Add touchpad magnify support for macOS

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Unreleased
 
 - **Breaking:** Rename the `Exit` variant of `ControlFlow` to `ExitWithCode`, which holds a value to control the exit code after running. Add an `Exit` constant which aliases to `ExitWithCode(0)` instead to avoid major breakage. This shouldn't affect most existing programs.
+- On macOS, add support for touchpad magnification gesture with new event `WindowEvent::TouchpadMagnify`.
 
 # 0.26.1 (2022-01-05)
 

examples/touchpad_magnify.rs

@@ -0,0 +1,37 @@
+use simple_logger::SimpleLogger;
+use winit::{
+    event::{Event, WindowEvent},
+    event_loop::{ControlFlow, EventLoop},
+    window::WindowBuilder,
+};
+
+fn main() {
+    SimpleLogger::new().init().unwrap();
+    let event_loop = EventLoop::new();
+
+    let _window = WindowBuilder::new()
+        .with_title("Touchpad magnify events")
+        .build(&event_loop)
+        .unwrap();
+
+    println!("Only supported on macOS at the moment.");
+
+    event_loop.run(move |event, _, control_flow| {
+        *control_flow = ControlFlow::Wait;
+
+        match event {
+            Event::WindowEvent { event, .. } => match event {
+                WindowEvent::CloseRequested => *control_flow = ControlFlow::Exit,
+                WindowEvent::TouchpadMagnify { delta, .. } => {
+                    if delta > 0.0 {
+                        println!("Zoomed in {}", delta);
+                    } else {
+                        println!("Zoomed out {}", delta);
+                    }
+                },
+                _ => (),
+            },
+            _ => (),
+        }
+    });
+}

src/event.rs

@@ -306,6 +306,18 @@ pub enum WindowEvent<'a> {
         modifiers: ModifiersState,
     },
 
+    /// Touchpad magnification event with two-finger pinch gesture.
+    ///
+    /// Positive delta values indicate magnification (zooming in) and
+    /// negative delta values indicate shrinking (zooming out).
+    ///
+    /// At the moment, only supported on macOS.
+    TouchpadMagnify {
+        device_id: DeviceId,
+        delta: f64,
+        phase: TouchPhase,
+    },
+
     /// Touchpad pressure event.
     ///
     /// At the moment, only supported on Apple forcetouch-capable macbooks.
@@ -418,6 +430,15 @@ impl Clone for WindowEvent<'static> {
                 button: *button,
                 modifiers: *modifiers,
             },
+            TouchpadMagnify {
+                device_id,
+                delta,
+                phase
+            } => TouchpadMagnify {
+                device_id: *device_id,
+                delta: *delta,
+                phase: *phase,
+            },
             TouchpadPressure {
                 device_id,
                 pressure,
@@ -504,6 +525,15 @@ impl<'a> WindowEvent<'a> {
                 button,
                 modifiers,
             }),
+            TouchpadMagnify {
+                device_id,
+                delta,
+                phase
+            } => Some(TouchpadMagnify {
+                device_id,
+                delta,
+                phase,
+            }),
             TouchpadPressure {
                 device_id,
                 pressure,

src/platform_impl/macos/view.rs

@@ -237,6 +237,10 @@ lazy_static! {
             sel!(scrollWheel:),
             scroll_wheel as extern "C" fn(&Object, Sel, id),
         );
+        decl.add_method(
+            sel!(magnifyWithEvent:),
+            magnify_with_event as extern "C" fn(&Object, Sel, id),
+        );
         decl.add_method(
             sel!(pressureChangeWithEvent:),
             pressure_change_with_event as extern "C" fn(&Object, Sel, id),
@@ -1046,6 +1050,37 @@ extern "C" fn scroll_wheel(this: &Object, _sel: Sel, event: id) {
     trace!("Completed `scrollWheel`");
 }
 
+extern "C" fn magnify_with_event(this: &Object, _sel: Sel, event: id) {
+    trace!("Triggered `magnifyWithEvent`");
+
+    mouse_motion(this, event);
+
+    unsafe {
+        let state_ptr: *mut c_void = *this.get_ivar("winitState");
+        let state = &mut *(state_ptr as *mut ViewState);
+
+        let delta = event.magnification();
+        let phase = match event.phase() {
+            NSEventPhase::NSEventPhaseBegan => TouchPhase::Started,
+            NSEventPhase::NSEventPhaseChanged => TouchPhase::Moved,
+            NSEventPhase::NSEventPhaseEnded => TouchPhase::Ended,
+            _ => return
+        };
+
+        let window_event = Event::WindowEvent {
+            window_id: WindowId(get_window_id(state.ns_window)),
+            event: WindowEvent::TouchpadMagnify {
+                device_id: DEVICE_ID,
+                delta,
+                phase,
+            },
+        };
+
+        AppState::queue_event(EventWrapper::StaticEvent(window_event));
+    }
+    trace!("Completed `magnifyWithEvent`");
+}
+
 extern "C" fn pressure_change_with_event(this: &Object, _sel: Sel, event: id) {
     trace!("Triggered `pressureChangeWithEvent`");