feat: add editor component

crates/editor/tests/code_view_bench.rs

@@ -0,0 +1,106 @@
+use std::cell::RefCell;
+use std::rc::Rc;
+use std::time::{Duration, Instant};
+
+use gpui::{
+    AppContext as _, Context, Entity, IntoElement, Modifiers, ParentElement as _, Render,
+    ScrollDelta, ScrollEvent, Styled as _, TestAppContext, VisualTestContext, Window, div, point,
+    px,
+};
+use gpui_native_editor::code_view::CodeViewState;
+use gpui_native_editor::highlight::Language;
+
+/// Deterministic pseudo-Rust with mixed tokens, roughly `lines` lines long.
+fn large_source(lines: usize) -> String {
+    let mut source = String::with_capacity(lines * 48);
+    let mut index = 0usize;
+    while source.lines().count() < lines {
+        let i = index;
+        source.push_str(&format!(
+            "// Section {i}: generated for the scroll performance test.\n"
+        ));
+        source.push_str(&format!("struct Section{i} {{\n"));
+        source.push_str("    id: u64,\n");
+        source.push_str("    label: String,\n");
+        source.push_str("    scores: Vec<f64>,\n");
+        source.push_str("}\n\n");
+        source.push_str(&format!("impl Section{i} {{\n"));
+        source.push_str("    /// A one-line summary of this section.\n");
+        source.push_str("    fn describe(&self) -> String {\n");
+        source.push_str(&format!(
+            "        format!(\"section {i}: {{}} at {{:?}}\", self.label, self.scores)\n"
+        ));
+        source.push_str("    }\n");
+        source.push_str("}\n\n");
+        index += 1;
+    }
+    source
+}
+
+struct Host {
+    code: Entity<CodeViewState>,
+}
+
+impl Render for Host {
+    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+        div().size_full().child(self.code.clone())
+    }
+}
+
+#[test]
+fn scrolling_a_large_file_is_not_pathologically_slow() {
+    let mut cx = TestAppContext::single();
+    cx.update(gpui_native_theme::Theme::init);
+
+    let source = large_source(5000);
+    let started = Instant::now();
+    let state = CodeViewState::new("bench-code", source.clone(), Language::Rust);
+    let highlight_elapsed = started.elapsed();
+
+    let state_cell: Rc<RefCell<Option<Entity<CodeViewState>>>> = Rc::new(RefCell::new(None));
+    let cell = state_cell.clone();
+    let window = cx.add_window(move |_, cx| {
+        let code = cx.new(|_| state);
+        cell.borrow_mut().replace(code.clone());
+        Host { code }
+    });
+    let state = state_cell.borrow().clone().expect("state captured");
+    let mut visual = VisualTestContext::from_window(window.into(), &cx);
+    visual.update(|window, cx| {
+        window.draw(cx).clear(cx);
+    });
+
+    let line_count = cx.update(|cx| state.read(cx).code().lines.len());
+    assert!(
+        (5000..=5020).contains(&line_count),
+        "the whole file highlighted, got {line_count} lines"
+    );
+
+    let started = Instant::now();
+    for _ in 0..30 {
+        visual.simulate_event(ScrollEvent {
+            position: point(px(300.), px(300.)),
+            delta: ScrollDelta::Pixels(point(px(0.), px(-240.))),
+            modifiers: Modifiers::default(),
+            ..Default::default()
+        });
+        visual.update(|window, cx| {
+            window.draw(cx).clear(cx);
+        });
+    }
+    let scroll_elapsed = started.elapsed();
+
+    println!(
+        "highlighting {line_count} lines took {highlight_elapsed:?}; 30 wheel frames over {} lines took {scroll_elapsed:?} ({:?} per frame)",
+        line_count,
+        scroll_elapsed / 30
+    );
+    assert!(
+        highlight_elapsed < Duration::from_secs(3),
+        "highlighting took {highlight_elapsed:?}"
+    );
+    assert!(
+        scroll_elapsed < Duration::from_secs(2),
+        "scrolling 30 frames took {scroll_elapsed:?}"
+    );
+}