Fix mac scroll modifier

egui_demo_lib/src/apps/demo/plot_demo.rs

@@ -95,7 +95,15 @@ impl PlotDemo {
             });
         });
 
-        ui.label("Drag to pan, ctrl + scroll to zoom. Double-click to reset view.");
+        ui.label("Pan by dragging, or scroll (+ shift = horizontal).");
+        if cfg!(target_arch = "wasm32") {
+            ui.label("Zoom with ctrl / ⌘ + mouse wheel, or with pinch gesture.");
+        } else if cfg!(target_os = "macos") {
+            ui.label("Zoom with ctrl / ⌘ + scroll.");
+        } else {
+            ui.label("Zoom with ctrl + scroll.");
+        }
+        ui.label("Reset view with double-click.");
     }
 
     fn circle(&self) -> Curve {

egui_glium/CHANGELOG.md

@@ -5,6 +5,7 @@ All notable changes to the `egui_glium` integration will be noted in this file.
 
 ## Unreleased
 
+* [Fix modifier key for zoom with mouse wheel on Mac](https://github.com/emilk/egui/issues/401)
 
 ## 0.12.0 - 2021-05-10
 

egui_glium/src/lib.rs

@@ -188,7 +188,7 @@ pub fn input_to_egui(
                 delta.x *= -1.0;
             }
 
-            if input_state.raw.modifiers.ctrl {
+            if input_state.raw.modifiers.ctrl || input_state.raw.modifiers.command {
                 // Treat as zoom instead:
                 input_state.raw.zoom_delta *= (delta.y / 200.0).exp();
             } else {

egui_web/src/lib.rs

@@ -1053,7 +1053,10 @@ fn install_canvas_events(runner_ref: &AppRunnerRef) -> Result<(), JsValue> {
             let delta = -scroll_multiplier
                 * egui::Vec2::new(event.delta_x() as f32, event.delta_y() as f32);
 
-            if event.ctrl_key() {
+            // Report a zoom event in case CTRL (on Windows or Linux) or CMD (on Mac) is pressed.
+            // This if-statement is equivalent to how `Modifiers.command` is determined in
+            // `modifiers_from_event()`, but we cannot directly use that fn for a `WheelEvent`.
+            if event.ctrl_key() || event.meta_key() {
                 runner_lock.input.raw.zoom_delta *= (delta.y / 200.0).exp();
             } else {
                 runner_lock.input.raw.scroll_delta += delta;