From 1d4910a1e3280ea4cc175c2ec2b4a8a6108a4d74 Mon Sep 17 00:00:00 2001
From: Rob Parrett <robparrett@gmail.com>
Date: Tue, 14 Mar 2023 23:50:37 -0700
Subject: [PATCH] Fix scrolling in UI example (#8069)

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
---
 examples/ui/ui.rs | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/examples/ui/ui.rs b/examples/ui/ui.rs
index 827a75aa198ae..647299048e13a 100644
--- a/examples/ui/ui.rs
+++ b/examples/ui/ui.rs
@@ -124,7 +124,6 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
                                     NodeBundle {
                                         style: Style {
                                             flex_direction: FlexDirection::Column,
-                                            flex_grow: 1.0,
                                             align_items: AlignItems::Center,
                                             ..default()
                                         },
@@ -145,12 +144,7 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
                                                     font_size: 20.,
                                                     color: Color::WHITE,
                                                 },
-                                            )
-                                            .with_style(Style {
-                                                flex_shrink: 0.,
-                                                size: Size::height(Val::Px(20.)),
-                                                ..default()
-                                            }),
+                                            ),
                                             Label,
                                             AccessibilityNode(NodeBuilder::new(Role::ListItem)),
                                         ));
@@ -291,21 +285,21 @@ struct ScrollingList {
 
 fn mouse_scroll(
     mut mouse_wheel_events: EventReader<MouseWheel>,
-    mut query_list: Query<(&mut ScrollingList, &mut Style, &Children, &Node)>,
-    query_item: Query<&Node>,
+    mut query_list: Query<(&mut ScrollingList, &mut Style, &Parent, &Node)>,
+    query_node: Query<&Node>,
 ) {
     for mouse_wheel_event in mouse_wheel_events.iter() {
-        for (mut scrolling_list, mut style, children, uinode) in &mut query_list {
-            let items_height: f32 = children
-                .iter()
-                .map(|entity| query_item.get(*entity).unwrap().size().y)
-                .sum();
-            let panel_height = uinode.size().y;
-            let max_scroll = (items_height - panel_height).max(0.);
+        for (mut scrolling_list, mut style, parent, list_node) in &mut query_list {
+            let items_height = list_node.size().y;
+            let container_height = query_node.get(parent.get()).unwrap().size().y;
+
+            let max_scroll = (items_height - container_height).max(0.);
+
             let dy = match mouse_wheel_event.unit {
                 MouseScrollUnit::Line => mouse_wheel_event.y * 20.,
                 MouseScrollUnit::Pixel => mouse_wheel_event.y,
             };
+
             scrolling_list.position += dy;
             scrolling_list.position = scrolling_list.position.clamp(-max_scroll, 0.);
             style.top = Val::Px(scrolling_list.position);