From 741022b2b29617a4cf64914a177993dc8e900737 Mon Sep 17 00:00:00 2001
From: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
Date: Thu, 2 Jan 2025 15:24:16 +0100
Subject: [PATCH] Put `Shape::Mesh` in an `Arc` to reduce the size of `Shape`

---
 crates/epaint/src/shape_transform.rs | 14 ++++++++------
 crates/epaint/src/shapes/shape.rs    | 22 ++++++++++++++++++----
 crates/epaint/src/tessellator.rs     |  4 ++--
 3 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/crates/epaint/src/shape_transform.rs b/crates/epaint/src/shape_transform.rs
index 5ff087d926a..25ff0d4699b 100644
--- a/crates/epaint/src/shape_transform.rs
+++ b/crates/epaint/src/shape_transform.rs
@@ -86,7 +86,7 @@ pub fn adjust_colors(
             }
 
             if !galley.is_empty() {
-                let galley = std::sync::Arc::make_mut(galley);
+                let galley = Arc::make_mut(galley);
                 for row in &mut galley.rows {
                     for vertex in &mut row.visuals.mesh.vertices {
                         adjust_color(&mut vertex.color);
@@ -95,11 +95,13 @@ pub fn adjust_colors(
             }
         }
 
-        Shape::Mesh(Mesh {
-            indices: _,
-            vertices,
-            texture_id: _,
-        }) => {
+        Shape::Mesh(mesh) => {
+            let Mesh {
+                indices: _,
+                vertices,
+                texture_id: _,
+            } = Arc::make_mut(mesh);
+
             for v in vertices {
                 adjust_color(&mut v.color);
             }
diff --git a/crates/epaint/src/shapes/shape.rs b/crates/epaint/src/shapes/shape.rs
index 93fff9e06d1..62af1b58166 100644
--- a/crates/epaint/src/shapes/shape.rs
+++ b/crates/epaint/src/shapes/shape.rs
@@ -56,7 +56,9 @@ pub enum Shape {
     /// A general triangle mesh.
     ///
     /// Can be used to display images.
-    Mesh(Mesh),
+    ///
+    /// Wrapped in an [`Arc`] to minimize the size of [`Shape`].
+    Mesh(Arc<Mesh>),
 
     /// A quadratic [Bézier Curve](https://en.wikipedia.org/wiki/B%C3%A9zier_curve).
     QuadraticBezier(QuadraticBezierShape),
@@ -71,9 +73,13 @@ pub enum Shape {
 #[test]
 fn shape_size() {
     assert_eq!(
-        std::mem::size_of::<Shape>(), 72,
+        std::mem::size_of::<Shape>(), 64,
         "Shape changed size! If it shrank - good! Update this test. If it grew - bad! Try to find a way to avoid it."
     );
+    assert!(
+        std::mem::size_of::<Shape>() <= 64,
+        "Shape is getting way too big!"
+    );
 }
 
 #[test]
@@ -92,6 +98,13 @@ impl From<Vec<Self>> for Shape {
 impl From<Mesh> for Shape {
     #[inline(always)]
     fn from(mesh: Mesh) -> Self {
+        Self::Mesh(mesh.into())
+    }
+}
+
+impl From<Arc<Mesh>> for Shape {
+    #[inline(always)]
+    fn from(mesh: Arc<Mesh>) -> Self {
         Self::Mesh(mesh)
     }
 }
@@ -322,7 +335,8 @@ impl Shape {
     }
 
     #[inline]
-    pub fn mesh(mesh: Mesh) -> Self {
+    pub fn mesh(mesh: impl Into<Arc<Mesh>>) -> Self {
+        let mesh = mesh.into();
         debug_assert!(mesh.is_valid());
         Self::Mesh(mesh)
     }
@@ -454,7 +468,7 @@ impl Shape {
                 galley.rect = transform.scaling * galley.rect;
             }
             Self::Mesh(mesh) => {
-                mesh.transform(transform);
+                Arc::make_mut(mesh).transform(transform);
             }
             Self::QuadraticBezier(bezier_shape) => {
                 bezier_shape.points[0] = transform * bezier_shape.points[0];
diff --git a/crates/epaint/src/tessellator.rs b/crates/epaint/src/tessellator.rs
index 8e5eb47dd40..57d30b11be8 100644
--- a/crates/epaint/src/tessellator.rs
+++ b/crates/epaint/src/tessellator.rs
@@ -1406,7 +1406,7 @@ impl Tessellator {
                     return;
                 }
 
-                out.append(mesh);
+                out.append_ref(&mesh);
             }
             Shape::LineSegment { points, stroke } => {
                 self.tessellate_line_segment(points, stroke, out);
@@ -2177,7 +2177,7 @@ impl Tessellator {
 
         profiling::scope!("distribute results", tessellated.len().to_string());
         for (index, mesh) in tessellated {
-            shapes[index].shape = Shape::Mesh(mesh);
+            shapes[index].shape = Shape::Mesh(mesh.into());
         }
     }