Formulas: trace arrows stay when the sheet is zoomed (#3097)

A zoom changes the workbook's revision, which the trace arrows are tied
to, so every zoom removed the arrows of Trace Precedents and Trace
Dependents. Zooming moves no cell: Trace::keep_through_zoom carries
arrows that were current over a zoom from the View tab, the Zoom dialog,
the status bar's buttons and slider, Ctrl+wheel and the control channel.
Undoing a zoom is still an edit and removes them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SAgnkqJiy3v24Hp25dQLRj

crates/ui-egui/src/app/commands.rs

@@ -47,7 +47,11 @@ impl SheetApp {
             return r;
         }
         let before = self.session.active_window();
+        let zoom_from = matches!(id, "view.zoom" | "view.zoom100" | "view.zoomToSelection").then(|| crate::grid::Trace::key(self));
         let r = self.session.run(id, params);
+        if let Some(from) = zoom_from {
+            crate::grid::Trace::keep_through_zoom(self, from);
+        }
         if id.starts_with("file.") && self.session.active_window() != before {
             // File › New or Open from the Backstage view: the window it was in goes back to its sheet.
             self.backstage = None;

crates/ui-egui/src/grid.rs

@@ -154,7 +154,7 @@ pub struct FillTag {
 }
 
 /// Trace Precedents / Trace Dependents arrows: they stay on the cell they were traced from, on its
-/// sheet, while the selection moves. They go away when anything changes the workbook
+/// sheet, while the selection moves. They go away when anything but a zoom changes the workbook
 /// (`revision`): Excel removes them on edits to the traced formula and on inserted, deleted or
 /// moved cells, this also on a new value in a precedent.
 pub struct Trace {
@@ -171,6 +171,24 @@ impl Trace {
     pub fn new(app: &SheetApp, items: serde_json::Value) -> Option<Trace> {
         app.session.active().map(|d| Trace { uid: d.uid, revision: d.revision, sheet: d.wb.active_sheet(), cell: d.selection.active, items })
     }
+
+    /// The active document's uid and revision, to hand [`Trace::keep_through_zoom`] after a zoom.
+    pub fn key(app: &SheetApp) -> Option<(u64, u64)> {
+        app.session.active().map(|d| (d.uid, d.revision))
+    }
+
+    /// Zooming changes the workbook (its revision) but moves no cell: arrows that were shown
+    /// before a zoom stay after it, as in Excel (#3097). `before` is [`Trace::key`] from then.
+    pub fn keep_through_zoom(app: &mut SheetApp, before: Option<(u64, u64)>) {
+        let now = Trace::key(app);
+        if let Some(t) = app.grid.trace.as_mut()
+            && before == Some((t.uid, t.revision))
+            && let Some((uid, revision)) = now
+            && uid == t.uid
+        {
+            t.revision = revision;
+        }
+    }
 }
 
 #[derive(Default)]

crates/ui-egui/src/grid/show.rs

@@ -1,4 +1,3 @@
-#[cfg(test)]
 use super::Trace;
 use super::cursor::update_cursor;
 use super::editor::{in_cell_editor, list_picker, validation_arrow};
@@ -358,7 +357,9 @@ fn update_zoom_glide(app: &mut SheetApp, ui: &egui::Ui, place: (u64, usize), zoo
         let glides = app.ui.animations && ui.ctx().global_style().animation_time > 0.0 && !app.shots.in_flight();
         let share = egui::emath::exponential_smooth_factor(0.9, 0.1, ui.input(|i| i.stable_dt).min(0.1));
         let z = if glides { zoom_glide_step(shown, to, share) } else { to };
+        let from = Trace::key(app);
         let _ = app.session.run("view.zoom", json!({"percent": z}));
+        Trace::keep_through_zoom(app, from);
         zooming.glide = (z != to).then_some((to, z));
         ui.ctx().request_repaint();
     }
@@ -945,4 +946,25 @@ mod trace_arrow_tests {
         assert_eq!(revisions[0], revisions[1]);
         assert!(arrows(&mut app).1.is_empty(), "Book1's arrows are not drawn on Book2");
     }
+
+    #[test]
+    fn precedent_arrows_stay_through_a_zoom() {
+        let mut app = app();
+        app.run("home.insertSheet", json!({"name": "Two"})).unwrap();
+        app.run("sheet.activate", json!({"sheet": "Sheet1"})).unwrap();
+        app.run("cell.set", json!({"cell": "B2", "input": "1"})).unwrap();
+        app.run("cell.set", json!({"cell": "F7", "input": "=B2"})).unwrap();
+        select(&mut app, "F7");
+        trace(&mut app, "formulas.tracePrecedents");
+        app.run("view.zoom", json!({"percent": 75})).unwrap();
+        let (geo, lines) = arrows(&mut app);
+        assert_eq!(lines, [(center(&app, &geo, "B2"), center(&app, &geo, "F7"))], "#3097");
+        // Zooming another sheet leaves them too, and they are back on returning to their sheet.
+        app.run("sheet.activate", json!({"sheet": "Two"})).unwrap();
+        app.run("view.zoom", json!({"percent": 200})).unwrap();
+        assert!(arrows(&mut app).1.is_empty());
+        app.run("sheet.activate", json!({"sheet": "Sheet1"})).unwrap();
+        let (geo, lines) = arrows(&mut app);
+        assert_eq!(lines, [(center(&app, &geo, "B2"), center(&app, &geo, "F7"))]);
+    }
 }

crates/ui-egui/src/tabs.rs

@@ -387,7 +387,9 @@ pub fn status_bar(app: &mut SheetApp, ui: &mut Ui) {
                     let slider = ui.add(egui::Slider::new(&mut z, 10.0..=400.0).show_value(false).logarithmic(true));
                     ui.ctx().accesskit_node_builder(slider.id, |node| node.set_label(app.ui.language.tr("Zoom")));
                     if slider.changed() {
+                        let from = crate::grid::Trace::key(app);
                         let _ = app.session.run("view.zoom", json!({"percent": z.round()}));
+                        crate::grid::Trace::keep_through_zoom(app, from);
                     }
                     if crate::widgets::icon_button(ui, Icon::Minus, t.text_dim, "Zoom Out", vec2(18.0, 18.0)).clicked() {
                         let z = ((zoom as f32 / 10.0).ceil() * 10.0 - 10.0).max(10.0);

crates/ui-egui/tests/it/wheel_zoom.rs

@@ -276,3 +276,26 @@ fn page_and_point_units_scroll_the_grid_by_their_converted_distance() {
     let point = h.state().view().scroll.y;
     assert!(point > 0.0 && point < page, "40 points scroll less than a page: point {point}, page {page}");
 }
+
+#[test]
+/// Zooming moves no cell: trace arrows shown before a Ctrl+wheel zoom are still shown after its
+/// glide (#3097), while an edit still removes them.
+fn trace_arrows_stay_through_a_wheel_zoom() {
+    let mut h = animated();
+    h.state_mut().run("cell.set", json!({"cell": "B2", "input": "1"})).unwrap();
+    h.state_mut().run("cell.set", json!({"cell": "F7", "input": "=B2"})).unwrap();
+    h.state_mut().run("selection.set", json!({"range": "F7"})).unwrap();
+    let r = h.state_mut().run("formulas.tracePrecedents", json!({})).unwrap();
+    let app = h.state_mut();
+    app.grid.trace = gridcraft_ui_egui::grid::Trace::new(app, r);
+    let current = |h: &Harness| {
+        let d = h.state().session.active().unwrap();
+        h.state().grid.trace.as_ref().is_some_and(|t| (t.uid, t.revision) == (d.uid, d.revision))
+    };
+    assert!(current(&h));
+    let seen = turn_and_watch(&mut h, 1.0, 40);
+    assert!(seen.windows(2).filter(|w| w[0] != w[1]).count() > 1, "the zoom glides over several frames: {seen:?}");
+    assert!(current(&h), "the arrows stay at {}%", zoom(&h));
+    h.state_mut().run("cell.set", json!({"cell": "B2", "input": "2"})).unwrap();
+    assert!(!current(&h), "an edit removes them");
+}

docs/ui-parity.md

@@ -1,6 +1,6 @@
 # UI parity
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-31 · **Change:** minor (Formulas › Function Library as labelled buttons with category menus; Recently Used and the Insert Function categories; Esc leaves a File-page text field before closing the view; earlier: checkbox cells print as boxes; Ctrl+arrow and Ctrl+Shift+arrow while pointing a formula reference; editing a hyperlink loads its existing fields; AutoSum over a selected row puts its total to the right; ribbon catalog count 276 / 292) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-11-01 · **Change:** minor (trace arrows stay through a zoom (#3097); earlier: Formulas › Function Library as labelled buttons with category menus; Recently Used and the Insert Function categories; Esc leaves a File-page text field before closing the view; earlier: checkbox cells print as boxes; Ctrl+arrow and Ctrl+Shift+arrow while pointing a formula reference; editing a hyperlink loads its existing fields; AutoSum over a selected row puts its total to the right; ribbon catalog count 276 / 292) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
 
 Interaction, controls and feel, against Excel. Part of [target-app-parity.md](target-app-parity.md).
 **UI/UX fidelity: ~55% ready, 50–80 h** (estimated). Ribbon command coverage is measured
@@ -196,6 +196,7 @@ scrollbar bugs 2–4 · pixel/feel pass against observed Excel 7–12.
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-11-01 | minor | Trace arrows stay when the sheet is zoomed (View › Zoom, the status bar, Ctrl+wheel), as in Excel; every zoom used to remove them (#3097) |
 | 2026-10-31 | minor | Esc in a File-page text field leaves the field and cancels editing; the next Esc returns to the sheet (#3035) |
 | 2026-10-31 | minor | Recently Used lists the functions most recently entered in a formula from any source, kept with the preferences; the Insert Function dialog is titled as in Excel, its category list (Most Recently Used, All, each category) works, and its category column follows the widest name shown |
 | 2026-10-31 | minor | Formulas › Function Library: Insert Function, the AutoSum split button and three columns of labelled small buttons with category colours; category menus end with Insert Function…; More Functions cascades; Home › Editing shares the AutoSum menu; MR key tip for Recently Used |