Timeline: Shift ranges and key boxes stagger in comp order (#1012)

In After Effects a marquee selection staggers in the comp's layer order,
not in the direction the box was drawn. A Shift-click range of layer
bars and a box of keys already come out top layer first; this test makes
both with the pointer (the range from the bottom layer up, the box from
the bottom right to the top left) and checks the Quick Offset that
follows: the top layer stays and the bottom one moves the whole delta.

crates/ui-egui/tests/ui_quick_offset.rs

@@ -160,3 +160,42 @@ fn a_quick_offset_drag_shows_the_total_and_per_layer_offset() {
         .collect();
     assert!(text.iter().any(|t| t.starts_with("Total Offset: +") && t.contains("Per Layer: +")), "{text:?}");
 }
+
+fn click(h: &mut Harness<'_, EffectcraftApp>, at: Pos2, modifiers: Modifiers) {
+    h.input_mut().events.push(Event::PointerMoved(at));
+    h.step();
+    h.input_mut().events.push(Event::ModifiersChanged(modifiers));
+    h.input_mut().events.push(Event::PointerButton { pos: at, button: egui::PointerButton::Primary, pressed: true, modifiers });
+    h.step();
+    h.input_mut().events.push(Event::PointerButton { pos: at, button: egui::PointerButton::Primary, pressed: false, modifiers });
+    h.step();
+    h.input_mut().events.push(Event::ModifiersChanged(Modifiers::default()));
+    h.run_steps(2);
+}
+
+/// A Shift-click range of layers and a box of keys, drawn from the bottom right up to the top left,
+/// stagger in the comp's layer order (top first), whichever way they were made (#1012).
+#[test]
+fn shift_ranges_and_key_boxes_stagger_in_comp_order() {
+    let (mut h, ids) = harness();
+    // ids[2] is the top layer, ids[0] the bottom one. Click the bottom bar, Shift-click the top.
+    let bar = |h: &Harness<'_, EffectcraftApp>, id: u64| center(h, &format!("timeline.layer.{id}.bar"));
+    let (bottom, top) = (bar(&h, ids[0]), bar(&h, ids[2]));
+    click(&mut h, bottom, Modifiers::default());
+    click(&mut h, top, Modifiers::SHIFT);
+    let selected: Vec<u64> = h.state().session.state.selected_layers.iter().map(|l| l.0).collect();
+    assert_eq!(selected, vec![ids[2], ids[1], ids[0]], "a Shift range is in comp order");
+    h.state_mut().session.execute("layer.quickOffset", json!({"delta": 2.0 / 30.0})).unwrap();
+    assert_eq!([start(&h, ids[2]), start(&h, ids[1]), start(&h, ids[0])], [0, F, 2 * F]);
+    h.state_mut().session.execute("edit.undo", json!({})).unwrap();
+    h.run_steps(2);
+    // A box around the 1 s keys, drawn upwards and to the left.
+    let one = Tick::from_seconds_f64(1.0).0;
+    let key = |h: &Harness<'_, EffectcraftApp>, id: u64| center(h, &format!("timeline.keyAt.{}.{one}", opacity_uid(h, id)));
+    let (low, high) = (key(&h, ids[0]), key(&h, ids[2]));
+    drag(&mut h, low + vec2(30.0, 5.0), high - vec2(30.0, 5.0), Modifiers::default());
+    let order: Vec<u64> = h.state().session.state.selected_keys.iter().map(|k| k.layer.0).collect();
+    assert_eq!(order, vec![ids[2], ids[1], ids[0]], "a key box is in comp order");
+    h.state_mut().session.execute("keys.quickOffset", json!({"delta": 2.0 / 30.0})).unwrap();
+    assert_eq!([key_times(&h, ids[2])[1], key_times(&h, ids[1])[1], key_times(&h, ids[0])[1]], [one, one + F, one + 2 * F]);
+}