fix(engine): extend touch scroll to achievements and stats panels via generic helper

Extracts touch_scroll_panel<M: Component> into ui_modal.rs and wires it
to SettingsPanelScrollable, AchievementsScrollable, and StatsScrollable
so all three panels respond to finger swipe on Android.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_engine/src/achievement_plugin.rs

@@ -116,6 +116,7 @@ impl Plugin for AchievementPlugin {
             // achievements-scroll system also runs cleanly under
             // `MinimalPlugins` in tests.
             .add_message::<MouseWheel>()
+            .add_message::<bevy::input::touch::TouchInput>()
             // Run after GameMutation (so GameWonEvent is available), after
             // StatsUpdate (so stats reflect this win), and after ProgressUpdate
             // (so daily_challenge_streak is up to date for daily_devotee).
@@ -139,6 +140,7 @@ impl Plugin for AchievementPlugin {
             .add_systems(Update, toggle_achievements_screen)
             .add_systems(Update, handle_achievements_close_button)
             .add_systems(Update, scroll_achievements_panel)
+            .add_systems(Update, crate::ui_modal::touch_scroll_panel::<AchievementsScrollable>)
             // Event-driven unlock: observe `ReplayPlaybackState` and unlock
             // `cinephile` the first time playback runs to natural completion.
             // Reads the resource via `Option<Res<_>>` so headless tests that

solitaire_engine/src/settings_plugin.rs

@@ -12,7 +12,6 @@
 use std::path::PathBuf;
 
 use bevy::input::mouse::{MouseScrollUnit, MouseWheel};
-use bevy::input::touch::{TouchInput, TouchPhase};
 use bevy::prelude::*;
 use bevy::ui::{ComputedNode, UiGlobalTransform};
 use bevy::window::{WindowMoved, WindowResized};
@@ -371,7 +370,7 @@ impl Plugin for SettingsPlugin {
                     handle_volume_keys,
                     toggle_settings_screen,
                     scroll_settings_panel,
-                    touch_scroll_settings_panel,
+                    crate::ui_modal::touch_scroll_panel::<SettingsPanelScrollable>,
                     record_window_geometry_changes,
                     persist_window_geometry_after_debounce,
                 ),
@@ -1370,43 +1369,6 @@ fn scroll_settings_panel(
     }
 }
 
-/// Scrolls the settings panel in response to touch pan gestures (Android).
-/// Tracks the most recent touch Y so each `Moved` event's delta can be
-/// applied to `ScrollPosition`. `MouseWheel` handles desktop; this system
-/// fills the gap for single-finger swipe on touchscreen devices.
-fn touch_scroll_settings_panel(
-    mut touch_evr: MessageReader<TouchInput>,
-    screen: Res<SettingsScreen>,
-    mut scrollables: Query<&mut ScrollPosition, With<SettingsPanelScrollable>>,
-    mut last_y: Local<Option<f32>>,
-) {
-    if !screen.0 {
-        touch_evr.clear();
-        *last_y = None;
-        return;
-    }
-    for event in touch_evr.read() {
-        match event.phase {
-            TouchPhase::Started => {
-                *last_y = Some(event.position.y);
-            }
-            TouchPhase::Moved => {
-                if let Some(prev) = *last_y {
-                    let delta = event.position.y - prev;
-                    for mut sp in scrollables.iter_mut() {
-                        // Swiping up (delta < 0) scrolls content down (sp.y increases).
-                        sp.0.y = (sp.0.y - delta).max(0.0);
-                    }
-                }
-                *last_y = Some(event.position.y);
-            }
-            TouchPhase::Ended | TouchPhase::Canceled => {
-                *last_y = None;
-            }
-        }
-    }
-}
-
 // ---------------------------------------------------------------------------
 // Window geometry persistence
 // ---------------------------------------------------------------------------

solitaire_engine/src/stats_plugin.rs

@@ -203,6 +203,7 @@ impl Plugin for StatsPlugin {
             // `DefaultPlugins`; register it explicitly so the stats-scroll
             // system also runs cleanly under `MinimalPlugins` in tests.
             .add_message::<MouseWheel>()
+            .add_message::<bevy::input::touch::TouchInput>()
             // record_abandoned must read `move_count` BEFORE handle_new_game
             // clobbers it with a fresh game. These are NOT in StatsUpdate because
             // StatsUpdate (as a set) is ordered after GameMutation by external
@@ -238,7 +239,8 @@ impl Plugin for StatsPlugin {
                 )
                     .chain(),
             )
-            .add_systems(Update, scroll_stats_panel);
+            .add_systems(Update, scroll_stats_panel)
+            .add_systems(Update, crate::ui_modal::touch_scroll_panel::<StatsScrollable>);
     }
 }
 

solitaire_engine/src/ui_modal.rs

@@ -48,6 +48,7 @@
 //! );
 //! ```
 
+use bevy::input::touch::{TouchInput, TouchPhase};
 use bevy::prelude::*;
 use bevy::ui::{ComputedNode, UiGlobalTransform};
 use bevy::window::PrimaryWindow;
@@ -390,6 +391,47 @@ pub fn spawn_modal_button<M: Component>(
         });
 }
 
+// ---------------------------------------------------------------------------
+// Generic touch-scroll helper
+// ---------------------------------------------------------------------------
+
+/// Scrolls any `Overflow::scroll_y()` panel marked with `M` via single-finger
+/// touch pan. Add this as a system for each scrollable modal panel:
+///
+/// ```ignore
+/// app.add_message::<TouchInput>()
+///    .add_systems(Update, touch_scroll_panel::<MyScrollable>);
+/// ```
+///
+/// On desktop `TouchInput` events never fire, so the system is a no-op.
+pub fn touch_scroll_panel<M: Component>(
+    mut touch_evr: MessageReader<TouchInput>,
+    mut scrollables: Query<&mut ScrollPosition, With<M>>,
+    mut last_y: Local<Option<f32>>,
+) {
+    for event in touch_evr.read() {
+        match event.phase {
+            TouchPhase::Started => {
+                *last_y = Some(event.position.y);
+            }
+            TouchPhase::Moved => {
+                if let Some(prev) = *last_y {
+                    let delta = event.position.y - prev;
+                    for mut sp in scrollables.iter_mut() {
+                        // Swiping up (delta < 0 in screen coords) scrolls
+                        // content down, so sp.y increases.
+                        sp.0.y = (sp.0.y - delta).max(0.0);
+                    }
+                }
+                *last_y = Some(event.position.y);
+            }
+            TouchPhase::Ended | TouchPhase::Canceled => {
+                *last_y = None;
+            }
+        }
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Helpers + paint system
 // ---------------------------------------------------------------------------