Add a scrolling list to the ui example

bevyengine · Dec 16, 2021 · ada6fa2 · ada6fa2
1 parent 56e3500
commit ada6fa2
Showing 1 changed file with 124 additions and 8 deletions.
diff --git a/examples/ui/ui.rs b/examples/ui/ui.rs
@@ -1,10 +1,14 @@
-use bevy::prelude::*;
+use bevy::{
+    input::mouse::{MouseScrollUnit, MouseWheel},
+    prelude::*,
+};
 
 /// This example illustrates the various features of Bevy UI.
 fn main() {
     App::new()
         .add_plugins(DefaultPlugins)
         .add_startup_system(setup)
+        .add_system(mouse_scroll)
         .run();
 }
 
@@ -68,14 +72,97 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
                         });
                 });
             // right vertical fill
-            parent.spawn_bundle(NodeBundle {
-                style: Style {
-                    size: Size::new(Val::Px(200.0), Val::Percent(100.0)),
+            parent
+                .spawn_bundle(NodeBundle {
+                    style: Style {
+                        flex_direction: FlexDirection::ColumnReverse,
+                        justify_content: JustifyContent::Center,
+                        size: Size::new(Val::Px(200.0), Val::Percent(100.0)),
+                        ..Default::default()
+                    },
+                    color: Color::rgb(0.15, 0.15, 0.15).into(),
                     ..Default::default()
-                },
-                color: Color::rgb(0.15, 0.15, 0.15).into(),
-                ..Default::default()
-            });
+                })
+                .with_children(|parent| {
+                    // Title
+                    parent.spawn_bundle(TextBundle {
+                        style: Style {
+                            size: Size::new(Val::Undefined, Val::Px(25.)),
+                            margin: Rect {
+                                left: Val::Auto,
+                                right: Val::Auto,
+                                ..Default::default()
+                            },
+                            ..Default::default()
+                        },
+                        text: Text::with_section(
+                            "Scrolling list",
+                            TextStyle {
+                                font: asset_server.load("fonts/FiraSans-Bold.ttf"),
+                                font_size: 25.,
+                                color: Color::WHITE,
+                            },
+                            Default::default(),
+                        ),
+                        ..Default::default()
+                    });
+                    // List with hidden overflow
+                    parent
+                        .spawn_bundle(NodeBundle {
+                            style: Style {
+                                flex_direction: FlexDirection::ColumnReverse,
+                                align_self: AlignSelf::Center,
+                                size: Size::new(Val::Percent(100.0), Val::Percent(50.0)),
+                                overflow: Overflow::Hidden,
+                                ..Default::default()
+                            },
+                            color: Color::rgb(0.10, 0.10, 0.10).into(),
+                            ..Default::default()
+                        })
+                        .with_children(|parent| {
+                            // Moving panel
+                            parent
+                                .spawn_bundle(NodeBundle {
+                                    style: Style {
+                                        flex_direction: FlexDirection::ColumnReverse,
+                                        flex_grow: 1.0,
+                                        max_size: Size::new(Val::Undefined, Val::Undefined),
+                                        ..Default::default()
+                                    },
+                                    color: Color::NONE.into(),
+                                    ..Default::default()
+                                })
+                                .insert(ScrollingList::default())
+                                .with_children(|parent| {
+                                    // List items
+                                    for i in 0..30 {
+                                        parent.spawn_bundle(TextBundle {
+                                            style: Style {
+                                                flex_shrink: 0.,
+                                                size: Size::new(Val::Undefined, Val::Px(20.)),
+                                                margin: Rect {
+                                                    left: Val::Auto,
+                                                    right: Val::Auto,
+                                                    ..Default::default()
+                                                },
+                                                ..Default::default()
+                                            },
+                                            text: Text::with_section(
+                                                format!("Item {}", i),
+                                                TextStyle {
+                                                    font: asset_server
+                                                        .load("fonts/FiraSans-Bold.ttf"),
+                                                    font_size: 20.,
+                                                    color: Color::WHITE,
+                                                },
+                                                Default::default(),
+                                            ),
+                                            ..Default::default()
+                                        });
+                                    }
+                                });
+                        });
+                });
             // absolute positioning
             parent
                 .spawn_bundle(NodeBundle {
@@ -212,3 +299,32 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
                 });
         });
 }
+
+#[derive(Component, Default)]
+struct ScrollingList {
+    position: f32,
+}
+
+fn mouse_scroll(
+    mut mouse_wheel_events: EventReader<MouseWheel>,
+    mut query_list: Query<(&mut ScrollingList, &mut Style, &Children, &Node)>,
+    query_item: Query<&Node>,
+) {
+    for mouse_wheel_event in mouse_wheel_events.iter() {
+        for (mut scrolling_list, mut style, children, uinode) in query_list.iter_mut() {
+            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.);
+            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.position.top = Val::Px(scrolling_list.position);
+        }
+    }
+}