M8: the canvas drag test waits for renders instead of fixed sleeps (#93)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/canvas_drag_tests.rs

@@ -40,19 +40,22 @@ fn a_drag_shows_on_the_canvas_while_it_moves() {
     // A move every frame, each one a new document and a new render request.
     u.app.canvas.render_work = None;
     let before = u.app.session.ds().unwrap().doc.clone();
-    for k in 1..=30 {
-        u.frame(vec![Event::PointerMoved(p + vec2(k as f32 * 3.0, k as f32))]);
+    // At least 30 moves, then on until a finished render shows (slow machines need longer).
+    for k in 1..=300 {
+        u.frame(vec![Event::PointerMoved(p + vec2(k as f32, k as f32 / 3.0))]);
         std::thread::sleep(Duration::from_millis(15));
+        if k >= 30 && u.app.canvas.render_work.is_some() {
+            break;
+        }
     }
     assert!(!Arc::ptr_eq(&before, &u.app.session.ds().unwrap().doc), "the drag moved the layer");
     assert!(u.app.canvas.render_work.is_some(), "renders finished during the drag are shown");
     // Held still: the same move each frame keeps the preview, and the canvas settles.
     let held = u.app.session.ds().unwrap().doc.clone();
-    for _ in 0..5 {
-        u.frame(vec![]);
-        std::thread::sleep(Duration::from_millis(15));
-    }
+    // Frames until the last render lands (slow machines take a while): a drag held still makes
+    // no new documents, so the worker runs dry.
+    settle(&mut u);
     assert!(Arc::ptr_eq(&held, &u.app.session.ds().unwrap().doc));
     assert!(u.app.worker.as_ref().is_some_and(|w| !w.in_flight), "nothing left to render");
-    u.button(p + vec2(90.0, 30.0), false);
+    u.button(p + vec2(30.0, 10.0), false);
 }