Fix #6419: Edit › Assign Profile… and Color Settings… scroll to the Color Settings

Both commands show the Separations Preview panel (#4542), whose Color Settings
section, with the Assign row, comes after the plates and Proof Setup. A
floated panel fits its content only up to 320 points, so the section opened
out of sight and the panel looked like the wrong one. The commands now leave a
one-shot flag that scrolls the section into view, without animation, the next
time the panel draws. Window › Separations Preview and edits made in the panel
leave the scroll alone.

crates/ui-egui/src/menus/run.rs

@@ -206,9 +206,13 @@ fn run_ui_part2(app: &mut VectorcraftApp, id: &str, p: &Value) -> Option<Result<
         }
         // Edit → Color Settings… / Assign Profile… (no params): show the colour-management panel
         // wherever it is, as Window › Separations Preview does (it isn't in an icon column, so a
-        // flyout for it never opened: #4542).
+        // flyout for it never opened: #4542), scrolled to its Color Settings section, which a short
+        // window shows only after scrolling past the plates and Proof Setup (#6419).
         "edit.colorSettings" | "edit.assignProfile" if p.as_object().is_none_or(|o| o.is_empty()) => {
-            crate::panel_docking::reveal_panel(app, "separations").and_then(|_| app.session.execute(id, p).map_err(|e| e.to_string()))
+            crate::panel_docking::reveal_panel(app, "separations").and_then(|_| {
+                app.ui.color_settings_scroll = true;
+                app.session.execute(id, p).map_err(|e| e.to_string())
+            })
         }
         // Outline or Preview is a setting of the active document's view.
         "view.outline" => match app.view_mut() {

crates/ui-egui/src/panels/separations.rs

@@ -84,6 +84,21 @@ fn profile_dropdown(ui: &mut Ui, id: &str, current: &str, kind: ProfileKind, ext
 }
 
 fn settings_section(app: &mut VectorcraftApp, ui: &mut Ui) {
+    let top = ui.cursor().top();
+    settings_rows(app, ui);
+    // Edit › Color Settings… / Assign Profile… opened the panel for this section: scroll it into
+    // view once, as the plates and Proof Setup above it fill a short window (#6419). At once, not
+    // animated: the panel has just opened. egui moves the scroll area on a later frame, so ask for
+    // one rather than wait for the pointer to move.
+    if app.ui.color_settings_scroll && !ui.is_sizing_pass() {
+        let rect = egui::Rect::from_x_y_ranges(ui.max_rect().x_range(), top..=ui.min_rect().bottom().max(top));
+        ui.scroll_to_rect_animation(rect, Some(egui::Align::TOP), egui::style::ScrollAnimation::none());
+        ui.ctx().request_repaint();
+        app.ui.color_settings_scroll = false;
+    }
+}
+
+fn settings_rows(app: &mut VectorcraftApp, ui: &mut Ui) {
     let st = cms::active_settings();
     widgets::section_header(ui, tl!("Color Settings"));
     ui.horizontal(|ui| {
@@ -215,4 +230,55 @@ mod tests {
         assert!(panel.iter().any(|(id, _)| id == "tritanopia"));
         assert!(panel.iter().all(|(id, _)| cms::ProofTarget::parse(id).is_some_and(|t| t.id() == *id)));
     }
+
+    /// #6419: Edit › Assign Profile… and Color Settings… show the panel scrolled to its Color
+    /// Settings section, which a window shorter than the panel (a floated panel stops at 320
+    /// points) otherwise shows only after scrolling past the plates and Proof Setup. Once: a
+    /// scroll away afterwards stays.
+    #[test]
+    fn color_settings_and_assign_profile_scroll_the_color_settings_into_view() {
+        const VIEW: f32 = 120.0;
+        fn find(s: &egui::Shape, text: &str) -> Option<f32> {
+            match s {
+                egui::Shape::Text(t) if t.galley.text() == text => Some(t.pos.y),
+                egui::Shape::Vec(v) => v.iter().find_map(|s| find(s, text)),
+                _ => None,
+            }
+        }
+        // One frame of the panel in a scroll area VIEW points high, scrolled to `offset` when
+        // given: where the section's Black Point Compensation box shows in the view.
+        fn frame(ctx: &egui::Context, app: &mut VectorcraftApp, offset: Option<f32>) -> f32 {
+            let mut top = 0.0;
+            let mut out = ctx.run_ui(egui::RawInput::default(), |ui| {
+                top = ui.cursor().top();
+                let mut area = egui::ScrollArea::vertical().id_salt("separations").max_height(VIEW);
+                if let Some(y) = offset {
+                    area = area.vertical_scroll_offset(y);
+                }
+                area.show(ui, |ui| show(app, ui));
+            });
+            out.textures_delta.clear();
+            out.shapes.iter().find_map(|c| find(&c.shape, "Use Black Point Compensation")).unwrap() - top
+        }
+        let visible = |y: f32| (0.0..VIEW).contains(&y);
+        for id in ["edit.assignProfile", "edit.colorSettings"] {
+            let mut app = VectorcraftApp::new(Session::new(), Default::default());
+            app.run("file.new", json!({})).unwrap();
+            let ctx = egui::Context::default();
+            let before = frame(&ctx, &mut app, None);
+            assert!(!visible(before), "the section starts below the view: {before}");
+            app.run(id, json!({})).unwrap();
+            frame(&ctx, &mut app, None);
+            assert!(!app.ui.color_settings_scroll);
+            // egui moves a scroll area on the frame after the request and paints it moved on the
+            // one after that; both ask for a repaint.
+            assert!(ctx.has_requested_repaint());
+            frame(&ctx, &mut app, None);
+            assert!(ctx.has_requested_repaint());
+            let shown = frame(&ctx, &mut app, None);
+            assert!(visible(shown), "{id} scrolls the section into the view: {shown}");
+            frame(&ctx, &mut app, Some(0.0));
+            assert_eq!(frame(&ctx, &mut app, None), before, "scrolled back to the top, it stays there");
+        }
+    }
 }

crates/ui-egui/src/state.rs

@@ -392,6 +392,11 @@ pub struct UiState {
     /// That popup's first text field is still to take the keyboard.
     #[serde(skip)]
     pub transient_focus: bool,
+    /// The Separations Preview panel is still to scroll its Color Settings section into view:
+    /// Edit › Color Settings… and Assign Profile… show the panel for it, and the section sits below
+    /// the plates and Proof Setup, out of sight in a short window (#6419).
+    #[serde(skip)]
+    pub color_settings_scroll: bool,
     /// Type › Find Font…'s last Find In choice (`find_font::FIND_IN`), kept while the app runs.
     #[serde(skip)]
     pub find_font_in: String,
@@ -1009,6 +1014,7 @@ impl Default for UiState {
             open_panel: None,
             transient_panel: None,
             transient_focus: false,
+            color_settings_scroll: false,
             find_font_in: String::new(),
             control_bar: false,
             control_bar_bottom: false,