From fb725ce33fa92764861d93c42937479339a9c90c Mon Sep 17 00:00:00 2001
From: Vikram Bhaskaran <vikram.bhaskaran@outlook.com>
Date: Tue, 13 Oct 2026 01:23:51 +1100
Subject: [PATCH] Scroll the filmstrip when the same photo is shown from
 another source.

---
 crates/ui-egui/src/panels/detail.rs |  2 +-
 crates/ui-egui/src/panels/grid.rs   | 32 ++++++++++++++++++++++++-----
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/crates/ui-egui/src/panels/detail.rs b/crates/ui-egui/src/panels/detail.rs
index 23447616..53f8df73 100644
--- a/crates/ui-egui/src/panels/detail.rs
+++ b/crates/ui-egui/src/panels/detail.rs
@@ -2145,7 +2145,7 @@ pub(crate) fn filmstrip(app: &mut LightcraftApp, ui: &mut egui::Ui, r: Rect) {
     // a vertical mouse wheel scrolls the strip sideways (horizontal trackpad scrolls still work)
     child.style_mut().always_scroll_the_only_direction = true;
     // only a new active photo (or the strip appearing) scrolls it; see `grid::follow_active`
-    let follow = super::grid::follow_active(child.ctx(), egui::Id::new("film-follow-active"), active);
+    let follow = super::grid::follow_active(child.ctx(), egui::Id::new("film-follow-active"), active, app.session.source);
     egui::ScrollArea::horizontal().id_salt("filmstrip").auto_shrink([false, false]).show_viewport(&mut child, |ui, vp| {
         let (area, _) = ui.allocate_exact_size(vec2(ids.len() as f32 * cell_w, r.height() - 16.0), Sense::hover());
         app.film_scroll = Some(vp.left());
diff --git a/crates/ui-egui/src/panels/grid.rs b/crates/ui-egui/src/panels/grid.rs
index 7b6d5cf6..2d620725 100644
--- a/crates/ui-egui/src/panels/grid.rs
+++ b/crates/ui-egui/src/panels/grid.rs
@@ -229,7 +229,7 @@ fn show_inner(app: &mut LightcraftApp, ui: &mut egui::Ui) {
     let active = app.session.selection.active;
     // bring the active photo into view when it changes (keyboard, click, command) or the grid
     // comes back on screen; otherwise the scroll position is the user's
-    let scroll_to: Option<Rect> = if follow_active(ui.ctx(), egui::Id::new("grid-follow-active"), active) {
+    let scroll_to: Option<Rect> = if follow_active(ui.ctx(), egui::Id::new("grid-follow-active"), active, app.session.source) {
         active.and_then(|a| ids.iter().position(|x| *x == a)).and_then(|i| lay.cells.get(i).copied())
     } else {
         None
@@ -295,16 +295,29 @@ fn show_inner(app: &mut LightcraftApp, ui: &mut egui::Ui) {
 /// the strip was not drawn on the previous pass (view switch, panel shown again). Otherwise the
 /// scroll position is the user's: time passing, finished renders, edits to the photo or a released
 /// scroll bar never move it (issue #11).
-pub(crate) fn follow_active(ctx: &egui::Context, key: egui::Id, active: Option<PhotoId>) -> bool {
+pub(crate) fn follow_active(ctx: &egui::Context, key: egui::Id, active: Option<PhotoId>, source: lightcraft_engine::LibrarySource) -> bool {
     let pass = ctx.cumulative_pass_nr();
-    let last: Option<(Option<PhotoId>, u64)> = ctx.data(|d| d.get_temp(key));
-    ctx.data_mut(|d| d.insert_temp(key, (active, pass)));
+    let last: Option<(Option<PhotoId>, lightcraft_engine::LibrarySource, u64)> = ctx.data(|d| d.get_temp(key));
+    ctx.data_mut(|d| d.insert_temp(key, (active, source, pass)));
     match last {
-        Some((was, drawn)) => was != active || drawn + 1 < pass,
+        Some((was, where_, drawn)) => follow_changed(was, where_, drawn, active, source, pass),
         None => true,
     }
 }
 
+/// Scroll when the active photo changes, the strip was not drawn last pass, or the same photo
+/// sits in a different library source (another album) (#1142).
+pub(crate) fn follow_changed(
+    was: Option<PhotoId>,
+    where_was: lightcraft_engine::LibrarySource,
+    drawn: u64,
+    active: Option<PhotoId>,
+    source: lightcraft_engine::LibrarySource,
+    pass: u64,
+) -> bool {
+    was != active || where_was != source || drawn + 1 < pass
+}
+
 /// Height of a date header row (points).
 pub const HEADER_H: f32 = 40.0;
 
@@ -1146,6 +1159,15 @@ pub fn context_menu(app: &mut LightcraftApp, ui: &mut egui::Ui, id: PhotoId) {
 mod tests {
     use super::*;
 
+    #[test]
+    fn the_same_photo_in_another_source_scrolls_into_view() {
+        let id = PhotoId(3);
+        let all = lightcraft_engine::LibrarySource::All;
+        let album = lightcraft_engine::LibrarySource::Album(lightcraft_catalog::AlbumId(9));
+        assert!(!follow_changed(Some(id), all, 4, Some(id), all, 5));
+        assert!(follow_changed(Some(id), all, 4, Some(id), album, 5));
+    }
+
     #[test]
     fn ungrouped_justified_rows_fill_the_width() {
         let aspects = [1.5f32, 1.5, 0.66, 1.0, 1.5, 1.5, 1.5];