Reviews: T16a–e done. After the cap: a lagging synced chart leaves the shared window alone, and a price step keeps its places by magnitude

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/finance/tests.rs

@@ -2,7 +2,7 @@ use std::rc::Rc;
 
 use gpui::{
     AppContext as _, Context, Entity, IntoElement, ParentElement, Render, Styled, TestAppContext,
-    Window, div, px,
+    VisualTestContext, Window, div, px,
 };
 use jiff::Timestamp;
 
@@ -21,7 +21,8 @@ fn candles(count: usize) -> Rc<Vec<Candle>> {
 }
 
 struct Pair {
-    candles: Rc<Vec<Candle>>,
+    first: Rc<Vec<Candle>>,
+    second: Rc<Vec<Candle>>,
     sync: Entity<ChartSync>,
 }
 
@@ -29,18 +30,19 @@ impl Render for Pair {
     fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
         div()
             .w(px(800.))
-            .child(CandlestickChart::new("first", self.candles.clone()).sync(&self.sync))
-            .child(CandlestickChart::new("second", self.candles.clone()).sync(&self.sync))
+            .child(CandlestickChart::new("first", self.first.clone()).sync(&self.sync))
+            .child(CandlestickChart::new("second", self.second.clone()).sync(&self.sync))
     }
 }
 
-#[gpui::test]
-fn synced_charts_move_their_shared_window_once_per_append(cx: &mut TestAppContext) {
+/// Two synced charts of 40 candles, their shared window held on the newest 20.
+fn held(cx: &mut TestAppContext) -> (Entity<Pair>, Entity<ChartSync>, &mut VisualTestContext) {
     cx.update(Theme::init);
     let sync = cx.new(|_| ChartSync::default());
     let shared = sync.clone();
     let (view, cx) = cx.add_window_view(|_, _| Pair {
-        candles: candles(40),
+        first: candles(40),
+        second: candles(40),
         sync: shared,
     });
     cx.run_until_parked();
@@ -53,14 +55,54 @@ fn synced_charts_move_their_shared_window_once_per_append(cx: &mut TestAppContex
     });
     view.update(cx, |_, cx| cx.notify());
     cx.run_until_parked();
+    (view, sync, cx)
+}
+
+fn start(sync: &Entity<ChartSync>, cx: &mut VisualTestContext) -> f64 {
+    sync.read_with(cx, |sync, _| sync.visible.expect("held").start)
+}
+
+#[gpui::test]
+fn synced_charts_move_their_shared_window_once_per_append(cx: &mut TestAppContext) {
+    let (view, sync, cx) = held(cx);
     view.update(cx, |pair, cx| {
-        pair.candles = candles(45);
+        pair.first = candles(45);
+        pair.second = candles(45);
         cx.notify();
     });
     cx.run_until_parked();
-    let start = sync.read_with(cx, |sync, _| sync.visible.expect("held").start);
     assert_eq!(
-        start, 25.0,
+        start(&sync, cx),
+        25.0,
         "five new candles move the shared window five, not ten"
     );
 }
+
+#[gpui::test]
+fn a_lagging_chart_leaves_the_shared_window_alone(cx: &mut TestAppContext) {
+    let (view, sync, cx) = held(cx);
+    view.update(cx, |pair, cx| {
+        pair.second = candles(45);
+        cx.notify();
+    });
+    cx.run_until_parked();
+    for _ in 0..2 {
+        view.update(cx, |_, cx| cx.notify());
+        cx.run_until_parked();
+    }
+    assert_eq!(
+        (start(&sync, cx), sync.read_with(cx, |sync, _| sync.seen)),
+        (25.0, 45),
+        "redraws while the first chart lags move nothing"
+    );
+    view.update(cx, |pair, cx| {
+        pair.first = candles(45);
+        cx.notify();
+    });
+    cx.run_until_parked();
+    assert_eq!(
+        start(&sync, cx),
+        25.0,
+        "the lagging chart's append is already shown"
+    );
+}