Implement DeviceEvent::MouseWheel

CHANGELOG.md

@@ -79,7 +79,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On Web, fix scale factor resize suggestion always overwriting the canvas size.
 - On macOS, fix crash when dropping `Window`.
 - On Web, fix `DeviceEvent::MouseMotion` being triggered for each canvas instead of the whole window.
-- On Web, add `DeviceEvent::Motion` support.
+- On Web, add `DeviceEvent::Motion` and `DeviceEvent::MouseWheel` support.
 
 # 0.28.6
 

src/platform_impl/web/event_loop/runner.rs

@@ -15,7 +15,7 @@ use std::{
     rc::{Rc, Weak},
 };
 use wasm_bindgen::prelude::Closure;
-use web_sys::PointerEvent;
+use web_sys::{PointerEvent, WheelEvent};
 use web_time::{Duration, Instant};
 
 pub struct Shared<T: 'static>(Rc<Execution<T>>);
@@ -41,6 +41,8 @@ pub struct Execution<T: 'static> {
     device_events: Cell<DeviceEvents>,
     #[allow(clippy::type_complexity)]
     on_mouse_move: RefCell<Option<EventListenerHandle<dyn FnMut(PointerEvent)>>>,
+    #[allow(clippy::type_complexity)]
+    on_wheel: RefCell<Option<EventListenerHandle<dyn FnMut(WheelEvent)>>>,
 }
 
 enum RunnerEnum<T: 'static> {
@@ -121,6 +123,7 @@ impl<T: 'static> Shared<T> {
             unload_event_handle: RefCell::new(None),
             device_events: Cell::default(),
             on_mouse_move: RefCell::new(None),
+            on_wheel: RefCell::new(None),
         }))
     }
 
@@ -215,6 +218,24 @@ impl<T: 'static> Shared<T> {
                 }));
             }),
         ));
+        let runner = self.clone();
+        let window = self.window().clone();
+        *self.0.on_wheel.borrow_mut() = Some(EventListenerHandle::new(
+            self.window(),
+            "wheel",
+            Closure::new(move |event: WheelEvent| {
+                if !runner.device_events() {
+                    return;
+                }
+
+                if let Some(delta) = backend::event::mouse_scroll_delta(&window, &event) {
+                    runner.send_event(Event::DeviceEvent {
+                        device_id: RootDeviceId(DeviceId(0)),
+                        event: DeviceEvent::MouseWheel { delta },
+                    });
+                }
+            }),
+        ));
     }
 
     pub(crate) fn set_on_scale_change<F>(&self, handler: F)
@@ -556,6 +577,7 @@ impl<T: 'static> Shared<T> {
         *self.0.scale_change_detector.borrow_mut() = None;
         *self.0.unload_event_handle.borrow_mut() = None;
         *self.0.on_mouse_move.borrow_mut() = None;
+        *self.0.on_wheel.borrow_mut() = None;
         // Dropping the `Runner` drops the event handler closure, which will in
         // turn drop all `Window`s moved into the closure.
         *self.0.runner.borrow_mut() = RunnerEnum::Destroyed;

src/platform_impl/web/event_loop/window_target.rs

@@ -602,16 +602,21 @@ impl<T> EventLoopWindowTarget<T> {
                         }
                     });
 
-                runner.send_events(modifiers_changed.into_iter().chain(iter::once(
-                    Event::WindowEvent {
+                let device_event = runner.device_events().then_some(Event::DeviceEvent {
+                    device_id: RootDeviceId(DeviceId(pointer_id)),
+                    event: DeviceEvent::MouseWheel { delta },
+                });
+
+                runner.send_events(modifiers_changed.into_iter().chain(device_event).chain(
+                    iter::once(Event::WindowEvent {
                         window_id: RootWindowId(id),
                         event: WindowEvent::MouseWheel {
                             device_id: RootDeviceId(DeviceId(pointer_id)),
                             delta,
                             phase: TouchPhase::Moved,
                         },
-                    },
-                )));
+                    }),
+                ));
             },
             prevent_default,
         );