C14.8 r1: the outline scrolls in its pane

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

apps/ely-mark/src/side/tests.rs

@@ -0,0 +1,47 @@
+use gpui::{ScrollDelta, ScrollWheelEvent, TestAppContext, point, px};
+
+use super::Pane;
+use crate::desk::tests::{open, start};
+
+#[gpui::test]
+fn a_long_outline_scrolls_to_its_last_heading(cx: &mut TestAppContext) {
+    let (data, files) = (
+        tempfile::tempdir().expect("data"),
+        tempfile::tempdir().expect("files"),
+    );
+    let path = files.path().join("long.md");
+    let text: String = (0..100).map(|n| format!("# Heading {n}\n\n")).collect();
+    std::fs::write(&path, text).expect("a file");
+    let (desk, cx) = start(cx, data.path());
+    open(&desk, &path, cx);
+    let side = desk.read_with(cx, |desk, _| desk.side.clone());
+    side.update(cx, |side, cx| {
+        side.pane = Pane::Outline;
+        cx.notify();
+    });
+    cx.run_until_parked();
+    let before = cx
+        .debug_bounds("mark-outline")
+        .expect("the outline is drawn");
+    let window = cx.update(|window, _| window.viewport_size());
+    assert!(
+        before.bottom() > window.height,
+        "the outline is longer than the window"
+    );
+    let at = point(before.left() + px(20.0), px(300.0));
+    for _ in 0..20 {
+        cx.simulate_event(ScrollWheelEvent {
+            position: at,
+            delta: ScrollDelta::Pixels(point(px(0.0), px(-1000.0))),
+            ..Default::default()
+        });
+        cx.run_until_parked();
+    }
+    let after = cx
+        .debug_bounds("mark-outline")
+        .expect("the outline is drawn");
+    assert!(
+        after.bottom() <= window.height,
+        "the last heading is in view: {after:?}"
+    );
+}