feat: add separator component

crates/core/tests/separator.rs

@@ -0,0 +1,61 @@
+use gpui::{
+    AppContext as _, Context, IntoElement, ParentElement as _, Render, Styled as _, TestAppContext,
+    VisualTestContext, Window, div, px,
+};
+use gpui_native_core::separator::{Separator, SeparatorOrientation};
+use gpui_native_theme::Theme;
+
+struct Harness {
+    orientation: SeparatorOrientation,
+}
+
+impl Render for Harness {
+    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+        let separator = Separator::horizontal()
+            .orientation(self.orientation)
+            .debug_selector(|| "test-separator".to_string());
+        if self.orientation == SeparatorOrientation::Horizontal {
+            div()
+                .w(px(200.))
+                .h(px(50.))
+                .flex()
+                .flex_col()
+                .child(separator)
+        } else {
+            div().w(px(200.)).h(px(50.)).flex().child(separator)
+        }
+    }
+}
+
+fn separator_window(orientation: SeparatorOrientation) -> (TestAppContext, VisualTestContext) {
+    let mut cx = TestAppContext::single();
+    cx.update(Theme::init);
+    let window = cx.add_window(move |_, _| Harness { orientation });
+    let window = window.into();
+    cx.update_window(window, |_, window, cx| {
+        window.draw(cx).clear(cx);
+    })
+    .unwrap();
+    let visual = VisualTestContext::from_window(window, &cx);
+    (cx, visual)
+}
+
+#[test]
+fn the_horizontal_rule_spans_its_container_at_hairline_height() {
+    let (_cx, mut visual) = separator_window(SeparatorOrientation::Horizontal);
+    let bounds = visual
+        .debug_bounds("test-separator")
+        .expect("horizontal separator rendered");
+    assert_eq!(bounds.size.width, px(200.));
+    assert_eq!(bounds.size.height, px(1.));
+}
+
+#[test]
+fn the_vertical_rule_spans_its_container_at_hairline_width() {
+    let (_cx, mut visual) = separator_window(SeparatorOrientation::Vertical);
+    let bounds = visual
+        .debug_bounds("test-separator")
+        .expect("vertical separator rendered");
+    assert_eq!(bounds.size.width, px(1.));
+    assert_eq!(bounds.size.height, px(50.));
+}