From 912ced2622fb3b6c04f14bd45e6d211f66df2fbe Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Fri, 12 Apr 2024 16:49:23 -0600
Subject: [PATCH 01/27] added ability to add custom gradients to paths

---
 crates/egui/src/painter.rs            |  12 +--
 crates/epaint/src/bezier.rs           |  28 +++---
 crates/epaint/src/lib.rs              |   2 +-
 crates/epaint/src/shape.rs            |  36 ++++---
 crates/epaint/src/shape_transform.rs  |  48 +++++----
 crates/epaint/src/stroke.rs           |  83 +++++++++++++++
 crates/epaint/src/tessellator.rs      | 139 +++++++++++++++++++-------
 crates/epaint/src/text/text_layout.rs |   4 +-
 examples/hello_world/src/main.rs      |  24 ++++-
 9 files changed, 278 insertions(+), 98 deletions(-)

diff --git a/crates/egui/src/painter.rs b/crates/egui/src/painter.rs
index 788319dc936..9baeb208191 100644
--- a/crates/egui/src/painter.rs
+++ b/crates/egui/src/painter.rs
@@ -7,7 +7,7 @@ use crate::{
 };
 use epaint::{
     text::{Fonts, Galley, LayoutJob},
-    CircleShape, ClippedShape, RectShape, Rounding, Shape, Stroke,
+    CircleShape, ClippedShape, PathStroke, RectShape, Rounding, Shape, Stroke,
 };
 
 /// Helper to paint shapes and text to a specific region on a specific layer.
@@ -280,7 +280,7 @@ impl Painter {
 /// # Paint different primitives
 impl Painter {
     /// Paints a line from the first point to the second.
-    pub fn line_segment(&self, points: [Pos2; 2], stroke: impl Into<Stroke>) -> ShapeIdx {
+    pub fn line_segment(&self, points: [Pos2; 2], stroke: impl Into<PathStroke>) -> ShapeIdx {
         self.add(Shape::LineSegment {
             points,
             stroke: stroke.into(),
@@ -288,13 +288,13 @@ impl Painter {
     }
 
     /// Paints a horizontal line.
-    pub fn hline(&self, x: impl Into<Rangef>, y: f32, stroke: impl Into<Stroke>) -> ShapeIdx {
-        self.add(Shape::hline(x, y, stroke))
+    pub fn hline(&self, x: impl Into<Rangef>, y: f32, stroke: impl Into<PathStroke>) -> ShapeIdx {
+        self.add(Shape::hline(x, y, stroke.into()))
     }
 
     /// Paints a vertical line.
-    pub fn vline(&self, x: f32, y: impl Into<Rangef>, stroke: impl Into<Stroke>) -> ShapeIdx {
-        self.add(Shape::vline(x, y, stroke))
+    pub fn vline(&self, x: f32, y: impl Into<Rangef>, stroke: impl Into<PathStroke>) -> ShapeIdx {
+        self.add(Shape::vline(x, y, stroke.into()))
     }
 
     pub fn circle(
diff --git a/crates/epaint/src/bezier.rs b/crates/epaint/src/bezier.rs
index 3da99f33b65..4ad9a28228f 100644
--- a/crates/epaint/src/bezier.rs
+++ b/crates/epaint/src/bezier.rs
@@ -3,7 +3,7 @@
 
 use std::ops::Range;
 
-use crate::{shape::Shape, Color32, PathShape, Stroke};
+use crate::{shape::Shape, Color32, PathShape, PathStroke};
 use emath::*;
 
 // ----------------------------------------------------------------------------
@@ -11,7 +11,7 @@ use emath::*;
 /// A cubic [Bézier Curve](https://en.wikipedia.org/wiki/B%C3%A9zier_curve).
 ///
 /// See also [`QuadraticBezierShape`].
-#[derive(Copy, Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct CubicBezierShape {
     /// The first point is the starting point and the last one is the ending point of the curve.
@@ -20,7 +20,7 @@ pub struct CubicBezierShape {
     pub closed: bool,
 
     pub fill: Color32,
-    pub stroke: Stroke,
+    pub stroke: PathStroke,
 }
 
 impl CubicBezierShape {
@@ -32,7 +32,7 @@ impl CubicBezierShape {
         points: [Pos2; 4],
         closed: bool,
         fill: Color32,
-        stroke: impl Into<Stroke>,
+        stroke: impl Into<PathStroke>,
     ) -> Self {
         Self {
             points,
@@ -52,7 +52,7 @@ impl CubicBezierShape {
             points,
             closed: self.closed,
             fill: self.fill,
-            stroke: self.stroke,
+            stroke: self.stroke.clone(),
         }
     }
 
@@ -69,7 +69,7 @@ impl CubicBezierShape {
                 points,
                 closed: self.closed,
                 fill: self.fill,
-                stroke: self.stroke,
+                stroke: self.stroke.clone(),
             };
             pathshapes.push(pathshape);
         }
@@ -156,7 +156,7 @@ impl CubicBezierShape {
             points: [d_from, d_ctrl, d_to],
             closed: self.closed,
             fill: self.fill,
-            stroke: self.stroke,
+            stroke: self.stroke.clone(),
         };
         let delta_t = t_range.end - t_range.start;
         let q_start = q.sample(t_range.start);
@@ -168,7 +168,7 @@ impl CubicBezierShape {
             points: [from, ctrl1, ctrl2, to],
             closed: self.closed,
             fill: self.fill,
-            stroke: self.stroke,
+            stroke: self.stroke.clone(),
         }
     }
 
@@ -375,7 +375,7 @@ impl From<CubicBezierShape> for Shape {
 /// A quadratic [Bézier Curve](https://en.wikipedia.org/wiki/B%C3%A9zier_curve).
 ///
 /// See also [`CubicBezierShape`].
-#[derive(Copy, Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct QuadraticBezierShape {
     /// The first point is the starting point and the last one is the ending point of the curve.
@@ -384,7 +384,7 @@ pub struct QuadraticBezierShape {
     pub closed: bool,
 
     pub fill: Color32,
-    pub stroke: Stroke,
+    pub stroke: PathStroke,
 }
 
 impl QuadraticBezierShape {
@@ -397,7 +397,7 @@ impl QuadraticBezierShape {
         points: [Pos2; 3],
         closed: bool,
         fill: Color32,
-        stroke: impl Into<Stroke>,
+        stroke: impl Into<PathStroke>,
     ) -> Self {
         Self {
             points,
@@ -417,7 +417,7 @@ impl QuadraticBezierShape {
             points,
             closed: self.closed,
             fill: self.fill,
-            stroke: self.stroke,
+            stroke: self.stroke.clone(),
         }
     }
 
@@ -429,7 +429,7 @@ impl QuadraticBezierShape {
             points,
             closed: self.closed,
             fill: self.fill,
-            stroke: self.stroke,
+            stroke: self.stroke.clone(),
         }
     }
 
@@ -688,7 +688,7 @@ fn single_curve_approximation(curve: &CubicBezierShape) -> QuadraticBezierShape
         points: [curve.points[0], c, curve.points[3]],
         closed: curve.closed,
         fill: curve.fill,
-        stroke: curve.stroke,
+        stroke: curve.stroke.clone(),
     }
 }
 
diff --git a/crates/epaint/src/lib.rs b/crates/epaint/src/lib.rs
index 18298484679..c21f41bd108 100644
--- a/crates/epaint/src/lib.rs
+++ b/crates/epaint/src/lib.rs
@@ -53,7 +53,7 @@ pub use self::{
         Rounding, Shape, TextShape,
     },
     stats::PaintStats,
-    stroke::Stroke,
+    stroke::{ColorMode, PathStroke, Stroke},
     tessellator::{TessellationOptions, Tessellator},
     text::{FontFamily, FontId, Fonts, Galley},
     texture_atlas::TextureAtlas,
diff --git a/crates/epaint/src/shape.rs b/crates/epaint/src/shape.rs
index 7922a92d6d5..07a9251fad1 100644
--- a/crates/epaint/src/shape.rs
+++ b/crates/epaint/src/shape.rs
@@ -3,6 +3,7 @@
 use std::{any::Any, sync::Arc};
 
 use crate::{
+    stroke::PathStroke,
     text::{FontId, Fonts, Galley},
     Color32, Mesh, Stroke, TextureId,
 };
@@ -34,7 +35,10 @@ pub enum Shape {
     Ellipse(EllipseShape),
 
     /// A line between two points.
-    LineSegment { points: [Pos2; 2], stroke: Stroke },
+    LineSegment {
+        points: [Pos2; 2],
+        stroke: PathStroke,
+    },
 
     /// A series of lines between points.
     /// The path can have a stroke and/or fill (if closed).
@@ -63,11 +67,11 @@ pub enum Shape {
     Callback(PaintCallback),
 }
 
-#[test]
-fn shape_impl_send_sync() {
-    fn assert_send_sync<T: Send + Sync>() {}
-    assert_send_sync::<Shape>();
-}
+// #[test]
+// fn shape_impl_send_sync() {
+//     fn assert_send_sync<T: Send + Sync>() {}
+//     assert_send_sync::<Shape>();
+// }
 
 impl From<Vec<Self>> for Shape {
     #[inline(always)]
@@ -88,7 +92,7 @@ impl Shape {
     /// A line between two points.
     /// More efficient than calling [`Self::line`].
     #[inline]
-    pub fn line_segment(points: [Pos2; 2], stroke: impl Into<Stroke>) -> Self {
+    pub fn line_segment(points: [Pos2; 2], stroke: impl Into<PathStroke>) -> Self {
         Self::LineSegment {
             points,
             stroke: stroke.into(),
@@ -96,7 +100,7 @@ impl Shape {
     }
 
     /// A horizontal line.
-    pub fn hline(x: impl Into<Rangef>, y: f32, stroke: impl Into<Stroke>) -> Self {
+    pub fn hline(x: impl Into<Rangef>, y: f32, stroke: impl Into<PathStroke>) -> Self {
         let x = x.into();
         Self::LineSegment {
             points: [pos2(x.min, y), pos2(x.max, y)],
@@ -105,7 +109,7 @@ impl Shape {
     }
 
     /// A vertical line.
-    pub fn vline(x: f32, y: impl Into<Rangef>, stroke: impl Into<Stroke>) -> Self {
+    pub fn vline(x: f32, y: impl Into<Rangef>, stroke: impl Into<PathStroke>) -> Self {
         let y = y.into();
         Self::LineSegment {
             points: [pos2(x, y.min), pos2(x, y.max)],
@@ -117,13 +121,13 @@ impl Shape {
     ///
     /// Use [`Self::line_segment`] instead if your line only connects two points.
     #[inline]
-    pub fn line(points: Vec<Pos2>, stroke: impl Into<Stroke>) -> Self {
+    pub fn line(points: Vec<Pos2>, stroke: impl Into<PathStroke>) -> Self {
         Self::Path(PathShape::line(points, stroke))
     }
 
     /// A line that closes back to the start point again.
     #[inline]
-    pub fn closed_line(points: Vec<Pos2>, stroke: impl Into<Stroke>) -> Self {
+    pub fn closed_line(points: Vec<Pos2>, stroke: impl Into<PathStroke>) -> Self {
         Self::Path(PathShape::closed_line(points, stroke))
     }
 
@@ -224,7 +228,7 @@ impl Shape {
     pub fn convex_polygon(
         points: Vec<Pos2>,
         fill: impl Into<Color32>,
-        stroke: impl Into<Stroke>,
+        stroke: impl Into<PathStroke>,
     ) -> Self {
         Self::Path(PathShape::convex_polygon(points, fill, stroke))
     }
@@ -586,7 +590,7 @@ pub struct PathShape {
     pub fill: Color32,
 
     /// Color and thickness of the line.
-    pub stroke: Stroke,
+    pub stroke: PathStroke,
     // TODO(emilk): Add texture support either by supplying uv for each point,
     // or by some transform from points to uv (e.g. a callback or a linear transform matrix).
 }
@@ -596,7 +600,7 @@ impl PathShape {
     ///
     /// Use [`Shape::line_segment`] instead if your line only connects two points.
     #[inline]
-    pub fn line(points: Vec<Pos2>, stroke: impl Into<Stroke>) -> Self {
+    pub fn line(points: Vec<Pos2>, stroke: impl Into<PathStroke>) -> Self {
         Self {
             points,
             closed: false,
@@ -607,7 +611,7 @@ impl PathShape {
 
     /// A line that closes back to the start point again.
     #[inline]
-    pub fn closed_line(points: Vec<Pos2>, stroke: impl Into<Stroke>) -> Self {
+    pub fn closed_line(points: Vec<Pos2>, stroke: impl Into<PathStroke>) -> Self {
         Self {
             points,
             closed: true,
@@ -623,7 +627,7 @@ impl PathShape {
     pub fn convex_polygon(
         points: Vec<Pos2>,
         fill: impl Into<Color32>,
-        stroke: impl Into<Stroke>,
+        stroke: impl Into<PathStroke>,
     ) -> Self {
         Self {
             points,
diff --git a/crates/epaint/src/shape_transform.rs b/crates/epaint/src/shape_transform.rs
index 8ff65d2a045..296f5d9f483 100644
--- a/crates/epaint/src/shape_transform.rs
+++ b/crates/epaint/src/shape_transform.rs
@@ -10,8 +10,34 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
                 adjust_colors(shape, adjust_color);
             }
         }
-        Shape::LineSegment { stroke, points: _ } => {
-            adjust_color(&mut stroke.color);
+        Shape::LineSegment { stroke, points: _ } => match stroke.color {
+            stroke::ColorMode::Solid(mut col) => adjust_color(&mut col),
+            stroke::ColorMode::UV(_) => {}
+        },
+
+        Shape::Path(PathShape {
+            points: _,
+            closed: _,
+            fill,
+            stroke,
+        })
+        | Shape::QuadraticBezier(QuadraticBezierShape {
+            points: _,
+            closed: _,
+            fill,
+            stroke,
+        })
+        | Shape::CubicBezier(CubicBezierShape {
+            points: _,
+            closed: _,
+            fill,
+            stroke,
+        }) => {
+            adjust_color(fill);
+            match stroke.color {
+                stroke::ColorMode::Solid(mut col) => adjust_color(&mut col),
+                stroke::ColorMode::UV(_) => {}
+            }
         }
 
         Shape::Circle(CircleShape {
@@ -26,12 +52,6 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
             fill,
             stroke,
         })
-        | Shape::Path(PathShape {
-            points: _,
-            closed: _,
-            fill,
-            stroke,
-        })
         | Shape::Rect(RectShape {
             rect: _,
             rounding: _,
@@ -40,18 +60,6 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
             blur_width: _,
             fill_texture_id: _,
             uv: _,
-        })
-        | Shape::QuadraticBezier(QuadraticBezierShape {
-            points: _,
-            closed: _,
-            fill,
-            stroke,
-        })
-        | Shape::CubicBezier(CubicBezierShape {
-            points: _,
-            closed: _,
-            fill,
-            stroke,
         }) => {
             adjust_color(fill);
             adjust_color(&mut stroke.color);
diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index 15ddd231f1b..7b4b865c548 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -1,5 +1,7 @@
 #![allow(clippy::derived_hash_with_manual_eq)] // We need to impl Hash for f32, but we don't implement Eq, which is fine
 
+use std::{fmt::Debug, sync::Arc};
+
 use super::*;
 
 /// Describes the width and color of a line.
@@ -52,3 +54,84 @@ impl std::hash::Hash for Stroke {
         color.hash(state);
     }
 }
+
+#[derive(Clone)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub enum ColorMode {
+    Solid(Color32),
+    #[cfg_attr(feature = "serde", serde(skip))]
+    UV(Arc<Box<dyn Fn(Pos2) -> Color32 + Send + Sync>>),
+}
+
+impl Default for ColorMode {
+    fn default() -> Self {
+        Self::Solid(Color32::TRANSPARENT)
+    }
+}
+
+impl Debug for ColorMode {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Solid(arg0) => f.debug_tuple("Solid").field(arg0).finish(),
+            Self::UV(_arg0) => f.debug_tuple("UV").field(&"<closure>").finish(),
+        }
+    }
+}
+
+impl PartialEq for ColorMode {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Self::Solid(l0), Self::Solid(r0)) => l0 == r0,
+            (Self::UV(_l0), Self::UV(_r0)) => false,
+            _ => false,
+        }
+    }
+}
+
+#[derive(Clone, Debug, Default, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub struct PathStroke {
+    pub width: f32,
+    pub color: ColorMode,
+}
+
+impl PathStroke {
+    /// Same as [`Stroke::default`].
+    pub const NONE: Self = Self {
+        width: 0.0,
+        color: ColorMode::Solid(Color32::TRANSPARENT),
+    };
+
+    #[inline]
+    pub fn new(width: impl Into<f32>, color: impl Into<Color32>) -> Self {
+        Self {
+            width: width.into(),
+            color: ColorMode::Solid(color.into()),
+        }
+    }
+
+    /// True if width is zero or color is transparent
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.width <= 0.0 || self.color == ColorMode::Solid(Color32::TRANSPARENT)
+    }
+}
+
+impl<Color> From<(f32, Color)> for PathStroke
+where
+    Color: Into<Color32>,
+{
+    #[inline(always)]
+    fn from((width, color): (f32, Color)) -> Self {
+        Self::new(width, color)
+    }
+}
+
+impl From<Stroke> for PathStroke {
+    fn from(value: Stroke) -> Self {
+        Self {
+            width: value.width,
+            color: ColorMode::Solid(value.color),
+        }
+    }
+}
diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index f5b3d9e3cb1..ff61f20c2f5 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -9,6 +9,11 @@ use crate::texture_atlas::PreparedDisc;
 use crate::*;
 use emath::*;
 
+use self::{
+    stroke::{ColorMode, PathStroke},
+    util::OrderedFloat,
+};
+
 // ----------------------------------------------------------------------------
 
 #[allow(clippy::approx_constant)]
@@ -471,16 +476,22 @@ impl Path {
     }
 
     /// Open-ended.
-    pub fn stroke_open(&self, feathering: f32, stroke: Stroke, out: &mut Mesh) {
+    pub fn stroke_open(&self, feathering: f32, stroke: &PathStroke, out: &mut Mesh) {
         stroke_path(feathering, &self.0, PathType::Open, stroke, out);
     }
 
     /// A closed path (returning to the first point).
-    pub fn stroke_closed(&self, feathering: f32, stroke: Stroke, out: &mut Mesh) {
+    pub fn stroke_closed(&self, feathering: f32, stroke: &PathStroke, out: &mut Mesh) {
         stroke_path(feathering, &self.0, PathType::Closed, stroke, out);
     }
 
-    pub fn stroke(&self, feathering: f32, path_type: PathType, stroke: Stroke, out: &mut Mesh) {
+    pub fn stroke(
+        &self,
+        feathering: f32,
+        path_type: PathType,
+        stroke: &PathStroke,
+        out: &mut Mesh,
+    ) {
         stroke_path(feathering, &self.0, path_type, stroke, out);
     }
 
@@ -864,19 +875,53 @@ fn stroke_path(
     feathering: f32,
     path: &[PathPoint],
     path_type: PathType,
-    stroke: Stroke,
+    stroke: &PathStroke,
     out: &mut Mesh,
 ) {
     let n = path.len() as u32;
 
-    if stroke.width <= 0.0 || stroke.color == Color32::TRANSPARENT || n < 2 {
+    if stroke.width <= 0.0 || stroke.color == ColorMode::Solid(Color32::TRANSPARENT) || n < 2 {
         return;
     }
 
     let idx = out.vertices.len() as u32;
 
+    let min_x = path
+        .iter()
+        .map(|point| OrderedFloat::from(point.pos.x))
+        .min()
+        .map(OrderedFloat::into_inner)
+        .unwrap();
+    let max_x = path
+        .iter()
+        .map(|point| OrderedFloat::from(point.pos.x))
+        .max()
+        .map(OrderedFloat::into_inner)
+        .unwrap();
+    let min_y = path
+        .iter()
+        .map(|point| OrderedFloat::from(point.pos.y))
+        .min()
+        .map(OrderedFloat::into_inner)
+        .unwrap();
+    let max_y = path
+        .iter()
+        .map(|point| OrderedFloat::from(point.pos.y))
+        .max()
+        .map(OrderedFloat::into_inner)
+        .unwrap();
+
+    let get_color = |col: &ColorMode, pos: Pos2| match col {
+        ColorMode::Solid(col) => *col,
+        ColorMode::UV(fun) => {
+            let x = remap_clamp(pos.x, min_x..=max_x, 0.0..=1.0);
+            let y = remap_clamp(pos.y, min_y..=max_y, 0.0..=1.0);
+            fun(pos2(x, y))
+        }
+    };
+
     if feathering > 0.0 {
-        let color_inner = stroke.color;
+        let color_inner = &stroke.color;
         let color_outer = Color32::TRANSPARENT;
 
         let thin_line = stroke.width <= feathering;
@@ -889,9 +934,11 @@ fn stroke_path(
             */
 
             // Fade out as it gets thinner:
-            let color_inner = mul_color(color_inner, stroke.width / feathering);
-            if color_inner == Color32::TRANSPARENT {
-                return;
+            if let ColorMode::Solid(col) = color_inner {
+                let color_inner = mul_color(*col, stroke.width / feathering);
+                if color_inner == Color32::TRANSPARENT {
+                    return;
+                }
             }
 
             out.reserve_triangles(4 * n as usize);
@@ -904,7 +951,7 @@ fn stroke_path(
                 let p = p1.pos;
                 let n = p1.normal;
                 out.colored_vertex(p + n * feathering, color_outer);
-                out.colored_vertex(p, color_inner);
+                out.colored_vertex(p, get_color(color_inner, p));
                 out.colored_vertex(p - n * feathering, color_outer);
 
                 if connect_with_previous {
@@ -942,9 +989,10 @@ fn stroke_path(
                         let p1 = &path[i1 as usize];
                         let p = p1.pos;
                         let n = p1.normal;
+                        let color = get_color(color_inner, p);
                         out.colored_vertex(p + n * outer_rad, color_outer);
-                        out.colored_vertex(p + n * inner_rad, color_inner);
-                        out.colored_vertex(p - n * inner_rad, color_inner);
+                        out.colored_vertex(p + n * inner_rad, color);
+                        out.colored_vertex(p - n * inner_rad, color);
                         out.colored_vertex(p - n * outer_rad, color_outer);
 
                         out.add_triangle(idx + 4 * i0 + 0, idx + 4 * i0 + 1, idx + 4 * i1 + 0);
@@ -982,9 +1030,10 @@ fn stroke_path(
                         let p = end.pos;
                         let n = end.normal;
                         let back_extrude = n.rot90() * feathering;
+                        let color = get_color(color_inner, p);
                         out.colored_vertex(p + n * outer_rad + back_extrude, color_outer);
-                        out.colored_vertex(p + n * inner_rad, color_inner);
-                        out.colored_vertex(p - n * inner_rad, color_inner);
+                        out.colored_vertex(p + n * inner_rad, color);
+                        out.colored_vertex(p - n * inner_rad, color);
                         out.colored_vertex(p - n * outer_rad + back_extrude, color_outer);
 
                         out.add_triangle(idx + 0, idx + 1, idx + 2);
@@ -996,9 +1045,10 @@ fn stroke_path(
                         let point = &path[i1 as usize];
                         let p = point.pos;
                         let n = point.normal;
+                        let color = get_color(color_inner, p);
                         out.colored_vertex(p + n * outer_rad, color_outer);
-                        out.colored_vertex(p + n * inner_rad, color_inner);
-                        out.colored_vertex(p - n * inner_rad, color_inner);
+                        out.colored_vertex(p + n * inner_rad, color);
+                        out.colored_vertex(p - n * inner_rad, color);
                         out.colored_vertex(p - n * outer_rad, color_outer);
 
                         out.add_triangle(idx + 4 * i0 + 0, idx + 4 * i0 + 1, idx + 4 * i1 + 0);
@@ -1019,9 +1069,10 @@ fn stroke_path(
                         let p = end.pos;
                         let n = end.normal;
                         let back_extrude = -n.rot90() * feathering;
+                        let color = get_color(color_inner, p);
                         out.colored_vertex(p + n * outer_rad + back_extrude, color_outer);
-                        out.colored_vertex(p + n * inner_rad, color_inner);
-                        out.colored_vertex(p - n * inner_rad, color_inner);
+                        out.colored_vertex(p + n * inner_rad, color);
+                        out.colored_vertex(p - n * inner_rad, color);
                         out.colored_vertex(p - n * outer_rad + back_extrude, color_outer);
 
                         out.add_triangle(idx + 4 * i0 + 0, idx + 4 * i0 + 1, idx + 4 * i1 + 0);
@@ -1067,19 +1118,22 @@ fn stroke_path(
         if thin_line {
             // Fade out thin lines rather than making them thinner
             let radius = feathering / 2.0;
-            let color = mul_color(stroke.color, stroke.width / feathering);
-            if color == Color32::TRANSPARENT {
-                return;
+            if let ColorMode::Solid(color) = stroke.color {
+                let color = mul_color(color, stroke.width / feathering);
+                if color == Color32::TRANSPARENT {
+                    return;
+                }
             }
             for p in path {
+                let color = mul_color(get_color(&stroke.color, p.pos), stroke.width / feathering);
                 out.colored_vertex(p.pos + radius * p.normal, color);
                 out.colored_vertex(p.pos - radius * p.normal, color);
             }
         } else {
             let radius = stroke.width / 2.0;
             for p in path {
-                out.colored_vertex(p.pos + radius * p.normal, stroke.color);
-                out.colored_vertex(p.pos - radius * p.normal, stroke.color);
+                out.colored_vertex(p.pos + radius * p.normal, get_color(&stroke.color, p.pos));
+                out.colored_vertex(p.pos - radius * p.normal, get_color(&stroke.color, p.pos));
             }
         }
     }
@@ -1275,9 +1329,9 @@ impl Tessellator {
                 self.tessellate_text(&text_shape, out);
             }
             Shape::QuadraticBezier(quadratic_shape) => {
-                self.tessellate_quadratic_bezier(quadratic_shape, out);
+                self.tessellate_quadratic_bezier(&quadratic_shape, out);
             }
-            Shape::CubicBezier(cubic_shape) => self.tessellate_cubic_bezier(cubic_shape, out),
+            Shape::CubicBezier(cubic_shape) => self.tessellate_cubic_bezier(&cubic_shape, out),
             Shape::Callback(_) => {
                 panic!("Shape::Callback passed to Tessellator");
             }
@@ -1337,7 +1391,7 @@ impl Tessellator {
         self.scratchpad_path.add_circle(center, radius);
         self.scratchpad_path.fill(self.feathering, fill, out);
         self.scratchpad_path
-            .stroke_closed(self.feathering, stroke, out);
+            .stroke_closed(self.feathering, &stroke.into(), out);
     }
 
     /// Tessellate a single [`EllipseShape`] into a [`Mesh`].
@@ -1404,7 +1458,7 @@ impl Tessellator {
         self.scratchpad_path.add_line_loop(&points);
         self.scratchpad_path.fill(self.feathering, fill, out);
         self.scratchpad_path
-            .stroke_closed(self.feathering, stroke, out);
+            .stroke_closed(self.feathering, &stroke.into(), out);
     }
 
     /// Tessellate a single [`Mesh`] into a [`Mesh`].
@@ -1430,7 +1484,13 @@ impl Tessellator {
     ///
     /// * `shape`: the mesh to tessellate.
     /// * `out`: triangles are appended to this.
-    pub fn tessellate_line(&mut self, points: [Pos2; 2], stroke: Stroke, out: &mut Mesh) {
+    pub fn tessellate_line(
+        &mut self,
+        points: [Pos2; 2],
+        stroke: impl Into<PathStroke>,
+        out: &mut Mesh,
+    ) {
+        let stroke = stroke.into();
         if stroke.is_empty() {
             return;
         }
@@ -1446,7 +1506,7 @@ impl Tessellator {
         self.scratchpad_path.clear();
         self.scratchpad_path.add_line_segment(points);
         self.scratchpad_path
-            .stroke_open(self.feathering, stroke, out);
+            .stroke_open(self.feathering, &stroke, out);
     }
 
     /// Tessellate a single [`PathShape`] into a [`Mesh`].
@@ -1493,7 +1553,7 @@ impl Tessellator {
             PathType::Open
         };
         self.scratchpad_path
-            .stroke(self.feathering, typ, *stroke, out);
+            .stroke(self.feathering, typ, stroke, out);
     }
 
     /// Tessellate a single [`Rect`] into a [`Mesh`].
@@ -1588,7 +1648,7 @@ impl Tessellator {
                 path.fill(self.feathering, fill, out);
             }
 
-            path.stroke_closed(self.feathering, stroke, out);
+            path.stroke_closed(self.feathering, &stroke.into(), out);
         }
 
         self.feathering = old_feathering; // restore
@@ -1707,8 +1767,11 @@ impl Tessellator {
                 self.scratchpad_path.clear();
                 self.scratchpad_path
                     .add_line_segment([row_rect.left_bottom(), row_rect.right_bottom()]);
-                self.scratchpad_path
-                    .stroke_open(self.feathering, *underline, out);
+                self.scratchpad_path.stroke_open(
+                    self.feathering,
+                    &PathStroke::from(*underline),
+                    out,
+                );
             }
         }
     }
@@ -1719,7 +1782,7 @@ impl Tessellator {
     /// * `out`: triangles are appended to this.
     pub fn tessellate_quadratic_bezier(
         &mut self,
-        quadratic_shape: QuadraticBezierShape,
+        quadratic_shape: &QuadraticBezierShape,
         out: &mut Mesh,
     ) {
         let options = &self.options;
@@ -1737,7 +1800,7 @@ impl Tessellator {
             &points,
             quadratic_shape.fill,
             quadratic_shape.closed,
-            quadratic_shape.stroke,
+            &quadratic_shape.stroke,
             out,
         );
     }
@@ -1746,7 +1809,7 @@ impl Tessellator {
     ///
     /// * `cubic_shape`: the shape to tessellate.
     /// * `out`: triangles are appended to this.
-    pub fn tessellate_cubic_bezier(&mut self, cubic_shape: CubicBezierShape, out: &mut Mesh) {
+    pub fn tessellate_cubic_bezier(&mut self, cubic_shape: &CubicBezierShape, out: &mut Mesh) {
         let options = &self.options;
         let clip_rect = self.clip_rect;
         if options.coarse_tessellation_culling
@@ -1763,7 +1826,7 @@ impl Tessellator {
                 &points,
                 cubic_shape.fill,
                 cubic_shape.closed,
-                cubic_shape.stroke,
+                &cubic_shape.stroke,
                 out,
             );
         }
@@ -1774,7 +1837,7 @@ impl Tessellator {
         points: &[Pos2],
         fill: Color32,
         closed: bool,
-        stroke: Stroke,
+        stroke: &PathStroke,
         out: &mut Mesh,
     ) {
         if points.len() < 2 {
diff --git a/crates/epaint/src/text/text_layout.rs b/crates/epaint/src/text/text_layout.rs
index 322026da3c5..59ecd8081d5 100644
--- a/crates/epaint/src/text/text_layout.rs
+++ b/crates/epaint/src/text/text_layout.rs
@@ -3,7 +3,7 @@ use std::sync::Arc;
 
 use emath::*;
 
-use crate::{text::font::Font, Color32, Mesh, Stroke, Vertex};
+use crate::{stroke::PathStroke, text::font::Font, Color32, Mesh, Stroke, Vertex};
 
 use super::{FontsImpl, Galley, Glyph, LayoutJob, LayoutSection, Row, RowVisuals};
 
@@ -853,7 +853,7 @@ fn add_hline(point_scale: PointScale, [start, stop]: [Pos2; 2], stroke: Stroke,
         let mut path = crate::tessellator::Path::default(); // TODO(emilk): reuse this to avoid re-allocations.
         path.add_line_segment([start, stop]);
         let feathering = 1.0 / point_scale.pixels_per_point();
-        path.stroke_open(feathering, stroke, mesh);
+        path.stroke_open(feathering, &PathStroke::from(stroke), mesh);
     } else {
         // Thin lines often lost, so this is a bad idea
 
diff --git a/examples/hello_world/src/main.rs b/examples/hello_world/src/main.rs
index b3fda5a5810..74a6aad7cae 100644
--- a/examples/hello_world/src/main.rs
+++ b/examples/hello_world/src/main.rs
@@ -1,6 +1,11 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
 
-use eframe::egui;
+use std::sync::Arc;
+
+use eframe::{
+    egui::{self, vec2, Color32, Pos2, Sense, Shape},
+    epaint::PathStroke,
+};
 
 fn main() -> Result<(), eframe::Error> {
     env_logger::init(); // Log to stderr (if you run with `RUST_LOG=debug`).
@@ -52,6 +57,23 @@ impl eframe::App for MyApp {
             ui.image(egui::include_image!(
                 "../../../crates/egui/assets/ferris.png"
             ));
+
+            let (rect, _) =
+                ui.allocate_exact_size(vec2(100.0, 50.0), Sense::focusable_noninteractive());
+
+            ui.painter_at(rect).add(Shape::line_segment(
+                [rect.left_center(), rect.right_center()],
+                PathStroke {
+                    width: 1.5,
+                    color: egui::epaint::ColorMode::UV(Arc::new(Box::new(|p: Pos2| {
+                        if p.x < 0.5 {
+                            Color32::RED
+                        } else {
+                            Color32::GREEN
+                        }
+                    }))),
+                },
+            ))
         });
     }
 }

From 18c561dc8fd67f79eb488689b0fe6db60f375e48 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Fri, 12 Apr 2024 16:54:15 -0600
Subject: [PATCH 02/27] add docs

---
 crates/epaint/src/stroke.rs | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index 7b4b865c548..a688e5c2554 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -55,10 +55,15 @@ impl std::hash::Hash for Stroke {
     }
 }
 
+/// How paths will be colored.
 #[derive(Clone)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub enum ColorMode {
+    /// The entire path is one solid color, this is the default.
     Solid(Color32),
+    /// Provide a callback which takes in a UV coordinate and converts it to a color. The values passed to this will always be one.
+    ///
+    /// # This cannot be serialized
     #[cfg_attr(feature = "serde", serde(skip))]
     UV(Arc<Box<dyn Fn(Pos2) -> Color32 + Send + Sync>>),
 }
@@ -96,7 +101,7 @@ pub struct PathStroke {
 }
 
 impl PathStroke {
-    /// Same as [`Stroke::default`].
+    /// Same as [`PathStroke::default`].
     pub const NONE: Self = Self {
         width: 0.0,
         color: ColorMode::Solid(Color32::TRANSPARENT),
@@ -110,6 +115,17 @@ impl PathStroke {
         }
     }
 
+    #[inline]
+    pub fn new_uv(
+        width: impl Into<f32>,
+        callback: impl Fn(Pos2) -> Color32 + Send + Sync + 'static,
+    ) -> Self {
+        Self {
+            width: width.into(),
+            color: ColorMode::UV(Arc::new(Box::new(callback))),
+        }
+    }
+
     /// True if width is zero or color is transparent
     #[inline]
     pub fn is_empty(&self) -> bool {

From 42798510ded8385d73ab49e33dc09cae0232c96b Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Fri, 12 Apr 2024 16:59:40 -0600
Subject: [PATCH 03/27] re-add send sync assertion

---
 crates/epaint/src/shape.rs | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/crates/epaint/src/shape.rs b/crates/epaint/src/shape.rs
index 07a9251fad1..336c9087316 100644
--- a/crates/epaint/src/shape.rs
+++ b/crates/epaint/src/shape.rs
@@ -67,11 +67,11 @@ pub enum Shape {
     Callback(PaintCallback),
 }
 
-// #[test]
-// fn shape_impl_send_sync() {
-//     fn assert_send_sync<T: Send + Sync>() {}
-//     assert_send_sync::<Shape>();
-// }
+#[test]
+fn shape_impl_send_sync() {
+    fn assert_send_sync<T: Send + Sync>() {}
+    assert_send_sync::<Shape>();
+}
 
 impl From<Vec<Self>> for Shape {
     #[inline(always)]

From fe92ba8c80505433667352deb3a19175515a209f Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Fri, 12 Apr 2024 19:21:30 -0600
Subject: [PATCH 04/27] better documentation

---
 crates/epaint/src/stroke.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index a688e5c2554..c5368e15d1a 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -61,9 +61,10 @@ impl std::hash::Hash for Stroke {
 pub enum ColorMode {
     /// The entire path is one solid color, this is the default.
     Solid(Color32),
+
     /// Provide a callback which takes in a UV coordinate and converts it to a color. The values passed to this will always be one.
     ///
-    /// # This cannot be serialized
+    /// **This cannot be serialized**
     #[cfg_attr(feature = "serde", serde(skip))]
     UV(Arc<Box<dyn Fn(Pos2) -> Color32 + Send + Sync>>),
 }
@@ -93,6 +94,9 @@ impl PartialEq for ColorMode {
     }
 }
 
+/// Describes the width and color of paths. The color can either be solid or provided by a callback. For more information, see [`ColorMode`]
+///
+/// The default stroke is the same as [`Stroke::NONE`].
 #[derive(Clone, Debug, Default, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct PathStroke {
@@ -126,7 +130,7 @@ impl PathStroke {
         }
     }
 
-    /// True if width is zero or color is transparent
+    /// True if width is zero or color is solid and transparent
     #[inline]
     pub fn is_empty(&self) -> bool {
         self.width <= 0.0 || self.color == ColorMode::Solid(Color32::TRANSPARENT)

From c433de35e2f7534a43f02fa1fc31e9e14daa046d Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Fri, 12 Apr 2024 19:24:57 -0600
Subject: [PATCH 05/27] fix typo in docs

---
 crates/epaint/src/stroke.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index c5368e15d1a..39171fef803 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -62,7 +62,7 @@ pub enum ColorMode {
     /// The entire path is one solid color, this is the default.
     Solid(Color32),
 
-    /// Provide a callback which takes in a UV coordinate and converts it to a color. The values passed to this will always be one.
+    /// Provide a callback which takes in a UV coordinate and converts it to a color. The values passed to this will always be between zero and one.
     ///
     /// **This cannot be serialized**
     #[cfg_attr(feature = "serde", serde(skip))]

From e03fe525a979558699a7bfdfa55e6f77578043c0 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sat, 13 Apr 2024 11:13:22 -0600
Subject: [PATCH 06/27] added rect bounds for uv mapping

---
 crates/epaint/src/shape_transform.rs |  2 ++
 crates/epaint/src/stroke.rs          | 14 +++++++++++++-
 crates/epaint/src/tessellator.rs     |  5 +++++
 examples/hello_world/src/main.rs     | 29 ++++++++++++++++++++--------
 4 files changed, 41 insertions(+), 9 deletions(-)

diff --git a/crates/epaint/src/shape_transform.rs b/crates/epaint/src/shape_transform.rs
index 296f5d9f483..5afdd735d81 100644
--- a/crates/epaint/src/shape_transform.rs
+++ b/crates/epaint/src/shape_transform.rs
@@ -13,6 +13,7 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
         Shape::LineSegment { stroke, points: _ } => match stroke.color {
             stroke::ColorMode::Solid(mut col) => adjust_color(&mut col),
             stroke::ColorMode::UV(_) => {}
+            stroke::ColorMode::UVBounds(_, _) => {}
         },
 
         Shape::Path(PathShape {
@@ -37,6 +38,7 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
             match stroke.color {
                 stroke::ColorMode::Solid(mut col) => adjust_color(&mut col),
                 stroke::ColorMode::UV(_) => {}
+                stroke::ColorMode::UVBounds(_, _) => {}
             }
         }
 
diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index 39171fef803..56233ba3833 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -62,11 +62,18 @@ pub enum ColorMode {
     /// The entire path is one solid color, this is the default.
     Solid(Color32),
 
-    /// Provide a callback which takes in a UV coordinate and converts it to a color. The values passed to this will always be between zero and one.
+    /// Provide a callback which takes in a UV coordinate and converts it to a color. The UVs are relative to the bounding box of the path.
+    /// If you need something more custom, consider [`ColorMode::UVBounds`]
     ///
     /// **This cannot be serialized**
     #[cfg_attr(feature = "serde", serde(skip))]
     UV(Arc<Box<dyn Fn(Pos2) -> Color32 + Send + Sync>>),
+
+    /// Provide a callback which takes in a UV coordinate and converts it to a color. The UVs are relative to the Rect provided.
+    ///
+    /// **This cannot be serialized**
+    #[cfg_attr(feature = "serde", serde(skip))]
+    UVBounds(Rect, Arc<Box<dyn Fn(Pos2) -> Color32 + Send + Sync>>),
 }
 
 impl Default for ColorMode {
@@ -80,6 +87,11 @@ impl Debug for ColorMode {
         match self {
             Self::Solid(arg0) => f.debug_tuple("Solid").field(arg0).finish(),
             Self::UV(_arg0) => f.debug_tuple("UV").field(&"<closure>").finish(),
+            Self::UVBounds(rect, _) => f
+                .debug_tuple("UV (custom rect)")
+                .field(rect)
+                .field(&"<closure>")
+                .finish(),
         }
     }
 }
diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index ff61f20c2f5..27a3eff87c6 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -918,6 +918,11 @@ fn stroke_path(
             let y = remap_clamp(pos.y, min_y..=max_y, 0.0..=1.0);
             fun(pos2(x, y))
         }
+        ColorMode::UVBounds(rect, fun) => {
+            let x = remap_clamp(pos.x, rect.min.x..=rect.max.x, 0.0..=1.0);
+            let y = remap_clamp(pos.y, rect.min.y..=rect.max.y, 0.0..=1.0);
+            fun(pos2(x, y))
+        }
     };
 
     if feathering > 0.0 {
diff --git a/examples/hello_world/src/main.rs b/examples/hello_world/src/main.rs
index 74a6aad7cae..81afa2fe79a 100644
--- a/examples/hello_world/src/main.rs
+++ b/examples/hello_world/src/main.rs
@@ -61,19 +61,32 @@ impl eframe::App for MyApp {
             let (rect, _) =
                 ui.allocate_exact_size(vec2(100.0, 50.0), Sense::focusable_noninteractive());
 
-            ui.painter_at(rect).add(Shape::line_segment(
-                [rect.left_center(), rect.right_center()],
-                PathStroke {
-                    width: 1.5,
-                    color: egui::epaint::ColorMode::UV(Arc::new(Box::new(|p: Pos2| {
+            let stroke = PathStroke {
+                width: 1.5,
+                color: egui::epaint::ColorMode::UVBounds(
+                    rect,
+                    Arc::new(Box::new(|p: Pos2| {
                         if p.x < 0.5 {
                             Color32::RED
                         } else {
                             Color32::GREEN
                         }
-                    }))),
-                },
-            ))
+                    })),
+                ),
+            };
+
+            ui.painter_at(rect).add(Shape::line_segment(
+                [rect.left_center(), rect.right_center()],
+                stroke.clone(),
+            ));
+
+            ui.painter_at(rect).add(Shape::line_segment(
+                [
+                    rect.left_center() + vec2(25.0, 15.0),
+                    rect.right_center() + vec2(0.0, 15.0),
+                ],
+                stroke.clone(),
+            ));
         });
     }
 }

From c9efc240d03842e16716a92d1077d84ee06e7543 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 09:11:52 -0600
Subject: [PATCH 07/27] added benchmarks for colors

---
 crates/epaint/benches/benchmark.rs | 36 ++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/crates/epaint/benches/benchmark.rs b/crates/epaint/benches/benchmark.rs
index 709adbfae9c..c27aa83f9e5 100644
--- a/crates/epaint/benches/benchmark.rs
+++ b/crates/epaint/benches/benchmark.rs
@@ -1,6 +1,6 @@
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
 
-use epaint::*;
+use epaint::{tessellator::Path, *};
 
 fn single_dashed_lines(c: &mut Criterion) {
     c.bench_function("single_dashed_lines", move |b| {
@@ -72,10 +72,42 @@ fn tessellate_circles(c: &mut Criterion) {
     });
 }
 
+fn thick_line_solid(c: &mut Criterion) {
+    c.bench_function("thick_solid_line", move |b| {
+        let line = [pos2(0.0, 0.0), pos2(50.0, 0.0), pos2(100.0, 1.0)];
+        let mut path = Path::default();
+        path.add_open_points(&line);
+
+        b.iter(|| {
+            let mut mesh = Mesh::default();
+            path.stroke_closed(1.5, &Stroke::new(2.0, Color32::RED).into(), &mut mesh);
+
+            black_box(mesh);
+        });
+    });
+}
+
+fn thin_line_solid(c: &mut Criterion) {
+    c.bench_function("thin_solid_line", move |b| {
+        let line = [pos2(0.0, 0.0), pos2(50.0, 0.0), pos2(100.0, 1.0)];
+        let mut path = Path::default();
+        path.add_open_points(&line);
+
+        b.iter(|| {
+            let mut mesh = Mesh::default();
+            path.stroke_closed(1.5, &Stroke::new(2.0, Color32::RED).into(), &mut mesh);
+
+            black_box(mesh);
+        });
+    });
+}
+
 criterion_group!(
     benches,
     single_dashed_lines,
     many_dashed_lines,
-    tessellate_circles
+    tessellate_circles,
+    thick_line_solid,
+    thin_line_solid
 );
 criterion_main!(benches);

From 66644820a93a76758da3d8f8f5d7b03ba88f79a9 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 09:29:03 -0600
Subject: [PATCH 08/27] simplify ColorMode and use a better method for
 calculating bounding boxes

---
 crates/epaint/src/shape_transform.rs |  2 --
 crates/epaint/src/stroke.rs          | 18 ++----------
 crates/epaint/src/tessellator.rs     | 41 ++--------------------------
 examples/hello_world/src/main.rs     | 20 ++++++--------
 4 files changed, 15 insertions(+), 66 deletions(-)

diff --git a/crates/epaint/src/shape_transform.rs b/crates/epaint/src/shape_transform.rs
index 5afdd735d81..296f5d9f483 100644
--- a/crates/epaint/src/shape_transform.rs
+++ b/crates/epaint/src/shape_transform.rs
@@ -13,7 +13,6 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
         Shape::LineSegment { stroke, points: _ } => match stroke.color {
             stroke::ColorMode::Solid(mut col) => adjust_color(&mut col),
             stroke::ColorMode::UV(_) => {}
-            stroke::ColorMode::UVBounds(_, _) => {}
         },
 
         Shape::Path(PathShape {
@@ -38,7 +37,6 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
             match stroke.color {
                 stroke::ColorMode::Solid(mut col) => adjust_color(&mut col),
                 stroke::ColorMode::UV(_) => {}
-                stroke::ColorMode::UVBounds(_, _) => {}
             }
         }
 
diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index 56233ba3833..dda1f646564 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -62,18 +62,11 @@ pub enum ColorMode {
     /// The entire path is one solid color, this is the default.
     Solid(Color32),
 
-    /// Provide a callback which takes in a UV coordinate and converts it to a color. The UVs are relative to the bounding box of the path.
-    /// If you need something more custom, consider [`ColorMode::UVBounds`]
+    /// Provide a callback which takes in the path's bounding box and a position and converts it to a color.
     ///
     /// **This cannot be serialized**
     #[cfg_attr(feature = "serde", serde(skip))]
-    UV(Arc<Box<dyn Fn(Pos2) -> Color32 + Send + Sync>>),
-
-    /// Provide a callback which takes in a UV coordinate and converts it to a color. The UVs are relative to the Rect provided.
-    ///
-    /// **This cannot be serialized**
-    #[cfg_attr(feature = "serde", serde(skip))]
-    UVBounds(Rect, Arc<Box<dyn Fn(Pos2) -> Color32 + Send + Sync>>),
+    UV(Arc<Box<dyn Fn(Rect, Pos2) -> Color32 + Send + Sync>>),
 }
 
 impl Default for ColorMode {
@@ -87,11 +80,6 @@ impl Debug for ColorMode {
         match self {
             Self::Solid(arg0) => f.debug_tuple("Solid").field(arg0).finish(),
             Self::UV(_arg0) => f.debug_tuple("UV").field(&"<closure>").finish(),
-            Self::UVBounds(rect, _) => f
-                .debug_tuple("UV (custom rect)")
-                .field(rect)
-                .field(&"<closure>")
-                .finish(),
         }
     }
 }
@@ -134,7 +122,7 @@ impl PathStroke {
     #[inline]
     pub fn new_uv(
         width: impl Into<f32>,
-        callback: impl Fn(Pos2) -> Color32 + Send + Sync + 'static,
+        callback: impl Fn(Rect, Pos2) -> Color32 + Send + Sync + 'static,
     ) -> Self {
         Self {
             width: width.into(),
diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index 27a3eff87c6..82f99d8e386 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -9,10 +9,7 @@ use crate::texture_atlas::PreparedDisc;
 use crate::*;
 use emath::*;
 
-use self::{
-    stroke::{ColorMode, PathStroke},
-    util::OrderedFloat,
-};
+use self::stroke::{ColorMode, PathStroke};
 
 // ----------------------------------------------------------------------------
 
@@ -886,43 +883,11 @@ fn stroke_path(
 
     let idx = out.vertices.len() as u32;
 
-    let min_x = path
-        .iter()
-        .map(|point| OrderedFloat::from(point.pos.x))
-        .min()
-        .map(OrderedFloat::into_inner)
-        .unwrap();
-    let max_x = path
-        .iter()
-        .map(|point| OrderedFloat::from(point.pos.x))
-        .max()
-        .map(OrderedFloat::into_inner)
-        .unwrap();
-    let min_y = path
-        .iter()
-        .map(|point| OrderedFloat::from(point.pos.y))
-        .min()
-        .map(OrderedFloat::into_inner)
-        .unwrap();
-    let max_y = path
-        .iter()
-        .map(|point| OrderedFloat::from(point.pos.y))
-        .max()
-        .map(OrderedFloat::into_inner)
-        .unwrap();
+    let bbox = Rect::from_points(&path.iter().map(|p| p.pos).collect::<Vec<Pos2>>());
 
     let get_color = |col: &ColorMode, pos: Pos2| match col {
         ColorMode::Solid(col) => *col,
-        ColorMode::UV(fun) => {
-            let x = remap_clamp(pos.x, min_x..=max_x, 0.0..=1.0);
-            let y = remap_clamp(pos.y, min_y..=max_y, 0.0..=1.0);
-            fun(pos2(x, y))
-        }
-        ColorMode::UVBounds(rect, fun) => {
-            let x = remap_clamp(pos.x, rect.min.x..=rect.max.x, 0.0..=1.0);
-            let y = remap_clamp(pos.y, rect.min.y..=rect.max.y, 0.0..=1.0);
-            fun(pos2(x, y))
-        }
+        ColorMode::UV(fun) => fun(bbox, pos),
     };
 
     if feathering > 0.0 {
diff --git a/examples/hello_world/src/main.rs b/examples/hello_world/src/main.rs
index 81afa2fe79a..a72d8b25cb6 100644
--- a/examples/hello_world/src/main.rs
+++ b/examples/hello_world/src/main.rs
@@ -3,7 +3,7 @@
 use std::sync::Arc;
 
 use eframe::{
-    egui::{self, vec2, Color32, Pos2, Sense, Shape},
+    egui::{self, remap_clamp, vec2, Color32, Sense, Shape},
     epaint::PathStroke,
 };
 
@@ -63,16 +63,14 @@ impl eframe::App for MyApp {
 
             let stroke = PathStroke {
                 width: 1.5,
-                color: egui::epaint::ColorMode::UVBounds(
-                    rect,
-                    Arc::new(Box::new(|p: Pos2| {
-                        if p.x < 0.5 {
-                            Color32::RED
-                        } else {
-                            Color32::GREEN
-                        }
-                    })),
-                ),
+                color: egui::epaint::ColorMode::UV(Arc::new(Box::new(|r, p| {
+                    let t = remap_clamp(p.x, r.x_range(), 0.0..=1.0);
+                    if t < 0.5 {
+                        Color32::RED
+                    } else {
+                        Color32::GREEN
+                    }
+                }))),
             };
 
             ui.painter_at(rect).add(Shape::line_segment(

From 5451e3043796568c4bce0895d01cfd118e2d1f01 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 09:32:02 -0600
Subject: [PATCH 09/27] fix feathering oversight

---
 crates/epaint/src/tessellator.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index 82f99d8e386..0e8ac0e7d5b 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -921,7 +921,10 @@ fn stroke_path(
                 let p = p1.pos;
                 let n = p1.normal;
                 out.colored_vertex(p + n * feathering, color_outer);
-                out.colored_vertex(p, get_color(color_inner, p));
+                out.colored_vertex(
+                    p,
+                    mul_color(get_color(color_inner, p), stroke.width / feathering),
+                );
                 out.colored_vertex(p - n * feathering, color_outer);
 
                 if connect_with_previous {

From 41f819214bfac6bb9da35667ff4a91a0bf2cc5c6 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 09:51:55 -0600
Subject: [PATCH 10/27] refactor ColorMode out into its own file

---
 crates/epaint/src/color.rs           | 43 ++++++++++++++++++++++++++++
 crates/epaint/src/lib.rs             |  4 ++-
 crates/epaint/src/shape_transform.rs |  8 +++---
 crates/epaint/src/stroke.rs          | 39 -------------------------
 crates/epaint/src/tessellator.rs     |  3 +-
 5 files changed, 52 insertions(+), 45 deletions(-)
 create mode 100644 crates/epaint/src/color.rs

diff --git a/crates/epaint/src/color.rs b/crates/epaint/src/color.rs
new file mode 100644
index 00000000000..5da0a152b26
--- /dev/null
+++ b/crates/epaint/src/color.rs
@@ -0,0 +1,43 @@
+use std::{fmt::Debug, sync::Arc};
+
+use ecolor::Color32;
+use emath::{Pos2, Rect};
+
+/// How paths will be colored.
+#[derive(Clone)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub enum ColorMode {
+    /// The entire path is one solid color, this is the default.
+    Solid(Color32),
+
+    /// Provide a callback which takes in the path's bounding box and a position and converts it to a color.
+    ///
+    /// **This cannot be serialized**
+    #[cfg_attr(feature = "serde", serde(skip))]
+    UV(Arc<Box<dyn Fn(Rect, Pos2) -> Color32 + Send + Sync>>),
+}
+
+impl Default for ColorMode {
+    fn default() -> Self {
+        Self::Solid(Color32::TRANSPARENT)
+    }
+}
+
+impl Debug for ColorMode {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Solid(arg0) => f.debug_tuple("Solid").field(arg0).finish(),
+            Self::UV(_arg0) => f.debug_tuple("UV").field(&"<closure>").finish(),
+        }
+    }
+}
+
+impl PartialEq for ColorMode {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Self::Solid(l0), Self::Solid(r0)) => l0 == r0,
+            (Self::UV(_l0), Self::UV(_r0)) => false,
+            _ => false,
+        }
+    }
+}
diff --git a/crates/epaint/src/lib.rs b/crates/epaint/src/lib.rs
index c21f41bd108..8a77015ab47 100644
--- a/crates/epaint/src/lib.rs
+++ b/crates/epaint/src/lib.rs
@@ -26,6 +26,7 @@
 #![cfg_attr(not(feature = "puffin"), forbid(unsafe_code))]
 
 mod bezier;
+pub mod color;
 pub mod image;
 mod margin;
 mod mesh;
@@ -44,6 +45,7 @@ pub mod util;
 
 pub use self::{
     bezier::{CubicBezierShape, QuadraticBezierShape},
+    color::ColorMode,
     image::{ColorImage, FontImage, ImageData, ImageDelta},
     margin::Margin,
     mesh::{Mesh, Mesh16, Vertex},
@@ -53,7 +55,7 @@ pub use self::{
         Rounding, Shape, TextShape,
     },
     stats::PaintStats,
-    stroke::{ColorMode, PathStroke, Stroke},
+    stroke::{PathStroke, Stroke},
     tessellator::{TessellationOptions, Tessellator},
     text::{FontFamily, FontId, Fonts, Galley},
     texture_atlas::TextureAtlas,
diff --git a/crates/epaint/src/shape_transform.rs b/crates/epaint/src/shape_transform.rs
index 296f5d9f483..e7e34369f96 100644
--- a/crates/epaint/src/shape_transform.rs
+++ b/crates/epaint/src/shape_transform.rs
@@ -11,8 +11,8 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
             }
         }
         Shape::LineSegment { stroke, points: _ } => match stroke.color {
-            stroke::ColorMode::Solid(mut col) => adjust_color(&mut col),
-            stroke::ColorMode::UV(_) => {}
+            color::ColorMode::Solid(mut col) => adjust_color(&mut col),
+            color::ColorMode::UV(_) => {}
         },
 
         Shape::Path(PathShape {
@@ -35,8 +35,8 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
         }) => {
             adjust_color(fill);
             match stroke.color {
-                stroke::ColorMode::Solid(mut col) => adjust_color(&mut col),
-                stroke::ColorMode::UV(_) => {}
+                color::ColorMode::Solid(mut col) => adjust_color(&mut col),
+                color::ColorMode::UV(_) => {}
             }
         }
 
diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index dda1f646564..936d15d5fb7 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -55,45 +55,6 @@ impl std::hash::Hash for Stroke {
     }
 }
 
-/// How paths will be colored.
-#[derive(Clone)]
-#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
-pub enum ColorMode {
-    /// The entire path is one solid color, this is the default.
-    Solid(Color32),
-
-    /// Provide a callback which takes in the path's bounding box and a position and converts it to a color.
-    ///
-    /// **This cannot be serialized**
-    #[cfg_attr(feature = "serde", serde(skip))]
-    UV(Arc<Box<dyn Fn(Rect, Pos2) -> Color32 + Send + Sync>>),
-}
-
-impl Default for ColorMode {
-    fn default() -> Self {
-        Self::Solid(Color32::TRANSPARENT)
-    }
-}
-
-impl Debug for ColorMode {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            Self::Solid(arg0) => f.debug_tuple("Solid").field(arg0).finish(),
-            Self::UV(_arg0) => f.debug_tuple("UV").field(&"<closure>").finish(),
-        }
-    }
-}
-
-impl PartialEq for ColorMode {
-    fn eq(&self, other: &Self) -> bool {
-        match (self, other) {
-            (Self::Solid(l0), Self::Solid(r0)) => l0 == r0,
-            (Self::UV(_l0), Self::UV(_r0)) => false,
-            _ => false,
-        }
-    }
-}
-
 /// Describes the width and color of paths. The color can either be solid or provided by a callback. For more information, see [`ColorMode`]
 ///
 /// The default stroke is the same as [`Stroke::NONE`].
diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index 0e8ac0e7d5b..fdfd625c542 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -9,7 +9,8 @@ use crate::texture_atlas::PreparedDisc;
 use crate::*;
 use emath::*;
 
-use self::stroke::{ColorMode, PathStroke};
+use self::color::ColorMode;
+use self::stroke::PathStroke;
 
 // ----------------------------------------------------------------------------
 

From 2d8ab0ce5d44c936657d61f815ca3eb4426febe4 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 09:56:43 -0600
Subject: [PATCH 11/27] add transparent helper

---
 crates/epaint/src/color.rs       | 4 ++++
 crates/epaint/src/tessellator.rs | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/crates/epaint/src/color.rs b/crates/epaint/src/color.rs
index 5da0a152b26..bddbcba2c48 100644
--- a/crates/epaint/src/color.rs
+++ b/crates/epaint/src/color.rs
@@ -41,3 +41,7 @@ impl PartialEq for ColorMode {
         }
     }
 }
+
+impl ColorMode {
+    pub const TRANSPARENT: Self = Self::Solid(Color32::TRANSPARENT);
+}
diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index fdfd625c542..c52d1d06372 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -878,7 +878,7 @@ fn stroke_path(
 ) {
     let n = path.len() as u32;
 
-    if stroke.width <= 0.0 || stroke.color == ColorMode::Solid(Color32::TRANSPARENT) || n < 2 {
+    if stroke.width <= 0.0 || stroke.color == ColorMode::TRANSPARENT || n < 2 {
         return;
     }
 

From a8e0e57dc2a4e0cc2933dd3c8bfd146beb88d2de Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 11:20:05 -0600
Subject: [PATCH 12/27] add proper stroke color demo

---
 Cargo.lock                                    | 83 +++++++++++++++++
 crates/egui_demo_lib/Cargo.toml               |  3 +
 .../src/demo/dancing_trans_strings.rs         | 90 +++++++++++++++++++
 .../src/demo/demo_app_windows.rs              |  1 +
 crates/egui_demo_lib/src/demo/mod.rs          |  1 +
 examples/hello_world/src/main.rs              | 35 +-------
 6 files changed, 179 insertions(+), 34 deletions(-)
 create mode 100644 crates/egui_demo_lib/src/demo/dancing_trans_strings.rs

diff --git a/Cargo.lock b/Cargo.lock
index c6d8727188a..4837da167e0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -847,6 +847,15 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3d7b894f5411737b7867f4827955924d7c254fc9f4d91a6aad6b097804b1018b"
 
+[[package]]
+name = "colorgrad"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a5f405d474b9d05e0a093d3120e77e9bf26461b57a84b40aa2a221ac5617fb6"
+dependencies = [
+ "csscolorparser",
+]
+
 [[package]]
 name = "com"
 version = "0.6.0"
@@ -1042,6 +1051,15 @@ dependencies = [
  "typenum",
 ]
 
+[[package]]
+name = "csscolorparser"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eb2a7d3066da2de787b7f032c736763eb7ae5d355f81a68bab2675a96008b0bf"
+dependencies = [
+ "phf",
+]
+
 [[package]]
 name = "cursor-icon"
 version = "1.1.0"
@@ -1315,12 +1333,15 @@ name = "egui_demo_lib"
 version = "0.27.2"
 dependencies = [
  "chrono",
+ "colorgrad",
  "criterion",
  "document-features",
  "egui",
  "egui_extras",
  "egui_plot",
  "log",
+ "noise",
+ "once_cell",
  "serde",
  "unicode_names2",
 ]
@@ -2511,6 +2532,17 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2bf50223579dc7cdcfb3bfcacf7069ff68243f8c363f62ffa99cf000a6b9c451"
 
+[[package]]
+name = "noise"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6da45c8333f2e152fc665d78a380be060eb84fad8ca4c9f7ac8ca29216cff0cc"
+dependencies = [
+ "num-traits",
+ "rand",
+ "rand_xorshift",
+]
+
 [[package]]
 name = "nom"
 version = "7.1.3"
@@ -2761,6 +2793,48 @@ version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9b2a4787296e9989611394c33f193f676704af1686e70b8f8033ab5ba9a35a94"
 
+[[package]]
+name = "phf"
+version = "0.11.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ade2d8b8f33c7333b51bcf0428d37e217e9f32192ae4772156f65063b8ce03dc"
+dependencies = [
+ "phf_macros",
+ "phf_shared",
+]
+
+[[package]]
+name = "phf_generator"
+version = "0.11.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48e4cc64c2ad9ebe670cb8fd69dd50ae301650392e81c05f9bfcb2d5bdbc24b0"
+dependencies = [
+ "phf_shared",
+ "rand",
+]
+
+[[package]]
+name = "phf_macros"
+version = "0.11.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3444646e286606587e49f3bcf1679b8cef1dc2c5ecc29ddacaffc305180d464b"
+dependencies = [
+ "phf_generator",
+ "phf_shared",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.48",
+]
+
+[[package]]
+name = "phf_shared"
+version = "0.11.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "90fcb95eef784c2ac79119d1dd819e162b5da872ce6f3c3abe1e8ca1c082f72b"
+dependencies = [
+ "siphasher",
+]
+
 [[package]]
 name = "pico-args"
 version = "0.5.0"
@@ -3008,6 +3082,15 @@ dependencies = [
  "getrandom",
 ]
 
+[[package]]
+name = "rand_xorshift"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d25bf25ec5ae4a3f1b92f929810509a2f53d7dca2f50b794ff57e3face536c8f"
+dependencies = [
+ "rand_core",
+]
+
 [[package]]
 name = "raw-window-handle"
 version = "0.5.2"
diff --git a/crates/egui_demo_lib/Cargo.toml b/crates/egui_demo_lib/Cargo.toml
index a08a88fe8d0..1083f5b8b47 100644
--- a/crates/egui_demo_lib/Cargo.toml
+++ b/crates/egui_demo_lib/Cargo.toml
@@ -50,6 +50,9 @@ chrono = { version = "0.4", optional = true, features = ["js-sys", "wasmbind"] }
 ## Enable this when generating docs.
 document-features = { workspace = true, optional = true }
 serde = { version = "1", optional = true, features = ["derive"] }
+once_cell = "1.19"
+colorgrad = "0.6"
+noise = "0.9"
 
 
 [dev-dependencies]
diff --git a/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs b/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs
new file mode 100644
index 00000000000..10ca84e092b
--- /dev/null
+++ b/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs
@@ -0,0 +1,90 @@
+use colorgrad::{Color, CustomGradient, Gradient};
+use egui::{containers::*, epaint::PathStroke, *};
+use noise::{NoiseFn, OpenSimplex};
+use once_cell::sync::Lazy;
+
+static GRADIENT: Lazy<Gradient> = Lazy::new(|| {
+    CustomGradient::new()
+        .colors(&[
+            Color::from_html("#5BCEFA").unwrap(),
+            Color::from_html("#F5A9B8").unwrap(),
+            Color::from_html("#FFFFFF").unwrap(),
+            Color::from_html("#F5A9B8").unwrap(),
+            Color::from_html("#5BCEFA").unwrap(),
+        ])
+        .build()
+        .unwrap_or(colorgrad::rainbow())
+});
+static NOISE: Lazy<OpenSimplex> = Lazy::new(|| OpenSimplex::new(6940));
+
+#[derive(Default)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "serde", serde(default))]
+pub struct DancingStrings {}
+
+impl super::Demo for DancingStrings {
+    fn name(&self) -> &'static str {
+        "♫ Dancing Strings (Colored)"
+    }
+
+    fn show(&mut self, ctx: &Context, open: &mut bool) {
+        use super::View as _;
+        Window::new(self.name())
+            .open(open)
+            .default_size(vec2(512.0, 256.0))
+            .vscroll(false)
+            .show(ctx, |ui| self.ui(ui));
+    }
+}
+
+impl super::View for DancingStrings {
+    fn ui(&mut self, ui: &mut Ui) {
+        Frame::canvas(ui.style()).show(ui, |ui| {
+            ui.ctx().request_repaint();
+            let time = ui.input(|i| i.time);
+
+            let desired_size = ui.available_width() * vec2(1.0, 0.35);
+            let (_id, rect) = ui.allocate_space(desired_size);
+
+            let to_screen =
+                emath::RectTransform::from_to(Rect::from_x_y_ranges(0.0..=1.0, -1.0..=1.0), rect);
+
+            let mut shapes = vec![];
+
+            for &mode in &[2, 3, 5] {
+                let mode = mode as f64;
+                let n = 120;
+                let speed = 1.5;
+
+                let points: Vec<Pos2> = (0..=n)
+                    .map(|i| {
+                        let t = i as f64 / (n as f64);
+                        let amp = (time * speed * mode).sin() / mode;
+                        let y = amp * (t * std::f64::consts::TAU / 2.0 * mode).sin();
+                        to_screen * pos2(t as f32, y as f32)
+                    })
+                    .collect();
+
+                let thickness = 10.0 / mode as f32;
+                shapes.push(epaint::Shape::line(
+                    points,
+                    PathStroke::new_uv(thickness, move |_r, p| {
+                        let time = time / 10.0;
+                        let x = remap(p.x, rect.x_range(), 0.0..=1.0) as f64;
+                        let y = remap(p.y, rect.y_range(), 0.0..=1.0) as f64;
+
+                        let noise = NOISE.get([x * 1.25 + time, y * 1.25 + time]);
+                        let color = GRADIENT.at(noise).to_rgba8();
+
+                        Color32::from_rgba_premultiplied(color[0], color[1], color[2], color[3])
+                    }),
+                ));
+            }
+
+            ui.painter().extend(shapes);
+        });
+        ui.vertical_centered(|ui| {
+            ui.add(crate::egui_github_link_file!());
+        });
+    }
+}
diff --git a/crates/egui_demo_lib/src/demo/demo_app_windows.rs b/crates/egui_demo_lib/src/demo/demo_app_windows.rs
index 0910df4ef56..b6647123abd 100644
--- a/crates/egui_demo_lib/src/demo/demo_app_windows.rs
+++ b/crates/egui_demo_lib/src/demo/demo_app_windows.rs
@@ -26,6 +26,7 @@ impl Default for Demos {
             Box::<super::code_example::CodeExample>::default(),
             Box::<super::context_menu::ContextMenus>::default(),
             Box::<super::dancing_strings::DancingStrings>::default(),
+            Box::<super::dancing_trans_strings::DancingStrings>::default(),
             Box::<super::drag_and_drop::DragAndDropDemo>::default(),
             Box::<super::extra_viewport::ExtraViewport>::default(),
             Box::<super::font_book::FontBook>::default(),
diff --git a/crates/egui_demo_lib/src/demo/mod.rs b/crates/egui_demo_lib/src/demo/mod.rs
index 8a911c9d68b..95c9fa7dfaa 100644
--- a/crates/egui_demo_lib/src/demo/mod.rs
+++ b/crates/egui_demo_lib/src/demo/mod.rs
@@ -9,6 +9,7 @@ pub mod code_editor;
 pub mod code_example;
 pub mod context_menu;
 pub mod dancing_strings;
+pub mod dancing_trans_strings;
 pub mod demo_app_windows;
 pub mod drag_and_drop;
 pub mod extra_viewport;
diff --git a/examples/hello_world/src/main.rs b/examples/hello_world/src/main.rs
index a72d8b25cb6..b3fda5a5810 100644
--- a/examples/hello_world/src/main.rs
+++ b/examples/hello_world/src/main.rs
@@ -1,11 +1,6 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
 
-use std::sync::Arc;
-
-use eframe::{
-    egui::{self, remap_clamp, vec2, Color32, Sense, Shape},
-    epaint::PathStroke,
-};
+use eframe::egui;
 
 fn main() -> Result<(), eframe::Error> {
     env_logger::init(); // Log to stderr (if you run with `RUST_LOG=debug`).
@@ -57,34 +52,6 @@ impl eframe::App for MyApp {
             ui.image(egui::include_image!(
                 "../../../crates/egui/assets/ferris.png"
             ));
-
-            let (rect, _) =
-                ui.allocate_exact_size(vec2(100.0, 50.0), Sense::focusable_noninteractive());
-
-            let stroke = PathStroke {
-                width: 1.5,
-                color: egui::epaint::ColorMode::UV(Arc::new(Box::new(|r, p| {
-                    let t = remap_clamp(p.x, r.x_range(), 0.0..=1.0);
-                    if t < 0.5 {
-                        Color32::RED
-                    } else {
-                        Color32::GREEN
-                    }
-                }))),
-            };
-
-            ui.painter_at(rect).add(Shape::line_segment(
-                [rect.left_center(), rect.right_center()],
-                stroke.clone(),
-            ));
-
-            ui.painter_at(rect).add(Shape::line_segment(
-                [
-                    rect.left_center() + vec2(25.0, 15.0),
-                    rect.right_center() + vec2(0.0, 15.0),
-                ],
-                stroke.clone(),
-            ));
         });
     }
 }

From f8e6b65007f118ab2bed8cb7521f9291d5a8dc92 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 11:46:35 -0600
Subject: [PATCH 13/27] actually use the ColorMode::TRANSPARENT

---
 crates/epaint/src/stroke.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index 936d15d5fb7..ef8c0d7f4d4 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -69,7 +69,7 @@ impl PathStroke {
     /// Same as [`PathStroke::default`].
     pub const NONE: Self = Self {
         width: 0.0,
-        color: ColorMode::Solid(Color32::TRANSPARENT),
+        color: ColorMode::TRANSPARENT,
     };
 
     #[inline]
@@ -94,7 +94,7 @@ impl PathStroke {
     /// True if width is zero or color is solid and transparent
     #[inline]
     pub fn is_empty(&self) -> bool {
-        self.width <= 0.0 || self.color == ColorMode::Solid(Color32::TRANSPARENT)
+        self.width <= 0.0 || self.color == ColorMode::TRANSPARENT
     }
 }
 

From b6c4ce2a05c30646f456e0ac8773264615702847 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 11:58:19 -0600
Subject: [PATCH 14/27] expand the bounding box to include the thickness of the
 path

---
 crates/epaint/src/tessellator.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index c52d1d06372..a00b63af4a7 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -884,7 +884,9 @@ fn stroke_path(
 
     let idx = out.vertices.len() as u32;
 
-    let bbox = Rect::from_points(&path.iter().map(|p| p.pos).collect::<Vec<Pos2>>());
+    // expand the bounding box to include the thickness of the path
+    let bbox = Rect::from_points(&path.iter().map(|p| p.pos).collect::<Vec<Pos2>>())
+        .expand(stroke.width / 2.0);
 
     let get_color = |col: &ColorMode, pos: Pos2| match col {
         ColorMode::Solid(col) => *col,

From 46cd485950154d981c981af91a6c4cbfde00c8d0 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 15:31:11 -0600
Subject: [PATCH 15/27] add a few more benchmarks

---
 crates/epaint/benches/benchmark.rs | 36 ++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/crates/epaint/benches/benchmark.rs b/crates/epaint/benches/benchmark.rs
index c27aa83f9e5..3c94499a85b 100644
--- a/crates/epaint/benches/benchmark.rs
+++ b/crates/epaint/benches/benchmark.rs
@@ -87,6 +87,21 @@ fn thick_line_solid(c: &mut Criterion) {
     });
 }
 
+fn thick_large_line_solid(c: &mut Criterion) {
+    c.bench_function("thick_large_solid_line", move |b| {
+        let line = (0..1000).map(|i| pos2(i as f32, 10.0)).collect::<Vec<_>>();
+        let mut path = Path::default();
+        path.add_open_points(&line);
+
+        b.iter(|| {
+            let mut mesh = Mesh::default();
+            path.stroke_closed(1.5, &Stroke::new(2.0, Color32::RED).into(), &mut mesh);
+
+            black_box(mesh);
+        });
+    });
+}
+
 fn thin_line_solid(c: &mut Criterion) {
     c.bench_function("thin_solid_line", move |b| {
         let line = [pos2(0.0, 0.0), pos2(50.0, 0.0), pos2(100.0, 1.0)];
@@ -95,7 +110,22 @@ fn thin_line_solid(c: &mut Criterion) {
 
         b.iter(|| {
             let mut mesh = Mesh::default();
-            path.stroke_closed(1.5, &Stroke::new(2.0, Color32::RED).into(), &mut mesh);
+            path.stroke_closed(1.5, &Stroke::new(0.5, Color32::RED).into(), &mut mesh);
+
+            black_box(mesh);
+        });
+    });
+}
+
+fn thin_large_line_solid(c: &mut Criterion) {
+    c.bench_function("thin_large_solid_line", move |b| {
+        let line = (0..1000).map(|i| pos2(i as f32, 10.0)).collect::<Vec<_>>();
+        let mut path = Path::default();
+        path.add_open_points(&line);
+
+        b.iter(|| {
+            let mut mesh = Mesh::default();
+            path.stroke_closed(1.5, &Stroke::new(0.5, Color32::RED).into(), &mut mesh);
 
             black_box(mesh);
         });
@@ -108,6 +138,8 @@ criterion_group!(
     many_dashed_lines,
     tessellate_circles,
     thick_line_solid,
-    thin_line_solid
+    thick_large_line_solid,
+    thin_line_solid,
+    thin_large_line_solid
 );
 criterion_main!(benches);

From 713f566c526d8dd961316f687344687b38c1a81c Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Tue, 16 Apr 2024 18:58:10 -0600
Subject: [PATCH 16/27] add a unit test to check if all points are within the
 given bounding box, and make each individual tessellated point invoke the
 callback

---
 crates/epaint/src/color.rs       |   1 +
 crates/epaint/src/stroke.rs      |   2 +
 crates/epaint/src/tessellator.rs | 122 ++++++++++++++++++++++++++-----
 3 files changed, 107 insertions(+), 18 deletions(-)

diff --git a/crates/epaint/src/color.rs b/crates/epaint/src/color.rs
index bddbcba2c48..b5d719c840d 100644
--- a/crates/epaint/src/color.rs
+++ b/crates/epaint/src/color.rs
@@ -11,6 +11,7 @@ pub enum ColorMode {
     Solid(Color32),
 
     /// Provide a callback which takes in the path's bounding box and a position and converts it to a color.
+    /// When used with a path, the bounding box will have a margin of ``feathering + 1.0``
     ///
     /// **This cannot be serialized**
     #[cfg_attr(feature = "serde", serde(skip))]
diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index ef8c0d7f4d4..c797996d834 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -80,6 +80,8 @@ impl PathStroke {
         }
     }
 
+    /// Create a new `PathStroke` with a UV function
+    /// The bounding box passed to the callback will have a margin of ``feathering + 1.0``
     #[inline]
     pub fn new_uv(
         width: impl Into<f32>,
diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index a00b63af4a7..d2e453f1b6b 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -885,8 +885,9 @@ fn stroke_path(
     let idx = out.vertices.len() as u32;
 
     // expand the bounding box to include the thickness of the path
+    // this tiny bit of margin is here because a rect doesn't think it contains a point if a pos' component is on a boundary. why? i have no idea.
     let bbox = Rect::from_points(&path.iter().map(|p| p.pos).collect::<Vec<Pos2>>())
-        .expand(stroke.width / 2.0);
+        .expand((stroke.width / 2.0) + feathering + 1.0);
 
     let get_color = |col: &ColorMode, pos: Pos2| match col {
         ColorMode::Solid(col) => *col,
@@ -965,10 +966,15 @@ fn stroke_path(
                         let p1 = &path[i1 as usize];
                         let p = p1.pos;
                         let n = p1.normal;
-                        let color = get_color(color_inner, p);
                         out.colored_vertex(p + n * outer_rad, color_outer);
-                        out.colored_vertex(p + n * inner_rad, color);
-                        out.colored_vertex(p - n * inner_rad, color);
+                        out.colored_vertex(
+                            p + n * inner_rad,
+                            get_color(color_inner, p + n * inner_rad),
+                        );
+                        out.colored_vertex(
+                            p - n * inner_rad,
+                            get_color(color_inner, p - n * inner_rad),
+                        );
                         out.colored_vertex(p - n * outer_rad, color_outer);
 
                         out.add_triangle(idx + 4 * i0 + 0, idx + 4 * i0 + 1, idx + 4 * i1 + 0);
@@ -1006,10 +1012,15 @@ fn stroke_path(
                         let p = end.pos;
                         let n = end.normal;
                         let back_extrude = n.rot90() * feathering;
-                        let color = get_color(color_inner, p);
                         out.colored_vertex(p + n * outer_rad + back_extrude, color_outer);
-                        out.colored_vertex(p + n * inner_rad, color);
-                        out.colored_vertex(p - n * inner_rad, color);
+                        out.colored_vertex(
+                            p + n * inner_rad,
+                            get_color(color_inner, p + n * inner_rad),
+                        );
+                        out.colored_vertex(
+                            p - n * inner_rad,
+                            get_color(color_inner, p - n * inner_rad),
+                        );
                         out.colored_vertex(p - n * outer_rad + back_extrude, color_outer);
 
                         out.add_triangle(idx + 0, idx + 1, idx + 2);
@@ -1021,10 +1032,15 @@ fn stroke_path(
                         let point = &path[i1 as usize];
                         let p = point.pos;
                         let n = point.normal;
-                        let color = get_color(color_inner, p);
                         out.colored_vertex(p + n * outer_rad, color_outer);
-                        out.colored_vertex(p + n * inner_rad, color);
-                        out.colored_vertex(p - n * inner_rad, color);
+                        out.colored_vertex(
+                            p + n * inner_rad,
+                            get_color(color_inner, p + n * inner_rad),
+                        );
+                        out.colored_vertex(
+                            p - n * inner_rad,
+                            get_color(color_inner, p - n * inner_rad),
+                        );
                         out.colored_vertex(p - n * outer_rad, color_outer);
 
                         out.add_triangle(idx + 4 * i0 + 0, idx + 4 * i0 + 1, idx + 4 * i1 + 0);
@@ -1045,10 +1061,15 @@ fn stroke_path(
                         let p = end.pos;
                         let n = end.normal;
                         let back_extrude = -n.rot90() * feathering;
-                        let color = get_color(color_inner, p);
                         out.colored_vertex(p + n * outer_rad + back_extrude, color_outer);
-                        out.colored_vertex(p + n * inner_rad, color);
-                        out.colored_vertex(p - n * inner_rad, color);
+                        out.colored_vertex(
+                            p + n * inner_rad,
+                            get_color(color_inner, p + n * inner_rad),
+                        );
+                        out.colored_vertex(
+                            p - n * inner_rad,
+                            get_color(color_inner, p - n * inner_rad),
+                        );
                         out.colored_vertex(p - n * outer_rad + back_extrude, color_outer);
 
                         out.add_triangle(idx + 4 * i0 + 0, idx + 4 * i0 + 1, idx + 4 * i1 + 0);
@@ -1101,15 +1122,38 @@ fn stroke_path(
                 }
             }
             for p in path {
-                let color = mul_color(get_color(&stroke.color, p.pos), stroke.width / feathering);
-                out.colored_vertex(p.pos + radius * p.normal, color);
-                out.colored_vertex(p.pos - radius * p.normal, color);
+                out.colored_vertex(
+                    p.pos + radius * p.normal,
+                    mul_color(
+                        get_color(&stroke.color, p.pos + radius * p.normal),
+                        stroke.width / feathering,
+                    ),
+                );
+                out.colored_vertex(
+                    p.pos - radius * p.normal,
+                    mul_color(
+                        get_color(&stroke.color, p.pos - radius * p.normal),
+                        stroke.width / feathering,
+                    ),
+                );
             }
         } else {
             let radius = stroke.width / 2.0;
             for p in path {
-                out.colored_vertex(p.pos + radius * p.normal, get_color(&stroke.color, p.pos));
-                out.colored_vertex(p.pos - radius * p.normal, get_color(&stroke.color, p.pos));
+                out.colored_vertex(
+                    p.pos + radius * p.normal,
+                    mul_color(
+                        get_color(&stroke.color, p.pos + radius * p.normal),
+                        stroke.width / feathering,
+                    ),
+                );
+                out.colored_vertex(
+                    p.pos - radius * p.normal,
+                    mul_color(
+                        get_color(&stroke.color, p.pos - radius * p.normal),
+                        stroke.width / feathering,
+                    ),
+                );
             }
         }
     }
@@ -2024,3 +2068,45 @@ fn test_tessellator() {
 
     assert_eq!(primitives.len(), 2);
 }
+
+#[test]
+fn path_bounding_box() {
+    use crate::*;
+
+    for i in 1..=100 {
+        let width = i as f32;
+
+        let rect = Rect::from_min_max(pos2(0.0, 0.0), pos2(10.0, 10.0));
+        let expected_rect = rect.expand((width / 2.0) + 2.5);
+
+        let mut mesh = Mesh::default();
+
+        let mut path = Path::default();
+        path.add_open_points(&[
+            pos2(0.0, 0.0),
+            pos2(2.0, 0.0),
+            pos2(5.0, 5.0),
+            pos2(0.0, 5.0),
+            pos2(0.0, 7.0),
+            pos2(10.0, 10.0),
+        ]);
+
+        path.stroke(
+            1.5,
+            PathType::Closed,
+            &PathStroke::new_uv(width, move |r, p| {
+                assert_eq!(r, expected_rect);
+                assert!(
+                    r.contains(p),
+                    "passed rect {r:?} didn't contain point {p:?}"
+                );
+                assert!(
+                    expected_rect.contains(p),
+                    "expected rect {expected_rect:?} didn't contain point {p:?}"
+                );
+                Color32::WHITE
+            }),
+            &mut mesh,
+        );
+    }
+}

From 4884aadda7233466986d75892667311096f373ae Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sat, 20 Apr 2024 17:36:25 -0600
Subject: [PATCH 17/27] have UV color modes be affected by tints

---
 crates/egui/src/painter.rs           |  4 ++--
 crates/epaint/src/shape_transform.rs | 29 +++++++++++++++++++++++-----
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/crates/egui/src/painter.rs b/crates/egui/src/painter.rs
index 9baeb208191..0935587cc7b 100644
--- a/crates/egui/src/painter.rs
+++ b/crates/egui/src/painter.rs
@@ -513,7 +513,7 @@ impl Painter {
 }
 
 fn tint_shape_towards(shape: &mut Shape, target: Color32) {
-    epaint::shape_transform::adjust_colors(shape, &|color| {
+    epaint::shape_transform::adjust_colors(shape, move |color| {
         if *color != Color32::PLACEHOLDER {
             *color = crate::ecolor::tint_color_towards(*color, target);
         }
@@ -521,7 +521,7 @@ fn tint_shape_towards(shape: &mut Shape, target: Color32) {
 }
 
 fn multiply_opacity(shape: &mut Shape, opacity: f32) {
-    epaint::shape_transform::adjust_colors(shape, &|color| {
+    epaint::shape_transform::adjust_colors(shape, move |color| {
         if *color != Color32::PLACEHOLDER {
             *color = color.gamma_multiply(opacity);
         }
diff --git a/crates/epaint/src/shape_transform.rs b/crates/epaint/src/shape_transform.rs
index e7e34369f96..d0ab91536d1 100644
--- a/crates/epaint/src/shape_transform.rs
+++ b/crates/epaint/src/shape_transform.rs
@@ -1,7 +1,12 @@
+use std::sync::Arc;
+
 use crate::*;
 
 /// Remember to handle [`Color32::PLACEHOLDER`] specially!
-pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
+pub fn adjust_colors(
+    shape: &mut Shape,
+    adjust_color: impl Fn(&mut Color32) + Send + Sync + Copy + 'static,
+) {
     #![allow(clippy::match_same_arms)]
     match shape {
         Shape::Noop => {}
@@ -10,9 +15,16 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
                 adjust_colors(shape, adjust_color);
             }
         }
-        Shape::LineSegment { stroke, points: _ } => match stroke.color {
+        Shape::LineSegment { stroke, points: _ } => match &stroke.color {
             color::ColorMode::Solid(mut col) => adjust_color(&mut col),
-            color::ColorMode::UV(_) => {}
+            color::ColorMode::UV(callback) => {
+                let callback = callback.clone();
+                stroke.color = color::ColorMode::UV(Arc::new(Box::new(move |rect, pos| {
+                    let mut col = callback(rect, pos);
+                    adjust_color(&mut col);
+                    col
+                })));
+            }
         },
 
         Shape::Path(PathShape {
@@ -34,9 +46,16 @@ pub fn adjust_colors(shape: &mut Shape, adjust_color: &impl Fn(&mut Color32)) {
             stroke,
         }) => {
             adjust_color(fill);
-            match stroke.color {
+            match &stroke.color {
                 color::ColorMode::Solid(mut col) => adjust_color(&mut col),
-                color::ColorMode::UV(_) => {}
+                color::ColorMode::UV(callback) => {
+                    let callback = callback.clone();
+                    stroke.color = color::ColorMode::UV(Arc::new(Box::new(move |rect, pos| {
+                        let mut col = callback(rect, pos);
+                        adjust_color(&mut col);
+                        col
+                    })));
+                }
             }
         }
 

From f71b011c914de621844b93720fc00874bf0a02b7 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sun, 21 Apr 2024 11:11:32 -0600
Subject: [PATCH 18/27] remove dependencies for dancing strings demo (doesn't
 compile for me for some reason)

---
 Cargo.lock                                    | 83 -------------------
 crates/ecolor/Cargo.toml                      |  1 -
 crates/egui_demo_lib/Cargo.toml               |  5 +-
 .../src/demo/dancing_trans_strings.rs         | 45 +++++-----
 4 files changed, 26 insertions(+), 108 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 4837da167e0..c6d8727188a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -847,15 +847,6 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3d7b894f5411737b7867f4827955924d7c254fc9f4d91a6aad6b097804b1018b"
 
-[[package]]
-name = "colorgrad"
-version = "0.6.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a5f405d474b9d05e0a093d3120e77e9bf26461b57a84b40aa2a221ac5617fb6"
-dependencies = [
- "csscolorparser",
-]
-
 [[package]]
 name = "com"
 version = "0.6.0"
@@ -1051,15 +1042,6 @@ dependencies = [
  "typenum",
 ]
 
-[[package]]
-name = "csscolorparser"
-version = "0.6.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eb2a7d3066da2de787b7f032c736763eb7ae5d355f81a68bab2675a96008b0bf"
-dependencies = [
- "phf",
-]
-
 [[package]]
 name = "cursor-icon"
 version = "1.1.0"
@@ -1333,15 +1315,12 @@ name = "egui_demo_lib"
 version = "0.27.2"
 dependencies = [
  "chrono",
- "colorgrad",
  "criterion",
  "document-features",
  "egui",
  "egui_extras",
  "egui_plot",
  "log",
- "noise",
- "once_cell",
  "serde",
  "unicode_names2",
 ]
@@ -2532,17 +2511,6 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2bf50223579dc7cdcfb3bfcacf7069ff68243f8c363f62ffa99cf000a6b9c451"
 
-[[package]]
-name = "noise"
-version = "0.9.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6da45c8333f2e152fc665d78a380be060eb84fad8ca4c9f7ac8ca29216cff0cc"
-dependencies = [
- "num-traits",
- "rand",
- "rand_xorshift",
-]
-
 [[package]]
 name = "nom"
 version = "7.1.3"
@@ -2793,48 +2761,6 @@ version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9b2a4787296e9989611394c33f193f676704af1686e70b8f8033ab5ba9a35a94"
 
-[[package]]
-name = "phf"
-version = "0.11.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ade2d8b8f33c7333b51bcf0428d37e217e9f32192ae4772156f65063b8ce03dc"
-dependencies = [
- "phf_macros",
- "phf_shared",
-]
-
-[[package]]
-name = "phf_generator"
-version = "0.11.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "48e4cc64c2ad9ebe670cb8fd69dd50ae301650392e81c05f9bfcb2d5bdbc24b0"
-dependencies = [
- "phf_shared",
- "rand",
-]
-
-[[package]]
-name = "phf_macros"
-version = "0.11.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3444646e286606587e49f3bcf1679b8cef1dc2c5ecc29ddacaffc305180d464b"
-dependencies = [
- "phf_generator",
- "phf_shared",
- "proc-macro2",
- "quote",
- "syn 2.0.48",
-]
-
-[[package]]
-name = "phf_shared"
-version = "0.11.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "90fcb95eef784c2ac79119d1dd819e162b5da872ce6f3c3abe1e8ca1c082f72b"
-dependencies = [
- "siphasher",
-]
-
 [[package]]
 name = "pico-args"
 version = "0.5.0"
@@ -3082,15 +3008,6 @@ dependencies = [
  "getrandom",
 ]
 
-[[package]]
-name = "rand_xorshift"
-version = "0.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d25bf25ec5ae4a3f1b92f929810509a2f53d7dca2f50b794ff57e3face536c8f"
-dependencies = [
- "rand_core",
-]
-
 [[package]]
 name = "raw-window-handle"
 version = "0.5.2"
diff --git a/crates/ecolor/Cargo.toml b/crates/ecolor/Cargo.toml
index 4cdbea9124b..611b9a4dec9 100644
--- a/crates/ecolor/Cargo.toml
+++ b/crates/ecolor/Cargo.toml
@@ -30,7 +30,6 @@ extra_debug_asserts = []
 ## Always enable additional checks.
 extra_asserts = []
 
-
 [dependencies]
 #! ### Optional dependencies
 
diff --git a/crates/egui_demo_lib/Cargo.toml b/crates/egui_demo_lib/Cargo.toml
index 1083f5b8b47..8c5a703b5d6 100644
--- a/crates/egui_demo_lib/Cargo.toml
+++ b/crates/egui_demo_lib/Cargo.toml
@@ -38,7 +38,7 @@ syntect = ["egui_extras/syntect"]
 
 
 [dependencies]
-egui = { workspace = true, default-features = false }
+egui = { workspace = true, default-features = false, features = ["color-hex"] }
 egui_extras = { workspace = true, features = ["default"] }
 egui_plot = { workspace = true, features = ["default"] }
 
@@ -50,9 +50,6 @@ chrono = { version = "0.4", optional = true, features = ["js-sys", "wasmbind"] }
 ## Enable this when generating docs.
 document-features = { workspace = true, optional = true }
 serde = { version = "1", optional = true, features = ["derive"] }
-once_cell = "1.19"
-colorgrad = "0.6"
-noise = "0.9"
 
 
 [dev-dependencies]
diff --git a/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs b/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs
index 10ca84e092b..605503ad7fe 100644
--- a/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs
+++ b/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs
@@ -1,21 +1,12 @@
-use colorgrad::{Color, CustomGradient, Gradient};
-use egui::{containers::*, epaint::PathStroke, *};
-use noise::{NoiseFn, OpenSimplex};
-use once_cell::sync::Lazy;
-
-static GRADIENT: Lazy<Gradient> = Lazy::new(|| {
-    CustomGradient::new()
-        .colors(&[
-            Color::from_html("#5BCEFA").unwrap(),
-            Color::from_html("#F5A9B8").unwrap(),
-            Color::from_html("#FFFFFF").unwrap(),
-            Color::from_html("#F5A9B8").unwrap(),
-            Color::from_html("#5BCEFA").unwrap(),
-        ])
-        .build()
-        .unwrap_or(colorgrad::rainbow())
-});
-static NOISE: Lazy<OpenSimplex> = Lazy::new(|| OpenSimplex::new(6940));
+use egui::{containers::*, ecolor::*, epaint::PathStroke, *};
+
+static GRADIENT: [Color32; 5] = [
+    hex_color!("#5BCEFA"),
+    hex_color!("#F5A9B8"),
+    Color32::WHITE,
+    hex_color!("#F5A9B8"),
+    hex_color!("#5BCEFA"),
+];
 
 #[derive(Default)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
@@ -73,8 +64,22 @@ impl super::View for DancingStrings {
                         let x = remap(p.x, rect.x_range(), 0.0..=1.0) as f64;
                         let y = remap(p.y, rect.y_range(), 0.0..=1.0) as f64;
 
-                        let noise = NOISE.get([x * 1.25 + time, y * 1.25 + time]);
-                        let color = GRADIENT.at(noise).to_rgba8();
+                        let amp = (time * speed * mode).sin() / mode;
+                        let sin = amp * (time * std::f64::consts::TAU / 2.0 * mode).sin();
+
+                        let value = x * sin + y * sin;
+
+                        let color = if value < 0.2 {
+                            GRADIENT[0]
+                        } else if value < 0.4 {
+                            GRADIENT[1]
+                        } else if value < 0.6 {
+                            GRADIENT[2]
+                        } else if value < 0.8 {
+                            GRADIENT[3]
+                        } else {
+                            GRADIENT[4]
+                        };
 
                         Color32::from_rgba_premultiplied(color[0], color[1], color[2], color[3])
                     }),

From 1e85d863a0747318e63c64c1a2e1c45ee10d958a Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sun, 21 Apr 2024 11:28:11 -0600
Subject: [PATCH 19/27] roll dancing strings examples into one

---
 .../egui_demo_lib/src/demo/dancing_strings.rs | 50 +++++++++-
 .../src/demo/dancing_trans_strings.rs         | 95 -------------------
 .../src/demo/demo_app_windows.rs              |  1 -
 crates/egui_demo_lib/src/demo/mod.rs          |  1 -
 4 files changed, 47 insertions(+), 100 deletions(-)
 delete mode 100644 crates/egui_demo_lib/src/demo/dancing_trans_strings.rs

diff --git a/crates/egui_demo_lib/src/demo/dancing_strings.rs b/crates/egui_demo_lib/src/demo/dancing_strings.rs
index 3beb323e75d..2218638c388 100644
--- a/crates/egui_demo_lib/src/demo/dancing_strings.rs
+++ b/crates/egui_demo_lib/src/demo/dancing_strings.rs
@@ -1,9 +1,19 @@
-use egui::{containers::*, *};
+use egui::{containers::*, epaint::PathStroke, *};
+
+static GRADIENT: [Color32; 5] = [
+    hex_color!("#5BCEFA"),
+    hex_color!("#F5A9B8"),
+    Color32::WHITE,
+    hex_color!("#F5A9B8"),
+    hex_color!("#5BCEFA"),
+];
 
 #[derive(Default)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "serde", serde(default))]
-pub struct DancingStrings {}
+pub struct DancingStrings {
+    colors: bool,
+}
 
 impl super::Demo for DancingStrings {
     fn name(&self) -> &'static str {
@@ -28,6 +38,10 @@ impl super::View for DancingStrings {
             Color32::from_black_alpha(240)
         };
 
+        ui.horizontal(|ui| ui.checkbox(&mut self.colors, "Show Colors"));
+
+        ui.separator();
+
         Frame::canvas(ui.style()).show(ui, |ui| {
             ui.ctx().request_repaint();
             let time = ui.input(|i| i.time);
@@ -55,7 +69,37 @@ impl super::View for DancingStrings {
                     .collect();
 
                 let thickness = 10.0 / mode as f32;
-                shapes.push(epaint::Shape::line(points, Stroke::new(thickness, color)));
+                shapes.push(epaint::Shape::line(
+                    points,
+                    if self.colors {
+                        PathStroke::new_uv(thickness, move |_r, p| {
+                            let time = time / 10.0;
+                            let x = remap(p.x, rect.x_range(), 0.0..=1.0) as f64;
+                            let y = remap(p.y, rect.y_range(), 0.0..=1.0) as f64;
+
+                            let amp = (time * speed * mode).sin() / mode;
+                            let sin = amp * (time * std::f64::consts::TAU / 2.0 * mode).sin();
+
+                            let value = x * sin + y * sin;
+
+                            let color = if value < 0.2 {
+                                GRADIENT[0]
+                            } else if value < 0.4 {
+                                GRADIENT[1]
+                            } else if value < 0.6 {
+                                GRADIENT[2]
+                            } else if value < 0.8 {
+                                GRADIENT[3]
+                            } else {
+                                GRADIENT[4]
+                            };
+
+                            Color32::from_rgba_premultiplied(color[0], color[1], color[2], color[3])
+                        })
+                    } else {
+                        PathStroke::new(thickness, color)
+                    },
+                ));
             }
 
             ui.painter().extend(shapes);
diff --git a/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs b/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs
deleted file mode 100644
index 605503ad7fe..00000000000
--- a/crates/egui_demo_lib/src/demo/dancing_trans_strings.rs
+++ /dev/null
@@ -1,95 +0,0 @@
-use egui::{containers::*, ecolor::*, epaint::PathStroke, *};
-
-static GRADIENT: [Color32; 5] = [
-    hex_color!("#5BCEFA"),
-    hex_color!("#F5A9B8"),
-    Color32::WHITE,
-    hex_color!("#F5A9B8"),
-    hex_color!("#5BCEFA"),
-];
-
-#[derive(Default)]
-#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
-#[cfg_attr(feature = "serde", serde(default))]
-pub struct DancingStrings {}
-
-impl super::Demo for DancingStrings {
-    fn name(&self) -> &'static str {
-        "♫ Dancing Strings (Colored)"
-    }
-
-    fn show(&mut self, ctx: &Context, open: &mut bool) {
-        use super::View as _;
-        Window::new(self.name())
-            .open(open)
-            .default_size(vec2(512.0, 256.0))
-            .vscroll(false)
-            .show(ctx, |ui| self.ui(ui));
-    }
-}
-
-impl super::View for DancingStrings {
-    fn ui(&mut self, ui: &mut Ui) {
-        Frame::canvas(ui.style()).show(ui, |ui| {
-            ui.ctx().request_repaint();
-            let time = ui.input(|i| i.time);
-
-            let desired_size = ui.available_width() * vec2(1.0, 0.35);
-            let (_id, rect) = ui.allocate_space(desired_size);
-
-            let to_screen =
-                emath::RectTransform::from_to(Rect::from_x_y_ranges(0.0..=1.0, -1.0..=1.0), rect);
-
-            let mut shapes = vec![];
-
-            for &mode in &[2, 3, 5] {
-                let mode = mode as f64;
-                let n = 120;
-                let speed = 1.5;
-
-                let points: Vec<Pos2> = (0..=n)
-                    .map(|i| {
-                        let t = i as f64 / (n as f64);
-                        let amp = (time * speed * mode).sin() / mode;
-                        let y = amp * (t * std::f64::consts::TAU / 2.0 * mode).sin();
-                        to_screen * pos2(t as f32, y as f32)
-                    })
-                    .collect();
-
-                let thickness = 10.0 / mode as f32;
-                shapes.push(epaint::Shape::line(
-                    points,
-                    PathStroke::new_uv(thickness, move |_r, p| {
-                        let time = time / 10.0;
-                        let x = remap(p.x, rect.x_range(), 0.0..=1.0) as f64;
-                        let y = remap(p.y, rect.y_range(), 0.0..=1.0) as f64;
-
-                        let amp = (time * speed * mode).sin() / mode;
-                        let sin = amp * (time * std::f64::consts::TAU / 2.0 * mode).sin();
-
-                        let value = x * sin + y * sin;
-
-                        let color = if value < 0.2 {
-                            GRADIENT[0]
-                        } else if value < 0.4 {
-                            GRADIENT[1]
-                        } else if value < 0.6 {
-                            GRADIENT[2]
-                        } else if value < 0.8 {
-                            GRADIENT[3]
-                        } else {
-                            GRADIENT[4]
-                        };
-
-                        Color32::from_rgba_premultiplied(color[0], color[1], color[2], color[3])
-                    }),
-                ));
-            }
-
-            ui.painter().extend(shapes);
-        });
-        ui.vertical_centered(|ui| {
-            ui.add(crate::egui_github_link_file!());
-        });
-    }
-}
diff --git a/crates/egui_demo_lib/src/demo/demo_app_windows.rs b/crates/egui_demo_lib/src/demo/demo_app_windows.rs
index b6647123abd..0910df4ef56 100644
--- a/crates/egui_demo_lib/src/demo/demo_app_windows.rs
+++ b/crates/egui_demo_lib/src/demo/demo_app_windows.rs
@@ -26,7 +26,6 @@ impl Default for Demos {
             Box::<super::code_example::CodeExample>::default(),
             Box::<super::context_menu::ContextMenus>::default(),
             Box::<super::dancing_strings::DancingStrings>::default(),
-            Box::<super::dancing_trans_strings::DancingStrings>::default(),
             Box::<super::drag_and_drop::DragAndDropDemo>::default(),
             Box::<super::extra_viewport::ExtraViewport>::default(),
             Box::<super::font_book::FontBook>::default(),
diff --git a/crates/egui_demo_lib/src/demo/mod.rs b/crates/egui_demo_lib/src/demo/mod.rs
index 95c9fa7dfaa..8a911c9d68b 100644
--- a/crates/egui_demo_lib/src/demo/mod.rs
+++ b/crates/egui_demo_lib/src/demo/mod.rs
@@ -9,7 +9,6 @@ pub mod code_editor;
 pub mod code_example;
 pub mod context_menu;
 pub mod dancing_strings;
-pub mod dancing_trans_strings;
 pub mod demo_app_windows;
 pub mod drag_and_drop;
 pub mod extra_viewport;

From cdc65888048edaf3a872b069aa4896e019387eea Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sun, 21 Apr 2024 12:27:45 -0600
Subject: [PATCH 20/27] from_hex! can't be used in statics

---
 Cargo.lock                                    |  1 +
 crates/egui_demo_lib/Cargo.toml               |  2 ++
 .../egui_demo_lib/src/demo/dancing_strings.rs | 19 +++++++++++--------
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 8698db26e7a..8d858c4eacb 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1321,6 +1321,7 @@ dependencies = [
  "egui_extras",
  "egui_plot",
  "log",
+ "once_cell",
  "serde",
  "unicode_names2",
 ]
diff --git a/crates/egui_demo_lib/Cargo.toml b/crates/egui_demo_lib/Cargo.toml
index 8c5a703b5d6..533b239a908 100644
--- a/crates/egui_demo_lib/Cargo.toml
+++ b/crates/egui_demo_lib/Cargo.toml
@@ -42,6 +42,8 @@ egui = { workspace = true, default-features = false, features = ["color-hex"] }
 egui_extras = { workspace = true, features = ["default"] }
 egui_plot = { workspace = true, features = ["default"] }
 
+once_cell = "1.19"
+
 log.workspace = true
 unicode_names2 = { version = "0.6.0", default-features = false } # this old version has fewer dependencies
 
diff --git a/crates/egui_demo_lib/src/demo/dancing_strings.rs b/crates/egui_demo_lib/src/demo/dancing_strings.rs
index 2218638c388..626edfbab8d 100644
--- a/crates/egui_demo_lib/src/demo/dancing_strings.rs
+++ b/crates/egui_demo_lib/src/demo/dancing_strings.rs
@@ -1,12 +1,15 @@
 use egui::{containers::*, epaint::PathStroke, *};
-
-static GRADIENT: [Color32; 5] = [
-    hex_color!("#5BCEFA"),
-    hex_color!("#F5A9B8"),
-    Color32::WHITE,
-    hex_color!("#F5A9B8"),
-    hex_color!("#5BCEFA"),
-];
+use once_cell::sync::Lazy;
+
+static GRADIENT: Lazy<[Color32; 5]> = Lazy::new(|| {
+    [
+        hex_color!("#5BCEFA"),
+        hex_color!("#F5A9B8"),
+        Color32::WHITE,
+        hex_color!("#F5A9B8"),
+        hex_color!("#5BCEFA"),
+    ]
+});
 
 #[derive(Default)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]

From 38bc7708e3a3acb0b50e6664a3c14db187524e87 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sun, 21 Apr 2024 13:15:50 -0600
Subject: [PATCH 21/27] remove margin, it seems that points can exit the rect
 by at most 0.55, i don't know why

---
 crates/epaint/src/tessellator.rs | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index d2e453f1b6b..566d11502f0 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -885,9 +885,8 @@ fn stroke_path(
     let idx = out.vertices.len() as u32;
 
     // expand the bounding box to include the thickness of the path
-    // this tiny bit of margin is here because a rect doesn't think it contains a point if a pos' component is on a boundary. why? i have no idea.
     let bbox = Rect::from_points(&path.iter().map(|p| p.pos).collect::<Vec<Pos2>>())
-        .expand((stroke.width / 2.0) + feathering + 1.0);
+        .expand((stroke.width / 2.0) + feathering);
 
     let get_color = |col: &ColorMode, pos: Pos2| match col {
         ColorMode::Solid(col) => *col,
@@ -2077,7 +2076,7 @@ fn path_bounding_box() {
         let width = i as f32;
 
         let rect = Rect::from_min_max(pos2(0.0, 0.0), pos2(10.0, 10.0));
-        let expected_rect = rect.expand((width / 2.0) + 2.5);
+        let expected_rect = rect.expand((width / 2.0) + 1.5);
 
         let mut mesh = Mesh::default();
 
@@ -2096,12 +2095,15 @@ fn path_bounding_box() {
             PathType::Closed,
             &PathStroke::new_uv(width, move |r, p| {
                 assert_eq!(r, expected_rect);
+                // see https://github.com/emilk/egui/pull/4353#discussion_r1573879940 for why .contains() isn't used here.
+                // TL;DR rounding errors.
                 assert!(
-                    r.contains(p),
-                    "passed rect {r:?} didn't contain point {p:?}"
+                    r.distance_to_pos(p) <= 0.55,
+                    "passed rect {r:?} didn't contain point {p:?} (distance: {})",
+                    r.distance_to_pos(p)
                 );
                 assert!(
-                    expected_rect.contains(p),
+                    expected_rect.distance_to_pos(p) <= 0.55,
                     "expected rect {expected_rect:?} didn't contain point {p:?}"
                 );
                 Color32::WHITE

From b1f7520f34572486f1a56160d3ef83ea3450d06d Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sun, 21 Apr 2024 15:21:46 -0600
Subject: [PATCH 22/27] remove unesecarry box for closure

---
 crates/epaint/src/color.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/epaint/src/color.rs b/crates/epaint/src/color.rs
index b5d719c840d..289783c70fb 100644
--- a/crates/epaint/src/color.rs
+++ b/crates/epaint/src/color.rs
@@ -15,7 +15,7 @@ pub enum ColorMode {
     ///
     /// **This cannot be serialized**
     #[cfg_attr(feature = "serde", serde(skip))]
-    UV(Arc<Box<dyn Fn(Rect, Pos2) -> Color32 + Send + Sync>>),
+    UV(Arc<dyn Fn(Rect, Pos2) -> Color32 + Send + Sync>),
 }
 
 impl Default for ColorMode {

From 2283268a307aa6d1add9ce4a96c858518e94ea7d Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sun, 21 Apr 2024 15:59:10 -0600
Subject: [PATCH 23/27] add benchmarks for uv mode lines

---
 crates/epaint/benches/benchmark.rs | 94 +++++++++++++++++++++++++++++-
 1 file changed, 93 insertions(+), 1 deletion(-)

diff --git a/crates/epaint/benches/benchmark.rs b/crates/epaint/benches/benchmark.rs
index 3c94499a85b..6323137fa50 100644
--- a/crates/epaint/benches/benchmark.rs
+++ b/crates/epaint/benches/benchmark.rs
@@ -132,6 +132,94 @@ fn thin_large_line_solid(c: &mut Criterion) {
     });
 }
 
+fn thick_line_uv(c: &mut Criterion) {
+    c.bench_function("thick_uv_line", move |b| {
+        let line = [pos2(0.0, 0.0), pos2(50.0, 0.0), pos2(100.0, 1.0)];
+        let mut path = Path::default();
+        path.add_open_points(&line);
+
+        b.iter(|| {
+            let mut mesh = Mesh::default();
+            path.stroke_closed(
+                1.5,
+                &PathStroke::new_uv(2.0, |_, p| {
+                    black_box(p * 2.0);
+                    Color32::RED
+                }),
+                &mut mesh,
+            );
+
+            black_box(mesh);
+        });
+    });
+}
+
+fn thick_large_line_uv(c: &mut Criterion) {
+    c.bench_function("thick_large_uv_line", move |b| {
+        let line = (0..1000).map(|i| pos2(i as f32, 10.0)).collect::<Vec<_>>();
+        let mut path = Path::default();
+        path.add_open_points(&line);
+
+        b.iter(|| {
+            let mut mesh = Mesh::default();
+            path.stroke_closed(
+                1.5,
+                &PathStroke::new_uv(2.0, |_, p| {
+                    black_box(p * 2.0);
+                    Color32::RED
+                }),
+                &mut mesh,
+            );
+
+            black_box(mesh);
+        });
+    });
+}
+
+fn thin_line_uv(c: &mut Criterion) {
+    c.bench_function("thin_uv_line", move |b| {
+        let line = [pos2(0.0, 0.0), pos2(50.0, 0.0), pos2(100.0, 1.0)];
+        let mut path = Path::default();
+        path.add_open_points(&line);
+
+        b.iter(|| {
+            let mut mesh = Mesh::default();
+            path.stroke_closed(
+                1.5,
+                &PathStroke::new_uv(2.0, |_, p| {
+                    black_box(p * 2.0);
+                    Color32::RED
+                }),
+                &mut mesh,
+            );
+
+            black_box(mesh);
+        });
+    });
+}
+
+fn thin_large_line_uv(c: &mut Criterion) {
+    c.bench_function("thin_large_uv_line", move |b| {
+        let line = (0..1000).map(|i| pos2(i as f32, 10.0)).collect::<Vec<_>>();
+        let mut path = Path::default();
+        path.add_open_points(&line);
+
+        b.iter(|| {
+            let mut mesh = Mesh::default();
+            path.stroke_closed(
+                1.5,
+                &PathStroke::new_uv(2.0, |_, p| {
+                    black_box(p * 2.0);
+                    Color32::RED
+                }),
+                &mut mesh,
+            );
+
+            black_box(mesh);
+        });
+    });
+}
+
 criterion_group!(
     benches,
     single_dashed_lines,
@@ -140,6 +228,10 @@ criterion_group!(
     thick_line_solid,
     thick_large_line_solid,
     thin_line_solid,
-    thin_large_line_solid
+    thin_large_line_solid,
+    thick_line_uv,
+    thick_large_line_uv,
+    thin_line_uv,
+    thin_large_line_uv
 );
 criterion_main!(benches);

From 5f3a7128072a41c38f7b3cb0717d08a8ca793856 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sun, 21 Apr 2024 20:06:25 -0600
Subject: [PATCH 24/27] why are you still here, mx. box?

---
 crates/epaint/src/stroke.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index c797996d834..cf95d1ed7a9 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -89,7 +89,7 @@ impl PathStroke {
     ) -> Self {
         Self {
             width: width.into(),
-            color: ColorMode::UV(Arc::new(Box::new(callback))),
+            color: ColorMode::UV(Arc::new(callback)),
         }
     }
 

From 1a95c4800e60328a43335a8fe91e604e6115dafc Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Sun, 21 Apr 2024 20:14:21 -0600
Subject: [PATCH 25/27] fix docs

---
 crates/epaint/src/color.rs  | 2 +-
 crates/epaint/src/stroke.rs | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/crates/epaint/src/color.rs b/crates/epaint/src/color.rs
index 289783c70fb..54106c10d3f 100644
--- a/crates/epaint/src/color.rs
+++ b/crates/epaint/src/color.rs
@@ -11,7 +11,7 @@ pub enum ColorMode {
     Solid(Color32),
 
     /// Provide a callback which takes in the path's bounding box and a position and converts it to a color.
-    /// When used with a path, the bounding box will have a margin of ``feathering + 1.0``
+    /// When used with a path, the bounding box will have a margin of [`TessellationOptions::feathering_size_in_pixels`](`crate::tessellator::TessellationOptions::feathering_size_in_pixels`)
     ///
     /// **This cannot be serialized**
     #[cfg_attr(feature = "serde", serde(skip))]
diff --git a/crates/epaint/src/stroke.rs b/crates/epaint/src/stroke.rs
index cf95d1ed7a9..54d7fe20e56 100644
--- a/crates/epaint/src/stroke.rs
+++ b/crates/epaint/src/stroke.rs
@@ -81,7 +81,8 @@ impl PathStroke {
     }
 
     /// Create a new `PathStroke` with a UV function
-    /// The bounding box passed to the callback will have a margin of ``feathering + 1.0``
+    ///
+    /// The bounding box passed to the callback will have a margin of [`TessellationOptions::feathering_size_in_pixels`](`crate::tessellator::TessellationOptions::feathering_size_in_pixels`)
     #[inline]
     pub fn new_uv(
         width: impl Into<f32>,

From 52a645935a32dd9f02140053709d3577293ce158 Mon Sep 17 00:00:00 2001
From: joe <hello@murl.digital>
Date: Mon, 22 Apr 2024 08:14:44 -0600
Subject: [PATCH 26/27] remove mul_color

---
 crates/epaint/src/tessellator.rs | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index 566d11502f0..c7dc31b75ab 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -1141,17 +1141,11 @@ fn stroke_path(
             for p in path {
                 out.colored_vertex(
                     p.pos + radius * p.normal,
-                    mul_color(
-                        get_color(&stroke.color, p.pos + radius * p.normal),
-                        stroke.width / feathering,
-                    ),
+                    get_color(&stroke.color, p.pos + radius * p.normal),
                 );
                 out.colored_vertex(
                     p.pos - radius * p.normal,
-                    mul_color(
-                        get_color(&stroke.color, p.pos - radius * p.normal),
-                        stroke.width / feathering,
-                    ),
+                    get_color(&stroke.color, p.pos - radius * p.normal),
                 );
             }
         }

From a92ed912db2cb58ecbe1f3431c497c77c991d49c Mon Sep 17 00:00:00 2001
From: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
Date: Mon, 22 Apr 2024 18:23:36 +0200
Subject: [PATCH 27/27] Simplify the dancing strings example

---
 Cargo.lock                                    |  1 -
 crates/egui_demo_lib/Cargo.toml               |  2 -
 .../egui_demo_lib/src/demo/dancing_strings.rs | 49 +++++--------------
 3 files changed, 12 insertions(+), 40 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 8d858c4eacb..8698db26e7a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1321,7 +1321,6 @@ dependencies = [
  "egui_extras",
  "egui_plot",
  "log",
- "once_cell",
  "serde",
  "unicode_names2",
 ]
diff --git a/crates/egui_demo_lib/Cargo.toml b/crates/egui_demo_lib/Cargo.toml
index 533b239a908..8c5a703b5d6 100644
--- a/crates/egui_demo_lib/Cargo.toml
+++ b/crates/egui_demo_lib/Cargo.toml
@@ -42,8 +42,6 @@ egui = { workspace = true, default-features = false, features = ["color-hex"] }
 egui_extras = { workspace = true, features = ["default"] }
 egui_plot = { workspace = true, features = ["default"] }
 
-once_cell = "1.19"
-
 log.workspace = true
 unicode_names2 = { version = "0.6.0", default-features = false } # this old version has fewer dependencies
 
diff --git a/crates/egui_demo_lib/src/demo/dancing_strings.rs b/crates/egui_demo_lib/src/demo/dancing_strings.rs
index 626edfbab8d..a2b560ee723 100644
--- a/crates/egui_demo_lib/src/demo/dancing_strings.rs
+++ b/crates/egui_demo_lib/src/demo/dancing_strings.rs
@@ -1,15 +1,4 @@
 use egui::{containers::*, epaint::PathStroke, *};
-use once_cell::sync::Lazy;
-
-static GRADIENT: Lazy<[Color32; 5]> = Lazy::new(|| {
-    [
-        hex_color!("#5BCEFA"),
-        hex_color!("#F5A9B8"),
-        Color32::WHITE,
-        hex_color!("#F5A9B8"),
-        hex_color!("#5BCEFA"),
-    ]
-});
 
 #[derive(Default)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
@@ -41,9 +30,8 @@ impl super::View for DancingStrings {
             Color32::from_black_alpha(240)
         };
 
-        ui.horizontal(|ui| ui.checkbox(&mut self.colors, "Show Colors"));
-
-        ui.separator();
+        ui.checkbox(&mut self.colors, "Colored")
+            .on_hover_text("Demonstrates how a path can have varying color across its length.");
 
         Frame::canvas(ui.style()).show(ui, |ui| {
             ui.ctx().request_repaint();
@@ -75,29 +63,16 @@ impl super::View for DancingStrings {
                 shapes.push(epaint::Shape::line(
                     points,
                     if self.colors {
-                        PathStroke::new_uv(thickness, move |_r, p| {
-                            let time = time / 10.0;
-                            let x = remap(p.x, rect.x_range(), 0.0..=1.0) as f64;
-                            let y = remap(p.y, rect.y_range(), 0.0..=1.0) as f64;
-
-                            let amp = (time * speed * mode).sin() / mode;
-                            let sin = amp * (time * std::f64::consts::TAU / 2.0 * mode).sin();
-
-                            let value = x * sin + y * sin;
-
-                            let color = if value < 0.2 {
-                                GRADIENT[0]
-                            } else if value < 0.4 {
-                                GRADIENT[1]
-                            } else if value < 0.6 {
-                                GRADIENT[2]
-                            } else if value < 0.8 {
-                                GRADIENT[3]
-                            } else {
-                                GRADIENT[4]
-                            };
-
-                            Color32::from_rgba_premultiplied(color[0], color[1], color[2], color[3])
+                        PathStroke::new_uv(thickness, move |rect, p| {
+                            let t = remap(p.x, rect.x_range(), -1.0..=1.0).abs();
+                            let center_color = hex_color!("#5BCEFA");
+                            let outer_color = hex_color!("#F5A9B8");
+
+                            Color32::from_rgb(
+                                lerp(center_color.r() as f32..=outer_color.r() as f32, t) as u8,
+                                lerp(center_color.g() as f32..=outer_color.g() as f32, t) as u8,
+                                lerp(center_color.b() as f32..=outer_color.b() as f32, t) as u8,
+                            )
                         })
                     } else {
                         PathStroke::new(thickness, color)