address review: index placeable array replacements, search past zero-length DIVIDE runs, per-part broken-table outlines

A path naming an endless device or a FIFO was buffered to EOF before any size check ran, so one short command could exhaust memory or block. These paths now go through capped_read::read_capped, which refuses non-regular files and enforces the byte limit while reading.

Cargo.lock

@@ -614,7 +614,7 @@ checksum = "fc652a48c352aef3ea3aed32080501cf3ef6ed5da78602a020c991775b0aff04"
 
 [[package]]
 name = "cadcraft"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-engine",
  "cadcraft-io",
@@ -631,6 +631,7 @@ dependencies = [
  "log",
  "muda",
  "objc2-app-kit 0.3.2",
+ "pollster 1.0.1",
  "rfd",
  "ron",
  "serde_json",
@@ -644,7 +645,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-cli"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-engine",
  "cadcraft-io",
@@ -660,14 +661,14 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-color"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "cadcraft-constraints"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-doc",
  "cadcraft-geom",
@@ -677,7 +678,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-doc"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-color",
  "cadcraft-geom",
@@ -688,7 +689,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-dwg"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "acadrust",
  "log",
@@ -696,7 +697,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-dxf"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "encoding_rs",
  "log",
@@ -705,7 +706,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-engine"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-color",
  "cadcraft-constraints",
@@ -726,7 +727,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-fonts"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-dxf",
  "cadcraft-geom",
@@ -739,14 +740,14 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-geom"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "serde",
 ]
 
 [[package]]
 name = "cadcraft-io"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "acadrust",
  "cadcraft-color",
@@ -768,7 +769,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-mcp"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-engine",
  "cadcraft-io",
@@ -782,7 +783,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-render"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-color",
  "cadcraft-doc",
@@ -796,7 +797,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-ui-egui"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-color",
  "cadcraft-doc",
@@ -823,7 +824,7 @@ dependencies = [
 
 [[package]]
 name = "cadcraft-web"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "cadcraft-engine",
  "cadcraft-fonts",
@@ -5991,7 +5992,7 @@ checksum = "9440ea3e5aeabb0ac63af70daf835274065238cdd0cec83418f417eae38bacee"
 
 [[package]]
 name = "xtask"
-version = "0.19.0"
+version = "0.17.0"
 dependencies = [
  "chrono",
  "serde_json",

Cargo.toml

@@ -4,7 +4,7 @@ members = ["crates/*", "apps/*", "xtask"]
 # default-members
 
 [workspace.package]
-version = "0.19.0"
+version = "0.17.0"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 rust-version = "1.95"

apps/cadcraft/Cargo.toml

@@ -55,7 +55,11 @@ muda = { version = "0.21", default-features = false }
 objc2-app-kit = { version = "0.3", default-features = false, features = ["std", "NSWorkspace", "NSAccessibility"] }
 # The same winit eframe uses (the storytold fork, patched in the workspace): its opt-in that turns
 # AppKit's terminate (Cmd+Q, Dock Quit) into a close request, so unsaved changes are asked about.
-winit = { version = "0.30", default-features = false }
+# `rwh_06`: the window handle a file dialog shown as a sheet attaches to (src/sheet.rs).
+winit = { version = "0.30", default-features = false, features = ["rwh_06"] }
+# Waits for the answer of a file dialog shown as a sheet (src/sheet.rs). MIT OR Apache-2.0, already
+# in Cargo.lock through eframe.
+pollster = "1"
 
 # Rust HID backends: no proprietary SDK or C HID library.
 [target.'cfg(target_os = "windows")'.dependencies]

apps/cadcraft/src/logging.rs

@@ -148,7 +148,20 @@ pub fn rotate(dir: &Path) -> std::io::Result<(PathBuf, File)> {
 /// One formatted log line: `<timestamp> <LEVEL> [<thread>] <target>: <message>\n`.
 pub fn format_line(ts: &str, level: log::Level, thread: &str, target: &str, message: &str) -> String {
     let message = message.strip_suffix('\n').unwrap_or(message);
-    format!("{ts} {level:<5} [{thread}] {target}: {message}\n")
+    // A message can carry text from a file (a code page name, a path), so it must not be able to
+    // start what looks like another record: control characters other than tab and line feed are
+    // shown escaped, and every continuation line is indented, so only this function's own
+    // timestamp is ever at the start of a line.
+    let mut safe = String::with_capacity(message.len());
+    for c in message.chars() {
+        match c {
+            '\n' => safe.push_str("\n    "),
+            '\t' => safe.push('\t'),
+            c if c.is_control() => safe.extend(c.escape_default()),
+            c => safe.push(c),
+        }
+    }
+    format!("{ts} {level:<5} [{thread}] {target}: {safe}\n")
 }
 
 /// Where formatted lines go besides standard error: kept in memory until a file is attached,
@@ -441,8 +454,14 @@ mod tests {
             format_line("2026-10-08T07:59:17.728Z", log::Level::Warn, "main", "cadcraft", "app icon: invalid PNG signature"),
             "2026-10-08T07:59:17.728Z WARN  [main] cadcraft: app icon: invalid PNG signature\n"
         );
-        // A multi-line message keeps its lines; the record still ends in exactly one newline.
-        assert!(format_line("t", log::Level::Error, "w", "x", "a\nb\n").ends_with("x: a\nb\n"));
+        // A multi-line message keeps its lines, indented so they can't pass for records; the
+        // record still ends in exactly one newline.
+        assert!(format_line("t", log::Level::Error, "w", "x", "a\nb\n").ends_with("x: a\n    b\n"));
+        // Control characters in a message (from a file) can't forge a record.
+        let forged = format_line("t", log::Level::Warn, "w", "x", "page\r\n2026-01-01T00:00:00Z ERROR [main] x: fake\u{1b}[0m");
+        assert_eq!(forged.lines().count(), 2);
+        assert!(forged.lines().skip(1).all(|l| l.starts_with("    ")));
+        assert!(!forged.contains('\r') && !forged.contains('\u{1b}'));
     }
 
     #[test]

apps/cadcraft/src/main.rs

@@ -23,13 +23,15 @@ mod launch_args;
 mod logging;
 #[cfg(target_os = "macos")]
 mod native_menu;
+#[cfg(target_os = "macos")]
+mod sheet;
 mod spacemouse;
 mod system_animations;
 mod workspace;
 
 use cadcraft_engine::Session;
 use cadcraft_ui_egui::switch::Switch;
-use cadcraft_ui_egui::{CadApp, Services, i18n};
+use cadcraft_ui_egui::{CadApp, Pick, Services, i18n};
 
 struct App {
     cad: CadApp,
@@ -159,39 +161,44 @@ pub fn install_io() {
 
 fn services() -> Services {
     Services {
-        pick_open: Some(Box::new(|| {
-            rfd::FileDialog::new()
-                .add_filter(i18n::t("Drawings (DWG, DXF)"), &["dwg", "dxf", "dwt"])
-                .add_filter(i18n::t("SVG drawings (SVG, SVGZ)"), &["svg", "svgz"])
-                .add_filter(i18n::t("All files"), &["*"])
-                .pick_file()
-                .map(|p| p.to_string_lossy().to_string())
-        })),
-        pick_save: Some(Box::new(|name: &str| {
-            filters_for_save(name)
-                .iter()
-                .fold(rfd::FileDialog::new().set_file_name(name), |d, (label, ext)| d.add_filter(i18n::t(label), &[*ext]))
-                .save_file()
-                .map(|p| p.to_string_lossy().to_string())
-        })),
+        pick_open: Some(Box::new(|| file_dialog(&Pick::Open).pick_file().map(|p| p.to_string_lossy().to_string()))),
+        pick_save: Some(Box::new(|name: &str| file_dialog(&Pick::Save(name.into())).save_file().map(|p| p.to_string_lossy().to_string()))),
+        // macOS shows the dialogs as sheets (`sheet::start_pick`), set once the window exists.
+        start_pick: None,
         // APPLOAD: AutoLISP routines only, starting where the last one was loaded from.
-        pick_lisp: Some(Box::new(|dir: &str| {
-            let dialog = rfd::FileDialog::new().add_filter(i18n::t("AutoLISP (LSP)"), &["lsp"]).add_filter(i18n::t("All files"), &["*"]);
-            let dialog = if dir.is_empty() { dialog } else { dialog.set_directory(dir) };
-            dialog.pick_file().map(|p| p.to_string_lossy().to_string())
-        })),
+        pick_lisp: Some(Box::new(|dir: &str| file_dialog(&Pick::Lisp(dir.into())).pick_file().map(|p| p.to_string_lossy().to_string()))),
         no_file_system: false,
         pick_pgp: Some(Box::new(|dir: Option<&str>| {
-            let dialog = rfd::FileDialog::new().add_filter(i18n::t("Alias files (PGP)"), &["pgp"]);
-            let dialog = match dir {
-                Some(dir) => dialog.set_directory(dir),
-                None => dialog,
-            };
-            dialog.pick_file().map(|p| p.to_string_lossy().to_string())
+            file_dialog(&Pick::Pgp(dir.unwrap_or_default().into())).pick_file().map(|p| p.to_string_lossy().to_string())
         })),
     }
 }
 
+/// The file types `pick` offers: (label, extensions). Shared by the blocking dialogs and the
+/// macOS sheets.
+fn filters(pick: &Pick) -> Vec<(&'static str, Vec<&'static str>)> {
+    match pick {
+        Pick::Open => vec![
+            (i18n::t("Drawings (DWG, DXF)"), vec!["dwg", "dxf", "dwt"]),
+            (i18n::t("SVG drawings (SVG, SVGZ)"), vec!["svg", "svgz"]),
+            (i18n::t("All files"), vec!["*"]),
+        ],
+        Pick::Save(name) => filters_for_save(name).iter().map(|(label, ext)| (i18n::t(label), vec![*ext])).collect(),
+        Pick::Lisp(_) => vec![(i18n::t("AutoLISP (LSP)"), vec!["lsp"]), (i18n::t("All files"), vec!["*"])],
+        Pick::Pgp(_) => vec![(i18n::t("Alias files (PGP)"), vec!["pgp"])],
+    }
+}
+
+/// The blocking dialog for `pick` (Windows, Linux, FreeBSD).
+fn file_dialog(pick: &Pick) -> rfd::FileDialog {
+    let dialog = filters(pick).iter().fold(rfd::FileDialog::new(), |d, (label, exts)| d.add_filter(*label, exts));
+    match pick {
+        Pick::Save(name) => dialog.set_file_name(name),
+        Pick::Lisp(dir) | Pick::Pgp(dir) if !dir.is_empty() => dialog.set_directory(dir),
+        _ => dialog,
+    }
+}
+
 /// File types for the Save dialog, the suggested name's type first: Windows adds the first
 /// filter's extension, and macOS accepts only listed extensions, replacing any other with the
 /// first one. DWG must be listed for a `.dwg` name to survive, and a drawing opened from DWG
@@ -361,6 +368,12 @@ fn main() -> eframe::Result {
         options,
         Box::new(move |cc| {
             let mut app = CadApp::new(Session::empty(), services());
+            // File dialogs are sheets on macOS: a modal loop inside the event handler crashes the
+            // app when the dialog is resized (#1527).
+            #[cfg(target_os = "macos")]
+            if let Some(window) = cc.winit_window().cloned() {
+                app.services.start_pick = Some(sheet::start_pick(window, cc.egui_ctx.clone()));
+            }
             let (workspace, restored, workspace_error) = workspace::Workspace::load(vars.config_dir.as_deref());
             if let Some(ui) = restored {
                 app.ui = ui;

apps/cadcraft/src/sheet.rs

@@ -0,0 +1,51 @@
+//! macOS file dialogs as sheets. Shown in line, or from a helper thread that rfd hands to the main
+//! thread's modal loop, a panel runs AppKit's modal event loop; resizing it sends window events
+//! back into winit's event handler and winit aborts the app (#1527). A sheet returns at once and
+//! the window keeps running; a thread of its own waits for the answer.
+
+use std::sync::Arc;
+
+use cadcraft_ui_egui::{Pick, StartPick};
+
+type Answer = std::pin::Pin<Box<dyn std::future::Future<Output = Option<String>> + Send>>;
+
+/// `Services::start_pick`: shows `pick` as a sheet on `window`; `ui` is woken when it answers.
+pub fn start_pick(window: Arc<winit::window::Window>, ui: egui::Context) -> StartPick {
+    Box::new(move |pick, done| {
+        let (sheet_tx, sheet_rx) = std::sync::mpsc::channel::<Answer>();
+        let ui = ui.clone();
+        // The thread first, so the answer of a sheet once shown always has somewhere to go. If it
+        // cannot start, `done` is dropped unanswered and the app says the dialog could not be
+        // shown.
+        let spawned = std::thread::Builder::new().name("file-dialog".into()).spawn(move || {
+            if let Ok(answer) = sheet_rx.recv() {
+                done(pollster::block_on(answer));
+                ui.request_repaint();
+            }
+        });
+        if let Err(e) = spawned {
+            log::warn!("file dialog: {e}");
+            return;
+        }
+        // rfd builds the panel and begins the sheet here, on the main thread (as it must).
+        let dialog =
+            crate::filters(&pick).iter().fold(rfd::AsyncFileDialog::new().set_parent(&*window), |d, (label, exts)| d.add_filter(*label, exts));
+        let path = |f: rfd::FileHandle| f.path().to_string_lossy().to_string();
+        let answer: Answer = match pick {
+            Pick::Save(name) => {
+                let picked = dialog.set_file_name(name).save_file();
+                Box::pin(async move { picked.await.map(path) })
+            }
+            Pick::Lisp(dir) | Pick::Pgp(dir) => {
+                let dialog = if dir.is_empty() { dialog } else { dialog.set_directory(dir) };
+                let picked = dialog.pick_file();
+                Box::pin(async move { picked.await.map(path) })
+            }
+            Pick::Open => {
+                let picked = dialog.pick_file();
+                Box::pin(async move { picked.await.map(path) })
+            }
+        };
+        let _ = sheet_tx.send(answer);
+    })
+}

crates/constraints/src/dof.rs

@@ -138,7 +138,9 @@ pub fn dof(d: &Drawing, handles: &[Handle]) -> Result<DofReport, SolveError> {
     let cons: Vec<&Constraint> = d.constraints.iter().take(MAX_CONSTRAINTS).collect();
     let mut prep = Prep::new(crate::model::MAX_RIGID_WORK);
     let (comps, _) = build_with(d, &cons, &SolveOptions::default(), &mut prep)?;
-    let want = |h: Handle| handles.is_empty() || handles.contains(&h);
+    // The selection as a set, built once: a scan of the list per slot multiplied the two sizes.
+    let selected: HashSet<Handle> = handles.iter().copied().collect();
+    let want = |h: Handle| handles.is_empty() || selected.contains(&h);
     let mut objects = Vec::new();
     let mut seen = HashSet::new();
     let mut total = Some(0usize);

crates/doc/src/array.rs

@@ -204,6 +204,23 @@ impl ArrayParams {
         self.replaced.iter().rev().find(|r| (r.i, r.j, r.level) == (i, j, level)).map_or(self.source.as_str(), |r| r.block.as_str())
     }
 
+    /// [`block_for`](Self::block_for) for many items: the replacements are indexed once (the last
+    /// entry for a place wins, as there), so each lookup is O(1) instead of a scan of `replaced`.
+    pub fn block_lookup<'a>(&'a self) -> impl Fn(u32, u32, u32) -> &'a str + 'a {
+        // Only places `items()` generates are indexed, so stray out-of-range records cost nothing.
+        let (cols, rows) = match &self.kind {
+            ArrayKind::Rect(r) => (r.cols, r.rows),
+            ArrayKind::Polar(p) => (p.items, p.rows),
+        };
+        let index: std::collections::HashMap<(u32, u32, u32), &str> = self
+            .replaced
+            .iter()
+            .filter(|r| r.i < cols && r.j < rows && r.level < self.levels)
+            .map(|r| ((r.i, r.j, r.level), r.block.as_str()))
+            .collect();
+        move |i, j, level| index.get(&(i, j, level)).copied().unwrap_or(self.source.as_str())
+    }
+
     /// The block references that make up the array block: one per item, on layer 0 with ByBlock
     /// properties so they take the array's. Handles are allocated from `d`. `None` when the
     /// parameters are not [valid](Self::is_valid).
@@ -217,9 +234,10 @@ impl ArrayParams {
             ..Common::default()
         };
         let mut out = Vec::with_capacity(items.len());
+        let block_for = self.block_lookup();
         for it in items {
             let ins = Insert {
-                block: self.block_for(it.i, it.j, it.level).to_string(),
+                block: block_for(it.i, it.j, it.level).to_string(),
                 insert: it.insert,
                 scale: Vec3::new(1.0, 1.0, 1.0),
                 rotation: it.rotation,
@@ -301,6 +319,18 @@ mod tests {
         }
     }
 
+    #[test]
+    fn block_lookup_agrees_with_block_for_and_the_last_replacement_wins() {
+        let mut p = rect(3, 2);
+        let r = |i, j, level, b: &str| ReplacedItem { i, j, level, block: b.into() };
+        p.replaced = vec![r(1, 0, 0, "A"), r(1, 0, 0, "B"), r(2, 1, 1, "C")];
+        let look = p.block_lookup();
+        for (i, j, level) in [(0, 0, 0), (1, 0, 0), (2, 1, 1), (2, 1, 0)] {
+            assert_eq!(look(i, j, level), p.block_for(i, j, level));
+        }
+        assert_eq!((look(1, 0, 0), look(0, 0, 0)), ("B", "*U1"));
+    }
+
     #[test]
     fn rect_items_go_column_row_level() {
         let items = rect(3, 2).items().unwrap_or_default();

crates/doc/src/dynblock/apply.rs

@@ -674,6 +674,10 @@ fn apply(
 /// Associative hatches of block `b` whose loop is one closed polyline of the block take its
 /// outline again (it may have been stretched).
 fn refill_hatches(b: &mut Block) {
+    // Each loop gets its own copy of the outline, so many small loops on one big outline multiply it;
+    // past this many vertices in all, the remaining loops keep the outline they have.
+    const MAX_REFILLED_VERTICES: usize = 4_000_000;
+    let mut budget = MAX_REFILLED_VERTICES;
     let outlines: HashMap<Handle, Vec<cadcraft_geom::PolyVertex>> = b
         .entities
         .iter()
@@ -689,7 +693,9 @@ fn refill_hatches(b: &mut Block) {
                 for l in &mut hh.loops {
                     if let [s] = l.sources.as_slice()
                         && let Some(vs) = outlines.get(s)
+                        && let Some(left) = budget.checked_sub(vs.len())
                     {
+                        budget = left;
                         l.vertices.clone_from(vs);
                     }
                 }

crates/doc/src/tables.rs

@@ -491,11 +491,18 @@ impl DimStyle {
         use serde_json::Value;
         let mut rejected = Vec::new();
         let Ok(mut cur) = serde_json::to_value(&*self) else { return src.keys().cloned().collect() };
+        // Spellings of one field (`DIMPOST`, `dimpost`, `textPrefix`…): only the last is applied, so
+        // the style is checked once per field, not once per spelling (each check copies its strings).
+        let last_spelling: std::collections::HashMap<&str, &String> =
+            src.keys().filter_map(|k| DimStyle::field_name(k).filter(|f| *f != "name").map(|f| (f, k))).collect();
         for (k, v) in src {
             let Some(field) = DimStyle::field_name(k).filter(|f| *f != "name") else {
                 rejected.push(k.clone());
                 continue;
             };
+            if last_spelling.get(field) != Some(&k) {
+                continue;
+            }
             let Some(obj) = cur.as_object_mut() else { break };
             let Some(old) = obj.get(field).cloned() else {
                 rejected.push(k.clone());

crates/doc/src/tests.rs

@@ -714,3 +714,14 @@ fn space_names_its_tab() {
     assert_eq!(p.layout(), Some("Sheet A"));
     assert_eq!(p.tab_name(), "Sheet A");
 }
+
+/// Several spellings of one DIM field apply once, the last in the map's order, and none is rejected.
+#[test]
+fn dim_style_spellings_of_one_field_apply_once() {
+    let mut st = DimStyle::default();
+    let m = serde_json::json!({ "textHeight": 2.5, "TEXTHEIGHT": 3.5, "DIMTXT": 4.5 });
+    let m = m.as_object().unwrap();
+    let want = m.values().next_back().and_then(serde_json::Value::as_f64).unwrap();
+    assert!(st.apply_fields(m).is_empty());
+    assert_eq!(st.text_height, want);
+}

crates/engine/src/cmd/array/edit.rs

@@ -188,8 +188,9 @@ fn item_at(d: &Drawing, h: Handle, at: Vec2, tol: f64) -> Option<(u32, u32, u32)
     let mut best: Option<((u32, u32, u32), f64)> = None;
     // Each block's own extents, measured once.
     let mut extents: HashMap<String, (Vec2, Bounds2)> = HashMap::new();
+    let block_for = p.block_lookup();
     for it in p.items()? {
-        let name = p.block_for(it.i, it.j, it.level);
+        let name = block_for(it.i, it.j, it.level);
         let (base, local) = match extents.get(name) {
             Some(x) => *x,
             None => {

crates/engine/src/cmd/audit.rs

@@ -157,7 +157,7 @@ fn write_audit_log(_: &Session, _: &crate::audit::Report) {}
 
 #[cfg(not(target_arch = "wasm32"))]
 fn read_path(cmd: &str, path: &str) -> Result<Vec<u8>> {
-    std::fs::read(path).map_err(|e| bad(cmd, format!("{path}: {e}")))
+    crate::capped_read::read_capped(std::path::Path::new(path), file::MAX_DRAWING_BYTES).map_err(|e| bad(cmd, format!("{path}: {e}")))
 }
 
 #[cfg(target_arch = "wasm32")]

crates/engine/src/cmd/blocks/insert_file.rs

@@ -85,7 +85,8 @@ fn read_drawing(path: &str) -> Result<Drawing> {
 fn read_file(_path: &str) -> Result<Vec<u8>> {
     #[cfg(not(target_arch = "wasm32"))]
     {
-        std::fs::read(_path).map_err(|e| bad("insert", format!("{_path}: {e}")))
+        crate::capped_read::read_capped(std::path::Path::new(_path), crate::cmd::file::MAX_DRAWING_BYTES)
+            .map_err(|e| bad("insert", format!("{_path}: {e}")))
     }
     #[cfg(target_arch = "wasm32")]
     Err(bad("insert", "paths are not available on the web"))

crates/engine/src/cmd/curves.rs

@@ -453,14 +453,32 @@ impl Chain {
     }
     /// Point and unit tangent at arc length `d` from the start (clamped).
     pub fn at_length(&self, d: f64) -> Option<(Vec2, Vec2)> {
-        let mut acc = 0.0;
-        for s in &self.segs {
-            let l = s.len();
-            if d <= acc + l + 1e-12 && l > 0.0 {
-                let t = ((d - acc) / l).clamp(0.0, 1.0);
-                return Some((s.at(t), s.tangent(t)));
-            }
-            acc += l;
+        self.at_length_in(&self.end_lengths(), d)
+    }
+    /// The arc length from the chain's start to the end of each segment, for [`Self::at_length_in`].
+    pub fn end_lengths(&self) -> Vec<f64> {
+        self.segs
+            .iter()
+            .scan(0.0, |acc, s| {
+                *acc += s.len();
+                Some(*acc)
+            })
+            .collect()
+    }
+    /// [`Self::at_length`] with the segment end lengths computed once (`ends` from
+    /// [`Self::end_lengths`]), so many samples along one chain each cost a binary search.
+    pub fn at_length_in(&self, ends: &[f64], d: f64) -> Option<(Vec2, Vec2)> {
+        let first = ends.partition_point(|e| d > e + 1e-12);
+        // A segment of no length can't hold the point; the next one that has length does.
+        // `ends` never decreases, so the first segment past `first` with length is found by search
+        // (a run of zero-length segments can be long) instead of a scan.
+        let base = first.checked_sub(1).and_then(|p| ends.get(p)).copied().unwrap_or(0.0);
+        let i = first + ends.get(first..).unwrap_or_default().partition_point(|e| *e <= base);
+        let i = (i < self.segs.len()).then_some(i);
+        if let Some(s) = i.and_then(|i| self.segs.get(i)) {
+            let start = i.and_then(|i| i.checked_sub(1)).and_then(|p| ends.get(p)).copied().unwrap_or(0.0);
+            let t = ((d - start) / s.len()).clamp(0.0, 1.0);
+            return Some((s.at(t), s.tangent(t)));
         }
         self.segs.last().map(|s| (s.end(), s.tangent(1.0)))
     }
@@ -640,6 +658,34 @@ pub fn reverse_vertices(vs: &[PolyVertex], closed: bool) -> Vec<PolyVertex> {
 mod tests {
     use super::*;
 
+    /// The indexed lookup gives the point and tangent a scan from the start gives, also past the
+    /// ends and over a segment of no length.
+    #[test]
+    fn at_length_in_matches_a_scan() {
+        let l = |a: (f64, f64), b: (f64, f64)| Segment::Line(Line::new(Vec2::new(a.0, a.1), Vec2::new(b.0, b.1)));
+        let c = Chain {
+            segs: vec![l((0.0, 0.0), (0.0, 0.0)), l((0.0, 0.0), (4.0, 0.0)), l((4.0, 0.0), (4.0, 0.0)), l((4.0, 0.0), (4.0, 3.0))],
+            closed: false,
+        };
+        let ends = c.end_lengths();
+        for d in [-1.0, 0.0, 1.5, 4.0, 4.0 + 1e-13, 5.0, 7.0, 9.0] {
+            // The scan this replaced.
+            let mut acc = 0.0;
+            let mut want = c.segs.last().map(|s| (s.end(), s.tangent(1.0)));
+            for s in &c.segs {
+                let len = s.len();
+                if d <= acc + len + 1e-12 && len > 0.0 {
+                    let t = ((d - acc) / len).clamp(0.0, 1.0);
+                    want = Some((s.at(t), s.tangent(t)));
+                    break;
+                }
+                acc += len;
+            }
+            assert_eq!(c.at_length_in(&ends, d), want, "d = {d}");
+            assert_eq!(c.at_length(d), want);
+        }
+    }
+
     #[test]
     fn arc_builders() {
         let a = arc_sca(Vec2::new(1.0, 0.0), Vec2::ZERO, std::f64::consts::FRAC_PI_2).unwrap();

crates/engine/src/cmd/draw2/divide.rs

@@ -36,16 +36,18 @@ fn check_block(s: &Session, b: Option<&str>) -> Result<()> {
 pub(crate) fn divide_points(c: &Chain, n: usize) -> Vec<(Vec2, Vec2)> {
     let l = c.len();
     let range = if c.closed { 0..n } else { 1..n };
-    range.filter_map(|i| c.at_length(l * i as f64 / n as f64)).collect()
+    let ends = c.end_lengths();
+    range.filter_map(|i| c.at_length_in(&ends, l * i as f64 / n as f64)).collect()
 }
 
 pub(crate) fn measure_points(c: &Chain, step: f64) -> Vec<(Vec2, Vec2)> {
     let l = c.len();
+    let ends = c.end_lengths();
     let mut out = Vec::new();
     let mut k = 1usize;
     while (k as f64) * step < l - 1e-9 && out.len() < MAX_GEN {
         let d = k as f64 * step;
-        out.extend(c.at_length(d));
+        out.extend(c.at_length_in(&ends, d));
         k += 1;
     }
     out

crates/engine/src/cmd/draw2/revcloud.rs

@@ -58,8 +58,9 @@ pub(crate) fn cloud_vertices(boundary: &[Vec2], arc_len: f64, per_edge: bool, re
             closed: true,
         };
         let k = ((perim / arc_len).round() as usize).clamp(3, MAX_GEN);
+        let ends = chain.end_lengths();
         for j in 0..k {
-            out.extend(chain.at_length(perim * j as f64 / k as f64).map(|x| x.0));
+            out.extend(chain.at_length_in(&ends, perim * j as f64 / k as f64).map(|x| x.0));
         }
     }
     let b = if reverse { -0.5 } else { 0.5 };

crates/engine/src/cmd/exchange.rs

@@ -204,7 +204,8 @@ fn import_drawing(s: &mut Session, src: &Drawing, at: Vec2, scale: f64, file: &s
 fn read_file(_path: &str) -> Result<Vec<u8>> {
     #[cfg(not(target_arch = "wasm32"))]
     {
-        std::fs::read(_path).map_err(|e| bad("import", format!("{_path}: {e}")))
+        crate::capped_read::read_capped(std::path::Path::new(_path), crate::cmd::file::MAX_DRAWING_BYTES)
+            .map_err(|e| bad("import", format!("{_path}: {e}")))
     }
     #[cfg(target_arch = "wasm32")]
     Err(bad("import", "paths are not available on the web; pass `data`"))

crates/engine/src/cmd/file.rs

@@ -24,7 +24,7 @@ pub use template::{qnew_template, set_qnew_template};
 /// endless device must be rejected before it exhausts memory (CWE-400), so native opens read
 /// through [`crate::capped_read`] rather than buffering to EOF.
 #[cfg(not(target_arch = "wasm32"))]
-const MAX_DRAWING_BYTES: usize = 512 << 20;
+pub(crate) const MAX_DRAWING_BYTES: usize = 512 << 20;
 /// Largest `.scr` script accepted from a local path.
 #[cfg(not(target_arch = "wasm32"))]
 const MAX_SCRIPT_BYTES: usize = 64 << 20;

crates/engine/src/cmd/file/compare.rs

@@ -110,7 +110,7 @@ fn other_drawing(s: &Session, p: &Value) -> Result<(Arc<Drawing>, String)> {
 fn read_path(_path: &str) -> Result<Vec<u8>> {
     #[cfg(not(target_arch = "wasm32"))]
     {
-        std::fs::read(_path).map_err(|e| bad("compare", format!("{_path}: {e}")))
+        crate::capped_read::read_capped(std::path::Path::new(_path), super::MAX_DRAWING_BYTES).map_err(|e| bad("compare", format!("{_path}: {e}")))
     }
     #[cfg(target_arch = "wasm32")]
     Err(bad("compare", "paths are not available on the web: open the other drawing and compare with it by name (`document`)"))

crates/engine/src/cmd/file/template.rs

@@ -74,7 +74,7 @@ fn read_template(path: &str) -> Result<Drawing> {
 
 #[cfg(not(target_arch = "wasm32"))]
 fn read_bytes(path: &str) -> Result<Vec<u8>> {
-    std::fs::read(path).map_err(|e| bad("new", format!("template {path}: {e}")))
+    crate::capped_read::read_capped(std::path::Path::new(path), super::MAX_DRAWING_BYTES).map_err(|e| bad("new", format!("template {path}: {e}")))
 }
 
 #[cfg(target_arch = "wasm32")]

crates/engine/src/cmd/layout/plotstyle.rs

@@ -303,11 +303,9 @@ fn run_stylesmanager(s: &mut Session, p: &Value) -> Result<Value> {
                 (None, Some(_path)) => {
                     #[cfg(not(target_arch = "wasm32"))]
                     {
-                        let meta = std::fs::metadata(_path).map_err(|e| bad(cmd, format!("{_path}: {e}")))?;
-                        if meta.len() > cadcraft_doc::MAX_TABLE_FILE as u64 {
-                            return Err(bad(cmd, format!("{_path}: the plot style table file is too large")));
-                        }
-                        std::fs::read_to_string(_path).map_err(|e| bad(cmd, format!("{_path}: {e}")))?
+                        let bytes = crate::capped_read::read_capped(std::path::Path::new(_path), cadcraft_doc::MAX_TABLE_FILE)
+                            .map_err(|e| bad(cmd, format!("{_path}: {e}")))?;
+                        String::from_utf8(bytes).map_err(|e| bad(cmd, format!("{_path}: {e}")))?
                     }
                     #[cfg(target_arch = "wasm32")]
                     return Err(bad(cmd, "files can't be read here: pass `text`"));

crates/engine/src/cmd/modify2/patharray.rs

@@ -34,10 +34,12 @@ pub(crate) fn arraypath(
         _ => (6, if c.closed { l / 6.0 } else { l / 5.0 }),
     };
     crate::cmd::array::check_size(s, n as u64, objs.len())?;
-    let Some((p0, t0)) = c.at_length(0.0) else { return Ok(Vec::new()) };
+    // Segment end lengths once: each sample is then a binary search, not a scan from the start.
+    let ends = c.end_lengths();
+    let Some((p0, t0)) = c.at_length_in(&ends, 0.0) else { return Ok(Vec::new()) };
     let mut mats = Vec::new();
     for i in 1..n {
-        let Some((p, t)) = c.at_length(step * i as f64) else { continue };
+        let Some((p, t)) = c.at_length_in(&ends, step * i as f64) else { continue };
         let mut m = Mat3::translate(p - p0);
         if align {
             m = Mat3::rotate_about(p, t.angle() - t0.angle()).then_before(m);

crates/engine/src/cmd/qselect.rs

@@ -175,8 +175,14 @@ pub fn compare(prop: &Value, op: Op, value: &Value) -> bool {
             if ptxt.eq_ignore_ascii_case(vtxt.trim()) {
                 return true;
             }
-            // Colours: `red` = `1` = `Red`; `bylayer` = `ByLayer`.
-            match (Color::parse(&ptxt), Color::parse(vtxt.trim())) {
+            // Colours: `red` = `1` = `Red`; `bylayer` = `ByLayer`. No colour spelling is long, so a
+            // long text (a layer name from a file) isn't parsed, copied and split per entity.
+            const MAX_COLOR_TEXT: usize = 64;
+            let (pc, vc) = (ptxt.trim(), vtxt.trim());
+            if pc.len() > MAX_COLOR_TEXT || vc.len() > MAX_COLOR_TEXT {
+                return false;
+            }
+            match (Color::parse(pc), Color::parse(vc)) {
                 (Some(a), Some(b)) => a == b,
                 _ => false,
             }
@@ -400,3 +406,26 @@ mod tests {
         assert!(!wildcard(&"*a".repeat(500), &"b".repeat(4000)));
     }
 }
+
+#[cfg(test)]
+mod long_text_tests {
+    use super::*;
+
+    /// A long string property is compared as text only, and a colour name still equals its index.
+    #[test]
+    fn long_values_skip_colour_parsing() {
+        let long = Value::String("x".repeat(100_000));
+        assert!(compare(&long, Op::Eq, &long));
+        assert!(!compare(&long, Op::Eq, &Value::String("red".into())));
+        assert!(compare(&Value::String("red".into()), Op::Eq, &Value::String("1".into())));
+    }
+
+    /// Padding is trimmed before the length limit, so a padded colour still matches.
+    #[test]
+    fn padded_colours_still_match() {
+        let padded = |c: &str| Value::String(format!("{}{c}{}", " ".repeat(100), " ".repeat(100)));
+        assert!(compare(&padded("red"), Op::Eq, &Value::String("1".into())));
+        assert!(compare(&Value::String("red".into()), Op::Eq, &padded("1")));
+        assert!(!compare(&padded("red"), Op::Ne, &padded("1")));
+    }
+}

crates/engine/src/cmd/table/breaks.rs

@@ -12,7 +12,7 @@ use crate::{Accept, Input, Interactive, Prompt, Result, Session, Step};
 
 /// Largest linked file read (bytes).
 #[cfg(not(target_arch = "wasm32"))]
-const MAX_LINK_BYTES: u64 = 8 << 20;
+const MAX_LINK_BYTES: usize = 8 << 20;
 
 pub fn specs() -> Vec<CommandSpec> {
     vec![
@@ -238,11 +238,9 @@ fn read_link(id: &str, file: &std::path::Path) -> Result<String> {
     let path = file.display();
     #[cfg(not(target_arch = "wasm32"))]
     {
-        let meta = std::fs::metadata(file).map_err(|e| bad(id, format!("{path}: {e}")))?;
-        if meta.len() > MAX_LINK_BYTES {
-            return Err(bad(id, format!("{path}: larger than {} MB", MAX_LINK_BYTES >> 20)));
-        }
-        let bytes = std::fs::read(file).map_err(|e| bad(id, format!("{path}: {e}")))?;
+        // The limit is enforced on the bytes read, not on reported metadata, so a device or FIFO
+        // that misreports its length can't be buffered to EOF.
+        let bytes = crate::capped_read::read_capped(file, MAX_LINK_BYTES).map_err(|e| bad(id, format!("{path}: {e}")))?;
         let text = String::from_utf8_lossy(&bytes);
         Ok(text.strip_prefix('\u{feff}').unwrap_or(&text).to_owned())
     }
@@ -370,6 +368,16 @@ fn run_update(s: &mut Session, p: &Value) -> Result<Value> {
 mod tests {
     use super::*;
 
+    /// A linked path naming an endless device is refused instead of buffered to EOF.
+    #[cfg(all(unix, not(target_arch = "wasm32")))]
+    #[test]
+    fn link_to_endless_device_is_rejected() {
+        let dev = std::path::Path::new("/dev/zero");
+        if dev.exists() {
+            assert!(read_link("datalink", dev).is_err());
+        }
+    }
+
     #[test]
     fn csv_parsing() {
         assert_eq!(parse_csv("a,b\r\n\"c,d\",\"e\"\"f\"\n", ','), vec![vec!["a", "b"], vec!["c,d", "e\"f"]]);

crates/engine/src/lisp.rs

@@ -415,9 +415,12 @@ impl Session {
 
     /// Move printed text to the command history: complete lines, and with `all` the rest too.
     fn lisp_flush(&mut self, env: &mut Env, all: bool) {
-        while let Some(i) = env.out.find('\n') {
-            let line: String = env.out.drain(..=i).collect();
-            let line = line.trim_end_matches(['\n', '\r']).to_string();
+        // One pass over the buffer, dropping the printed lines once at the end: draining each line
+        // from the front shifted the rest every time, quadratic in newline-dense output.
+        let mut done = 0;
+        while let Some(i) = env.out.get(done..).and_then(|rest| rest.find('\n')) {
+            let line = env.out.get(done..done + i).unwrap_or_default().trim_end_matches('\r').to_string();
+            done += i + 1;
             // `(princ "\nText")` after a prompt or a command's echo ends that line instead of
             // leaving an empty one; after LISP's own line it does print an empty line.
             if line.is_empty() && env.printed_at != Some(self.log.len()) {
@@ -427,6 +430,7 @@ impl Session {
             self.echo(line);
             env.printed_at = Some(self.log.len());
         }
+        env.out.drain(..done);
         if all && !env.out.is_empty() {
             let line = std::mem::take(&mut env.out);
             self.echo(line);

crates/engine/src/lisp/tests.rs

@@ -307,6 +307,16 @@ fn printing() {
     assert_eq!(ok(&mut s, "(rtos 12.5 2 2)"), "\"12.50\"");
 }
 
+/// Output with many lines moves to the history in one pass, not one buffer shift per line.
+#[test]
+fn printing_many_lines_is_linear() {
+    let mut s = session();
+    let started = std::time::Instant::now();
+    ok(&mut s, "(setq x \"a\\r\\n\") (repeat 17 (setq x (strcat x x))) (princ x) (princ)");
+    assert!(started.elapsed() < std::time::Duration::from_secs(10), "took {:?}", started.elapsed());
+    assert_eq!(s.log.last().map(String::as_str), Some("a"));
+}
+
 #[test]
 fn command_draws_and_one_routine_is_one_undo_step() {
     let mut s = session();

crates/geom/src/curve.rs

@@ -484,6 +484,9 @@ pub struct Polyline {
     pub closed: bool,
 }
 
+/// Sampled points one [`Polyline::tessellate`] call produces before arcs become chords.
+pub const MAX_TESSELLATED_POINTS: usize = 4_000_000;
+
 impl Polyline {
     pub fn from_points(pts: &[Vec2], closed: bool) -> Self {
         Polyline { vertices: pts.iter().map(|p| PolyVertex::new(*p)).collect(), closed }
@@ -516,10 +519,24 @@ impl Polyline {
         b
     }
     pub fn tessellate(&self, tol: f64) -> Vec<Vec2> {
+        let mut budget = MAX_TESSELLATED_POINTS;
+        self.tessellate_within(tol, &mut budget)
+    }
+    /// [`Polyline::tessellate`] spending about `budget` sampled points (shared by the caller
+    /// across many polylines). The budget is checked before each segment, so the last segment
+    /// started may overshoot it by that one segment's samples. Once it is spent, the remaining arcs are drawn as chords, so the
+    /// output stays proportional to the input vertices. Each arc can sample thousands of points,
+    /// so a compact polyline could otherwise expand into gigabytes (CWE-400).
+    pub fn tessellate_within(&self, tol: f64, budget: &mut usize) -> Vec<Vec2> {
         let mut out: Vec<Vec2> = Vec::new();
         for s in self.segments() {
             let mut pts = Vec::new();
-            s.tessellate(tol, &mut pts);
+            if *budget > 0 {
+                s.tessellate(tol, &mut pts);
+                *budget = budget.saturating_sub(pts.len());
+            } else {
+                pts.extend([s.start(), s.end()]);
+            }
             let skip = usize::from(out.last().is_some_and(|l| pts.first().is_some_and(|f| l.near(*f, 1e-9))));
             out.extend(pts.into_iter().skip(skip));
         }

crates/geom/src/lib.rs

@@ -20,7 +20,8 @@ mod vec;
 
 pub use bounds::Bounds2;
 pub use curve::{
-    Arc, Circle, Ellipse, Line, PolyVertex, Polyline, Segment, arc_to_bulge, bulge_to_arc, point_in_polygon, polygon_centroid, shoelace,
+    Arc, Circle, Ellipse, Line, MAX_TESSELLATED_POINTS, PolyVertex, Polyline, Segment, arc_to_bulge, bulge_to_arc, point_in_polygon,
+    polygon_centroid, shoelace,
 };
 pub use fillet::{CornerFit, TanCurve, tangent_circles};
 pub use intersect::{circle_circle, intersect_ext, intersect_segments, line_circle, line_line, line_line_infinite};

crates/geom/src/tests.rs

@@ -221,6 +221,18 @@ fn segment_offset() {
     assert!(s.offset(6.0).is_none());
 }
 
+/// A polyline of many fine arcs samples at most the point budget, then draws chords.
+#[test]
+fn polyline_tessellation_is_bounded() {
+    let vertices: Vec<PolyVertex> = (0..3000).map(|i| PolyVertex { bulge: 1.0, ..PolyVertex::new(Vec2::new(f64::from(i) * 1e6, 0.0)) }).collect();
+    let pl = Polyline { vertices, closed: false };
+    let pts = pl.tessellate(1e-9);
+    assert!(pts.len() <= MAX_TESSELLATED_POINTS + 2 * 3000 + 4096, "{}", pts.len());
+    assert!(pts.len() > 3000);
+    let mut budget = 10;
+    assert!(pl.tessellate_within(1e-9, &mut budget).len() <= 4096 + 2 * 3000);
+}
+
 #[test]
 fn arc_segments_bounded() {
     assert_eq!(arc_segments(0.0, 1.0, 0.1), 1);

crates/render/src/hatch.rs

@@ -128,7 +128,10 @@ const MAX_DEDUP_COMPARISONS: u64 = 50_000_000;
 /// within islands alternate), 1 outer keeps the outermost loops and their first islands, 2
 /// ignore keeps only the outermost loops. Nesting depth = how many other loops enclose a loop.
 pub fn fill_loops(h: &Hatch, tol: f64) -> Vec<Vec<Vec2>> {
-    let mut loops: Vec<Vec<Vec2>> = h.loops.iter().map(|l| Polyline { vertices: l.vertices.clone(), closed: true }.tessellate(tol)).collect();
+    // One point budget for all the loops: many short arcs across loops must not add up unbounded.
+    let mut budget = cadcraft_geom::MAX_TESSELLATED_POINTS;
+    let mut loops: Vec<Vec<Vec2>> =
+        h.loops.iter().map(|l| Polyline { vertices: l.vertices.clone(), closed: true }.tessellate_within(tol, &mut budget)).collect();
     dedup_polygons(&mut loops);
     let max_depth = match h.style {
         1 => 1,

crates/render/src/table.rs

@@ -133,6 +133,20 @@ pub fn table_geometry(d: &Drawing, t: &Table) -> TableGeom {
     if parts.len() <= 1 {
         return layout(d, t);
     }
+    // Every part is laid out and kept, so the cells of all of them count together (a header repeated
+    // on each part adds to each); past the limit only the table's outline is drawn.
+    let cols = t.col_widths.len().min(10_000);
+    let total: usize = parts.iter().map(|p| p.rows.len().min(10_000).saturating_mul(cols)).fold(0, usize::saturating_add);
+    if total > MAX_LAYOUT_CELLS {
+        // One outline per part, at the part's origin and as tall as its displayed rows.
+        let w = edges(&t.col_widths, cols).last().copied().unwrap_or(0.0);
+        let mut g = TableGeom::default();
+        for p in parts {
+            let h: f64 = p.rows.iter().take(10_000).map(|r| t.row_heights.get(*r).copied().filter(|v| v.is_finite()).unwrap_or(0.0)).sum();
+            outline_box(&mut g, p.origin, w, h);
+        }
+        return g;
+    }
     let mut g = TableGeom::default();
     for p in parts {
         let mut pg = layout(d, &part_table(t, &p.rows, p.origin));
@@ -156,16 +170,20 @@ fn part_table(t: &Table, rows: &[usize], origin: Vec2) -> Table {
     // Otherwise `layout` renders an outline, so materialising millions of empty cells here would be
     // wasted work an attacker can trigger with a compact dimension array (CWE-789).
     if rows.len().min(10_000).saturating_mul(cols) <= MAX_LAYOUT_CELLS {
+        // `run[i]`: how many rows from part row `i` follow one another in the table, found once so a
+        // merge is cut by a lookup, not by walking the rows it spans.
+        let mut run = vec![1u32; rows.len()];
+        for i in (0..rows.len().saturating_sub(1)).rev() {
+            if rows.get(i + 1).zip(rows.get(i)).is_some_and(|(next, this)| *next == this + 1) {
+                run[i] = run.get(i + 1).copied().unwrap_or(0).saturating_add(1);
+            }
+        }
         for (i, row) in cells.iter_mut().enumerate() {
             row.resize_with(cols, Default::default);
             for cell in row.iter_mut() {
                 if let Some((rs, cs)) = cell.merged {
                     // Rows of the merge that follow in this part.
-                    let start = rows.get(i).copied().unwrap_or(0);
-                    let mut n = 1u32;
-                    while n < rs && rows.get(i + n as usize).is_some_and(|r| *r == start + n as usize) {
-                        n += 1;
-                    }
+                    let n = rs.max(1).min(run.get(i).copied().unwrap_or(1));
                     cell.merged = (n > 1 || cs > 1).then_some((n, cs));
                 }
             }
@@ -186,6 +204,27 @@ fn part_table(t: &Table, rows: &[usize], origin: Vec2) -> Table {
     }
 }
 
+/// The table's outline alone, for a table too large to lay out.
+fn outline(t: &Table) -> TableGeom {
+    let rows = t.row_heights.len().min(10_000);
+    let cols = t.col_widths.len().min(10_000);
+    let (w, h) = (edges(&t.col_widths, cols).last().copied().unwrap_or(0.0), edges(&t.row_heights, rows).last().copied().unwrap_or(0.0));
+    let mut g = TableGeom::default();
+    outline_box(&mut g, t.insert.xy(), w, h);
+    g
+}
+
+/// The four sides of a `w` by `h` box hanging down from `o`.
+fn outline_box(g: &mut TableGeom, o: Vec2, w: f64, h: f64) {
+    let p = |x: f64, y: f64| o + Vec2::new(x, -y);
+    let corners = [p(0.0, 0.0), p(w, 0.0), p(w, h), p(0.0, h), p(0.0, 0.0)];
+    for s in corners.windows(2) {
+        if let [a, b] = s {
+            g.lines.push(TableLine { a: *a, b: *b, color: Color::ByBlock, lineweight: Lineweight::ByBlock });
+        }
+    }
+}
+
 /// Lay out one part.
 fn layout(d: &Drawing, t: &Table) -> TableGeom {
     let st = table_style_of(d, t);
@@ -203,14 +242,7 @@ fn layout(d: &Drawing, t: &Table) -> TableGeom {
     }
     let cov = coverage(t);
     if rows.saturating_mul(cols) > MAX_LAYOUT_CELLS || cov.is_err() {
-        let (w, h) = (x_at(cols), y_at(rows));
-        let corners = [p(0.0, 0.0), p(w, 0.0), p(w, h), p(0.0, h), p(0.0, 0.0)];
-        for s in corners.windows(2) {
-            if let [a, b] = s {
-                g.lines.push(TableLine { a: *a, b: *b, color: Color::ByBlock, lineweight: Lineweight::ByBlock });
-            }
-        }
-        return g;
+        return outline(t);
     }
     let k = style_scale(&st, t);
     // Cell styles by name, scaled to the table.

crates/render/src/tests.rs

@@ -1165,3 +1165,25 @@ fn without_linetypes_every_line_is_drawn_whole() {
     let drawn = build(&drawing("DASHED"), &Space::Model, &Options::default());
     assert!(drawn.prims.len() > 2 * continuous.prims.len(), "drawn with its linetype: {} primitives", drawn.prims.len());
 }
+
+/// A broken table whose parts, with their repeated labels, together hold more cells than a table may
+/// lay out is drawn as its outline, though the table's own cells are within the limit.
+#[test]
+fn broken_table_cells_count_across_its_parts() {
+    let d = Drawing::new_imperial();
+    let t = cadcraft_doc::Table {
+        col_widths: vec![1.0; 600],
+        row_heights: vec![1.0; 1000],
+        title: true,
+        header: true,
+        breaks: Some(cadcraft_doc::TableBreak { enabled: true, height: 3.0, ..Default::default() }),
+        ..Default::default()
+    };
+    assert!(t.parts().len() > 500 && 1000 * 600 <= crate::MAX_LAYOUT_CELLS);
+    let g = crate::table_geometry(&d, &t);
+    let parts = t.parts();
+    assert_eq!((g.lines.len(), g.texts.len(), g.fills.len()), (4 * parts.len(), 0, 0));
+    // Each part's box starts at its own origin.
+    let top = |i: usize| g.lines[4 * i].a;
+    assert!((0..parts.len()).all(|i| top(i) == parts[i].origin));
+}

crates/ui-egui/src/aliasdlg.rs

@@ -217,15 +217,14 @@ pub fn import(app: &mut CadApp, path: &str) -> Result<(), String> {
 /// then load it. A cancelled picker is a no-op; without a native picker (the web) the error names
 /// the ALIASEDIT `text` form, since the web has no file system to read a path from.
 pub fn pick_and_import(app: &mut CadApp) -> Result<(), String> {
-    let dir = app.ui.last_pgp_dir.clone();
-    let picked = app.services.pick_pgp.as_ref().map(|pick| pick(dir.as_deref()));
-    match picked {
+    let dir = app.ui.last_pgp_dir.clone().unwrap_or_default();
+    // Through `pick_for`, so macOS shows it as a sheet (#1527); aliases belong to no drawing.
+    match app.pick_for(crate::Pick::Pgp(dir), false, Box::new(|app, path| import(app, &path).map(|()| serde_json::Value::Null))) {
         None => Err(refused(
             app,
             crate::tl!("Import: there is no file dialog here; run ALIASEDIT with the file's contents using its text parameter.").to_string(),
         )),
-        Some(None) => Ok(()),
-        Some(Some(path)) => import(app, &path),
+        Some(r) => r.map(|_| ()),
     }
 }
 
@@ -450,6 +449,39 @@ mod tests {
         let _ = app.run("aliasedit", json!({ "clear": true }));
     }
 
+    /// Where the host shows dialogs without waiting (macOS sheets, #1527), Import… does not run
+    /// the blocking picker; the file loads once the sheet answers.
+    #[test]
+    fn import_waits_for_a_sheet_instead_of_blocking() {
+        type Done = Box<dyn FnOnce(Option<String>) + Send>;
+        let _guard = alone();
+        let dir = temp_dir("sheet");
+        let path = dir.join("aliases.pgp");
+        std::fs::write(&path, "XXS, *LINE\n").unwrap_or_default();
+        let asked = Rc::new(RefCell::new(Vec::new()));
+        let answer: Rc<RefCell<Option<Done>>> = Rc::default();
+        let (log, slot) = (Rc::clone(&asked), Rc::clone(&answer));
+        let services = Services {
+            pick_pgp: Some(Box::new(|_: Option<&str>| panic!("the blocking picker ran"))),
+            start_pick: Some(Box::new(move |pick, done| {
+                log.borrow_mut().push(pick);
+                *slot.borrow_mut() = Some(done);
+            })),
+            ..Services::default()
+        };
+        let mut app = CadApp::new(Session::new(), services);
+        open(&mut app);
+
+        pick_and_import(&mut app).expect("the sheet starts");
+        assert!(matches!(asked.borrow().as_slice(), [crate::Pick::Pgp(_)]));
+        answer.borrow_mut().take().expect("a sheet was started")(Some(path.to_string_lossy().to_string()));
+        app.finish_pick(&egui::Context::default());
+
+        let st = app.alias_dlg.as_ref().expect("the dialog stays open");
+        assert_eq!(st.user.get("xxs").map(String::as_str), Some("line"));
+        clear(&mut app);
+    }
+
     #[test]
     fn import_loads_the_aliases_shows_the_path_and_warnings() {
         let _guard = alone();

crates/ui-egui/src/closing.rs

@@ -88,6 +88,11 @@ impl CadApp {
     /// Answer the open close prompt (no-op without one).
     pub fn answer_close(&mut self, choice: Choice) {
         let Some(uid) = self.closing.as_ref().and_then(|c| c.asking) else { return };
+        // Its Save dialog is open (macOS): Save again or Don't Save would race it.
+        if choice != Choice::Cancel && self.pending_pick.as_ref().is_some_and(|p| p.for_close) {
+            self.set_status("Answer the Save dialog first.");
+            return;
+        }
         let i = match (choice, self.doc_index(uid)) {
             (Choice::Cancel, _) => {
                 self.closing = None;
@@ -114,26 +119,53 @@ impl CadApp {
                 // The Block Editor's unsaved changes go into the block first (BSAVE), then the
                 // drawing is saved with them.
                 let r = if self.session.state().is_ok_and(|st| st.block_unsaved()) { self.run("bsave", json!({})) } else { Ok(Value::Null) };
+                let waiting = self.pending_pick.is_some();
                 let r = r.and_then(|_| self.run("qsave", Value::Null));
-                let saved = r.is_ok() && self.doc_index(uid).and_then(|i| self.session.docs.get(i)).is_some_and(|d| !d.is_dirty());
-                match (saved, self.doc_index(uid)) {
-                    (true, Some(i)) => {
-                        self.close_front(i);
-                        self.advance_close();
-                    }
-                    _ => {
-                        // Not saved (picker cancelled, save failed or unavailable): keep the
-                        // drawing and its edits, and stop closing.
-                        self.closing = None;
-                        let title = self.doc_index(uid).and_then(|i| self.session.docs.get(i)).map(|d| d.title.clone()).unwrap_or_default();
-                        let msg = match r {
-                            Err(e) => format!("{title} was not saved ({e}); it stays open."),
-                            Ok(_) => format!("{title} was not saved; it stays open."),
-                        };
-                        self.session.echo(msg.clone());
-                        self.set_status(msg);
-                    }
+                // The Save dialog opened without waiting (macOS): closing goes on once it has
+                // saved; cancelling it leaves the prompt up.
+                // The dialog is bound to this drawing: if it is closed meanwhile, nothing is
+                // saved and the prompt goes on with the next drawing.
+                if !waiting && let Some(mut pending) = self.pending_pick.take() {
+                    let then = pending.then;
+                    pending.for_close = true;
+                    pending.then = Box::new(move |app: &mut CadApp, path| {
+                        let r = then(app, path);
+                        // Unless the prompt was answered otherwise meanwhile.
+                        if app.closing.as_ref().and_then(|c| c.asking) == Some(uid) {
+                            // It reports the outcome itself; an error returned here would
+                            // replace its message in the status bar.
+                            app.close_after_save(uid, r);
+                            return Ok(Value::Null);
+                        }
+                        r
+                    });
+                    self.pending_pick = Some(pending);
+                    return;
                 }
+                self.close_after_save(uid, r);
+            }
+        }
+    }
+
+    /// Go on closing after the drawing `uid` was asked to save with result `r`.
+    fn close_after_save(&mut self, uid: u64, r: Result<Value, String>) {
+        let saved = r.is_ok() && self.doc_index(uid).and_then(|i| self.session.docs.get(i)).is_some_and(|d| !d.is_dirty());
+        match (saved, self.doc_index(uid)) {
+            (true, Some(i)) => {
+                self.close_front(i);
+                self.advance_close();
+            }
+            _ => {
+                // Not saved (picker cancelled, save failed or unavailable): keep the
+                // drawing and its edits, and stop closing.
+                self.closing = None;
+                let title = self.doc_index(uid).and_then(|i| self.session.docs.get(i)).map(|d| d.title.clone()).unwrap_or_default();
+                let msg = match r {
+                    Err(e) => format!("{title} was not saved ({e}); it stays open."),
+                    Ok(_) => format!("{title} was not saved; it stays open."),
+                };
+                self.session.echo(msg.clone());
+                self.set_status(msg);
             }
         }
     }
@@ -264,6 +296,44 @@ mod tests {
         app.session.docs.iter().map(|d| d.title.clone()).collect()
     }
 
+    type Done = Box<dyn FnOnce(Option<String>) + Send>;
+
+    /// The host shows its Save dialog without waiting (macOS): the callback that answers it.
+    fn deferred_save(app: &mut CadApp) -> std::rc::Rc<std::cell::RefCell<Option<Done>>> {
+        let slot: std::rc::Rc<std::cell::RefCell<Option<Done>>> = std::rc::Rc::default();
+        let s = slot.clone();
+        app.services = Services {
+            pick_save: Some(Box::new(|_: &str| None)),
+            start_pick: Some(Box::new(move |_, done| *s.borrow_mut() = Some(done))),
+            ..Services::default()
+        };
+        slot
+    }
+
+    /// While the prompt's Save dialog is open, Don't Save (or Save again) does not race it; when
+    /// the save then fails, the prompt's own "was not saved" message is what the status bar shows.
+    #[test]
+    fn the_close_prompt_waits_for_its_save_dialog() {
+        let mut app = app_with(&["A", "B"]);
+        let answer = deferred_save(&mut app);
+        dirty(&mut app, 0);
+        app.request_close(Some(0));
+        app.answer_close(Choice::Save);
+        assert!(answer.borrow().is_some(), "the Save dialog is open");
+        app.answer_close(Choice::Discard);
+        app.answer_close(Choice::Save);
+        assert_eq!(titles(&app), ["A", "B"], "Don't Save waits for the Save dialog");
+        assert_eq!(app.close_prompt(), Some("A"));
+
+        let nowhere = std::env::temp_dir().join(format!("cadcraft-no-such-dir-{}", std::process::id())).join("A.dxf");
+        answer.borrow_mut().take().unwrap()(Some(nowhere.to_string_lossy().to_string()));
+        app.finish_pick(&egui::Context::default());
+        assert_eq!(titles(&app), ["A", "B"], "not saved, so not closed");
+        assert!(app.session.docs[0].is_dirty());
+        let status = app.status.as_ref().map(|(s, _)| s.as_str()).unwrap_or_default();
+        assert!(status.starts_with("A was not saved") && status.ends_with("it stays open."), "{status}");
+    }
+
     #[test]
     fn clean_drawing_closes_without_prompt() {
         let mut app = app_with(&["A", "B"]);

crates/ui-egui/src/exchange.rs

@@ -7,7 +7,7 @@ use std::sync::atomic::{AtomicU32, Ordering};
 use egui::TextureHandle;
 use serde_json::{Value, json};
 
-use crate::CadApp;
+use crate::{CadApp, Pick};
 
 /// Bumped each time PREVIEW is started, so the window renders the drawing as it is now.
 static PREVIEW_GEN: AtomicU32 = AtomicU32::new(0);
@@ -23,27 +23,15 @@ pub fn route(app: &mut CadApp, id: &str) -> Result<Value, String> {
             app.ui.dialog = Some("preview".into());
             Ok(Value::Null)
         }
-        "import" | "imp" => {
-            let Some(pick) = app.services.pick_open.as_ref() else { return no_picker(app, "IMPORT", r#"import {"path": "parts.dxf"}"#) };
-            match pick() {
-                Some(path) => app.run("import", json!({ "path": path })),
-                None => Ok(Value::Null),
-            }
-        }
-        "publish" => {
-            let Some(pick) = app.services.pick_save.as_ref() else { return no_picker(app, "PUBLISH", "publish {}") };
-            match pick(&format!("{stem}.pdf")) {
-                Some(path) => app.run("publish", json!({ "path": path })),
-                None => Ok(Value::Null),
-            }
-        }
-        _ => {
-            let Some(pick) = app.services.pick_save.as_ref() else { return no_picker(app, "EXPORT", r#"export {"format": "svg"}"#) };
-            match pick(&format!("{stem}.svg")) {
-                Some(path) => app.run("export", json!({ "path": path })),
-                None => Ok(Value::Null),
-            }
-        }
+        "import" | "imp" => app
+            .pick_then(Pick::Open, |app, path| app.run("import", json!({ "path": path })))
+            .unwrap_or_else(|| no_picker(app, "IMPORT", r#"import {"path": "parts.dxf"}"#)),
+        "publish" => app
+            .pick_then(Pick::Save(format!("{stem}.pdf")), |app, path| app.run("publish", json!({ "path": path })))
+            .unwrap_or_else(|| no_picker(app, "PUBLISH", "publish {}")),
+        _ => app
+            .pick_then(Pick::Save(format!("{stem}.svg")), |app, path| app.run("export", json!({ "path": path })))
+            .unwrap_or_else(|| no_picker(app, "EXPORT", r#"export {"format": "svg"}"#)),
     }
 }
 
@@ -161,7 +149,7 @@ mod tests {
     use cadcraft_engine::Session;
     use serde_json::json;
 
-    use crate::{CadApp, Services};
+    use crate::{CadApp, Pick, Services};
 
     /// An app whose file dialogs record what they were asked and cancel.
     fn app() -> (CadApp, Rc<RefCell<Vec<String>>>) {
@@ -207,4 +195,169 @@ mod tests {
         let e = app.run("share", json!({})).unwrap_err();
         assert!(e.contains("not available yet"), "{e}");
     }
+
+    type Done = Box<dyn FnOnce(Option<String>) + Send>;
+
+    /// An app whose host shows its dialogs without waiting (macOS, #1527): the dialogs asked
+    /// for, and the callback that answers the open one.
+    fn deferred_app() -> (CadApp, Rc<RefCell<Vec<Pick>>>, Rc<RefCell<Option<Done>>>) {
+        let asked = Rc::new(RefCell::new(Vec::new()));
+        let answer: Rc<RefCell<Option<Done>>> = Rc::default();
+        let (log, slot) = (asked.clone(), answer.clone());
+        let services = Services {
+            pick_open: Some(Box::new(|| None)),
+            pick_save: Some(Box::new(|_: &str| None)),
+            pick_lisp: Some(Box::new(|_: &str| None)),
+            start_pick: Some(Box::new(move |pick, done| {
+                log.borrow_mut().push(pick);
+                *slot.borrow_mut() = Some(done);
+            })),
+            ..Services::default()
+        };
+        (CadApp::new(Session::new(), services), asked, answer)
+    }
+
+    fn status(app: &CadApp) -> &str {
+        app.status.as_ref().map(|(s, _)| s.as_str()).unwrap_or_default()
+    }
+
+    fn uid(app: &CadApp) -> u64 {
+        app.session.state().unwrap().uid
+    }
+
+    /// Where the host shows its dialogs without waiting (macOS, #1527), the command acts on the
+    /// path in a later frame, and no second dialog opens while one is up.
+    #[test]
+    fn a_deferred_dialog_acts_when_its_answer_arrives() {
+        let (mut app, asked, answer) = deferred_app();
+        let ctx = egui::Context::default();
+
+        // Cancelled: nothing happens, and the next command may ask again.
+        app.start("export");
+        assert_eq!(*asked.borrow(), [Pick::Save("Drawing1.svg".into())]);
+        answer.borrow_mut().take().unwrap()(None);
+        app.finish_pick(&ctx);
+        assert!(app.pending_pick.is_none());
+
+        app.start("imp");
+        app.finish_pick(&ctx);
+        assert!(app.pending_pick.is_some() && app.status.is_none(), "nothing runs before the answer");
+        // A second dialog is refused, and says so: in the status bar for a typed or menu
+        // command, and as an error for a programmatic call.
+        app.start("publish");
+        assert!(status(&app).contains("already open"), "{:?}", app.status);
+        let e = app.run("ui.open", json!(null)).unwrap_err();
+        assert!(e.contains("already open"), "{e}");
+        assert_eq!(asked.borrow().len(), 2, "no second dialog while one is open");
+        app.status = None;
+        let missing = std::env::temp_dir().join(format!("cadcraft-missing-{}.dxf", std::process::id()));
+        answer.borrow_mut().take().unwrap()(Some(missing.to_string_lossy().to_string()));
+        app.finish_pick(&ctx);
+        assert!(app.pending_pick.is_none());
+        assert!(app.status.is_some(), "IMPORT ran with the picked file and reported its error");
+    }
+
+    /// A dialog's answer acts on the drawing that asked for it, even when another drawing was
+    /// made active before it arrived (a control-channel `document.switch` runs before the answer
+    /// in the same frame): Save As must not write the other drawing to the chosen file.
+    #[test]
+    fn a_deferred_dialog_acts_on_the_drawing_that_asked() {
+        let (mut app, _, answer) = deferred_app();
+        let ctx = egui::Context::default();
+        app.run("new", json!({})).unwrap();
+        app.run("document.switch", json!({ "index": 0 })).unwrap();
+        let first = uid(&app);
+        let acted_on = Rc::new(RefCell::new(None));
+        let seen = acted_on.clone();
+        let r = app.pick_then(Pick::Save("Drawing1.dxf".into()), move |app, path| {
+            *seen.borrow_mut() = Some((uid(app), path));
+            Ok(json!(null))
+        });
+        assert_eq!(r, Some(Ok(json!(null))));
+
+        app.run("document.switch", json!({ "index": 1 })).unwrap();
+        assert_ne!(uid(&app), first);
+        answer.borrow_mut().take().unwrap()(Some("a.dxf".into()));
+        app.finish_pick(&ctx);
+        assert_eq!(*acted_on.borrow(), Some((first, "a.dxf".to_string())));
+        assert_eq!(app.session.active, 0, "the drawing that asked is shown again");
+    }
+
+    /// The drawing that asked was closed before the answer: nothing is done, and the status bar
+    /// says so. A dialog that opens a drawing (OPEN, NEW from a template) still acts.
+    #[test]
+    fn a_deferred_dialog_for_a_closed_drawing_does_nothing() {
+        let (mut app, _, answer) = deferred_app();
+        let ctx = egui::Context::default();
+        app.run("new", json!({})).unwrap();
+        let ran = Rc::new(RefCell::new(0));
+        let r1 = ran.clone();
+        let _ = app.pick_then(Pick::Save("Drawing2.svg".into()), move |_, _| {
+            *r1.borrow_mut() += 1;
+            Ok(json!(null))
+        });
+        app.run("close", json!({ "index": 1 })).unwrap();
+        answer.borrow_mut().take().unwrap()(Some("b.svg".into()));
+        app.finish_pick(&ctx);
+        assert_eq!(*ran.borrow(), 0, "the closed drawing's export did not run on another drawing");
+        assert!(app.pending_pick.is_none());
+        assert!(app.status.as_ref().is_some_and(|(s, _)| s.contains("closed") && s.contains("b.svg")), "{:?}", app.status);
+
+        app.run("new", json!({})).unwrap();
+        let r2 = ran.clone();
+        let _ = app.pick_then_open(Pick::Open, move |_, _| {
+            *r2.borrow_mut() += 1;
+            Ok(json!(null))
+        });
+        app.run("close", json!({ "index": 1 })).unwrap();
+        answer.borrow_mut().take().unwrap()(Some("c.dxf".into()));
+        app.finish_pick(&ctx);
+        assert_eq!(*ran.borrow(), 1, "OPEN goes on whichever drawing closed meanwhile");
+    }
+
+    /// The host dropped the answer (its dialog thread could not start): the status bar says
+    /// the dialog could not be shown, unlike a cancelled dialog, and the next one may open.
+    #[test]
+    fn a_dialog_that_never_answers_is_reported() {
+        let services =
+            Services { pick_save: Some(Box::new(|_: &str| None)), start_pick: Some(Box::new(|_, done| drop(done))), ..Services::default() };
+        let mut app = CadApp::new(Session::new(), services);
+        app.start("export");
+        app.finish_pick(&egui::Context::default());
+        assert!(app.pending_pick.is_none());
+        assert!(status(&app).contains("could not be shown"), "{:?}", app.status);
+    }
+
+    /// With no drawing open, a dialog bound to the active drawing is not shown: its answer could
+    /// otherwise save or export a drawing opened while it was up.
+    #[test]
+    fn a_bound_dialog_needs_an_open_drawing() {
+        let (mut app, asked, _) = deferred_app();
+        app.run("close", json!({ "index": 0 })).unwrap();
+        assert!(app.session.state().is_err());
+        app.start("ui.saveas");
+        let r = app.run("ui.saveas", json!(null));
+        assert!(asked.borrow().is_empty(), "no dialog");
+        assert!(app.pending_pick.is_none());
+        assert!(r.is_err() && app.status.is_some(), "{r:?} {:?}", app.status);
+        // OPEN needs no drawing.
+        app.start("ui.open");
+        assert_eq!(*asked.borrow(), [Pick::Open]);
+    }
+
+    /// A command started while APPLOAD's dialog was open (a control request, say) keeps
+    /// running; APPLOAD is refused and says to run it again.
+    #[test]
+    fn appload_does_not_cancel_a_command_started_meanwhile() {
+        let (mut app, asked, answer) = deferred_app();
+        let ctx = egui::Context::default();
+        app.start("appload");
+        assert!(matches!(asked.borrow().as_slice(), [Pick::Lisp(_)]));
+        app.start("line");
+        assert!(app.session.prompting());
+        answer.borrow_mut().take().unwrap()(Some("routine.lsp".into()));
+        app.finish_pick(&ctx);
+        assert_eq!(app.session.running.as_ref().map(|r| r.id.as_str()), Some("line"), "LINE was not cancelled");
+        assert!(status(&app).starts_with("APPLOAD: another command started"), "{:?}", app.status);
+    }
 }

crates/ui-egui/src/lib.rs

@@ -227,6 +227,12 @@ impl Default for UiState {
 pub struct Services {
     pub pick_open: Option<Box<dyn Fn() -> Option<String>>>,
     pub pick_save: Option<Box<dyn Fn(&str) -> Option<String>>>,
+    /// Where set, the file dialogs are shown with this instead of calling `pick_open` /
+    /// `pick_save` / `pick_lisp` (which must still be set, to say which dialogs there are), and
+    /// the answer is acted on in a later frame ([`CadApp::pick_then`]). macOS needs it: a panel run modally
+    /// inside the window's event handler gets the window events of its own resizing sent back
+    /// into that handler, and winit aborts the app (#1527).
+    pub start_pick: Option<StartPick>,
     /// Pick a `.lsp` file for APPLOAD, starting in the given folder (empty for the default one).
     /// `None` where there is no native file dialog: the desktop without one asks for the name,
     /// and the web (no file system) says to drop the file (`no_file_system`).
@@ -238,6 +244,36 @@ pub struct Services {
     pub pick_pgp: Option<Box<dyn Fn(Option<&str>) -> Option<String>>>,
 }
 
+/// The file dialog to show: Open, Save with the suggested file name, APPLOAD's `.lsp` picker or
+/// ALIASEDIT's `.pgp` picker, starting in the given folder (empty for the default one).
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum Pick {
+    Open,
+    Save(String),
+    Lisp(String),
+    Pgp(String),
+}
+
+/// Shows a file dialog without waiting for it and calls the callback (from any thread) with the
+/// chosen path, or `None` when the dialog is cancelled ([`Services::start_pick`]).
+pub type StartPick = Box<dyn Fn(Pick, Box<dyn FnOnce(Option<String>) + Send>)>;
+
+/// What to do with the path a file dialog chose ([`CadApp::pick_then`]).
+type PickDone = Box<dyn FnOnce(&mut CadApp, String) -> Result<Value, String>>;
+
+/// A file dialog shown with [`Services::start_pick`] that has not answered yet.
+struct PendingPick {
+    answer: Receiver<Option<String>>,
+    /// The drawing (its `uid`) the answer is for: Save As writes that drawing, export and plot
+    /// read it, and so on, whichever drawing is active when the answer arrives. `None` for the
+    /// dialogs that open a drawing (Open, New from Template, Recover).
+    doc: Option<u64>,
+    /// The close prompt's Save is waiting for this dialog: its other answers wait too
+    /// ([`closing`]).
+    for_close: bool,
+    then: PickDone,
+}
+
 pub struct CadApp {
     pub system_languages: Vec<String>,
     /// Whether the operating system shows animations, as the host reads it; `None` when the OS
@@ -329,6 +365,8 @@ pub struct CadApp {
     pub hatch_dlg: Option<hatchdlg::HatchDlgState>,
     /// The Edit Block Definition dialog ([`bedit`]).
     pub bedit: bedit::State,
+    /// A file dialog shown with [`Services::start_pick`]: its answer, and what to do with it.
+    pending_pick: Option<PendingPick>,
     /// The startup update check and its prompt (desktop; [`updates_ui`]).
     #[cfg(not(target_arch = "wasm32"))]
     pub updates_rt: updates_ui::Runtime,
@@ -389,9 +427,139 @@ impl CadApp {
             bedit: bedit::State::default(),
             #[cfg(not(target_arch = "wasm32"))]
             updates_rt: updates_ui::Runtime::default(),
+            pending_pick: None,
         }
     }
 
+    /// Ask for a file with the host's dialog (`pick`) and run `then` with the chosen path, on the
+    /// drawing that is active now. `None` when the host has no dialog of that kind. Cancelling
+    /// gives `Ok(Null)`. With a synchronous picker the result is `then`'s; with
+    /// [`Services::start_pick`] the dialog opens and this returns `Ok(Null)` at once: `then` runs
+    /// in a later frame ([`Self::logic`]) with that drawing made active again (if something else
+    /// was switched to meanwhile, such as a control-channel `document.switch`), and not at all if
+    /// the drawing was closed. Its error, if any, shows in the status bar. With no drawing open
+    /// it refuses without showing a dialog. While one dialog is open, no other is shown: the
+    /// request is refused with an error, also shown in the status bar.
+    pub fn pick_then(
+        &mut self,
+        pick: Pick,
+        then: impl FnOnce(&mut CadApp, String) -> Result<Value, String> + 'static,
+    ) -> Option<Result<Value, String>> {
+        self.pick_for(pick, true, Box::new(then))
+    }
+
+    /// [`Self::pick_then`] for a dialog that opens a drawing (Open, New from Template, Recover):
+    /// `then` does not act on the drawing that was active, so it runs whatever was switched to
+    /// or closed meanwhile.
+    pub fn pick_then_open(
+        &mut self,
+        pick: Pick,
+        then: impl FnOnce(&mut CadApp, String) -> Result<Value, String> + 'static,
+    ) -> Option<Result<Value, String>> {
+        self.pick_for(pick, false, Box::new(then))
+    }
+
+    /// Show the dialog `pick` for `then`, bound to the active drawing when `bound`.
+    fn pick_for(&mut self, pick: Pick, bound: bool, then: PickDone) -> Option<Result<Value, String>> {
+        let available = match pick {
+            Pick::Open => self.services.pick_open.is_some(),
+            Pick::Save(_) => self.services.pick_save.is_some(),
+            Pick::Lisp(_) => self.services.pick_lisp.is_some(),
+            Pick::Pgp(_) => self.services.pick_pgp.is_some(),
+        };
+        if !available {
+            return None;
+        }
+        if self.pending_pick.is_some() {
+            return Some(Err(self.refuse_pick("A file dialog is already open; answer it first.".into())));
+        }
+        // A bound answer must not land on a drawing created or opened while the dialog is up.
+        let doc = match (bound, self.session.state()) {
+            (false, _) => None,
+            (true, Ok(st)) => Some(st.uid),
+            (true, Err(e)) => {
+                let why = e.to_string();
+                return Some(Err(self.refuse_pick(why)));
+            }
+        };
+        if let Some(start) = &self.services.start_pick {
+            let (tx, answer) = std::sync::mpsc::channel();
+            start(
+                pick,
+                Box::new(move |path| {
+                    let _ = tx.send(path);
+                }),
+            );
+            self.pending_pick = Some(PendingPick { answer, doc, for_close: false, then });
+            return Some(Ok(Value::Null));
+        }
+        let path = match &pick {
+            Pick::Open => self.services.pick_open.as_ref().and_then(|f| f()),
+            Pick::Save(name) => self.services.pick_save.as_ref().and_then(|f| f(name)),
+            Pick::Lisp(dir) => self.services.pick_lisp.as_ref().and_then(|f| f(dir)),
+            Pick::Pgp(dir) => self.services.pick_pgp.as_ref().and_then(|f| f(Some(dir.as_str()).filter(|d| !d.is_empty()))),
+        };
+        Some(match path {
+            Some(path) => then(self, path),
+            None => Ok(Value::Null),
+        })
+    }
+
+    /// A file dialog that is not shown: the reason goes to the status bar too, since a typed or
+    /// menu command's result is not shown ([`Self::start`]).
+    fn refuse_pick(&mut self, why: String) -> String {
+        self.set_status(why.clone());
+        why
+    }
+
+    /// Start the interactive command `id` with a dialog's answer. `was_prompting`: whether a
+    /// command was running when the dialog was asked for. Starting cancels the running command,
+    /// so a command started while the dialog was open (a control request, say) is kept and this
+    /// one refused instead; one that was already running is cancelled as when the dialog answers
+    /// at once.
+    pub fn start_after_pick(&mut self, id: &str, was_prompting: bool) -> Result<(), String> {
+        if !was_prompting && self.session.prompting() {
+            return Err(format!("{}: another command started while the file dialog was open; run it again.", id.to_ascii_uppercase()));
+        }
+        self.session.start(id).map_err(|e| e.to_string())
+    }
+
+    /// Act on the answer of a dialog started with [`Services::start_pick`], once it arrives.
+    fn finish_pick(&mut self, ctx: &egui::Context) {
+        let Some(pending) = &self.pending_pick else { return };
+        match pending.answer.try_recv() {
+            Err(std::sync::mpsc::TryRecvError::Empty) => ctx.request_repaint_after(std::time::Duration::from_millis(100)),
+            Ok(None) => self.pending_pick = None,
+            // The host dropped the answer without giving one: the dialog never opened (its
+            // thread could not start) or failed.
+            Err(std::sync::mpsc::TryRecvError::Disconnected) => {
+                self.pending_pick = None;
+                self.set_status("The file dialog could not be shown.");
+            }
+            Ok(Some(path)) => {
+                if let Some(PendingPick { doc, then, .. }) = self.pending_pick.take()
+                    && let Err(e) = self.make_active(doc, &path).and_then(|()| then(self, path))
+                {
+                    self.set_status(e);
+                }
+                ctx.request_repaint();
+            }
+        }
+    }
+
+    /// Make the drawing `uid` active again for the answer `path` of a dialog it asked for, or
+    /// refuse when it was closed meanwhile.
+    fn make_active(&mut self, uid: Option<u64>, path: &str) -> Result<(), String> {
+        let Some(uid) = uid else { return Ok(()) };
+        let Some(i) = self.session.docs.iter().position(|d| d.uid == uid) else {
+            return Err(format!("The drawing was closed before the file dialog answered; nothing was done with {path}."));
+        };
+        if self.session.active != i {
+            self.run("document.switch", json!({ "index": i }))?;
+        }
+        Ok(())
+    }
+
     /// The interface language shown: the chosen one, or English when this computer has no font
     /// for it (Chinese or Korean without a suitable font would be boxes).
     pub fn language(&self) -> &'static str {
@@ -702,6 +870,7 @@ impl CadApp {
         // Consume-based queues: each item is handled once, whichever callback delivers it. A
         // reply arriving during a later pass is never starved until the next frame.
         self.drain_control(ctx);
+        self.finish_pick(ctx);
         self.finish_opening();
         // Finishing an open switches to the new drawing.
         capture::note_identity(self, ctx);

crates/ui-egui/src/managers.rs

@@ -11,9 +11,9 @@ use std::sync::atomic::{AtomicU32, Ordering};
 use egui::{RichText, Sense, Stroke, vec2};
 use serde_json::{Value, json};
 
-use crate::CadApp;
 use crate::parametric::expr_field;
 use crate::theme::Tokens;
+use crate::{CadApp, Pick};
 
 /// The Block Attribute Manager (BATTMAN).
 mod battman;
@@ -121,6 +121,7 @@ fn linetype(app: &mut CadApp, ctx: &egui::Context, open: &mut bool) -> Action {
     let library: Vec<String> = cadcraft_doc::library::standard_linetypes().into_iter().map(|l| l.name).filter(|n| d.linetype(n).is_none()).collect();
     let mut sel = temp::<String>(ctx, "ltmgr_sel").filter(|s| rows.iter().any(|r| r.0.eq_ignore_ascii_case(s))).unwrap_or_else(|| current.clone());
     let mut action = None;
+    let mut pick_lin = false;
     egui::Window::new("Linetype Manager").open(open).default_size(vec2(520.0, 360.0)).resizable(true).show(ctx, |ui| {
         ui.horizontal(|ui| {
             craft_ui::ComboBox::from_id_salt("ltmgr_load").selected_text("Load...").width(110.0).show_ui(ui, |ui| {
@@ -135,12 +136,10 @@ fn linetype(app: &mut CadApp, ctx: &egui::Context, open: &mut bool) -> Action {
                     }
                 }
                 // The user's own .lin file (where the host has a file picker).
-                if let Some(pick) = app.services.pick_open.as_ref() {
+                if app.services.pick_open.is_some() {
                     ui.separator();
-                    if ui.selectable_label(false, "From File...").clicked()
-                        && let Some(path) = pick()
-                    {
-                        action = Some(("linetype", json!({ "load": "*", "file": path })));
+                    if ui.selectable_label(false, "From File...").clicked() {
+                        pick_lin = true;
                     }
                 }
             });
@@ -187,6 +186,10 @@ fn linetype(app: &mut CadApp, ctx: &egui::Context, open: &mut bool) -> Action {
         });
     });
     set_temp(ctx, "ltmgr_sel", sel);
+    // The user's .lin file, asked for once the window is drawn. Errors are echoed by `run`.
+    if pick_lin {
+        let _ = app.pick_then(Pick::Open, |app, path| app.run("linetype", json!({ "load": "*", "file": path })));
+    }
     action
 }
 
@@ -1038,33 +1041,46 @@ fn plot(app: &mut CadApp, ctx: &egui::Context, open: &mut bool) -> Action {
         return action;
     }
     if ok {
-        let mut params = plot_params(&st, None);
-        if let Some(pick) = app.services.pick_save.as_ref() {
+        let params = plot_params(&st, None);
+        let target = st.target.clone();
+        if app.services.pick_save.is_some() {
             let title = app.session.state().map(|s| s.title.clone()).unwrap_or_default();
             let stem = std::path::Path::new(&title).file_stem().map(|s| s.to_string_lossy().to_string()).filter(|s| !s.is_empty());
             let suggested = format!("{}-{}.{ext}", stem.unwrap_or_else(|| "Drawing".into()), st.target);
             // Cancelling the file dialog keeps the Plot dialog open with its settings.
-            let Some(path) = pick(&suggested) else { return action };
-            if let Some(o) = params.as_object_mut() {
-                o.insert("path".into(), json!(path));
-            }
-        }
-        *open = false;
-        match app.run("plot", params) {
-            Ok(r) => {
-                let msg = match r.get("path").and_then(Value::as_str) {
-                    Some(path) => format!("Plotted {} to {path}", st.target),
-                    None => format!("Plotted {} ({} bytes of PDF; there is no file dialog here)", st.target, r["bytes"]),
-                };
-                app.session.echo(msg);
-            }
-            // `run` already echoed the error; keep the dialog open to fix the settings.
-            Err(_) => *open = true,
+            let _ = app.pick_then(Pick::Save(suggested), move |app, path| {
+                let mut params = params;
+                if let Some(o) = params.as_object_mut() {
+                    o.insert("path".into(), json!(path));
+                }
+                run_plot(app, params, &target);
+                Ok(Value::Null)
+            });
+        } else {
+            run_plot(app, params, &target);
         }
     }
     action
 }
 
+/// Plot with the Plot dialog's settings: it closes, and opens again when the plot fails.
+fn run_plot(app: &mut CadApp, params: Value, target: &str) {
+    if app.ui.dialog.as_deref() == Some("plot") {
+        app.ui.dialog = None;
+    }
+    match app.run("plot", params) {
+        Ok(r) => {
+            let msg = match r.get("path").and_then(Value::as_str) {
+                Some(path) => format!("Plotted {target} to {path}"),
+                None => format!("Plotted {target} ({} bytes of PDF; there is no file dialog here)", r["bytes"]),
+            };
+            app.session.echo(msg);
+        }
+        // `run` already echoed the error; keep the dialog open to fix the settings.
+        Err(_) => app.ui.dialog = Some("plot".into()),
+    }
+}
+
 /// The sheet in the chosen orientation with its printable area, and its size.
 fn sheet_sketch(ui: &mut egui::Ui, page: &cadcraft_doc::PageSetup, t: &Tokens) {
     let (w, h) = if page.landscape { (page.height_mm, page.width_mm) } else { (page.width_mm, page.height_mm) };

crates/ui-egui/src/menus.rs

@@ -3,7 +3,7 @@
 
 use serde_json::{Value, json};
 
-use crate::CadApp;
+use crate::{CadApp, Pick};
 
 /// The top-level menus, in order.
 pub const MENUS: &[&str] = &["File", "Edit", "View", "Insert", "Format", "Tools", "Draw", "Dimension", "Modify", "Window", "Help"];
@@ -405,13 +405,12 @@ fn run_ui_command_inner(app: &mut CadApp, id: &str, params: &Value) -> Option<Re
         return Some(Ok(Value::Null));
     }
     let r = match id {
-        "ui.open" | "open" if no_path => {
-            let picked = app.services.pick_open.as_ref().and_then(|f| f());
-            if let Some(p) = picked {
+        "ui.open" | "open" if no_path => app
+            .pick_then_open(Pick::Open, |app, p| {
                 app.open_path(std::path::Path::new(&p));
-            }
-            Ok(Value::Null)
-        }
+                Ok(Value::Null)
+            })
+            .unwrap_or(Ok(Value::Null)),
         // APPLOAD typed or chosen from a menu: the `.lsp` file picker, starting where the last
         // one came from. JSON calls carry `path` and never open one. A picked file is loaded as a
         // typed name is, through the interactive command, so a routine it starts that asks for a
@@ -423,57 +422,54 @@ fn run_ui_command_inner(app: &mut CadApp, id: &str, params: &Value) -> Option<Re
                 app.set_status(hint);
                 return Some(Ok(Value::Null));
             }
-            let pick = app.services.pick_lisp.as_ref()?;
             let dir = app.ui.last_lisp_dir.clone().unwrap_or_default();
-            let Some(path) = pick(&dir) else { return Some(Ok(Value::Null)) };
-            if let Some(dir) = std::path::Path::new(&path).parent().and_then(std::path::Path::to_str).filter(|d| !d.is_empty()) {
-                app.ui.last_lisp_dir = Some(dir.to_string());
-            }
-            if let Err(e) = app.session.start("appload") {
-                return Some(Err(e.to_string()));
-            }
-            app.cmdline(&path);
-            Ok(Value::Null)
+            let was_prompting = app.session.prompting();
+            return app.pick_then(Pick::Lisp(dir), move |app, path| {
+                if let Some(dir) = std::path::Path::new(&path).parent().and_then(std::path::Path::to_str).filter(|d| !d.is_empty()) {
+                    app.ui.last_lisp_dir = Some(dir.to_string());
+                }
+                app.start_after_pick("appload", was_prompting)?;
+                app.cmdline(&path);
+                Ok(Value::Null)
+            });
         }
         // Pick a template (.dwt or .dxf) and start a new drawing from it.
-        "ui.newtemplate" => {
-            if let Some(p) = app.services.pick_open.as_ref().and_then(|f| f()) {
-                return Some(app.session.execute("new", &json!({ "template": p })).map_err(|e| e.to_string()));
-            }
-            Ok(Value::Null)
-        }
+        "ui.newtemplate" => app
+            .pick_then_open(Pick::Open, |app, p| app.session.execute("new", &json!({ "template": p })).map_err(|e| e.to_string()))
+            .unwrap_or(Ok(Value::Null)),
         // RECOVER from the menu or typed: pick the file. Without a picker the engine asks for the
         // file name on the command line.
-        "recover" if no_path && app.services.pick_open.is_some() => {
-            if let Some(p) = app.services.pick_open.as_ref().and_then(|f| f()) {
+        "recover" if no_path && app.services.pick_open.is_some() => app
+            .pick_then_open(Pick::Open, |app, p| {
                 let r = app.run("recover", json!({ "path": p }));
                 app.opened(r);
-            }
-            Ok(Value::Null)
-        }
+                Ok(Value::Null)
+            })
+            .unwrap_or(Ok(Value::Null)),
         "ui.saveas" | "saveas" if no_path => {
             let title = app.session.state().map(|s| s.title.clone()).ok();
             let name = app.ui.save_format.suggested_name(title.as_deref());
-            if let Some(p) = app.services.pick_save.as_ref().and_then(|f| f(&name)) {
-                return Some(app.session.execute("saveas", &saveas_params(&app.ui, &app.session, &p)).map_err(|e| e.to_string()));
-            }
-            Ok(Value::Null)
+            // Bound to this drawing: the answer saves it, not whichever drawing is active then.
+            app.pick_then(Pick::Save(name), |app, p| {
+                app.session.execute("saveas", &saveas_params(&app.ui, &app.session, &p)).map_err(|e| e.to_string())
+            })
+            .unwrap_or(Ok(Value::Null))
         }
         "qsave" if no_path => return user_qsave(app),
         // EXPORTPDF from the menu or typed: ask where to save the PDF (PLOT and PRINT open the Plot
         // dialog, `managers::route`). JSON calls (scripts, control channel, MCP) always carry
         // params, never get here and never open a dialog.
         "exportpdf" if params.is_null() && app.session.state().is_ok() => {
-            let pick = app.services.pick_save.as_ref()?;
             let title = app.session.state().map(|s| s.title.clone()).unwrap_or_default();
             let stem = std::path::Path::new(&title).file_stem().map(|s| s.to_string_lossy().to_string()).filter(|s| !s.is_empty());
-            let Some(path) = pick(&format!("{}.pdf", stem.unwrap_or_else(|| "Drawing".into()))) else { return Some(Ok(Value::Null)) };
-            let r = app.session.execute("exportpdf", &json!({ "path": path })).map_err(|e| e.to_string());
-            app.session.echo(match &r {
-                Ok(_) => format!("Plotted to {path}"),
-                Err(e) => e.clone(),
+            return app.pick_then(Pick::Save(format!("{}.pdf", stem.unwrap_or_else(|| "Drawing".into()))), |app, path| {
+                let r = app.session.execute("exportpdf", &json!({ "path": path })).map_err(|e| e.to_string());
+                app.session.echo(match &r {
+                    Ok(_) => format!("Plotted to {path}"),
+                    Err(e) => e.clone(),
+                });
+                r
             });
-            r
         }
         "ui.sample" => {
             let d = cadcraft_engine::sample::default_sample();

crates/ui-egui/src/xrefs.rs

@@ -6,8 +6,8 @@
 use egui::RichText;
 use serde_json::{Value, json};
 
-use crate::CadApp;
 use crate::docking::Panel;
+use crate::{CadApp, Pick};
 
 /// XREF typed or chosen from a menu opens this palette; XATTACH there asks for the file first
 /// (with the host's file picker, where there is one). JSON calls (with parameters) run the
@@ -19,19 +19,18 @@ pub fn route(app: &mut CadApp, id: &str, params: &Value) -> Option<Result<Value,
     match cadcraft_engine::cmd::resolve_alias(id).as_str() {
         "xref" => Some(open_palette(app)),
         "xattach" => {
-            let picked = app.services.pick_open.as_ref().and_then(|f| f())?;
-            let path = relative_to_host(app, &picked);
-            if let Err(e) = app.session.start("xattach") {
-                return Some(Err(e.to_string()));
-            }
-            // Submit the picked filename as literal text, not through the command line: a path is
-            // attacker-controlled (the file picker returns whatever the user selected), and
-            // `cmdline` interprets command syntax, so a name like `'closeall` would run an engine
-            // command instead of naming the file (CWE-74).
-            if let Err(e) = app.session.input(cadcraft_engine::Input::Text(path)) {
-                return Some(Err(e.to_string()));
-            }
-            Some(Ok(Value::Null))
+            app.services.pick_open.as_ref()?;
+            let was_prompting = app.session.prompting();
+            app.pick_then(Pick::Open, move |app, picked| {
+                let path = relative_to_host(app, &picked);
+                app.start_after_pick("xattach", was_prompting)?;
+                // Submit the picked filename as literal text, not through the command line: a
+                // path is attacker-controlled (the file picker returns whatever the user
+                // selected), and `cmdline` interprets command syntax, so a name like `'closeall`
+                // would run an engine command instead of naming the file (CWE-74).
+                app.session.input(cadcraft_engine::Input::Text(path)).map_err(|e| e.to_string())?;
+                Ok(Value::Null)
+            })
         }
         _ => None,
     }
@@ -78,10 +77,16 @@ fn rows(app: &CadApp, ui: &egui::Ui) -> Vec<Row> {
     let xrefs: Vec<_> = d.blocks.values().filter(|b| b.xref_path.is_some() && !b.name.contains('|')).collect();
     let mut counts = vec![0usize; xrefs.len()];
     if !xrefs.is_empty() {
+        // Xref name (ASCII-upper-cased) → its row, the first of names that differ only in case, so
+        // each INSERT is one lookup instead of a scan of the xref list.
+        let mut index: std::collections::HashMap<String, usize> = std::collections::HashMap::new();
+        for (k, b) in xrefs.iter().enumerate() {
+            index.entry(b.name.to_ascii_uppercase()).or_insert(k);
+        }
         let mut count = |store: &cadcraft_engine::doc::EntityStore| {
             for e in store.iter() {
                 if let cadcraft_engine::doc::EntityKind::Insert(i) = &e.kind
-                    && let Some(k) = xrefs.iter().position(|b| b.name.eq_ignore_ascii_case(&i.block))
+                    && let Some(&k) = index.get(&i.block.to_ascii_uppercase())
                     && let Some(c) = counts.get_mut(k)
                 {
                     *c += 1;