From d511a391780d9a6a6fcc3e287cd951dee80ac4e0 Mon Sep 17 00:00:00 2001
From: Matthew Deville <matthew@stockly.ai>
Date: Sun, 31 Aug 2025 13:36:29 +0200
Subject: [PATCH] wip

---
 Cargo.lock  | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 Cargo.toml  |  8 ++---
 src/main.rs | 30 +++++++++++++++++-
 3 files changed, 121 insertions(+), 5 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 67adf6e..45a3bc8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -400,6 +400,7 @@ dependencies = [
  "futures-io",
  "futures-lite",
  "js-sys",
+ "notify-debouncer-full",
  "parking_lot",
  "ron",
  "serde",
@@ -1971,6 +1972,15 @@ dependencies = [
  "simd-adler32",
 ]
 
+[[package]]
+name = "file-id"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e1fc6a637b6dc58414714eddd9170ff187ecb0933d4c7024d1abbd23a3cc26e9"
+dependencies = [
+ "windows-sys 0.60.2",
+]
+
 [[package]]
 name = "fixedbitset"
 version = "0.5.7"
@@ -2058,6 +2068,15 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "aa9a19cbb55df58761df49b23516a86d432839add4af60fc256da840f66ed35b"
 
+[[package]]
+name = "fsevent-sys"
+version = "4.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76ee7a02da4d231650c7cea31349b889be2f45ddb3ef3032d2ec8185f6313fd2"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "futures-channel"
 version = "0.3.31"
@@ -2535,6 +2554,26 @@ version = "3.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2db585e1d738fc771bf08a151420d3ed193d9d895a36df7f6f8a9456b911ddc"
 
+[[package]]
+name = "kqueue"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eac30106d7dce88daf4a3fcb4879ea939476d5074a9b7ddd0fb97fa4bed5596a"
+dependencies = [
+ "kqueue-sys",
+ "libc",
+]
+
+[[package]]
+name = "kqueue-sys"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed9625ffda8729b85e45cf04090035ac368927b8cebc34898e7c120f52e4838b"
+dependencies = [
+ "bitflags 1.3.2",
+ "libc",
+]
+
 [[package]]
 name = "ktx2"
 version = "0.3.0"
@@ -2711,6 +2750,18 @@ dependencies = [
  "simd-adler32",
 ]
 
+[[package]]
+name = "mio"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "78bed444cc8a2160f01cbcf811ef18cac863ad68ae8ca62092e8db51d51c761c"
+dependencies = [
+ "libc",
+ "log",
+ "wasi 0.11.1+wasi-snapshot-preview1",
+ "windows-sys 0.59.0",
+]
+
 [[package]]
 name = "naga"
 version = "24.0.0"
@@ -2847,6 +2898,43 @@ version = "0.5.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "610a5acd306ec67f907abe5567859a3c693fb9886eb1f012ab8f2a47bef3db51"
 
+[[package]]
+name = "notify"
+version = "8.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4d3d07927151ff8575b7087f245456e549fea62edf0ec4e565a5ee50c8402bc3"
+dependencies = [
+ "bitflags 2.9.3",
+ "fsevent-sys",
+ "inotify",
+ "kqueue",
+ "libc",
+ "log",
+ "mio",
+ "notify-types",
+ "walkdir",
+ "windows-sys 0.60.2",
+]
+
+[[package]]
+name = "notify-debouncer-full"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d2d88b1a7538054351c8258338df7c931a590513fb3745e8c15eb9ff4199b8d1"
+dependencies = [
+ "file-id",
+ "log",
+ "notify",
+ "notify-types",
+ "walkdir",
+]
+
+[[package]]
+name = "notify-types"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5e0826a989adedc2a244799e823aece04662b66609d96af8dff7ac6df9a8925d"
+
 [[package]]
 name = "ntapi"
 version = "0.4.1"
diff --git a/Cargo.toml b/Cargo.toml
index 0d59283..3271a97 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,8 +1,8 @@
 [package]
-name = "bevy_test"
-version = "0.1.0"
-edition = "2024"
+	edition = "2024"
+	name = "bevy_test"
+	version = "0.1.0"
 
 
 [dependencies]
-bevy = "0.16.1"
+	bevy = { version = "0.16.1", features = ["file_watcher"] }
diff --git a/src/main.rs b/src/main.rs
index 8d9cfa4..5c08a0c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,10 +1,11 @@
 //! A shader that uses the WGSL shading language.
 
 use bevy::{
+    asset::AssetEvent,
     input::common_conditions::*,
     prelude::*,
     reflect::TypePath,
-    render::render_resource::{AsBindGroup, ShaderRef},
+    render::render_resource::{AsBindGroup, Shader, ShaderRef},
     sprite::{AlphaMode2d, Material2d, Material2dPlugin},
     window::{PrimaryWindow, WindowMode},
 };
@@ -23,6 +24,7 @@ fn main() {
             (
                 update_material_time,
                 resize_fullscreen_quad,
+                shader_hot_reload,
                 exit_app.run_if(input_just_pressed(KeyCode::Escape)),
                 toggle_fullscreen.run_if(input_just_pressed(KeyCode::F11)),
             ),
@@ -88,6 +90,32 @@ fn toggle_fullscreen(mut primary_window: Single<&mut Window, With<PrimaryWindow>
     };
 }
 
+/// Listen for shader asset changes and force materials to update so the new shader is used.
+fn shader_hot_reload(
+    mut shader_events: EventReader<AssetEvent<Shader>>,
+    mut materials: ResMut<Assets<CustomMaterial>>,
+) {
+    let mut reload_needed = false;
+    for event in shader_events.read() {
+        match event {
+            AssetEvent::Modified { .. } => {
+                info!("shader changed: {event:?}");
+                reload_needed = true;
+            }
+            _ => {}
+        }
+    }
+
+    if reload_needed {
+        // iterate all materials and 'touch' them so Bevy updates bindings using the recompiled shader
+        for (_handle, material) in materials.iter_mut() {
+            // assign to itself to mark changed
+            let cloned = material.clone();
+            *material = cloned;
+        }
+    }
+}
+
 // This is the struct that will be passed to your shader
 #[derive(Asset, TypePath, AsBindGroup, Clone)]
 struct CustomMaterial {