T23d round 1 fix

- the conversation list reads the zone through format::system_zone, which
  fails loud; the gallery expects the system zone
- Combobox opens with its cursor on its value, MultiSelect on the first
  row ticked; tests for all three lists open r25 of thirty in view
- AGENTS: the zone rule; lists open on their choice

AGENTS.md

@@ -131,6 +131,8 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - Editor rows read their text through `CodeEditor::row_text`: a multi-line ghost cuts its line, and the rest follows the ghost's last line.
 - gpui styles a drag-over only on an element with its own hitbox. A veil that shows while files hover takes the drop itself (`chat::DragDropOverlay`).
 - gpui 0.2.2 never clears `debug_bounds`: a test sees an element appear, not leave.
+- The system time zone comes from `typography::format::system_zone`, which fails loud; jiff's `TimeZone::system()` falls back to UTC in silence.
+- A list opens with its cursor on the current choice: Select on the chosen row, Combobox on its value, MultiSelect on the first one ticked.
 
 ## Decisions
 

TASKS.md

@@ -264,3 +264,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T23c | 1 | FAIL | suggestion arrows landed on disabled rows and left the cursor out of view; a dot ended a file mention; the drop veil never showed, since gpui styles a drag-over only on an element with a hitbox; a parameter's places came from its step alone; the gallery's prompt menu and Reset only logged |
 | T23c | 2 | FAIL | a slash inside a path read as a new trigger, closing the file suggestions; a list whose first rows were disabled opened with its cursor out of view |
 | T23c | 3 | PASS | |
+| T23d | 1 | FAIL | the list grouped days in a silent UTC fallback when the system zone was unknown; Combobox and MultiSelect opened a long list at its top, away from the choice |

examples/gallery/pages/chat/history.rs

@@ -79,7 +79,9 @@ pub fn conversations_section(
     window: &mut Window,
     cx: &mut App,
 ) -> impl IntoElement + use<> {
-    let today = Timestamp::now().to_zoned(TimeZone::system()).date();
+    let today = Timestamp::now()
+        .to_zoned(TimeZone::try_system().expect("the gallery reads the system time zone"))
+        .date();
     let query = window.use_keyed_state("chat-find-conversation", cx, |window, cx| {
         TextInput::new(window, cx).placeholder("Search conversations")
     });

examples/gallery/pages/chat/talk.rs

@@ -115,7 +115,9 @@ fn row(ix: usize, row: &Row, today: Date, now: Timestamp) -> gpui::AnyElement {
 }
 
 pub fn conversation(_: &mut Window, cx: &mut App) -> impl IntoElement + use<> {
-    let today = Timestamp::now().to_zoned(TimeZone::system()).date();
+    let today = Timestamp::now()
+        .to_zoned(TimeZone::try_system().expect("the gallery reads the system time zone"))
+        .date();
     let now = Timestamp::now();
     let all = rows(today);
     let count = all.len();

src/chat/conversations.rs

@@ -13,7 +13,7 @@ use crate::{
     menus::{Menu, MenuItem, OverflowMenu},
     primitives::{FocusRing, Icon, IconName, tab_stop},
     theme::{ActiveTheme, ControlSize, IconSize, Radius, TextSize},
-    typography::Ellipsis,
+    typography::{Ellipsis, format::system_zone},
 };
 
 /// A conversation in a list: its key, its title, when it last moved, and whether it is pinned.
@@ -302,7 +302,7 @@ impl RenderOnce for ConversationList {
             &self.conversations,
             &self.query,
             self.today,
-            &TimeZone::system(),
+            &system_zone("conversation list"),
         );
         let empty = groups.is_empty();
         div()

src/forms/combobox.rs

@@ -158,6 +158,18 @@ impl RenderOnce for Combobox {
         };
         let rows = Rc::new(matching(&self.choices, query));
         let open = focused && !typing.read(cx).dismissed && !rows.is_empty();
+        if open != picker.read(cx).open {
+            let chosen = self.selected.as_ref().and_then(|value| {
+                rows.iter()
+                    .position(|row| !row.disabled && row.value == *value)
+            });
+            picker.update(cx, |picker, _| {
+                picker.open = open;
+                if let Some(at) = chosen.filter(|_| open) {
+                    picker.highlighted = at;
+                }
+            });
+        }
         let kept = picker.read(cx).highlighted;
         let highlighted = if rows.get(kept).is_some_and(|row| !row.disabled) {
             kept

src/forms/multi.rs

@@ -79,7 +79,10 @@ impl RenderOnce for MultiSelect {
             picker.update(cx, |picker, _| picker.open = false);
         }
         let (choices, selected) = (Rc::new(self.choices), Rc::new(self.selected));
-        let start = step(&choices, choices.len() - 1, 1);
+        let start = choices
+            .iter()
+            .position(|choice| !choice.disabled && selected.contains(&choice.value))
+            .unwrap_or_else(|| step(&choices, choices.len() - 1, 1));
         if picker.read(cx).highlighted >= choices.len() {
             picker.update(cx, |picker, _| picker.highlighted = start);
         }

src/forms/tests/choices.rs

@@ -87,38 +87,59 @@ fn select_opens_moves_and_picks_from_the_keyboard(cx: &mut TestAppContext) {
     assert_eq!(view.read_with(cx, |view, _| view.chosen.clone()), "b");
 }
 
-/// A select of thirty rows, low in the window, and the rows it picked.
+/// Which list of thirty rows a test opens.
+#[derive(Clone, Copy)]
+enum Kind {
+    Select,
+    Combobox,
+    Multi,
+}
+
+/// A list of thirty rows with r25 chosen, low in the window, and what each press picked.
 struct Long {
-    chosen: SharedString,
-    picks: Vec<SharedString>,
+    kind: Kind,
+    field: Entity<TextInput>,
+    picks: Vec<String>,
 }
 
 impl Render for Long {
     fn render(&mut self, _: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
-        let view = cx.entity();
         let rows = (0..30).map(|ix| Choice::new(format!("r{ix:02}"), format!("Row {ix:02}")));
-        div().pt(px(200.0)).w(px(240.0)).child(
-            Select::new("long", rows)
-                .selected(self.chosen.clone())
-                .on_change(move |value, _, cx| {
-                    view.update(cx, |view, cx| {
-                        view.chosen = value.clone();
-                        view.picks.push(value.clone());
-                        cx.notify();
-                    })
-                }),
-        )
+        let view = cx.entity();
+        let note = move |pick: String, cx: &mut gpui::App| {
+            view.update(cx, |view, cx| {
+                view.picks.push(pick);
+                cx.notify();
+            })
+        };
+        let list = match self.kind {
+            Kind::Select => Select::new("long", rows)
+                .selected("r25")
+                .on_change(move |value, _, cx| note(value.to_string(), cx))
+                .into_any_element(),
+            Kind::Combobox => Combobox::new("long", &self.field, rows)
+                .selected("r25")
+                .on_change(move |value, _, cx| note(value.to_string(), cx))
+                .into_any_element(),
+            Kind::Multi => MultiSelect::new("long", rows)
+                .selected([SharedString::from("r25")])
+                .on_change(move |next, _, cx| note(next.join(","), cx))
+                .into_any_element(),
+        };
+        div().pt(px(200.0)).w(px(240.0)).child(list)
     }
 }
 
-#[gpui::test]
-fn a_long_list_opens_with_its_choice_in_view(cx: &mut TestAppContext) {
+/// Opens the list with a press on its field, then presses the row at its foot.
+fn press_the_foot(kind: Kind, cx: &mut TestAppContext) -> Vec<String> {
     setup(cx);
     cx.update(|cx| Theme::update(cx, |theme| theme.reduced_motion = true));
-    let (view, cx) = cx.add_window_view(|_, _| Long {
-        chosen: "r25".into(),
+    let (view, cx) = cx.add_window_view(|window, cx| Long {
+        kind,
+        field: cx.new(|cx| TextInput::new(window, cx)),
         picks: Vec::new(),
     });
+    cx.update(|window, _| window.activate_window());
     let (trigger, list) = cx.update(|window, cx| {
         let theme = cx.theme();
         (
@@ -139,8 +160,26 @@ fn a_long_list_opens_with_its_choice_in_view(cx: &mut TestAppContext) {
     cx.simulate_mouse_move(foot, None, Modifiers::none());
     cx.simulate_click(foot, Modifiers::none());
     frames(cx);
-    let picks = view.read_with(cx, |view, _| view.picks.clone());
-    assert_eq!(picks, ["r25"], "the list opens with its choice at the foot");
+    view.read_with(cx, |view, _| view.picks.clone())
+}
+
+#[gpui::test]
+fn a_long_select_opens_with_its_choice_in_view(cx: &mut TestAppContext) {
+    assert_eq!(press_the_foot(Kind::Select, cx), ["r25"]);
+}
+
+#[gpui::test]
+fn a_long_combobox_opens_with_its_choice_in_view(cx: &mut TestAppContext) {
+    assert_eq!(press_the_foot(Kind::Combobox, cx), ["r25"]);
+}
+
+#[gpui::test]
+fn a_long_multi_select_opens_with_its_first_choice_in_view(cx: &mut TestAppContext) {
+    assert_eq!(
+        press_the_foot(Kind::Multi, cx),
+        [""],
+        "the press unticks r25"
+    );
 }
 
 /// Frames 2ms apart, past reduced motion's 1ms entrances.