Rework Zoom controls

README.md

@@ -40,6 +40,7 @@ reshuffle.
 | Middle- or right-drag | Pan |
 | Drop files on the window | A file node each; a `.canvas` file opens instead |
 | Wheel | Zoom around the pointer, anywhere on the canvas |
+| Double-click the wheel button | Back to 100% |
 
 **Markdown in text nodes**: headings, bold/italic/strikethrough, inline and
 fenced code, quotes, bullet, numbered and task lists, rules, images and links.

src/app.rs

@@ -910,14 +910,21 @@ impl App {
             }
             if ui
                 .button(format!("{:.0}%", self.view.zoom() * 100.0))
+                .on_hover_text("Actual size (Ctrl+1)")
+                .clicked()
+            {
+                self.view.set_zoom(1.0);
+            }
+            if ui.button("+").on_hover_text("Zoom in (Ctrl++)").clicked() {
+                self.view.set_zoom(self.view.zoom() * 1.2);
+            }
+            if ui
+                .button("⛶")
                 .on_hover_text("Zoom to fit (Ctrl+0)")
                 .clicked()
             {
                 self.view.zoom_to_fit(&self.doc.canvas);
             }
-            if ui.button("+").on_hover_text("Zoom in (Ctrl++)").clicked() {
-                self.view.set_zoom(self.view.zoom() * 1.2);
-            }
 
             ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
                 ui.toggle_value(&mut self.show_inspector, "Inspector");
@@ -1196,6 +1203,7 @@ const SHORTCUTS: &[(&str, &str)] = &[
     ("Arrow keys", "Nudge (hold Shift for 10 units)"),
     ("Double-click", "New note, or edit what is under the cursor"),
     ("Middle / right drag", "Pan the canvas"),
+    ("Double-click wheel", "Back to 100%"),
     ("Wheel", "Zoom around the pointer"),
     ("Ctrl+0 / Ctrl+1", "Zoom to fit / actual size"),
 ];

src/view.rs

@@ -809,7 +809,8 @@ impl CanvasView {
     // -- input ------------------------------------------------------------
 
     /// Panning is a drag or a two-finger swipe; the wheel zooms, and so does
-    /// a swipe with the zoom modifier held.
+    /// a swipe with the zoom modifier held. Two clicks of the wheel button
+    /// go back to 1:1.
     fn handle_pan_and_zoom(&mut self, ui: &egui::Ui, background: &egui::Response) {
         if background.dragged_by(PointerButton::Middle)
             || background.dragged_by(PointerButton::Secondary)
@@ -826,6 +827,10 @@ impl CanvasView {
         let Some(pointer) = ui.input(|i| i.pointer.latest_pos()) else {
             return;
         };
+        if ui.input(|i| i.pointer.button_double_clicked(PointerButton::Middle)) {
+            self.set_zoom(1.0);
+            return;
+        }
         // Held down, the zoom modifier turns scrolling into zooming before it
         // ever reaches here: egui reports it as a zoom and leaves no scroll
         // behind. A pinch on a touchscreen arrives the same way.

src/view/tests.rs

@@ -563,6 +563,44 @@ fn the_wheel_zooms_over_a_node() {
     assert!(moved < 1.0, "the canvas slid {moved} under the pointer");
 }
 
+/// Two clicks of the wheel button put the canvas back to 1:1, over a card
+/// as readily as over bare canvas.
+#[test]
+fn a_double_click_of_the_wheel_button_goes_back_to_actual_size() {
+    let ctx = egui::Context::default();
+    let mut doc = Document::new();
+    doc.canvas = canvas_with_two_nodes();
+    let mut view = CanvasView::new();
+    // Zoomed in, with node "a" in the middle of the view.
+    view.to_global =
+        TSTransform::from_translation(vec2(475.0, 325.0)) * TSTransform::from_scaling(2.5);
+
+    let screen = Rect::from_min_size(Pos2::ZERO, vec2(1200.0, 900.0));
+    let at = pos2(600.0, 450.0);
+    let wheel = |pressed| egui::Event::PointerButton {
+        pos: at,
+        button: PointerButton::Middle,
+        pressed,
+        modifiers: egui::Modifiers::default(),
+    };
+    pass(
+        &ctx,
+        &mut view,
+        &mut doc,
+        screen,
+        vec![egui::Event::PointerMoved(at)],
+    );
+    pass(
+        &ctx,
+        &mut view,
+        &mut doc,
+        screen,
+        vec![wheel(true), wheel(false), wheel(true), wheel(false)],
+    );
+
+    assert_eq!(view.zoom(), 1.0, "the wheel button did not reset the zoom");
+}
+
 /// A two-finger swipe on a touchpad slides the canvas about, sideways as
 /// readily as up and down, rather than zooming the way the wheel does.
 #[test]