Fix #1881: a Ctrl/Cmd drag while typing keeps what was typed

With the Type tool editing, a press with Ctrl (Cmd on the Mac) lends the
Selection tool for the drag. Its drag joined the open typing session, so its
preview started from the document before the typing: the type moved or
scaled and lost what had just been typed. The typing is now kept as its own
undo step before the lent tool takes the press, as Undo already does, and
typing goes on after the drag.

crates/engine/src/tests_textedit.rs

@@ -150,6 +150,30 @@ fn undo_while_typing_takes_back_only_the_typing_and_redo_returns_it() {
     assert_eq!(obj(&s, id).plain_text(), "abc!");
 }
 
+/// #1881: a Cmd/Ctrl drag while typing (the Selection tool lent to the Type tool) moves the type
+/// and keeps what was typed, and typing goes on after it.
+#[test]
+fn a_cmd_drag_while_typing_moves_the_type_and_keeps_the_typing() {
+    let mut s = session();
+    let v = ViewInfo::default();
+    s.select_tool("type", v).unwrap();
+    click(&mut s, 200.0, 200.0);
+    let id = s.doc().unwrap().selection.objects[0];
+    s.tool_text("Hello", v).unwrap();
+    let before = s.doc().unwrap().doc.bounds_of(&[id], false).unwrap();
+    let (at, cmd) = (before.center(), Mods { cmd: true, ..Default::default() });
+    for (kind, dx) in [(PointerKind::Down, 0.0), (PointerKind::Drag, 100.0), (PointerKind::Up, 100.0)] {
+        s.pointer(&PointerEvent::new(kind, at.x + dx, at.y).with_mods(cmd), v).unwrap();
+    }
+    assert_eq!(obj(&s, id).plain_text(), "Hello", "the typing is kept");
+    let moved = s.doc().unwrap().doc.bounds_of(&[id], false).unwrap();
+    assert!(moved.x0 - before.x0 > 50.0, "the type moved: {before:?} → {moved:?}");
+    s.tool_text("!", v).unwrap();
+    assert_eq!(obj(&s, id).plain_text(), "Hello!");
+    let after = s.doc().unwrap().doc.bounds_of(&[id], false).unwrap();
+    assert!((after.x0 - moved.x0).abs() < 1e-6, "and stays where it was moved: {after:?}");
+}
+
 #[test]
 fn undo_during_a_drag_takes_back_only_the_drag() {
     let mut s = session();