Merge #557: Fix #525: Image Trace of a large photo no longer crashes the app

# Conflicts:
#	ROADMAP.md

crates/engine/src/cmd/buildcmds.rs

@@ -640,6 +640,11 @@ fn trace_params(p: &Value) -> Result<tr::TraceParams> {
     serde_json::from_value(v).map_err(|e| bad("imageTrace.make", e.to_string()))
 }
 
+/// The most anchor points an Image Trace may make: a photo traced at high fidelity can make
+/// millions, more than the canvas draws smoothly or a laptop has memory for, so the trace is
+/// refused with advice instead (#525).
+pub const MAX_TRACE_ANCHORS: usize = 2_000_000;
+
 fn trace_make(s: &mut Session, p: &Value, expand: bool) -> Result<Value> {
     const C: &str = "imageTrace.make";
     let params = trace_params(p)?;
@@ -671,7 +676,7 @@ fn trace_make(s: &mut Session, p: &Value, expand: bool) -> Result<Value> {
     };
     let blob = s.doc()?.doc.images.get(&img.key).ok_or_else(|| EngineError::Other(format!("image data `{}` is missing", img.key)))?;
     let raster = tr::Raster::decode(&blob.bytes).map_err(|e| EngineError::Other(e.to_string()))?;
-    let res = tr::trace(&raster, &params);
+    let res = tr::trace_within(&raster, &params, MAX_TRACE_ANCHORS).map_err(|e| EngineError::Other(e.to_string()))?;
     // Pixel space of the decoded raster → the image object's pixel space → document.
     let sx = img.width.max(1) as f64 / raster.width.max(1) as f64;
     let sy = img.height.max(1) as f64 / raster.height.max(1) as f64;

crates/trace/src/lib.rs

@@ -27,6 +27,8 @@ mod fit;
 mod mosaic;
 mod quantize;
 
+use std::sync::atomic::{AtomicUsize, Ordering};
+
 use serde::{Deserialize, Serialize};
 use vectorcraft_geom::PathData;
 
@@ -41,8 +43,18 @@ pub enum TraceError {
     Decode(String),
     #[error("image is empty")]
     Empty,
+    #[error("the image is {width} × {height} pixels, more than Image Trace takes ({max} megapixels)")]
+    TooLarge { width: u32, height: u32, max: u64 },
+    #[error(
+        "this trace would make more than {max} anchor points, more than the document can show smoothly: raise Noise, lower Paths or Colors, or pick a lower-fidelity preset"
+    )]
+    TooComplex { max: usize },
 }
 
+/// The most pixels an image to trace may have (64 megapixels: 256 MB decoded); larger images are
+/// refused instead of running out of memory.
+pub const MAX_PIXELS: u64 = 64 << 20;
+
 /// An RGBA8 raster (row-major, top row first).
 #[derive(Clone, Debug, PartialEq)]
 pub struct Raster {
@@ -67,13 +79,19 @@ impl Raster {
         }
         Self { width, height, rgba }
     }
-    /// Decode PNG / JPEG / WebP / GIF bytes.
+    /// Decode PNG / JPEG / WebP / GIF bytes (at most [`MAX_PIXELS`], checked before decoding).
     pub fn decode(bytes: &[u8]) -> Result<Self, TraceError> {
-        let img = image::load_from_memory(bytes).map_err(|e| TraceError::Decode(e.to_string()))?.to_rgba8();
-        let (w, h) = img.dimensions();
+        let decode_err = |e: image::ImageError| TraceError::Decode(e.to_string());
+        let reader = image::ImageReader::new(std::io::Cursor::new(bytes)).with_guessed_format().map_err(|e| TraceError::Decode(e.to_string()))?;
+        let (w, h) = reader.into_dimensions().map_err(decode_err)?;
         if w == 0 || h == 0 {
             return Err(TraceError::Empty);
         }
+        if u64::from(w) * u64::from(h) > MAX_PIXELS {
+            return Err(TraceError::TooLarge { width: w, height: h, max: MAX_PIXELS >> 20 });
+        }
+        let img = image::load_from_memory(bytes).map_err(decode_err)?.to_rgba8();
+        let (w, h) = img.dimensions();
         Ok(Self { width: w, height: h, rgba: img.into_raw() })
     }
     /// Encode as PNG.
@@ -262,17 +280,25 @@ fn is_white(c: [u8; 3]) -> bool {
 
 /// Trace `img` with `params`.
 pub fn trace(img: &Raster, params: &TraceParams) -> TraceResult {
+    // No trace has more than `usize::MAX` anchors.
+    trace_within(img, params, usize::MAX).unwrap_or_default()
+}
+
+/// Trace `img` with `params`, giving up with [`TraceError::TooComplex`] once the paths have more
+/// than `max_anchors` anchor points (a photo traced at high fidelity can make millions). The
+/// colour layers are traced in parallel where threads are available.
+pub fn trace_within(img: &Raster, params: &TraceParams, max_anchors: usize) -> Result<TraceResult, TraceError> {
     let (w, h) = (img.width as usize, img.height as usize);
-    if w == 0 || h == 0 {
-        return TraceResult::default();
+    if w == 0 || h == 0 || img.rgba.len() != w * h * 4 {
+        return Ok(TraceResult::default());
     }
     let mut q = quantize(img, params);
     denoise(&mut q.labels, w, h, params.noise as usize);
     // Pixel count per palette entry.
     let mut counts = vec![0usize; q.palette.len()];
     for &l in &q.labels {
-        if l != TRANSPARENT {
-            counts[l as usize] += 1;
+        if let Some(c) = counts.get_mut(l as usize) {
+            *c += 1;
         }
     }
     // Layers bottom → top: largest area first.
@@ -282,46 +308,117 @@ pub fn trace(img: &Raster, params: &TraceParams) -> TraceResult {
     for (r, &i) in order.iter().enumerate() {
         rank[i] = r;
     }
-    let opts = fit::FitOptions {
-        polygon_tol: params.polygon_tolerance(),
-        fit_tol: params.fit_tolerance(),
-        corner_angle: params.corner_angle(),
-        snap_lines: params.snap_curves_to_lines,
+    let layers: Vec<(usize, usize)> =
+        order.iter().copied().enumerate().filter(|&(_, ci)| !(params.ignore_white && is_white(q.palette[ci]))).collect();
+    let job = Layers {
+        q: &q,
+        rank: &rank,
+        params,
+        opts: fit::FitOptions {
+            polygon_tol: params.polygon_tolerance(),
+            fit_tol: params.fit_tolerance(),
+            corner_angle: params.corner_angle(),
+            snap_lines: params.snap_curves_to_lines,
+        },
+        w,
+        h,
+        anchors: AtomicUsize::new(0),
+        max_anchors,
     };
-    let min_hole = params.noise.max(1) as i64;
     let mut out = TraceResult::default();
-    let mut mask = vec![false; w * h];
-    for (r, &ci) in order.iter().enumerate() {
+    for (paths, &(_, ci)) in parallel_map(&layers, |&(r, ci)| job.layer(r, ci)).into_iter().zip(&layers) {
+        out.paths.extend(paths.ok_or(TraceError::TooComplex { max: max_anchors })?);
         let color = q.palette[ci];
-        if params.ignore_white && is_white(color) {
-            continue;
-        }
-        let overlapping = params.method == Method::Overlapping;
-        for (m, &l) in mask.iter_mut().zip(&q.labels) {
-            *m = l != TRANSPARENT && if overlapping { rank[l as usize] >= r } else { l as usize == ci };
-        }
-        for comp in trace_mask(&mask, w, h) {
-            let mut subs = Vec::with_capacity(1 + comp.holes.len());
-            if let Some(sp) = fit::fit_loop(&comp.outer, &opts) {
-                subs.push(sp);
-            } else {
-                continue;
-            }
-            for hole in &comp.holes {
-                if hole.area2.abs() / 2 < min_hole && params.noise > 0 {
-                    continue;
-                }
-                if let Some(sp) = fit::fit_loop(hole, &opts) {
-                    subs.push(sp);
-                }
-            }
-            out.paths.push(TracedPath { path: PathData::new(subs), color, pixels: comp.pixels });
-        }
         if !out.palette.contains(&color) {
             out.palette.push(color);
         }
     }
-    out
+    Ok(out)
+}
+
+/// What tracing one colour layer needs.
+struct Layers<'a> {
+    q: &'a Quantized,
+    /// Each palette entry's layer, bottom (0) up.
+    rank: &'a [usize],
+    params: &'a TraceParams,
+    opts: fit::FitOptions,
+    w: usize,
+    h: usize,
+    /// Anchor points made so far, by every layer.
+    anchors: AtomicUsize,
+    max_anchors: usize,
+}
+
+impl Layers<'_> {
+    /// The paths of layer `r` (palette entry `ci`), or `None` once the anchors made pass the
+    /// maximum.
+    fn layer(&self, r: usize, ci: usize) -> Option<Vec<TracedPath>> {
+        let (params, opts) = (self.params, &self.opts);
+        let color = *self.q.palette.get(ci)?;
+        let overlapping = params.method == Method::Overlapping;
+        let mask: Vec<bool> = self
+            .q
+            .labels
+            .iter()
+            .map(|&l| l != TRANSPARENT && if overlapping { self.rank.get(l as usize).is_some_and(|&lr| lr >= r) } else { l as usize == ci })
+            .collect();
+        let min_hole = params.noise.max(1) as i64;
+        let mut paths = vec![];
+        for comp in trace_mask(&mask, self.w, self.h) {
+            let Some(outer) = fit::fit_loop(&comp.outer, opts) else { continue };
+            let mut subs = vec![outer];
+            for hole in &comp.holes {
+                if hole.area2.abs() / 2 < min_hole && params.noise > 0 {
+                    continue;
+                }
+                subs.extend(fit::fit_loop(hole, opts));
+            }
+            let path = PathData::new(subs);
+            let n = path.anchor_count();
+            if self.anchors.fetch_add(n, Ordering::Relaxed).saturating_add(n) > self.max_anchors {
+                return None;
+            }
+            paths.push(TracedPath { path, color, pixels: comp.pixels });
+        }
+        Some(paths)
+    }
+}
+
+/// `f` of each of `items`, in order, spread over the available cores.
+#[cfg(not(target_arch = "wasm32"))]
+fn parallel_map<T: Sync, R: Send>(items: &[T], f: impl Fn(&T) -> R + Sync) -> Vec<R> {
+    let threads = std::thread::available_parallelism().map_or(1, |n| n.get()).min(items.len());
+    if threads <= 1 {
+        return items.iter().map(f).collect();
+    }
+    let next = AtomicUsize::new(0);
+    let mut done: Vec<(usize, R)> = std::thread::scope(|s| {
+        let workers: Vec<_> = (0..threads)
+            .map(|_| {
+                s.spawn(|| {
+                    let mut mine = vec![];
+                    loop {
+                        let i = next.fetch_add(1, Ordering::Relaxed);
+                        let Some(item) = items.get(i) else { break };
+                        mine.push((i, f(item)));
+                    }
+                    mine
+                })
+            })
+            .collect();
+        // A worker's panic goes on in this thread, as if it had run here (the engine's guard
+        // reports it).
+        workers.into_iter().flat_map(|w| w.join().unwrap_or_else(|e| std::panic::resume_unwind(e))).collect()
+    });
+    done.sort_by_key(|(i, _)| *i);
+    done.into_iter().map(|(_, r)| r).collect()
+}
+
+/// `f` of each of `items`, in order (no threads on the web).
+#[cfg(target_arch = "wasm32")]
+fn parallel_map<T: Sync, R: Send>(items: &[T], f: impl Fn(&T) -> R + Sync) -> Vec<R> {
+    items.iter().map(f).collect()
 }
 
 #[cfg(test)]

crates/trace/src/tests.rs

@@ -278,3 +278,73 @@ fn timing_1000x1000_bw_under_300ms() {
     assert!(!res.paths.is_empty());
     assert!(ms < 300.0, "{ms} ms");
 }
+
+/// Stripes of `n` colours, each with a few dots of the next one: many layers, many small shapes.
+fn stripes(size: u32, n: u32) -> Raster {
+    let colour = |i: u32| [(i * 37 % 256) as u8, (i * 91 % 256) as u8, (i * 53 % 256) as u8, 255];
+    Raster::from_fn(size, size, |x, y| {
+        let band = x * n / size;
+        if (x % 9 < 3) && (y % 9 < 3) { colour(band + 1) } else { colour(band) }
+    })
+}
+
+/// #525: past the anchor budget the trace gives up with advice instead of making millions of
+/// anchors; under it, it is the plain trace.
+#[test]
+fn a_trace_past_its_anchor_budget_is_refused() {
+    let img = stripes(120, 8);
+    let p = TraceParams { mode: Mode::Color, colors: 16, noise: 1, ..TraceParams::default() };
+    let full = trace(&img, &p);
+    let anchors = full.anchor_count();
+    assert!(anchors > 100, "{anchors} anchors");
+    assert!(matches!(trace_within(&img, &p, anchors / 2), Err(TraceError::TooComplex { max }) if max == anchors / 2));
+    assert_eq!(trace_within(&img, &p, anchors).unwrap(), full);
+}
+
+/// Layers traced in parallel come out in the same order every time: bottom (largest) first.
+#[test]
+fn parallel_layers_keep_their_order() {
+    let img = stripes(90, 12);
+    let p = TraceParams { mode: Mode::Color, colors: 24, noise: 1, method: Method::Overlapping, ..TraceParams::default() };
+    let a = trace(&img, &p);
+    assert!(a.palette.len() > 8, "{} colours", a.palette.len());
+    for _ in 0..4 {
+        assert_eq!(trace(&img, &p), a);
+    }
+    // Overlapping: each layer's shapes cover the layers above, so the pixel counts fall upwards.
+    let firsts: Vec<usize> = a.palette.iter().filter_map(|c| a.paths.iter().find(|t| t.color == *c).map(|t| t.pixels)).collect();
+    assert!(firsts.windows(2).all(|w| w[0] >= w[1]), "{firsts:?}");
+}
+
+/// A PNG whose header says `w` × `h` pixels, with no image data.
+fn png_header(w: u32, h: u32) -> Vec<u8> {
+    fn crc(bytes: &[u8]) -> u32 {
+        let mut c = !0u32;
+        for &b in bytes {
+            c ^= u32::from(b);
+            for _ in 0..8 {
+                c = if c & 1 != 0 { 0xEDB8_8320 ^ (c >> 1) } else { c >> 1 };
+            }
+        }
+        !c
+    }
+    let mut ihdr = b"IHDR".to_vec();
+    ihdr.extend(w.to_be_bytes());
+    ihdr.extend(h.to_be_bytes());
+    ihdr.extend([8, 6, 0, 0, 0]);
+    let mut png = b"\x89PNG\r\n\x1a\n".to_vec();
+    for chunk in [ihdr, b"IDAT".to_vec(), b"IEND".to_vec()] {
+        png.extend((chunk.len() as u32 - 4).to_be_bytes());
+        png.extend(&chunk);
+        png.extend(crc(&chunk).to_be_bytes());
+    }
+    png
+}
+
+/// An image too large to trace is refused from its header, before it is decoded.
+#[test]
+fn an_image_too_large_to_trace_is_refused_before_decoding() {
+    let err = Raster::decode(&png_header(30_000, 30_000)).unwrap_err();
+    assert!(matches!(err, TraceError::TooLarge { width: 30_000, height: 30_000, .. }), "{err}");
+    assert!(matches!(Raster::decode(&png_header(64, 64)), Err(TraceError::Decode(_))), "a small header goes on to decoding");
+}

crates/ui-egui/src/canvas.rs

@@ -1041,6 +1041,27 @@ fn node_outline(n: &Node) -> BezPath {
     bp
 }
 
+/// The most anchor points the selection's outlines and anchors, and the hover highlight, are drawn
+/// for: an Image Trace of a photo selects hundreds of thousands of paths at once, whose outlines
+/// would make a mesh larger than the GPU takes in one buffer (#525).
+const OVERLAY_MAX_ANCHORS: usize = 100_000;
+
+/// Whether `nodes` have more than [`OVERLAY_MAX_ANCHORS`] anchor points to outline (counting
+/// stops there).
+fn too_many_anchors<'a>(nodes: impl IntoIterator<Item = &'a Node>) -> bool {
+    fn over(n: &Node, left: &mut usize) -> bool {
+        if let NodeKind::Path { path, .. } = &n.kind {
+            match left.checked_sub(path.anchor_count()) {
+                Some(l) => *left = l,
+                None => return true,
+            }
+        }
+        !matches!(n.kind, NodeKind::Envelope { .. }) && n.children().into_iter().flatten().any(|c| over(c, left))
+    }
+    let mut left = OVERLAY_MAX_ANCHORS;
+    nodes.into_iter().any(|n| over(n, &mut left))
+}
+
 /// [`Node::walk`] over what a selection highlight shows: an envelope's content is left out (the
 /// envelope shows its mesh instead).
 fn walk_drawn<'a>(n: &'a Node, f: &mut impl FnMut(&'a Node)) {
@@ -1160,7 +1181,7 @@ fn hover_highlight(app: &VectorcraftApp, p: &egui::Painter, xf: &Xf) {
     if st.selection.contains(id) {
         return;
     }
-    if let Some(n) = st.doc.node(id) {
+    if let Some(n) = st.doc.node(id).filter(|n| !too_many_anchors([*n])) {
         let color = c32(st.doc.layer_color(id));
         stroke_path(p, &node_outline(n), xf, Stroke::new(1.5, color));
     }
@@ -1351,6 +1372,9 @@ fn selection_overlay(app: &mut VectorcraftApp, p: &egui::Painter, xf: &Xf) {
         && app.ui.view.bounding_box
         && app.session.active().is_some_and(|st| !st.selection.is_empty() && st.selection.anchors.is_empty());
     let bbox = if show_box { app.selection_box() } else { None };
+    let st = app.session.active();
+    let big = st.is_some_and(|st| too_many_anchors(st.selection.objects.iter().filter_map(|id| st.doc.node(*id))));
+    let big_bounds = if big { app.selection_bounds() } else { None };
     let app = &*app;
     let Some(st) = app.session.active() else { return };
     let tool = app.session.tool_id();
@@ -1363,7 +1387,11 @@ fn selection_overlay(app: &mut VectorcraftApp, p: &egui::Painter, xf: &Xf) {
     // The selected anchors' handles (drawn once they are counted: Show handles when multiple
     // anchors are selected off shows them for a single one only).
     let (mut handles, mut with_handles) = (vec![], 0);
-    for id in &st.selection.objects {
+    // Too many paths to outline: the selection's bounds stand for them.
+    if let Some((b, id)) = big_bounds.zip(st.selection.objects.first()) {
+        stroke_path(p, &vectorcraft_geom::shapes::rectangle(b).to_bezpath(), xf, Stroke::new(1.0, c32(st.doc.layer_color(*id))));
+    }
+    for id in st.selection.objects.iter().filter(|_| !big) {
         let Some(n) = st.doc.node(*id) else { continue };
         let color = c32(st.doc.layer_color(*id));
         let partial = st.selection.partial(*id);
@@ -1633,11 +1661,13 @@ pub(crate) fn task_bar_rect(ctx: &egui::Context) -> Option<egui::Rect> {
 /// selection, pinned it stays put ([`crate::state::TaskBarPlace`]).
 fn task_bar(app: &mut VectorcraftApp, ui: &mut Ui, xf: &Xf) {
     let t = Tokens::get(ui.ctx());
-    let Some(st) = app.session.active() else { return };
-    if st.selection.is_empty() || !matches!(app.session.tool_id(), "selection" | "directSelection" | "groupSelection") {
+    if app.session.active().is_none_or(|st| st.selection.is_empty())
+        || !matches!(app.session.tool_id(), "selection" | "directSelection" | "groupSelection")
+    {
         return;
     }
-    let Some(b) = st.doc.bounds_of(&st.selection.objects, true) else { return };
+    let Some(b) = app.selection_bounds() else { return };
+    let Some(st) = app.session.active() else { return };
     let n = st.selection.len();
     let first = st.selection.objects.first().and_then(|id| st.doc.node(*id)).cloned();
     let is_group = first.as_ref().is_some_and(|f| matches!(f.kind, NodeKind::Group { .. }));
@@ -2024,6 +2054,29 @@ mod tests {
         assert_eq!(cmd_drag(&mut app, inside, inside), "selection");
     }
 
+    /// #525: a selection with more anchors than the overlay draws (a traced photo) shows its bounds,
+    /// not every outline and anchor, which made a mesh larger than the GPU takes; an ordinary one
+    /// still shows its outline and anchors.
+    #[test]
+    fn a_huge_selection_shows_its_bounds_instead_of_every_outline() {
+        let mut app = VectorcraftApp::new(Session::new(), Default::default());
+        app.session.execute("file.new", &json!({"width": 400, "height": 300})).unwrap();
+        let points = |n: usize| (0..n).map(|i| format!("L{} {}", 20.0 + 360.0 * i as f64 / n as f64, 100 + (i % 2) * 50)).collect::<String>();
+        let ctx = egui::Context::default();
+        let mut drawn = |n: usize| {
+            app.session.execute("path.create", &json!({"d": format!("M20 20 {} Z", points(n))})).unwrap();
+            frame(&mut app, &ctx, vec![]);
+            let shapes = shapes(&mut app, &ctx);
+            let points: usize = shapes.iter().map(|s| if let Shape::Path(ps) = s { ps.points.len() } else { 0 }).sum();
+            let squares = shapes.iter().filter(|s| matches!(s, Shape::Rect(_))).count();
+            (points, squares)
+        };
+        let (points, squares) = drawn(OVERLAY_MAX_ANCHORS + 10);
+        assert!(points < 100 && squares < 100, "{points} outline points, {squares} squares");
+        let (points, squares) = drawn(200);
+        assert!(points > 200 && squares > 200, "{points} outline points, {squares} squares");
+    }
+
     /// One headless canvas frame → the shapes drawn, `Shape::Vec`s flattened.
     fn shapes(app: &mut VectorcraftApp, ctx: &egui::Context) -> Vec<Shape> {
         let (shapes, mut delta) = frame_output(app, ctx);

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

@@ -3415,6 +3415,10 @@ axis	Both	Ambos
 @msg	select a stroke with a variable width	selecciona un trazo con anchura variable
 @msg	select a symbol instance	selecciona una instancia de símbolo
 @msg	select an Image Trace object	selecciona un objeto de calco de imagen
+@msg	could not decode image: {0}	no se pudo decodificar la imagen: {0}
+@msg	image is empty	la imagen está vacía
+@msg	the image is {width} × {height} pixels, more than Image Trace takes ({max} megapixels)	la imagen mide {width} × {height} píxeles, más de lo que admite Calco de imagen ({max} megapíxeles)
+@msg	this trace would make more than {max} anchor points, more than the document can show smoothly: raise Noise, lower Paths or Colors, or pick a lower-fidelity preset	este calco crearía más de {max} puntos de ancla, más de los que el documento puede mostrar con fluidez: sube Ruido, baja Trazados o Colores, o elige un preajuste de menor fidelidad
 @msg	select an envelope	selecciona una envolvente
 @msg	select an image	selecciona una imagen
 @msg	select an object in perspective	selecciona un objeto en perspectiva

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

@@ -3415,6 +3415,10 @@ axis	Both	Entrambi
 @msg	select a stroke with a variable width	seleziona una traccia con larghezza variabile
 @msg	select a symbol instance	seleziona un'istanza di simbolo
 @msg	select an Image Trace object	seleziona un oggetto di ricalco immagine
+@msg	could not decode image: {0}	impossibile decodificare l'immagine: {0}
+@msg	image is empty	l'immagine è vuota
+@msg	the image is {width} × {height} pixels, more than Image Trace takes ({max} megapixels)	l'immagine misura {width} × {height} pixel, più di quanto accetti Ricalco immagine ({max} megapixel)
+@msg	this trace would make more than {max} anchor points, more than the document can show smoothly: raise Noise, lower Paths or Colors, or pick a lower-fidelity preset	questo ricalco creerebbe più di {max} punti di ancoraggio, più di quanti il documento possa mostrare in modo fluido: aumenta Disturbo, riduci Tracciati o Colori, oppure scegli un preset a fedeltà inferiore
 @msg	select an envelope	seleziona un involucro
 @msg	select an image	seleziona un'immagine
 @msg	select an object in perspective	seleziona un oggetto in prospettiva

crates/ui-egui/src/i18n/tests.rs

@@ -711,7 +711,7 @@ fn complete_languages_translate_every_message() {
 const COMPLETE_MESSAGES: &[&str] = &["es", "it"];
 
 /// Crates whose error and status messages reach the status bar.
-const MESSAGE_CRATES: &[&str] = &["ui-egui", "engine", "doc", "format", "svg", "pdf", "eps", "text", "plugins", "metafile", "cad"];
+const MESSAGE_CRATES: &[&str] = &["ui-egui", "engine", "doc", "format", "svg", "pdf", "eps", "text", "plugins", "metafile", "cad", "trace"];
 
 /// Where a message literal starts: a status, an error value, a `thiserror` message.
 const MESSAGE_MARKERS: &[&str] = &[".status(", "ui.status = ", "status = ", "Other(", "Err(", "ok_or(", "ok_or_else(|| ", "#[error("];

crates/ui-egui/src/lib.rs

@@ -249,6 +249,8 @@ pub struct CanvasCache {
     pub print_tiling: Option<PrintTilingCache>,
     /// [`VectorcraftApp::selection_box`] for (document uid, revision, Use Preview Bounds).
     pub selection_box: Option<((u64, u64, bool), Option<vectorcraft_doc::OrientedBox>)>,
+    /// [`VectorcraftApp::selection_bounds`] for (document uid, revision).
+    pub selection_bounds: Option<((u64, u64), Option<vectorcraft_geom::Rect>)>,
     /// The tools' cursors as OS cursor bitmaps.
     pub cursors: cursors::Images,
 }
@@ -389,6 +391,7 @@ impl VectorcraftApp {
                 slices: None,
                 print_tiling: None,
                 selection_box: None,
+                selection_bounds: None,
                 cursors: Default::default(),
             },
             perf: Perf::default(),
@@ -704,6 +707,22 @@ impl VectorcraftApp {
         self.canvas.selection_box = Some((key, b));
         b
     }
+
+    /// The selection's visual bounds (stroke and effects included), square to the page: measured
+    /// once per revision, as the canvas reads it every frame (a traced photo selects a group of
+    /// hundreds of thousands of paths).
+    pub fn selection_bounds(&mut self) -> Option<vectorcraft_geom::Rect> {
+        let st = self.session.active()?;
+        let key = (st.uid, st.revision);
+        if let Some((k, b)) = self.canvas.selection_bounds
+            && k == key
+        {
+            return b;
+        }
+        let b = st.doc.bounds_of(&st.selection.objects, true);
+        self.canvas.selection_bounds = Some((key, b));
+        b
+    }
 }
 
 /// eframe isn't a dependency of this crate (the host owns the event loop); these entry points are