Review: a headless test of the font menu's highlight across a list rebuild (#1116)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/font_menu.rs

@@ -747,7 +747,7 @@ pub(crate) fn sample_text(app: &VectorcraftApp) -> Option<String> {
 }
 
 #[cfg(test)]
-mod highlight_rebuild_tests {
+mod tests {
     use super::{Row, remap_highlight};
 
     fn family(name: &str) -> Row {

crates/ui-egui/src/tests_font_menu.rs

@@ -224,6 +224,57 @@ fn right_arrow_lists_a_familys_styles_and_they_preview() {
     assert_eq!(picked, Some(FontPick::Chosen("Source Sans 3".into(), Some(styles[1].clone()))));
 }
 
+/// #1116: styles listed above the highlight (a click on another family's triangle) leave it on its
+/// family; it doesn't land on one of those styles and preview it.
+#[test]
+fn styles_listed_above_the_highlight_leave_it_on_its_family() {
+    let ctx = egui::Context::default();
+    crate::theme::install_fonts(&ctx);
+    let frame = |events: Vec<egui::Event>| {
+        let input =
+            egui::RawInput { events, screen_rect: Some(egui::Rect::from_min_size(egui::Pos2::ZERO, egui::vec2(600.0, 800.0))), ..Default::default() };
+        let (mut at, mut picked) = (egui::Pos2::ZERO, None);
+        let mut out = ctx.run_ui(input, |ui| {
+            at = ui.next_widget_position();
+            picked = font_menu(ui, "test-rebuild", "Source Sans 3", 260.0, None, MenuLook::default());
+        });
+        out.textures_delta.clear();
+        // The family's row: the lowest text naming it (the menu's button above names it too).
+        let row = out
+            .shapes
+            .iter()
+            .filter_map(|s| match &s.shape {
+                egui::Shape::Text(t) if t.galley.text() == "Source Sans 3" => Some(t.pos + egui::vec2(0.0, t.galley.size().y * 0.5)),
+                _ => None,
+            })
+            .max_by(|a, b| a.y.total_cmp(&b.y));
+        (at, picked, row)
+    };
+    let (at, ..) = frame(vec![]);
+    let click = at + egui::vec2(40.0, 10.0);
+    let button = |pos, pressed| egui::Event::PointerButton { pos, button: egui::PointerButton::Primary, pressed, modifiers: Default::default() };
+    frame(vec![egui::Event::PointerMoved(click), button(click, true)]);
+    frame(vec![button(click, false)]);
+    let mut row = None;
+    for _ in 0..5 {
+        row = frame(vec![]).2;
+    }
+    // The family's disclosure triangle, left of its name: hovered, it highlights the family.
+    let triangle = row.expect("the family is listed") - egui::vec2(7.0, 0.0);
+    frame(vec![egui::Event::PointerMoved(triangle)]);
+    let (_, picked, _) = frame(key(egui::Key::ArrowDown));
+    let Some(FontPick::Preview(next, None)) = picked else { panic!("↓ previews the next family: {picked:?}") };
+    // A click on the triangle, the pointer still: the styles are listed between the two families.
+    frame(vec![button(triangle, true)]);
+    frame(vec![button(triangle, false)]);
+    for _ in 0..3 {
+        let (_, picked, _) = frame(vec![]);
+        assert_eq!(picked, None, "{next} stays highlighted and previewed");
+    }
+    let (_, picked, _) = frame(key(egui::Key::Enter));
+    assert_eq!(picked, Some(FontPick::Chosen(next, None)));
+}
+
 #[test]
 fn stars_mark_favourites_and_the_preferences_size_the_rows() {
     let mut app = VectorcraftApp::new(Session::new(), crate::Services::default());