Touchpad magnify and rotate events (#8791)

# Objective

The goal of this PR is to receive touchpad magnification and rotation
events.

## Solution

Implement pendants for winit's `TouchpadMagnify` and `TouchpadRotate`
events.

Adjust the `mouse_input_events.rs` example to debug magnify and rotate
events.

Since winit only reports these events on macOS, the Bevy events for
touchpad magnification and rotation are currently only fired on macOS.

crates/bevy_input/src/lib.rs

@@ -8,6 +8,7 @@ mod input;
 pub mod keyboard;
 pub mod mouse;
 pub mod touch;
+pub mod touchpad;
 
 pub use axis::*;
 pub use input::*;
@@ -34,6 +35,7 @@ use mouse::{
     MouseWheel,
 };
 use touch::{touch_screen_input_system, ForceTouch, TouchInput, TouchPhase, Touches};
+use touchpad::{TouchpadMagnify, TouchpadRotate};
 
 use gamepad::{
     gamepad_axis_event_system, gamepad_button_event_system, gamepad_connection_system,
@@ -67,6 +69,8 @@ impl Plugin for InputPlugin {
             .add_event::<MouseWheel>()
             .init_resource::<Input<MouseButton>>()
             .add_systems(PreUpdate, mouse_button_input_system.in_set(InputSystem))
+            .add_event::<TouchpadMagnify>()
+            .add_event::<TouchpadRotate>()
             // gamepad
             .add_event::<GamepadConnectionEvent>()
             .add_event::<GamepadButtonChangedEvent>()
@@ -112,6 +116,10 @@ impl Plugin for InputPlugin {
             .register_type::<MouseScrollUnit>()
             .register_type::<MouseWheel>();
 
+        // Register touchpad types
+        app.register_type::<TouchpadMagnify>()
+            .register_type::<TouchpadRotate>();
+
         // Register touch types
         app.register_type::<TouchInput>()
             .register_type::<ForceTouch>()

crates/bevy_input/src/touchpad.rs

@@ -0,0 +1,39 @@
+use bevy_ecs::event::Event;
+use bevy_reflect::{FromReflect, Reflect, ReflectFromReflect};
+
+#[cfg(feature = "serialize")]
+use bevy_reflect::{ReflectDeserialize, ReflectSerialize};
+
+/// Touchpad magnification event with two-finger pinch gesture.
+///
+/// Positive delta values indicate magnification (zooming in) and
+/// negative delta values indicate shrinking (zooming out).
+///
+/// ## Platform-specific
+///
+/// - Only available on **`macOS`**.
+#[derive(Event, Debug, Clone, Copy, PartialEq, Reflect, FromReflect)]
+#[reflect(Debug, PartialEq, FromReflect)]
+#[cfg_attr(
+    feature = "serialize",
+    derive(serde::Serialize, serde::Deserialize),
+    reflect(Serialize, Deserialize)
+)]
+pub struct TouchpadMagnify(pub f32);
+
+/// Touchpad rotation event with two-finger rotation gesture.
+///
+/// Positive delta values indicate rotation counterclockwise and
+/// negative delta values indicate rotation clockwise.
+///
+/// ## Platform-specific
+///
+/// - Only available on **`macOS`**.
+#[derive(Event, Debug, Clone, Copy, PartialEq, Reflect, FromReflect)]
+#[reflect(Debug, PartialEq, FromReflect)]
+#[cfg_attr(
+    feature = "serialize",
+    derive(serde::Serialize, serde::Deserialize),
+    reflect(Serialize, Deserialize)
+)]
+pub struct TouchpadRotate(pub f32);

crates/bevy_winit/src/lib.rs

@@ -31,6 +31,7 @@ use bevy_input::{
     keyboard::KeyboardInput,
     mouse::{MouseButtonInput, MouseMotion, MouseScrollUnit, MouseWheel},
     touch::TouchInput,
+    touchpad::{TouchpadMagnify, TouchpadRotate},
 };
 use bevy_math::{ivec2, DVec2, Vec2};
 use bevy_utils::{
@@ -236,6 +237,8 @@ struct InputEvents<'w> {
     keyboard_input: EventWriter<'w, KeyboardInput>,
     character_input: EventWriter<'w, ReceivedCharacter>,
     mouse_button_input: EventWriter<'w, MouseButtonInput>,
+    touchpad_magnify_input: EventWriter<'w, TouchpadMagnify>,
+    touchpad_rotate_input: EventWriter<'w, TouchpadRotate>,
     mouse_wheel_input: EventWriter<'w, MouseWheel>,
     touch_input: EventWriter<'w, TouchInput>,
     ime_input: EventWriter<'w, Ime>,
@@ -481,6 +484,16 @@ pub fn winit_runner(mut app: App) {
                             state: converters::convert_element_state(state),
                         });
                     }
+                    WindowEvent::TouchpadMagnify { delta, .. } => {
+                        input_events
+                            .touchpad_magnify_input
+                            .send(TouchpadMagnify(delta as f32));
+                    }
+                    WindowEvent::TouchpadRotate { delta, .. } => {
+                        input_events
+                            .touchpad_rotate_input
+                            .send(TouchpadRotate(delta));
+                    }
                     WindowEvent::MouseWheel { delta, .. } => match delta {
                         event::MouseScrollDelta::LineDelta(x, y) => {
                             input_events.mouse_wheel_input.send(MouseWheel {

examples/input/mouse_input_events.rs

@@ -1,7 +1,10 @@
 //! Prints all mouse events to the console.
 
 use bevy::{
-    input::mouse::{MouseButtonInput, MouseMotion, MouseWheel},
+    input::{
+        mouse::{MouseButtonInput, MouseMotion, MouseWheel},
+        touchpad::{TouchpadMagnify, TouchpadRotate},
+    },
     prelude::*,
 };
 
@@ -18,6 +21,8 @@ fn print_mouse_events_system(
     mut mouse_motion_events: EventReader<MouseMotion>,
     mut cursor_moved_events: EventReader<CursorMoved>,
     mut mouse_wheel_events: EventReader<MouseWheel>,
+    mut touchpad_magnify_events: EventReader<TouchpadMagnify>,
+    mut touchpad_rotate_events: EventReader<TouchpadRotate>,
 ) {
     for event in mouse_button_input_events.iter() {
         info!("{:?}", event);
@@ -34,4 +39,14 @@ fn print_mouse_events_system(
     for event in mouse_wheel_events.iter() {
         info!("{:?}", event);
     }
+
+    // This event will only fire on macOS
+    for event in touchpad_magnify_events.iter() {
+        info!("{:?}", event);
+    }
+
+    // This event will only fire on macOS
+    for event in touchpad_rotate_events.iter() {
+        info!("{:?}", event);
+    }
 }