Refactor: put each shape into its own file (#5564)

Much easier to navigate the code

crates/epaint/src/shapes/circle_shape.rs

@@ -0,0 +1,52 @@
+use crate::{Color32, Pos2, Rect, Shape, Stroke, Vec2};
+
+/// How to paint a circle.
+#[derive(Copy, Clone, Debug, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub struct CircleShape {
+    pub center: Pos2,
+    pub radius: f32,
+    pub fill: Color32,
+    pub stroke: Stroke,
+}
+
+impl CircleShape {
+    #[inline]
+    pub fn filled(center: Pos2, radius: f32, fill_color: impl Into<Color32>) -> Self {
+        Self {
+            center,
+            radius,
+            fill: fill_color.into(),
+            stroke: Default::default(),
+        }
+    }
+
+    #[inline]
+    pub fn stroke(center: Pos2, radius: f32, stroke: impl Into<Stroke>) -> Self {
+        Self {
+            center,
+            radius,
+            fill: Default::default(),
+            stroke: stroke.into(),
+        }
+    }
+
+    /// The visual bounding rectangle (includes stroke width)
+    pub fn visual_bounding_rect(&self) -> Rect {
+        if self.fill == Color32::TRANSPARENT && self.stroke.is_empty() {
+            Rect::NOTHING
+        } else {
+            Rect::from_center_size(
+                self.center,
+                Vec2::splat(self.radius * 2.0 + self.stroke.width),
+            )
+        }
+    }
+}
+
+impl From<CircleShape> for Shape {
+    #[inline(always)]
+    fn from(shape: CircleShape) -> Self {
+        Self::Circle(shape)
+    }
+}