From 97aad95d4de347bca1aafd09422c8a14b0d54960 Mon Sep 17 00:00:00 2001
From: Si <simontgn@gmail.com>
Date: Sat, 10 Oct 2026 21:17:33 +1100
Subject: [PATCH] Zoom the page with Ctrl+scroll and pinch (#139) (#179)

The canvas ignored egui's zoom delta, so Ctrl/Cmd+wheel and trackpad pinch
did nothing over the document. Apply it through view.zoom, starting from the
shown scale so fit modes (Page Width etc.) zoom from where they are.

Co-authored-by: Simon Geljic <simon.geljic2@det.nsw.edu.au>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
---
 crates/ui-egui/src/canvas.rs |  7 ++++++
 crates/ui-egui/src/lib.rs    | 42 ++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/crates/ui-egui/src/canvas.rs b/crates/ui-egui/src/canvas.rs
index 6cad1f3a2..ca9ae352d 100644
--- a/crates/ui-egui/src/canvas.rs
+++ b/crates/ui-egui/src/canvas.rs
@@ -168,6 +168,13 @@ pub fn show(app: &mut WordApp, ui: &mut Ui) {
         (None, None, full)
     };
     app.canvas.canvas_rect = Some(area);
+    // Ctrl/⌘ + wheel (and trackpad pinch) zooms the document, like Word. egui reports both as a
+    // zoom factor and doesn't scroll for them. Start from the shown scale so fit modes zoom too.
+    let zoom_delta = ui.input(|i| i.zoom_delta());
+    if (zoom_delta - 1.0).abs() > 1e-3 && ui.rect_contains_pointer(area) {
+        let pct = (app.canvas.scale / PX_PER_PT * zoom_delta * 100.0).clamp(10.0, 500.0);
+        let _ = app.run("view.zoom", json!({"value": pct}));
+    }
     let geo = geometry(app, &layout, area.size() - vec2(14.0, 0.0));
     app.canvas.scale = geo.scale;
     let caret = layout.caret_on(&app.session.sel.focus, app.session.page_hint);
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index ba81539cd..1165f5ae2 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -612,6 +612,48 @@ mod tests {
         WordApp::new(Session::new(wordcraft_doc::Document::new()), Services::default())
     }
 
+    /// Issue #139: Ctrl+wheel over the page didn't zoom.
+    #[test]
+    fn ctrl_wheel_over_canvas_zooms() {
+        let ctx = egui::Context::default();
+        let mut a = app();
+        let screen = egui::Rect::from_min_size(egui::Pos2::ZERO, egui::vec2(1280.0, 800.0));
+        let mut t = 0.0;
+        let mut frame = |a: &mut WordApp, events: Vec<egui::Event>| {
+            t += 1.0 / 60.0;
+            let input = egui::RawInput { events, time: Some(t), screen_rect: Some(screen), ..Default::default() };
+            ctx.run_ui(input, |ui| {
+                a.logic(ui.ctx());
+                a.ui(ui);
+            })
+            .drop_without_applying_deltas();
+        };
+        // The first frames install fonts; the canvas appears after them.
+        for _ in 0..3 {
+            frame(&mut a, Vec::new());
+        }
+        let over_page = a.canvas.canvas_rect.unwrap().center();
+        frame(&mut a, vec![egui::Event::PointerMoved(over_page)]);
+        let before = a.canvas.scale;
+        let wheel = |y: f32| egui::Event::MouseWheel {
+            unit: egui::MouseWheelUnit::Line,
+            delta: egui::vec2(0.0, y),
+            phase: egui::TouchPhase::Move,
+            modifiers: egui::Modifiers::COMMAND,
+        };
+        frame(&mut a, vec![wheel(1.0)]);
+        for _ in 0..30 {
+            frame(&mut a, Vec::new());
+        }
+        assert!(a.canvas.scale > before * 1.05, "Ctrl+wheel up zooms in: {before} -> {}", a.canvas.scale);
+        let zoomed = a.canvas.scale;
+        frame(&mut a, vec![wheel(-1.0)]);
+        for _ in 0..30 {
+            frame(&mut a, Vec::new());
+        }
+        assert!(a.canvas.scale < zoomed, "Ctrl+wheel down zooms out");
+    }
+
     #[test]
     fn user_name_survives_restart() {
         let mut first = app();