Replace MouseScrollUnit::SCROLL_UNIT_CONVERSION_FACTOR with a Resource

crates/bevy_camera_controller/src/free_camera.rs

@@ -20,7 +20,8 @@ use bevy_camera::Camera;
 use bevy_ecs::prelude::*;
 use bevy_input::keyboard::KeyCode;
 use bevy_input::mouse::{
-    AccumulatedMouseMotion, AccumulatedMouseScroll, MouseButton, MouseScrollUnit,
+    AccumulatedMouseMotion, AccumulatedMouseScroll, MouseButton, MouseScrollPixelsPerLine,
+    MouseScrollUnit,
 };
 use bevy_input::touch::Touches;
 use bevy_input::ButtonInput;
@@ -267,6 +268,7 @@ pub fn run_freecamera_controller(
     mut windows: Query<(&Window, &mut CursorOptions)>,
     accumulated_mouse_motion: Res<AccumulatedMouseMotion>,
     accumulated_mouse_scroll: Res<AccumulatedMouseScroll>,
+    mouse_scroll_conversion: Res<MouseScrollPixelsPerLine>,
     touch_input: Res<Touches>,
     mouse_button_input: Res<ButtonInput<MouseButton>>,
     key_input: Res<ButtonInput<KeyCode>>,
@@ -304,9 +306,7 @@ pub fn run_freecamera_controller(
 
     let scroll = match accumulated_mouse_scroll.unit {
         MouseScrollUnit::Line => accumulated_mouse_scroll.delta.y,
-        MouseScrollUnit::Pixel => {
-            accumulated_mouse_scroll.delta.y / MouseScrollUnit::SCROLL_UNIT_CONVERSION_FACTOR
-        }
+        MouseScrollUnit::Pixel => accumulated_mouse_scroll.delta.y / *mouse_scroll_conversion,
     };
     // By using exponentiation we ensure that this scales up and down smoothly
     // regardless of the amount of scrolling processed per frame

crates/bevy_camera_controller/src/pan_camera.rs

@@ -9,7 +9,9 @@ use bevy_app::{App, Plugin, RunFixedMainLoop, RunFixedMainLoopSystems};
 use bevy_camera::{Camera, RenderTarget};
 use bevy_ecs::prelude::*;
 use bevy_input::keyboard::KeyCode;
-use bevy_input::mouse::{AccumulatedMouseScroll, MouseButton, MouseScrollUnit};
+use bevy_input::mouse::{
+    AccumulatedMouseScroll, MouseButton, MouseScrollPixelsPerLine, MouseScrollUnit,
+};
 use bevy_input::ButtonInput;
 use bevy_math::{Vec2, Vec3};
 use bevy_picking::events::{Drag, DragEnd, DragStart, Pointer};
@@ -167,6 +169,7 @@ fn run_pancamera_controller(
     time: Res<Time<Real>>,
     key_input: Res<ButtonInput<KeyCode>>,
     accumulated_mouse_scroll: Res<AccumulatedMouseScroll>,
+    mouse_scroll_conversion: Res<MouseScrollPixelsPerLine>,
     mut query: Query<(&mut Transform, &mut PanCamera), With<Camera>>,
 ) {
     let dt = time.delta_secs();
@@ -242,9 +245,7 @@ fn run_pancamera_controller(
     // (with mouse wheel)
     let mouse_scroll = match accumulated_mouse_scroll.unit {
         MouseScrollUnit::Line => accumulated_mouse_scroll.delta.y,
-        MouseScrollUnit::Pixel => {
-            accumulated_mouse_scroll.delta.y / MouseScrollUnit::SCROLL_UNIT_CONVERSION_FACTOR
-        }
+        MouseScrollUnit::Pixel => accumulated_mouse_scroll.delta.y / *mouse_scroll_conversion,
     };
     zoom_amount += mouse_scroll * controller.zoom_speed;
 

crates/bevy_input/src/lib.rs

@@ -80,7 +80,7 @@ use keyboard::{keyboard_input_system, Key, KeyCode, KeyboardFocusLost, KeyboardI
 use mouse::{
     accumulate_mouse_motion_system, accumulate_mouse_scroll_system, mouse_button_input_system,
     AccumulatedMouseMotion, AccumulatedMouseScroll, MouseButton, MouseButtonInput, MouseMotion,
-    MouseWheel,
+    MouseScrollPixelsPerLine, MouseWheel,
 };
 
 #[cfg(feature = "touch")]
@@ -122,6 +122,7 @@ impl Plugin for InputPlugin {
             .add_message::<MouseWheel>()
             .init_resource::<AccumulatedMouseMotion>()
             .init_resource::<AccumulatedMouseScroll>()
+            .init_resource::<MouseScrollPixelsPerLine>()
             .init_resource::<ButtonInput<MouseButton>>()
             .add_systems(
                 PreUpdate,

crates/bevy_input/src/mouse.rs

@@ -1,5 +1,7 @@
 //! The mouse input functionality.
 
+use core::ops::{Div, Mul};
+
 use crate::{touch::TouchPhase, ButtonInput, ButtonState};
 #[cfg(feature = "bevy_reflect")]
 use bevy_ecs::prelude::ReflectMessage;
@@ -11,6 +13,8 @@ use bevy_ecs::{
     system::ResMut,
 };
 use bevy_math::Vec2;
+use derive_more::{Deref, DerefMut};
+
 #[cfg(feature = "bevy_reflect")]
 use {
     bevy_ecs::reflect::ReflectResource,
@@ -139,18 +143,53 @@ pub enum MouseScrollUnit {
     Pixel,
 }
 
-impl MouseScrollUnit {
-    /// An approximate conversion factor to account for the difference between
-    /// [`MouseScrollUnit::Line`] and [`MouseScrollUnit::Pixel`].
-    ///
-    /// Each line corresponds to many pixels; this must be corrected for in order to ensure that
-    /// mouse wheel controls are scaled properly regardless of the provided input events for the end user.
-    ///
-    /// This value is correct for Microsoft Edge, but its validity has not been broadly tested.
-    /// Please file an issue if you find that this differs on certain platforms or hardware!
-    pub const SCROLL_UNIT_CONVERSION_FACTOR: f32 = 100.;
+/// Describes the quantity of [`MouseScrollUnit::Pixel`]s per [`MouseScrollUnit::Line`]
+#[derive(Debug, Clone, Copy, PartialEq, Resource, Deref, DerefMut)]
+#[cfg_attr(
+    feature = "bevy_reflect",
+    derive(Reflect),
+    reflect(Debug, PartialEq, Clone)
+)]
+#[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(
+    all(feature = "serialize", feature = "bevy_reflect"),
+    reflect(Serialize, Deserialize)
+)]
+pub struct MouseScrollPixelsPerLine(f32);
+
+impl Default for MouseScrollPixelsPerLine {
+    fn default() -> Self {
+        MouseScrollPixelsPerLine(100.0)
+    }
 }
 
+impl Mul<MouseScrollPixelsPerLine> for f32 {
+    type Output = f32;
+    fn mul(self, rhs: MouseScrollPixelsPerLine) -> Self::Output {
+        self * rhs.0
+    }
+}
+
+impl Div<MouseScrollPixelsPerLine> for f32 {
+    type Output = f32;
+    fn div(self, rhs: MouseScrollPixelsPerLine) -> Self::Output {
+        self / rhs.0
+    }
+}
+
+impl Mul<MouseScrollPixelsPerLine> for Vec2 {
+    type Output = Vec2;
+    fn mul(self, rhs: MouseScrollPixelsPerLine) -> Self::Output {
+        self * rhs.0
+    }
+}
+
+impl Div<MouseScrollPixelsPerLine> for Vec2 {
+    type Output = Vec2;
+    fn div(self, rhs: MouseScrollPixelsPerLine) -> Self::Output {
+        self / rhs.0
+    }
+}
 /// A mouse wheel event.
 ///
 /// This event is the translated version of the `WindowEvent::MouseWheel` from the `winit` crate.
@@ -254,6 +293,31 @@ impl Default for AccumulatedMouseScroll {
     }
 }
 
+impl AccumulatedMouseScroll {
+    /// Converts the units to [`MouseScrollUnit::Line`]
+    pub fn to_lines(&self, conversion_ratio: &MouseScrollPixelsPerLine) -> Self {
+        if self.unit == MouseScrollUnit::Line {
+            AccumulatedMouseScroll {
+                unit: MouseScrollUnit::Line,
+                delta: self.delta / *conversion_ratio,
+            }
+        } else {
+            *self
+        }
+    }
+    /// Converts the units to [`MouseScrollUnit::Pixel`]
+    pub fn to_pixels(&self, conversion_ratio: &MouseScrollPixelsPerLine) -> Self {
+        if self.unit == MouseScrollUnit::Pixel {
+            AccumulatedMouseScroll {
+                unit: MouseScrollUnit::Line,
+                delta: self.delta * *conversion_ratio,
+            }
+        } else {
+            *self
+        }
+    }
+}
+
 /// Updates the [`AccumulatedMouseMotion`] resource using the [`MouseMotion`] event.
 /// The value of [`AccumulatedMouseMotion`] is reset to zero every frame
 pub fn accumulate_mouse_motion_system(

examples/camera/projection_zoom.rs

@@ -3,7 +3,8 @@
 use std::{f32::consts::PI, ops::Range};
 
 use bevy::{
-    camera::ScalingMode, input::mouse::AccumulatedMouseScroll, input::mouse::MouseScrollUnit,
+    camera::ScalingMode,
+    input::mouse::{AccumulatedMouseScroll, MouseScrollPixelsPerLine},
     prelude::*,
 };
 
@@ -138,17 +139,13 @@ fn zoom(
     camera: Single<&mut Projection, With<Camera>>,
     camera_settings: Res<CameraSettings>,
     mouse_wheel_input: Res<AccumulatedMouseScroll>,
+    scroll_conversion: Res<MouseScrollPixelsPerLine>,
 ) {
     // Usually, you won't need to handle both types of projection,
     // but doing so makes for a more complete example.
 
     // Get a scroll amount proportional to the kind of input that generated it.
-    let scroll = match mouse_wheel_input.unit {
-        MouseScrollUnit::Line => mouse_wheel_input.delta.y,
-        MouseScrollUnit::Pixel => {
-            mouse_wheel_input.delta.y / MouseScrollUnit::SCROLL_UNIT_CONVERSION_FACTOR
-        }
-    };
+    let scroll = mouse_wheel_input.to_lines(&scroll_conversion).delta.y;
 
     match *camera.into_inner() {
         Projection::Orthographic(ref mut orthographic) => {