From 50823c3c397d4d6543e0b8bfa4aeb79bf301f615 Mon Sep 17 00:00:00 2001
From: Piotr Siuszko <siuszko@zoho.com>
Date: Wed, 28 Feb 2024 21:47:13 +0100
Subject: [PATCH] Rename components, move scroll offset update to separate
 method

---
 examples/simple.rs |  4 ++--
 src/lib.rs         | 48 +++++++++++++++++++++++++++-------------------
 2 files changed, 30 insertions(+), 22 deletions(-)

diff --git a/examples/simple.rs b/examples/simple.rs
index 232c290..efa8128 100644
--- a/examples/simple.rs
+++ b/examples/simple.rs
@@ -42,12 +42,12 @@ fn prepare(mut commands: Commands) {
                     background_color: BackgroundColor(Color::YELLOW),
                     ..default()
                 },
-                ScrollViewport::default(),
+                ScrollView::default(),
             ));
         });
 }
 
-fn add_content(mut commands: Commands, q: Query<Entity, Added<ScrollViewContent>>) {
+fn add_content(mut commands: Commands, q: Query<Entity, Added<ScrollableContent>>) {
     for e in q.iter() {
         commands.entity(e).with_children(|parent| {
             for _ in 0..10 {
diff --git a/src/lib.rs b/src/lib.rs
index 59791e9..10a7e15 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -8,21 +8,27 @@ pub struct ScrollViewPlugin;
 
 impl Plugin for ScrollViewPlugin {
     fn build(&self, app: &mut App) {
-        app.register_type::<ScrollViewport>()
-            .register_type::<ScrollViewContent>()
+        app.register_type::<ScrollView>()
+            .register_type::<ScrollableContent>()
             .add_systems(
                 Update,
-                (create_scroll_view, input_mouse_pressed_move, scroll_events),
+                (
+                    create_scroll_view,
+                    input_mouse_pressed_move,
+                    scroll_events,
+                    scroll_update,
+                )
+                    .chain(),
             );
     }
 }
 
 #[derive(Component, Debug, Reflect)]
-pub struct ScrollViewport {
+pub struct ScrollView {
     pub scroll_speed: f32,
 }
 
-impl Default for ScrollViewport {
+impl Default for ScrollView {
     fn default() -> Self {
         Self {
             scroll_speed: 500.0,
@@ -31,13 +37,13 @@ impl Default for ScrollViewport {
 }
 
 #[derive(Component, Debug, Reflect)]
-pub struct ScrollViewContent {
+pub struct ScrollableContent {
     pub pos_y: f32,
 }
 
 pub fn create_scroll_view(
     mut commands: Commands,
-    mut q: Query<(Entity, &mut Style), Added<ScrollViewport>>,
+    mut q: Query<(Entity, &mut Style), Added<ScrollView>>,
 ) {
     for (e, mut style) in q.iter_mut() {
         style.overflow = Overflow::clip();
@@ -55,7 +61,7 @@ pub fn create_scroll_view(
                         },
                         ..default()
                     },
-                    ScrollViewContent { pos_y: 0.0 },
+                    ScrollableContent { pos_y: 0.0 },
                 ));
             });
     }
@@ -63,8 +69,8 @@ pub fn create_scroll_view(
 
 fn input_mouse_pressed_move(
     mut motion_evr: EventReader<MouseMotion>,
-    mut q: Query<(&Children, &Interaction, &Node), With<ScrollViewport>>,
-    mut content_q: Query<(&mut Style, &mut ScrollViewContent, &Node)>,
+    mut q: Query<(&Children, &Interaction, &Node), With<ScrollView>>,
+    mut content_q: Query<(&mut ScrollableContent, &Node)>,
 ) {
     for evt in motion_evr.read() {
         for (children, &interaction, node) in q.iter_mut() {
@@ -74,23 +80,27 @@ fn input_mouse_pressed_move(
             let container_height = node.size().y;
             for &child in children.iter() {
                 if let Ok(item) = content_q.get_mut(child) {
-                    let mut style = item.0;
-                    let mut scroll = item.1;
-                    let max_scroll = (item.2.size().y - container_height).max(0.0);
+                    let mut scroll = item.0;
+                    let max_scroll = (item.1.size().y - container_height).max(0.0);
                     scroll.pos_y += evt.delta.y;
                     scroll.pos_y = scroll.pos_y.clamp(-max_scroll, 0.);
-                    style.top = Val::Px(scroll.pos_y);
                 }
             }
         }
     }
 }
 
+fn scroll_update(mut q: Query<(&ScrollableContent, &mut Style), Changed<ScrollableContent>>) {
+    for (scroll, mut style) in q.iter_mut() {
+        style.top = Val::Px(scroll.pos_y);
+    }
+}
+
 fn scroll_events(
     mut scroll_evr: EventReader<MouseWheel>,
-    mut q: Query<(&Children, &Interaction, &ScrollViewport, &Node), With<ScrollViewport>>,
+    mut q: Query<(&Children, &Interaction, &ScrollView, &Node), With<ScrollView>>,
     time: Res<Time>,
-    mut content_q: Query<(&mut Style, &mut ScrollViewContent, &Node)>,
+    mut content_q: Query<(&mut ScrollableContent, &Node)>,
 ) {
     use bevy::input::mouse::MouseScrollUnit;
     for ev in scroll_evr.read() {
@@ -109,12 +119,10 @@ fn scroll_events(
             for &child in children.iter() {
                 if let Ok(item) = content_q.get_mut(child) {
                     let y = y * time.delta().as_secs_f32() * scroll_view.scroll_speed;
-                    let mut style = item.0;
-                    let mut scroll = item.1;
-                    let max_scroll = (item.2.size().y - container_height).max(0.0);
+                    let mut scroll = item.0;
+                    let max_scroll = (item.1.size().y - container_height).max(0.0);
                     scroll.pos_y += y;
                     scroll.pos_y = scroll.pos_y.clamp(-max_scroll, 0.);
-                    style.top = Val::Px(scroll.pos_y);
                 }
             }
         }