From 364590e05f6702bf68f9a8d80b2705dd17687fb0 Mon Sep 17 00:00:00 2001
From: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>
Date: Mon, 14 Jun 2021 08:20:55 +0100
Subject: [PATCH] Use bytemuck for the push constants (#668)
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* Use bytemuck for the push constants

* Use the released version of bytemuck

https://github.com/Lokathor/bytemuck/pull/69 landed

That version also works 🎉
---
 Cargo.lock                            | 22 ++++++++++++++++++++++
 examples/runners/wgpu/Cargo.toml      |  1 +
 examples/runners/wgpu/src/graphics.rs | 12 +++++-------
 examples/shaders/shared/Cargo.toml    |  1 +
 examples/shaders/shared/src/lib.rs    |  4 +++-
 5 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 73eef7bd18..0b95fb3f8a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -197,6 +197,26 @@ version = "3.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "63396b8a4b9de3f4fdfb320ab6080762242f66a8ef174c49d8e19b674db4cdbe"
 
+[[package]]
+name = "bytemuck"
+version = "1.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9966d2ab714d0f785dbac0a0396251a35280aeb42413281617d0209ab4898435"
+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"
 version = "1.4.3"
@@ -767,6 +787,7 @@ dependencies = [
 name = "example-runner-wgpu"
 version = "0.4.0-alpha.9"
 dependencies = [
+ "bytemuck",
  "cfg-if 1.0.0",
  "clap 3.0.0-beta.2",
  "console_error_panic_hook",
@@ -2339,6 +2360,7 @@ dependencies = [
 name = "shared"
 version = "0.4.0-alpha.9"
 dependencies = [
+ "bytemuck",
  "spirv-std",
 ]
 
diff --git a/examples/runners/wgpu/Cargo.toml b/examples/runners/wgpu/Cargo.toml
index f76338526b..7580be0b29 100644
--- a/examples/runners/wgpu/Cargo.toml
+++ b/examples/runners/wgpu/Cargo.toml
@@ -23,6 +23,7 @@ wgpu = "0.7.0"
 winit = { version = "0.24", features = ["web-sys"] }
 clap = "3.0.0-beta.2"
 strum = { version = "0.20", default_features = false, features = ["derive"] }
+bytemuck = "1.6.3"
 
 [target.'cfg(not(any(target_os = "android", target_arch = "wasm32")))'.dependencies]
 spirv-builder = { path = "../../../crates/spirv-builder", default-features = false, features = ["watch"] }
diff --git a/examples/runners/wgpu/src/graphics.rs b/examples/runners/wgpu/src/graphics.rs
index ed95fd4c47..9f19a63d65 100644
--- a/examples/runners/wgpu/src/graphics.rs
+++ b/examples/runners/wgpu/src/graphics.rs
@@ -23,10 +23,6 @@ mod shaders {
     include!(concat!(env!("OUT_DIR"), "/entry_points.rs"));
 }
 
-unsafe fn any_as_u8_slice<T: Sized>(p: &T) -> &[u8] {
-    ::std::slice::from_raw_parts((p as *const T) as *const u8, ::std::mem::size_of::<T>())
-}
-
 fn mouse_button_index(button: MouseButton) -> usize {
     match button {
         MouseButton::Left => 0,
@@ -198,9 +194,11 @@ async fn run(
                         };
 
                         rpass.set_pipeline(render_pipeline);
-                        rpass.set_push_constants(wgpu::ShaderStage::all(), 0, unsafe {
-                            any_as_u8_slice(&push_constants)
-                        });
+                        rpass.set_push_constants(
+                            wgpu::ShaderStage::all(),
+                            0,
+                            bytemuck::bytes_of(&push_constants),
+                        );
                         rpass.draw(0..3, 0..1);
                     }
 
diff --git a/examples/shaders/shared/Cargo.toml b/examples/shaders/shared/Cargo.toml
index 88aec6cc86..e7cd8cac85 100644
--- a/examples/shaders/shared/Cargo.toml
+++ b/examples/shaders/shared/Cargo.toml
@@ -8,3 +8,4 @@ publish = false
 
 [dependencies]
 spirv-std = { path = "../../../crates/spirv-std", features = ["glam"] }
+bytemuck = { version = "1.6.3", features = ["derive"] }
diff --git a/examples/shaders/shared/src/lib.rs b/examples/shaders/shared/src/lib.rs
index 524a6f4645..69b1dd6378 100644
--- a/examples/shaders/shared/src/lib.rs
+++ b/examples/shaders/shared/src/lib.rs
@@ -12,7 +12,9 @@ pub use spirv_std::glam;
 #[cfg(target_arch = "spirv")]
 use spirv_std::num_traits::Float;
 
-#[derive(Copy, Clone)]
+use bytemuck::{Pod, Zeroable};
+
+#[derive(Copy, Clone, Pod, Zeroable)]
 #[repr(C)]
 pub struct ShaderConstants {
     pub width: u32,