move gizmo arcs to their own file (#10660)

## Objective

- Split different types of gizmos into their own files

## Solution

- Move `arc_2d` and `Arc2dBuilder` into `arcs.rs`
- turns out there's no 3d arc function! I'll add one Soon(TM) in another
MR

## Changelog

- Changed
  - moved `gizmos::Arc2dBuilder` to `gizmos::arcs::Arc2dBuilder`

## Migration Guide

- `gizmos::Arc2dBuilder` -> `gizmos::arcs::Arc2dBuilder`

crates/bevy_gizmos/src/arcs.rs

@@ -0,0 +1,108 @@
+//! Additional [`Gizmos`] Functions -- Arcs
+//!
+//! Includes the implementation of [`Gizmos::arc_2d`],
+//! and assorted support items.
+
+use crate::circles::DEFAULT_CIRCLE_SEGMENTS;
+use crate::prelude::Gizmos;
+use bevy_math::Vec2;
+use bevy_render::color::Color;
+use std::f32::consts::TAU;
+
+impl<'s> Gizmos<'s> {
+    /// Draw an arc, which is a part of the circumference of a circle, in 2D.
+    ///
+    /// This should be called for each frame the arc needs to be rendered.
+    ///
+    /// # Arguments
+    /// - `position` sets the center of this circle.
+    /// - `radius` controls the distance from `position` to this arc, and thus its curvature.
+    /// - `direction_angle` sets the clockwise  angle in radians between `Vec2::Y` and
+    /// the vector from `position` to the midpoint of the arc.
+    /// - `arc_angle` sets the length of this arc, in radians.
+    ///
+    /// # Example
+    /// ```
+    /// # use bevy_gizmos::prelude::*;
+    /// # use bevy_render::prelude::*;
+    /// # use bevy_math::prelude::*;
+    /// # use std::f32::consts::PI;
+    /// fn system(mut gizmos: Gizmos) {
+    ///     gizmos.arc_2d(Vec2::ZERO, 0., PI / 4., 1., Color::GREEN);
+    ///
+    ///     // Arcs have 32 line-segments by default.
+    ///     // You may want to increase this for larger arcs.
+    ///     gizmos
+    ///         .arc_2d(Vec2::ZERO, 0., PI / 4., 5., Color::RED)
+    ///         .segments(64);
+    /// }
+    /// # bevy_ecs::system::assert_is_system(system);
+    /// ```
+    #[inline]
+    pub fn arc_2d(
+        &mut self,
+        position: Vec2,
+        direction_angle: f32,
+        arc_angle: f32,
+        radius: f32,
+        color: Color,
+    ) -> Arc2dBuilder<'_, 's> {
+        Arc2dBuilder {
+            gizmos: self,
+            position,
+            direction_angle,
+            arc_angle,
+            radius,
+            color,
+            segments: None,
+        }
+    }
+}
+
+/// A builder returned by [`Gizmos::arc_2d`].
+pub struct Arc2dBuilder<'a, 's> {
+    gizmos: &'a mut Gizmos<'s>,
+    position: Vec2,
+    direction_angle: f32,
+    arc_angle: f32,
+    radius: f32,
+    color: Color,
+    segments: Option<usize>,
+}
+
+impl Arc2dBuilder<'_, '_> {
+    /// Set the number of line-segments for this arc.
+    pub fn segments(mut self, segments: usize) -> Self {
+        self.segments = Some(segments);
+        self
+    }
+}
+
+impl Drop for Arc2dBuilder<'_, '_> {
+    fn drop(&mut self) {
+        let segments = match self.segments {
+            Some(segments) => segments,
+            // Do a linear interpolation between 1 and `DEFAULT_CIRCLE_SEGMENTS`
+            // using the arc angle as scalar.
+            None => ((self.arc_angle.abs() / TAU) * DEFAULT_CIRCLE_SEGMENTS as f32).ceil() as usize,
+        };
+
+        let positions = arc_inner(self.direction_angle, self.arc_angle, self.radius, segments)
+            .map(|vec2| (vec2 + self.position));
+        self.gizmos.linestrip_2d(positions, self.color);
+    }
+}
+
+fn arc_inner(
+    direction_angle: f32,
+    arc_angle: f32,
+    radius: f32,
+    segments: usize,
+) -> impl Iterator<Item = Vec2> {
+    (0..segments + 1).map(move |i| {
+        let start = direction_angle - arc_angle / 2.;
+
+        let angle = start + (i as f32 * (arc_angle / segments as f32));
+        Vec2::from(angle.sin_cos()) * radius
+    })
+}

crates/bevy_gizmos/src/gizmos.rs

@@ -1,6 +1,6 @@
 //! A module for the [`Gizmos`] [`SystemParam`].
 
-use std::{f32::consts::TAU, iter};
+use std::iter;
 
 use crate::circles::DEFAULT_CIRCLE_SEGMENTS;
 use bevy_ecs::{
@@ -427,54 +427,6 @@ impl<'s> Gizmos<'s> {
         self.line_gradient_2d(start, start + vector, start_color, end_color);
     }
 
-    /// Draw an arc, which is a part of the circumference of a circle, in 2D.
-    ///
-    /// This should be called for each frame the arc needs to be rendered.
-    ///
-    /// # Arguments
-    /// - `position` sets the center of this circle.
-    /// - `radius` controls the distance from `position` to this arc, and thus its curvature.
-    /// - `direction_angle` sets the clockwise  angle in radians between `Vec2::Y` and
-    /// the vector from `position` to the midpoint of the arc.
-    /// - `arc_angle` sets the length of this arc, in radians.
-    ///
-    /// # Example
-    /// ```
-    /// # use bevy_gizmos::prelude::*;
-    /// # use bevy_render::prelude::*;
-    /// # use bevy_math::prelude::*;
-    /// # use std::f32::consts::PI;
-    /// fn system(mut gizmos: Gizmos) {
-    ///     gizmos.arc_2d(Vec2::ZERO, 0., PI / 4., 1., Color::GREEN);
-    ///
-    ///     // Arcs have 32 line-segments by default.
-    ///     // You may want to increase this for larger arcs.
-    ///     gizmos
-    ///         .arc_2d(Vec2::ZERO, 0., PI / 4., 5., Color::RED)
-    ///         .segments(64);
-    /// }
-    /// # bevy_ecs::system::assert_is_system(system);
-    /// ```
-    #[inline]
-    pub fn arc_2d(
-        &mut self,
-        position: Vec2,
-        direction_angle: f32,
-        arc_angle: f32,
-        radius: f32,
-        color: Color,
-    ) -> Arc2dBuilder<'_, 's> {
-        Arc2dBuilder {
-            gizmos: self,
-            position,
-            direction_angle,
-            arc_angle,
-            radius,
-            color,
-            segments: None,
-        }
-    }
-
     /// Draw a wireframe rectangle in 2D.
     ///
     /// This should be called for each frame the rectangle needs to be rendered.
@@ -556,54 +508,6 @@ impl Drop for SphereBuilder<'_, '_> {
     }
 }
 
-/// A builder returned by [`Gizmos::arc_2d`].
-pub struct Arc2dBuilder<'a, 's> {
-    gizmos: &'a mut Gizmos<'s>,
-    position: Vec2,
-    direction_angle: f32,
-    arc_angle: f32,
-    radius: f32,
-    color: Color,
-    segments: Option<usize>,
-}
-
-impl Arc2dBuilder<'_, '_> {
-    /// Set the number of line-segments for this arc.
-    pub fn segments(mut self, segments: usize) -> Self {
-        self.segments = Some(segments);
-        self
-    }
-}
-
-impl Drop for Arc2dBuilder<'_, '_> {
-    fn drop(&mut self) {
-        let segments = match self.segments {
-            Some(segments) => segments,
-            // Do a linear interpolation between 1 and `DEFAULT_CIRCLE_SEGMENTS`
-            // using the arc angle as scalar.
-            None => ((self.arc_angle.abs() / TAU) * DEFAULT_CIRCLE_SEGMENTS as f32).ceil() as usize,
-        };
-
-        let positions = arc_inner(self.direction_angle, self.arc_angle, self.radius, segments)
-            .map(|vec2| (vec2 + self.position));
-        self.gizmos.linestrip_2d(positions, self.color);
-    }
-}
-
-fn arc_inner(
-    direction_angle: f32,
-    arc_angle: f32,
-    radius: f32,
-    segments: usize,
-) -> impl Iterator<Item = Vec2> {
-    (0..segments + 1).map(move |i| {
-        let start = direction_angle - arc_angle / 2.;
-
-        let angle = start + (i as f32 * (arc_angle / segments as f32));
-        Vec2::from(angle.sin_cos()) * radius
-    })
-}
-
 fn rect_inner(size: Vec2) -> [Vec2; 4] {
     let half_size = size / 2.;
     let tl = Vec2::new(-half_size.x, half_size.y);

crates/bevy_gizmos/src/lib.rs

@@ -15,6 +15,7 @@
 //!
 //! See the documentation on [`Gizmos`] for more examples.
 
+pub mod arcs;
 pub mod arrows;
 pub mod circles;
 pub mod gizmos;