Integration: the edit composer stays visible while part of its comment is on screen (#4095)

Editing a large comment whose top-right corner was scrolled away opened a composer that was hidden and could not be cancelled. The card now stays, clamped into the document, while any part of the comment shows.

crates/ui-egui/src/comments.rs

@@ -1593,10 +1593,23 @@ pub(crate) fn composer(ctx: &egui::Context, view: &mut DocView, info: &DocInfo,
         ComposerKind::Edit(_) => "Edit comment",
     };
     // Its comment scrolled out of the document: keep the draft until it is back, rather than
-    // pushing the card into the window over the mode bar and toolbar (#4021).
+    // pushing the card into the window over the mode bar and toolbar (#4021). An edited comment
+    // that is only partly scrolled away keeps its card, at the nearest point inside the document.
+    let mut anchor = anchor;
     if !viewport.contains(anchor) {
-        c.focus = true;
-        return None;
+        let part_visible = matches!(c.kind, ComposerKind::Edit(index)
+        if info.annotations.iter().any(|a| a.page == page && a.index == index && {
+            let r = a.rect;
+            viewport.intersects(egui::Rect::from_two_pos(
+                cx.to_screen([f64::from(r[0]), f64::from(r[1])]),
+                cx.to_screen([f64::from(r[2]), f64::from(r[3])]),
+            ))
+        }));
+        if !part_visible {
+            c.focus = true;
+            return None;
+        }
+        anchor = anchor.clamp(viewport.min, viewport.max);
     }
     let pos = pos2(anchor.x + 12.0, anchor.y);
     let area = egui::Area::new(egui::Id::new(("comment-composer", view.id.0))).order(egui::Order::Foreground).constrain_to(viewport);

crates/ui-egui/tests/it/comments.rs

@@ -725,6 +725,33 @@ fn the_composer_hides_while_its_comment_is_scrolled_away() {
     assert_eq!(h.state().views[0].comments.composer.as_ref().map(|c| c.text.as_str()), Some("Draft"));
 }
 
+/// Editing a large comment whose top-right corner is scrolled away still shows the composer
+/// while the rest of the comment is on screen, so it can be posted or cancelled (#4095).
+#[test]
+fn the_edit_composer_shows_while_part_of_its_comment_is_on_screen() {
+    let mut h = harness(|app| app.set_option("quick", "square").unwrap());
+    drag_pt(&mut h, (20.0, 190.0), (280.0, 10.0));
+    // What "Edit text…" opens: the composer anchored at the comment's top-right corner.
+    h.state_mut().views[0].comments.composer = Some(pdfcraft_ui_egui::comments::Composer {
+        page: 0,
+        at: [280.0, 190.0],
+        kind: pdfcraft_ui_egui::comments::ComposerKind::Edit(0),
+        text: String::new(),
+        focus: true,
+    });
+    h.run_steps(2);
+    let viewport = h.state().views[0].viewport_rect();
+    h.state_mut().views[0].goto = Some((0, 0.4));
+    h.run_steps(4);
+    assert!(at(&h, 280.0, 190.0).y < viewport.top(), "the comment's top-right corner is scrolled away");
+    assert!(at(&h, 280.0, 10.0).y > viewport.top(), "part of the comment is still on screen");
+    let editors: Vec<_> = h.query_all_by(|n| n.role() == egui::accesskit::Role::MultilineTextInput).map(|n| n.rect()).collect();
+    assert!(editors.iter().any(|r| viewport.contains(r.center())), "the editor is drawn: {editors:?} (document {viewport:?})");
+    h.get_by_label("Cancel").click();
+    h.run_steps(2);
+    assert!(h.state().views[0].comments.composer.is_none(), "Cancel closes it");
+}
+
 /// With its whole page scrolled off the screen the composer keeps its draft, and the editor takes
 /// the keyboard again when the page comes back (#4021).
 #[test]