Implement `bytemuck` behind a feature (#775)

Cargo.lock

@@ -243,6 +243,20 @@ name = "bytemuck"
 version = "1.7.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72957246c41db82b8ef88a5486143830adeb8227ef9837740bdec67724cf2c5b"
+dependencies = [
+ "bytemuck_derive",
+]
+
+[[package]]
+name = "bytemuck_derive"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e215f8c2f9f79cb53c8335e687ffd07d5bfcb6fe5fc80723762d0be46e7cc54"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
 
 [[package]]
 name = "byteorder"
@@ -928,6 +942,7 @@ checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
 name = "emath"
 version = "0.14.0"
 dependencies = [
+ "bytemuck",
  "mint",
  "serde",
 ]
@@ -973,6 +988,7 @@ dependencies = [
  "ab_glyph",
  "ahash",
  "atomic_refcell",
+ "bytemuck",
  "cint",
  "emath",
  "nohash-hasher",

egui-winit/Cargo.toml

@@ -46,3 +46,6 @@ links = ["webbrowser"]
 screen_reader = ["tts"]
 
 serialize = ["egui/serialize", "serde"]
+
+# implement bytemuck on most types.
+convert_bytemuck = ["egui/convert_bytemuck"]

egui/Cargo.toml

@@ -53,6 +53,9 @@ persistence = ["serde", "epaint/serialize", "ron"]
 # implement serde on most types.
 serialize = ["serde", "epaint/serialize"]
 
+# implement bytemuck on most types.
+convert_bytemuck = ["epaint/convert_bytemuck"]
+
 # multi_threaded is only needed if you plan to use the same egui::Context
 # from multiple threads. It comes with a minor performance impact.
 single_threaded = ["epaint/single_threaded"]

emath/Cargo.toml

@@ -26,6 +26,7 @@ all-features = true
 # Add compatability with https://github.com/kvark/mint
 mint = { version = "0.5.6", optional = true }
 serde = { version = "1", features = ["derive"], optional = true }
+bytemuck = { version = "1.7.2", features = ["derive"], optional = true }
 
 [features]
 default = []

emath/src/pos2.rs

@@ -8,8 +8,10 @@ use crate::*;
 ///
 /// Mathematically this is known as a "point", but the term position was chosen so not to
 /// conflict with the unit (one point = X physical pixels).
+#[repr(C)]
 #[derive(Clone, Copy, Default, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
 pub struct Pos2 {
     pub x: f32,
     pub y: f32,

emath/src/rect.rs

@@ -6,8 +6,10 @@ use crate::*;
 /// A rectangular region of space.
 ///
 /// Normally given in points, e.g. logical pixels.
+#[repr(C)]
 #[derive(Clone, Copy, Eq, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
 pub struct Rect {
     pub min: Pos2,
     pub max: Pos2,

emath/src/rect_transform.rs

@@ -3,7 +3,10 @@ use crate::*;
 /// Linearly transforms positions from one [`Rect`] to another.
 ///
 /// `RectTransform` stores the rectangles, and therefore supports clamping and culling.
+#[repr(C)]
 #[derive(Clone, Copy, Debug, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
 pub struct RectTransform {
     from: Rect,
     to: Rect,

emath/src/rot2.rs

@@ -13,7 +13,10 @@ use super::Vec2;
 //
 /// Normally a `Rot2` is normalized (unit-length).
 /// If not, it will also scale vectors.
+#[repr(C)]
 #[derive(Clone, Copy, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
 pub struct Rot2 {
     /// angle.sin()
     s: f32,

emath/src/vec2.rs

@@ -6,8 +6,10 @@ use std::ops::{Add, AddAssign, Div, Mul, MulAssign, Neg, Sub, SubAssign};
 /// emath represents positions using [`crate::Pos2`].
 ///
 /// Normally the units are points (logical pixels).
+#[repr(C)]
 #[derive(Clone, Copy, Default, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
 pub struct Vec2 {
     pub x: f32,
     pub y: f32,

epaint/Cargo.toml

@@ -34,6 +34,7 @@ cint = { version = "^0.2.2", optional = true }
 nohash-hasher = "0.2"
 parking_lot = { version = "0.11", optional = true } # Using parking_lot over std::sync::Mutex gives 50% speedups in some real-world scenarios.
 serde = { version = "1", features = ["derive"], optional = true }
+bytemuck = { version = "1.7.2", features = ["derive"], optional = true }
 
 [features]
 default = ["default_fonts", "multi_threaded"]
@@ -53,6 +54,9 @@ mint = ["emath/mint"]
 # implement serde on most types.
 serialize = ["serde", "emath/serde"]
 
+# implement bytemuck on most types.
+convert_bytemuck = ["bytemuck", "emath/bytemuck"]
+
 single_threaded = ["atomic_refcell"]
 
 # Only needed if you plan to use the same fonts from multiple threads.

epaint/src/color.rs

@@ -13,8 +13,10 @@
 ///
 /// Internally this uses 0-255 gamma space `sRGBA` color with premultiplied alpha.
 /// Alpha channel is in linear space.
+#[repr(C)]
 #[derive(Clone, Copy, Debug, Default, Eq, Hash, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
 pub struct Color32(pub(crate) [u8; 4]);
 
 impl std::ops::Index<usize> for Color32 {

epaint/src/mesh.rs

@@ -7,6 +7,7 @@ use emath::*;
 #[repr(C)]
 #[derive(Clone, Copy, Debug, Default, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "bytemuck", derive(bytemuck::Pod, bytemuck::Zeroable))]
 pub struct Vertex {
     /// Logical pixel coordinates (points).
     /// (0,0) is the top left corner of the screen.