Update scrollbar while scrolling

src/simulation/sprite_pack.rs

@@ -348,7 +348,7 @@ impl SkinSet {
         // Make a reasonable attempt to prevent duplicates
         const MAX_ATTEMPTS: usize = 64;
         for _ in 0..MAX_ATTEMPTS {
-            let skin = self.sprite_pack.random(&atlas_list, &mut rng);
+            let skin = self.sprite_pack.random(atlas_list, &mut rng);
             if !self.skins.contains(&skin) {
                 self.skins.push(skin);
                 return true;

src/state/editor_screen/outline_panel.rs

@@ -123,38 +123,43 @@ pub fn spawn_outline_panel(commands: &mut Commands, theme: &EditorScreenTheme) -
         .set_parent(hbox)
         .id();
 
-    commands
+    let scrollbar = commands
         .spawn((
-            Name::new("OutlineContainer"),
+            Name::new("OutlineScrollbar"),
             NodeBundle {
                 style: Style {
-                    width: Percent(100.0),
-                    flex_direction: FlexDirection::Column,
+                    width: Px(8.0),
+                    height: Percent(100.0),
+                    justify_self: JustifySelf::End,
                     ..default()
                 },
+                // TODO
+                background_color: theme.info_bar_background_color.into(),
                 ..default()
             },
-            ScrollContent::with_sensitivity(2.0),
-            IsOutlineContainer,
         ))
-        .set_parent(scroll_view);
+        .set_parent(hbox)
+        .id();
 
     commands
         .spawn((
-            Name::new("OutlineScrollbar"),
+            Name::new("OutlineContainer"),
             NodeBundle {
                 style: Style {
-                    width: Px(8.0),
-                    height: Percent(100.0),
-                    justify_self: JustifySelf::End,
+                    width: Percent(100.0),
+                    flex_direction: FlexDirection::Column,
                     ..default()
                 },
-                // TODO
-                background_color: theme.info_bar_background_color.into(),
                 ..default()
             },
+            ScrollContent {
+                position: 0.0,
+                sensitivity: 1.5,
+                scrollbar,
+            },
+            IsOutlineContainer,
         ))
-        .set_parent(hbox);
+        .set_parent(scroll_view);
 
     outline_panel
 }

src/ui/scroll.rs

@@ -13,24 +13,17 @@ impl Plugin for ScrollPlugin {
     }
 }
 
-#[derive(Component, Reflect, Default)]
+#[derive(Component, Reflect)]
 pub struct ScrollContent {
-    position: f32,
-    sensitivity: f32,
-}
-
-impl ScrollContent {
-    pub fn with_sensitivity(sensitivity: f32) -> Self {
-        Self {
-            sensitivity,
-            ..default()
-        }
-    }
+    pub position: f32,
+    pub sensitivity: f32,
+    pub scrollbar: Entity,
 }
 
 fn mouse_scroll(
     mut events: EventReader<MouseWheel>,
     mut scroll_query: Query<(&mut ScrollContent, &mut Style, &Parent, &Node)>,
+    mut scrollbar_query: Query<&mut Style, Without<ScrollContent>>,
     node_query: Query<&Node>,
 ) {
     let pixels = events
@@ -49,9 +42,20 @@ fn mouse_scroll(
 
         let height = node.size().y;
         let parent_height = node_query.get(parent.get()).unwrap().size().y;
-        let max_scroll = (height - parent_height).max(0.0);
-        scroll.position = scroll.position.clamp(-max_scroll, 0.0);
+        if parent_height <= 0.0 {
+            return;
+        }
+        let overflow = (height - parent_height).max(0.0);
+        scroll.position = scroll.position.clamp(-overflow, 0.0);
 
         style.top = Val::Px(scroll.position);
+
+        // Update scrollbar
+        if let Ok(mut style) = scrollbar_query.get_mut(scroll.scrollbar) {
+            let height = (1.0 - overflow / parent_height).max(0.1);
+            let top = (-scroll.position / parent_height).max(1.0 - height);
+            style.height = Val::Percent(100.0 * height);
+            style.top = Val::Percent(100.0 * top);
+        }
     }
 }