Preserve rename preview scroll through full details

crates/oa-desktop/src/app/source_rename.rs

@@ -49,6 +49,7 @@ pub enum Event {
     Line(Id, Id, bool),
     Segment(Id, Id, bool),
     Details(Id, bool),
+    PreviewScrolled(Id, Id, Id, f32),
     DetailSegment(Id, bool),
     ReadOnly(Id, text_editor::Action),
     Undo(Id),
@@ -112,6 +113,7 @@ struct Form {
     line: usize,
     segment: usize,
     preview_destination: Id,
+    preview_offset: f32,
     details: bool,
     detail_segment: usize,
     detail_editor: text_editor::Content,
@@ -170,6 +172,17 @@ impl App {
             return false;
         };
         match event {
+            Event::PreviewScrolled(invocation, approval, destination, offset) => {
+                *invocation == form.invocation
+                    && !form.details
+                    && form
+                        .approval
+                        .as_ref()
+                        .is_some_and(|ready| ready.id == *approval)
+                    && *destination == form.preview_destination
+                    && offset.is_finite()
+                    && *offset >= 0.
+            }
             Event::Preview(invocation, generation) => {
                 *invocation == form.invocation && *generation == form.generation
             }
@@ -435,11 +448,23 @@ impl App {
                 }
                 form.details = value;
                 // Leaving or returning to the preview ends the old visit. Keep
-                // its selected page and retained scroll; only retire delayed
-                // operations, without scheduling another return-to-top.
+                // its selected page and scroll; the Details widget replaces the
+                // preview subtree, so restore the reported offset on return.
                 form.preview_destination = Id::new_v4();
                 form.detail_segment = 0;
                 refresh_details(form);
+                if !value && let Some(ready) = &form.approval {
+                    return iced::widget::operation::scroll_to(
+                        preview_scroll_id(form, ready.id),
+                        iced::widget::scrollable::AbsoluteOffset {
+                            x: None,
+                            y: Some(form.preview_offset),
+                        },
+                    );
+                }
+            }
+            Event::PreviewScrolled(_, _, _, offset) => {
+                self.source_rename.form.as_mut().unwrap().preview_offset = offset;
             }
             Event::DetailSegment(_, next) => {
                 let form = self.source_rename.form.as_mut().unwrap();
@@ -516,6 +541,7 @@ impl App {
             line: 0,
             segment: 0,
             preview_destination: Id::new_v4(),
+            preview_offset: 0.,
             details: false,
             detail_segment: 0,
             detail_editor: text_editor::Content::new(),
@@ -953,6 +979,7 @@ fn input_id(invocation: Id) -> iced::widget::Id {
 // or changing a filter that leaves the page tuple unchanged (the ABA case).
 fn reset_preview_position(form: &mut Form) -> Task<Message> {
     form.preview_destination = Id::new_v4();
+    form.preview_offset = 0.;
     if !form.details
         && let Some(ready) = &form.approval
     {
@@ -1118,7 +1145,15 @@ where
             pager(format!("Row segments {}/{} · both sides", form.segment + 1, segments.max(1)),
                 (form.segment > 0).then(|| message(Event::Segment(invocation, preview_id, false))),
                 (form.segment + 1 < segments).then(|| message(Event::Segment(invocation, preview_id, true)))),
-            scrollable(displayed).id(preview_scroll_id(form, preview_id)).height(Fill).width(Fill).spacing(8),
+            scrollable(displayed)
+                .id(preview_scroll_id(form, preview_id))
+                .on_scroll({
+                    let destination = form.preview_destination;
+                    move |viewport| message(Event::PreviewScrolled(
+                        invocation, preview_id, destination, viewport.absolute_offset().y,
+                    ))
+                })
+                .height(Fill).width(Fill).spacing(8),
         ].spacing(6).height(Fill).into()
     } else {
         scrollable(column![