Starting on ui example

Cargo.toml

@@ -20,3 +20,6 @@ features = ["wayland", "dynamic_linking"]
 [build-dependencies]
 chrono = "*"
 walkdir = "*"
+
+# [hints]
+# mostly-unused = true

build.rs

@@ -50,10 +50,16 @@ fn write_monologues_file() {
     walkdir::WalkDir::new("assets/trees")
         .into_iter()
         .filter_map(|entry| entry.ok())
-        .filter(|entry| {
-            entry.path().extension() == Some(std::ffi::OsStr::new("mono"))
-        })
+        .filter(|entry| entry.path().extension() == Some(std::ffi::OsStr::new("mono")))
         .for_each(|entry| {
-            let _ = writeln!(file, "{}", entry.path().to_string_lossy().strip_prefix("assets/").unwrap());
+            let _ = writeln!(
+                file,
+                "{}",
+                entry
+                    .path()
+                    .to_string_lossy()
+                    .strip_prefix("assets/")
+                    .unwrap()
+            );
         });
 }

examples/ui.rs

@@ -0,0 +1,53 @@
+//! This example illustrates scrolling in Bevy UI.
+
+use games::*;
+
+fn main() {
+    let mut app = App::new();
+    app.add_plugins(BaseGamePlugin::default())
+        .add_systems(Startup, setup);
+    app.run();
+}
+
+const LINE_HEIGHT: f32 = 21.;
+
+fn setup(mut commands: Commands) {
+    // Scrolling list
+    commands
+        .spawn((
+            Node {
+                flex_direction: FlexDirection::Column,
+                // If height is not set, we need both align_self: Stetch and overflow: scroll()
+                height: Val::Percent(50.0),
+                // align_self: AlignSelf::Stretch,
+                overflow: Overflow::scroll(),
+                ..default()
+            },
+            BackgroundColor(Color::srgb(0.10, 0.10, 0.10)),
+        ))
+        .with_children(|parent| {
+            // List items
+            (0..250).for_each(|i| {
+                parent.spawn(Text(format!("Item {i}")));
+            });
+        })
+        .observe(scroll);
+}
+
+/// Updates the scroll position of scrollable nodes in response to mouse input
+pub fn scroll(
+    trigger: Trigger<Pointer<Scroll>>,
+    mut scrollers: Query<&mut ScrollPosition>,
+) {
+    let Pointer { event: Scroll { unit, x, y, .. }, .. } = trigger.event();
+
+    let (dx, dy) = match unit {
+        MouseScrollUnit::Line => (x * LINE_HEIGHT, y * LINE_HEIGHT),
+        MouseScrollUnit::Pixel => (x * 1., y * 1.),
+    };
+
+    if let Ok(mut pos) = scrollers.get_mut(trigger.target()) {
+        pos.offset_x -= dx;
+        pos.offset_y -= dy;
+    }
+}

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1750506804,
-        "narHash": "sha256-VLFNc4egNjovYVxDGyBYTrvVCgDYgENp5bVi9fPTDYc=",
+        "lastModified": 1752480373,
+        "narHash": "sha256-JHQbm+OcGp32wAsXTE/FLYGNpb+4GLi5oTvCxwSoBOA=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "4206c4cb56751df534751b058295ea61357bbbaa",
+        "rev": "62e0f05ede1da0d54515d4ea8ce9c733f12d9f08",
         "type": "github"
       },
       "original": {

rust-toolchain.toml

@@ -1,4 +1,4 @@
 [toolchain]
-channel = "nightly-2025-06-16"
+channel = "nightly-2025-07-16"
 components = [ "rustfmt", "rustc-dev", "cargo", "clippy", "rust-analyzer", "rustc-codegen-cranelift" ]
 targets = [ "x86_64-unknown-linux-gnu", "wasm32-unknown-unknown" ]

src/base_game.rs

@@ -27,6 +27,7 @@ impl Plugin for BaseGamePlugin {
         .add_plugins(MeshPickingPlugin)
         .add_plugins(RapierPhysicsPlugin::<NoUserData>::default())
         .add_plugins(LoadingPlugin)
+        .add_plugins(BaseUiPlugin)
         .add_systems(Startup, setup_camera);
     }
 }

src/bin/trees/main.rs

@@ -528,13 +528,11 @@ fn delete_tree(trigger: Trigger<Pointer<Click>>, mut commands: Commands) {
 }
 
 /// Load all monologues so they are in the asset store and trigger on-load events
-fn load_monologues(
-    server: ResMut<AssetServer>,
-    mut loaded_assets: Local<Vec<Handle<Monologue>>>,
-) {
-    *loaded_assets = include_str!("../../../assets/trees/MONOLOGUES").split("\n").map(|path| {
-        server.load(path)
-    }).collect();
+fn load_monologues(server: ResMut<AssetServer>, mut loaded_assets: Local<Vec<Handle<Monologue>>>) {
+    *loaded_assets = include_str!("../../../assets/trees/MONOLOGUES")
+        .split("\n")
+        .map(|path| server.load(path))
+        .collect();
 }
 
 fn spawn_debug_buttons(
@@ -700,6 +698,7 @@ fn hide_monologue_preview(
     mut commands: Commands,
 ) {
     if !query.contains(trigger.target()) {
+        info!("Processing over: {:?}", trigger.target());
         commands.entity(*preview).despawn_related::<Children>();
     }
 }
@@ -709,17 +708,18 @@ fn drag_tree(
     state: Res<State<DebuggingState>>,
     mut query: Query<&mut Transform, With<Tree>>,
     camera: Single<(&Camera, &GlobalTransform), With<Camera>>,
-    window: Single<&Window>
+    window: Single<&Window>,
 ) {
     if *state.get() == DebuggingState::On {
         if let Ok(mut t) = query.get_mut(trigger.target()) {
             let world_position = window
                 .cursor_position()
-                .and_then(|cursor| {
-                    camera.0.viewport_to_world(camera.1, cursor).ok()
-                }).map(|ray| {
+                .and_then(|cursor| camera.0.viewport_to_world(camera.1, cursor).ok())
+                .map(|ray| {
                     // Compute ray's distance to entity
-                    let distance = ray.intersect_plane(t.translation, InfinitePlane3d::new(t.up())).unwrap();
+                    let distance = ray
+                        .intersect_plane(t.translation, InfinitePlane3d::new(t.up()))
+                        .unwrap();
                     ray.get_point(distance)
                 });
             t.translation = world_position.unwrap();

src/bin/trees/mono.rs

@@ -42,9 +42,7 @@ impl Display for MonologueLine {
 
 impl From<String> for MonologueLine {
     fn from(value: String) -> Self {
-        MonologueLine {
-            value
-        }
+        MonologueLine { value }
     }
 }
 
@@ -57,7 +55,7 @@ impl Into<String> for MonologueLine {
 impl From<&str> for MonologueLine {
     fn from(value: &str) -> Self {
         MonologueLine {
-            value: value.into()
+            value: value.into(),
         }
     }
 }
@@ -102,7 +100,7 @@ impl AssetLoader for MonologueLoader {
             // Skip any empty lines or comments
             } else if line.starts_with("#") || line.is_empty() {
                 // Skip comments and blank lines
-            // everything else we read as a monologue line
+                // everything else we read as a monologue line
             } else {
                 monologue.batches.last_mut().unwrap().add_line(line.into());
             }

src/ui.rs

@@ -1,5 +1,13 @@
 use super::*;
 
+pub(crate) struct BaseUiPlugin;
+
+impl Plugin for BaseUiPlugin {
+    fn build(&self, app: &mut App) {
+        // Nope!
+    }
+}
+
 /// Marker component for handling Resource -> Ui Sync
 #[derive(Component, Default, Debug)]
 pub struct SyncResource<R: Resource + Default + Display>(R);