Forms: an option list stays inside the window; media ratios are checked in one place

The floating list under a Select, Combobox or MultiSelect was at least its
trigger's width with no ceiling, so a long choice ran it past the window
and its rows never ellipsized. It now stops at the window's width less the
window margin on each side, so gpui snaps it inside. The camera preview
and the model viewer check their ratio through primitives::checked_ratio.

src/forms/options.rs

@@ -286,10 +286,12 @@ impl Popup<'_> {
             })
         });
         let list = surface(self.id, cx)
+            .debug_selector(|| "option-list".into())
             .min_w(theme.tooltip_max_width())
             .when(anchor.size.width > Pixels::ZERO, |list| {
                 list.min_w(anchor.size.width)
             })
+            .max_w(window.viewport_size().width - theme.window_margin() * 2.0)
             .max_h(theme.list_max_height())
             .overflow_y_scroll()
             .when_some(self.scroll, |list, handle| list.track_scroll(handle))

src/forms/tests/choices.rs

@@ -446,3 +446,32 @@ fn an_open_select_with_nothing_to_pick_fails(cx: &mut TestAppContext) {
     setup(cx);
     cx.add_window_view(|_, _| Empty(false));
 }
+
+/// A select whose one choice runs long.
+struct Named;
+
+impl Render for Named {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let long = Choice::new("long", "A very long microphone name that runs past the box");
+        div()
+            .w(px(200.0))
+            .child(Select::new("long", [long, Choice::new("b", "B")]))
+    }
+}
+
+#[gpui::test]
+fn a_long_choice_keeps_its_list_inside_the_window(cx: &mut TestAppContext) {
+    setup(cx);
+    let (_, cx) = cx.add_window_view(|_, _| Named);
+    cx.simulate_resize(gpui::size(px(280.0), px(600.0)));
+    cx.run_until_parked();
+    cx.update(|window, _| window.focus_next());
+    cx.simulate_keystrokes("enter");
+    release("enter", cx);
+    cx.run_until_parked();
+    let list = cx.debug_bounds("option-list").expect("the list opens");
+    assert!(
+        list.left() >= px(0.0) && list.right() <= px(280.0),
+        "{list:?}"
+    );
+}