Layout: a float anchored on a later page of a long paragraph is drawn there (#4250) (#4267)

Lands #4267.

Co-Authored-By: RatkoR <6648783+RatkoR@users.noreply.github.com>

crates/engine/src/cmd/objects/arrange.rs

@@ -161,8 +161,9 @@ fn move_object_once(s: &mut Session, pos: &Pos, page: usize, x: f32, y: f32, (w,
         Some(path) => (Pos { story, path, off: 0 }, false),
         None => (nearest_line(&layout, page, y, story).ok_or_else(|| CmdError::Params("no text on that page to anchor to".into()))?, true),
     };
-    // Move its character to the anchor (unless it's already in that paragraph).
-    let at = if anchor.story == pos.story && anchor.path == pos.path && !on_page {
+    // Move its character to the anchor, unless it's already in that paragraph and drawn on this
+    // page (one anchored on a later page of it is drawn there, #4250).
+    let at = if anchor.story == pos.story && anchor.path == pos.path && !on_page && layout.object(pos, page).is_some_and(|o| o.page == page) {
         pos.clone()
     } else {
         let obj = s.doc.para_at(pos).and_then(|p| p.object_at(pos.off)).cloned().ok_or_else(|| CmdError::Failed("object vanished".into()))?;

crates/engine/src/cmd/objects/tests.rs

@@ -14,6 +14,48 @@ fn object_area(s: &mut Session) -> wordcraft_layout::hit::ObjectHit {
     s.layout().find_object(0, |o| o.text_box.is_none()).unwrap()
 }
 
+/// #4250: a shape dragged into the middle of a page that only continues a long paragraph
+/// stays there, as in Word: anchored at the line beside it, it's drawn on that page, not
+/// thrown back to the page the paragraph starts on. One undo step puts it back.
+#[test]
+fn a_shape_dropped_on_a_page_a_paragraph_continues_onto_stays_there() {
+    let mut s = Session::new(wordcraft_doc::Document::new());
+    s.run("text.insert", &json!({"text": "The quick brown fox jumps over the lazy dog. ".repeat(400)})).unwrap();
+    s.run("caret.docStart", &json!({})).unwrap();
+    s.run("insert.shape", &json!({"kind": "rectangle"})).unwrap();
+    s.run("arrange.wrap", &json!({"wrap": "square"})).unwrap();
+    s.run("arrange.bounds", &json!({"page": 0, "x": 100, "y": 250, "width": 100, "height": 50})).unwrap();
+    assert!(s.layout().pages.len() > 2);
+    let before = (object_area(&mut s), s.undo_depth());
+    s.run("arrange.bounds", &json!({"page": 1, "x": 100, "y": 275})).unwrap();
+    let o = object_area(&mut s);
+    assert_eq!(o.page, 1, "on the page it was dropped on: {o:?}");
+    assert!((o.rect.x - 100.0).abs() < 0.5 && (o.rect.y - 275.0).abs() < 0.5, "where it was dropped: {:?}", o.rect);
+    assert_eq!(s.undo_depth(), before.1 + 1);
+    s.run("edit.undo", &json!({})).unwrap();
+    let back = object_area(&mut s);
+    assert_eq!((back.page, back.rect), (before.0.page, before.0.rect));
+}
+
+/// #4250: and dragged back onto the page the paragraph starts on, it stays there: its anchor
+/// goes back to the paragraph's start rather than staying on the later page's line.
+#[test]
+fn a_shape_dragged_back_to_the_page_its_paragraph_starts_on_stays_there() {
+    let mut s = Session::new(wordcraft_doc::Document::new());
+    s.run("text.insert", &json!({"text": "The quick brown fox jumps over the lazy dog. ".repeat(400)})).unwrap();
+    s.run("caret.docStart", &json!({})).unwrap();
+    s.run("insert.shape", &json!({"kind": "rectangle"})).unwrap();
+    s.run("arrange.wrap", &json!({"wrap": "square"})).unwrap();
+    s.run("arrange.bounds", &json!({"page": 1, "x": 100, "y": 275, "width": 100, "height": 50})).unwrap();
+    let before = (object_area(&mut s), s.undo_depth());
+    assert!(before.0.page == 1 && before.0.off > 0, "anchored on page 2's line: {:?}", before.0);
+    s.run("arrange.bounds", &json!({"page": 0, "x": 120, "y": 300})).unwrap();
+    let o = object_area(&mut s);
+    assert_eq!((o.page, o.off), (0, 0), "on the page it was dropped on, anchored at the paragraph's start: {o:?}");
+    assert!((o.rect.x - 120.0).abs() < 0.5 && (o.rect.y - 300.0).abs() < 0.5, "where it was dropped: {:?}", o.rect);
+    assert_eq!(s.undo_depth(), before.1 + 1);
+}
+
 /// What a click and a handle or body drag do in the editor (#142, #82): hit-test the object,
 /// select it, then resize and move it with `arrange.bounds`.
 fn click_resize_and_drag(insert: &str, params: Value) {