egui/src/i18n/ko.tsv

@@ -2760,6 +2760,8 @@ mark-style	Japanese	일본식
 	Show Note	메모 표시
 	Show Options	옵션 표시
 	Show Original Path	원래 패스 표시
+	Open this dialog with these settings next time	다음에 이 설정으로 이 대화상자 열기
+	Auto-Simplify	자동 단순화
 	Color Panel Options	색상 패널 옵션
 	Show Package	패키지 표시
 	Show Panel	패널 표시
@@ -4157,6 +4159,7 @@ theme	Appearance	외관
 @msg	no blend options	혼합 옵션이 없습니다
 @msg	bad color {v}	잘못된 색상 {v}
 @msg	the Color Picker is not open	색상 피커가 열려 있지 않습니다
+@msg	the Simplify slider is not open	단순화 슬라이더가 열려 있지 않습니다
 @msg	the screen color sampler is already open	화면 색상 추출기가 이미 열려 있습니다
 @msg	this system has no screen color sampler	이 시스템에는 화면 색상 추출기가 없습니다
 @msg	Corners edits the corners of a path	모퉁이는 패스의 모퉁이를 편집합니다

crates/ui-egui/src/i18n/nl.tsv

@@ -5064,6 +5064,8 @@ swatch	Bright Violet	Felviolet
 	Outline Object	Object omtrekken
 	Update Selection	Selectie bijwerken
 	Show Original Path	Oorspronkelijk pad tonen
+	Open this dialog with these settings next time	Dit dialoogvenster de volgende keer met deze instellingen openen
+	Auto-Simplify	Automatisch vereenvoudigen
 @msg	check a layer to export	vink een laag aan om te exporteren
 @msg	select the art to export first	selecteer eerst de illustratie die je wilt exporteren
 @msg	no saved selection recalled	geen opgeslagen selectie opgeroepen

crates/ui-egui/src/i18n/pl.tsv

@@ -1632,6 +1632,8 @@ lighting	Light	Światło
 	Corner Point Angle Threshold:	Próg kąta punktów narożnych:
 	Convert to Straight Lines	Konwertuj na linie proste
 	Show Original Path	Pokaż oryginalną ścieżkę
+	Open this dialog with these settings next time	Następnym razem otwórz to okno dialogowe z tymi ustawieniami
+	Auto-Simplify	Uprość automatycznie
 	Transparency Options	Opcje przezroczystości
 	Color Mixer (Shift-click the chip)	Mikser kolorów (kliknij próbkę z Shift)
 	Fill: click for swatches, Shift-click for the color mixer	Wypełnienie: kliknij, aby wybrać próbkę, z Shift — mikser kolorów
@@ -3995,6 +3997,7 @@ imageTrace	Outline	Kontur
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	tło {other}: transparent, white, black lub kolor, np. "#ff8800"
 @msg	bad color {v}	nieprawidłowy kolor {v}
 @msg	the Color Picker is not open	Próbnik kolorów nie jest otwarty
+@msg	the Simplify slider is not open	Suwak Uprość nie jest otwarty
 @msg	the screen color sampler is already open	narzędzie do pobierania koloru z ekranu jest już otwarte
 @msg	this system has no screen color sampler	ten system nie ma narzędzia do pobierania koloru z ekranu
 @msg	bad colour `{hex}` (#rrggbb)	nieprawidłowy kolor `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/pt-br.tsv

@@ -2430,6 +2430,8 @@
 	Show Note	Mostrar Nota
 	Show Options	Mostrar Opções
 	Show Original Path	Mostrar Caminho Original
+	Open this dialog with these settings next time	Abrir este diálogo com estas configurações na próxima vez
+	Auto-Simplify	Simplificar Automaticamente
 	Show Package	Mostrar Pacote
 	Show Panel	Mostrar Painel
 	Show Perspective Grid	Mostrar Grade de Perspectiva
@@ -5068,6 +5070,7 @@ mark-style	Japanese	Japonesas
 @msg	Unknown dimension mode	Modo de cota desconhecido
 @msg	Unknown dimension option {k}	Opção de cota desconhecida {k}
 @msg	the Color Picker is not open	o Seletor de Cores não está aberto
+@msg	the Simplify slider is not open	o controle deslizante Simplificar não está aberto
 @msg	the screen color sampler is already open	o coletor de cores da tela já está aberto
 @msg	this system has no screen color sampler	este sistema não tem coletor de cores da tela
 	Darkness	Escuridão

crates/ui-egui/src/i18n/ru.tsv

@@ -2954,6 +2954,8 @@ mark-style	Japanese	Японский
 	Show Note	Показать примечание
 	Show Options	Показать параметры
 	Show Original Path	Показать исходный контур
+	Open this dialog with these settings next time	Открывать это диалоговое окно с этими параметрами в следующий раз
+	Auto-Simplify	Автоматическое упрощение
 	Color Panel Options	Параметры панели «Цвет»
 	Show Package	Показать пакет
 	Show Panel	Показать панель
@@ -3906,6 +3908,7 @@ axis	Both	Оба
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	фон {other}: transparent, white, black или цвет, например "#ff8800"
 @msg	bad color {v}	недопустимый цвет {v}
 @msg	the Color Picker is not open	палитра цветов не открыта
+@msg	the Simplify slider is not open	ползунок «Упростить» не открыт
 @msg	the screen color sampler is already open	средство выбора цвета с экрана уже открыто
 @msg	this system has no screen color sampler	в этой системе нет средства выбора цвета с экрана
 @msg	bad colour `{hex}` (#rrggbb)	недопустимый цвет `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/sv.tsv

@@ -2868,6 +2868,8 @@
 	Show Note	Visa anteckning
 	Show Options	Visa alternativ
 	Show Original Path	Visa ursprunglig bana
+	Open this dialog with these settings next time	Öppna den här dialogrutan med de här inställningarna nästa gång
+	Auto-Simplify	Förenkla automatiskt
 	Show Package	Visa paket
 	Show Panel	Visa panel
 	Show Pattern Swatches	Visa mönsterprover
@@ -5117,6 +5119,7 @@ theme	Appearance	Utseende
 @msg	span: "selection" places a linear or radial gradient, not a freeform one	span: "selection" placerar en linjär eller radiell övertoning, inte en fri
 @msg	span: "selection" places the gradient itself: leave out `start` and `end` (they already place it in document coordinates)	span: "selection" placerar själva övertoningen: utelämna `start` och `end` (de placerar den redan i dokumentkoordinater)
 @msg	the Color Picker is not open	färgväljaren är inte öppen
+@msg	the Simplify slider is not open	Förenkla-reglaget är inte öppet
 @msg	the action has no steps	åtgärden har inga steg
 @msg	the file's layers weren't read ({_1}): it comes in as its page, in one layer	filens lager lästes inte ({_1}): den hämtas in som en sida, i ett enda lager
 @msg	the file's layers weren't read from its editing data ({_1}): they come from its PDF part	filens lager lästes inte från dess redigeringsdata ({_1}): de kommer från dess PDF-del

crates/ui-egui/src/i18n/uk.tsv

@@ -2950,6 +2950,8 @@ mark-style	Japanese	Японський
 	Show Note	Показати примітку
 	Show Options	Показати параметри
 	Show Original Path	Показати початковий контур
+	Open this dialog with these settings next time	Наступного разу відкривати це діалогове вікно з цими параметрами
+	Auto-Simplify	Автоматичне спрощення
 	Color Panel Options	Параметри панелі «Колір»
 	Show Package	Показати пакет
 	Show Panel	Показати панель
@@ -3894,6 +3896,7 @@ axis	Both	Обидві
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	фон {other}: transparent, white, black або колір, наприклад "#ff8800"
 @msg	bad color {v}	неприпустимий колір {v}
 @msg	the Color Picker is not open	палітра кольорів не відкрита
+@msg	the Simplify slider is not open	повзунок «Спростити» не відкрито
 @msg	the screen color sampler is already open	засіб вибору кольору з екрана вже відкритий
 @msg	this system has no screen color sampler	у цій системі немає засобу вибору кольору з екрана
 @msg	bad colour `{hex}` (#rrggbb)	неприпустимий колір `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/vi.tsv

@@ -3283,6 +3283,8 @@ mark-style	Japanese	Kiểu Nhật
 	Show Note	Hiện ghi chú
 	Show Options	Hiện tùy chọn
 	Show Original Path	Hiện đường dẫn gốc
+	Open this dialog with these settings next time	Lần sau mở hộp thoại này với các cài đặt này
+	Auto-Simplify	Tự động đơn giản hóa
 	Color Panel Options	Tùy chọn bảng màu
 	Show Package	Hiện gói
 	Show Panel	Hiện bảng
@@ -4062,6 +4064,7 @@ theme	Appearance	Giao diện
 @msg	background {other}: transparent, white, black or a colour such as "#ff8800"	background {other}: transparent, white, black hoặc màu như "#ff8800"
 @msg	bad color {v}	màu không hợp lệ {v}
 @msg	the Color Picker is not open	Bộ chọn màu chưa được mở
+@msg	the Simplify slider is not open	Thanh trượt Đơn giản hóa chưa được mở
 @msg	the screen color sampler is already open	công cụ lấy mẫu màu trên màn hình đã được mở
 @msg	this system has no screen color sampler	hệ thống này không có công cụ lấy mẫu màu trên màn hình
 @msg	bad colour `{hex}` (#rrggbb)	màu không hợp lệ `{hex}` (#rrggbb)

crates/ui-egui/src/i18n/zh-hans.tsv

@@ -2809,6 +2809,8 @@ font-script	Japanese	汉字
 	Show Note	显示注解
 	Show Options	显示选项
 	Show Original Path	显示原始路径
+	Open this dialog with these settings next time	下次以这些设置打开此对话框
+	Auto-Simplify	自动简化
 	Color Panel Options	颜色面板选项
 	Show Package	显示打包
 	Show Panel	显示面板
@@ -3971,6 +3973,7 @@ imageTrace	Outline	轮廓
 @msg	no blend options	没有混合选项
 @msg	bad color {v}	颜色 {v} 无效
 @msg	the Color Picker is not open	拾色器未打开
+@msg	the Simplify slider is not open	简化滑块未打开
 @msg	the screen color sampler is already open	屏幕取色器已打开
 @msg	this system has no screen color sampler	此系统没有屏幕取色器
 @msg	Corners edits the corners of a path	转角用于编辑路径的转角

crates/ui-egui/src/i18n/zh-hant.tsv

@@ -1979,6 +1979,7 @@ file-filter	Templates	範本
 @msg	no blend options	沒有漸變選項
 @msg	bad color {v}	顏色 {v} 無效
 @msg	the Color Picker is not open	「顏色選擇器」未開啟
+@msg	the Simplify slider is not open	「簡化」滑桿未開啟
 @msg	the screen color sampler is already open	螢幕取色器已開啟
 @msg	this system has no screen color sampler	此系統沒有螢幕取色器
 @msg	Corners edits the corners of a path	「轉角」用於編輯路徑的轉角
@@ -3676,6 +3677,8 @@ font-script	Japanese	漢字
 	Show Note	顯示註解
 	Show Options	顯示選項
 	Show Original Path	顯示原始路徑
+	Open this dialog with these settings next time	下次以這些設定開啟此對話方塊
+	Auto-Simplify	自動簡化
 	Color Panel Options	顏色面板選項
 	Show Package	顯示封裝
 	Show Panel	顯示面板

crates/ui-egui/src/menus.rs

@@ -666,6 +666,18 @@ pub const UI_COMMANDS: &[(&str, &str, &str, &str)] = &[
         "",
         "{id?, corners?: [i…]} open Corners for path `id` (default: the selected one) and its corners (anchor indices of the path with its corners uncut, as object.setLiveShape takes them: a rectangle's 0 top-left, 1 top-right, 2 bottom-right, 3 bottom-left; default: the Direct-Selected corners, else every corner) (dialog `corners`: kind (round|invertedRound|chamfer), radius (pt); double-clicking a corner widget opens it too): OK runs object.setLiveShape",
     ),
+    (
+        "ui.simplifyAuto",
+        "Auto-Simplify",
+        "",
+        "{} the open Simplify slider (Object › Path › Simplify opens it: dialog `simplifySlider` with field `level` 0..100, object.path.simplify's level, 50 as it opens, previewed on the canvas until ui.dialog.confirm keeps it as one undo step; after OK in the Simplify dialog with `retain` ticked, the menu item opens the dialog `simplify` with the fields of that OK instead) moves to the level object.path.simplify {auto: true} picks for the selection and previews it → {level}; an error when the slider isn't open",
+    ),
+    (
+        "ui.simplifyMoreOptions",
+        "More Options",
+        "",
+        "{} the Simplify dialog (dialog `simplify`: tolerance (pt), angleThreshold, straightLines, showOriginal, retain: ticked, OK makes Object › Path › Simplify open this dialog with these fields next time) takes the open Simplify slider's place, at the slider's tolerance → {tolerance}; an error when the slider isn't open",
+    ),
     (
         "ui.justification",
         "Justification…",
@@ -1583,6 +1595,8 @@ pub fn run_ui_command(app: &mut VectorcraftApp, id: &str, p: &Value) -> Option<R
             None => Err("no such user library".into()),
         },
         "ui.expandDialog" => crate::dialogs::expand::open(app),
+        "ui.simplifyAuto" => crate::dialogs::simplify_slider::auto(app),
+        "ui.simplifyMoreOptions" => crate::dialogs::simplify_slider::more_options(app),
         "attributes.openUrl" => crate::panels::attributes::open_url(app, p),
         "ui.javascriptFilesDialog" => crate::panels::svg_interactivity::files_dialog(app, p),
         "ui.spotColors" => crate::dialogs::spot_colors::open(app),
@@ -2292,6 +2306,7 @@ pub fn enabled(app: &VectorcraftApp, id: &str) -> bool {
         "ui.expandDialog" => app.session.active().is_some_and(|d| !d.selection.is_empty()),
         "ui.spotColors" => app.session.active().is_some(),
         "ui.menuDialog" => app.session.active().is_some_and(|d| !d.selection.is_empty()),
+        "ui.simplifyAuto" | "ui.simplifyMoreOptions" => crate::dialogs::simplify_slider::showing(app),
         "ui.dxfOptionsDialog" => app.session.active().is_some(),
         "links.editOriginal" | "links.reveal" => selected_image(app, |im| im.link.is_some()) || selected_placed(app),
         "ui.placementOptionsDialog" => selected_image(app, |_| true) || selected_placed(app),
@@ -3369,10 +3384,10 @@ fn menu_dialog(app: &VectorcraftApp, id: &str) -> Option<(&'static str, Value)>
         // Offset Path opens on the values it was last confirmed with.
         "object.path.offsetPath" if app.ui.offset_path.is_object() => ("offsetPath", app.ui.offset_path.clone()),
         "object.path.offsetPath" => ("offsetPath", json!({"offset": "10 pt", "joins": "miter", "miterLimit": 4})),
-        "object.path.simplify" => (
-            "simplify",
-            json!({"tolerance": "1 pt", "angleThreshold": crate::dialogs::path_ops::ANGLE_THRESHOLD, "straightLines": false, "showOriginal": false, "preview": true}),
-        ),
+        // Simplify opens its slider, or the dialog on the fields it was last confirmed with when
+        // "Open this dialog with these settings next time" was ticked.
+        "object.path.simplify" if app.ui.simplify.is_object() => ("simplify", app.ui.simplify.clone()),
+        "object.path.simplify" => (crate::dialogs::simplify_slider::KIND, crate::dialogs::simplify_slider::fields()),
         "object.path.splitIntoGrid" => {
             // The grid starts at the size of the selection.
             let size =

crates/ui-egui/src/state.rs

@@ -488,6 +488,11 @@ pub struct UiState {
     /// dialog opens on them (#1152).
     #[serde(default)]
     pub offset_path: Value,
+    /// The Simplify dialog's fields confirmed last with "Open this dialog with these settings next
+    /// time" ticked (null: not ticked): Object › Path › Simplify opens the dialog on them instead
+    /// of the Simplify slider.
+    #[serde(default)]
+    pub simplify: Value,
     /// The Move dialog's checkboxes as it was last confirmed with (copy, objects, preview; null:
     /// never used): it opens with them.
     #[serde(default)]
@@ -823,6 +828,7 @@ impl Default for UiState {
             dxf_options: Value::Null,
             eps_options: Value::Null,
             offset_path: Value::Null,
+            simplify: Value::Null,
             move_options: Value::Null,
             dxf_import: Value::Null,
             home: None,

docs/mcp.md

@@ -2024,6 +2024,23 @@ the path it had begun while that stays selected. Its reply's `tool` is the tool
 {"name":"run_command","arguments":{"command":"path.moveAnchors","params":{"dx":0,"dy":40}}}
 ```
 
+## Simplify
+
+`object.path.simplify` takes the amount as `tolerance` (points, 1 by default) or as the Simplify slider's `level`, a whole
+number from 0 (the fewest anchor points) to 100 (the closest fit). Level 50 is a tolerance of 1 pt, and every 10 levels
+halve or double it, so level 0 is 32 pt and level 100 is 1/32 pt. `auto: true` (Auto-Simplify) uses the lowest level
+whose tolerance is at most 1/400 of the selection's longer side, or level 100 when that side is under 12.5 pt. With
+`level` or `auto`, the reply also has the `level` used:
+
+```json
+{"name":"run_command","arguments":{"command":"object.path.simplify","params":{"auto":true}}}
+```
+
+In the desktop app, Object › Path › Simplify opens the slider (`ui.menuDialog {command: "object.path.simplify"}`,
+dialog `simplifySlider` with field `level`) and previews the result until `ui.dialog.confirm`. `ui.simplifyAuto` moves
+the open slider to the Auto-Simplify level, and `ui.simplifyMoreOptions` opens the Simplify dialog at the slider's
+tolerance. When OK confirms the dialog with `retain` ticked, the menu item opens the dialog on those settings next time.
+
 ## Editing a path with the Curvature tool
 
 The Curvature tool edits any selected path, whatever drew it, keeping its shape except where edited (#798). Each edit

docs/ui-parity.md

@@ -65,7 +65,7 @@ tools, never checked side by side) isn't captured row by row.
 | Join tool scrubbing, Average, Join | done | Join merges the direct-selected anchors lying on one another along a path, as after Average, into one (#1533) |
 | Average and Join in one step, with a corner or smooth choice for the joined anchor | partial | `path.join` accepts `to: corner|smooth` on the merged anchor; Average and Join are still separate commands; [gap 1](gaps.md) |
 | Smooth tool smooths only the stretch of path under the drag | done | #1512 |
-| Simplify (slider, auto, corner angle threshold) | partial | Tolerance, default-on Preview and original/new point counts (#1272); Corner Point Angle Threshold, Convert to Straight Lines and Show Original Path; slider, auto-simplify and Retain my latest settings remain missing |
+| Simplify (slider, auto, corner angle threshold) | partial | Tolerance, default-on Preview and original/new point counts (#1272); Corner Point Angle Threshold, Convert to Straight Lines and Show Original Path; the slider under the selection with Auto-Simplify and More Options, and the dialog's option to open it directly with its last settings; the slider opens at 1 pt rather than at the Auto-Simplify level, and simplifying only a Direct Selection part of a path remains missing |
 
 ## Direct Selection, anchors and handles