T24f Agent: control and cost

HumanInputRequest asks a question with answers to pick and a line to
write one; CostBreakdown totals a session and splits it by part.
InterruptButton, TokenUsageChart, TraceViewer and EvalResultTable
point to chat::stop_button, a stacked BarChart, TimelineProfiler and
DataTable.

UsageBar shows amounts as its owner writes them. MemoryPanel and
HumanInputRequest share agent::line::send_line; the chapter's bool
callbacks take forms::OnFlag.

DataTable scrolls columns wider than its box sideways, pinned or not,
and leaves a plain wheel to the page; sortable headers are Tab stops.
TimelineProfiler fits its ruler to its lane, its spans are Tab stops,
and a picked span takes accent.

src/agent/tests/control.rs

@@ -0,0 +1,96 @@
+use gpui::{
+    AppContext as _, Context, Entity, IntoElement, KeyBinding, ParentElement, Render, Styled,
+    TestAppContext, VisualTestContext, Window, div, px,
+};
+
+use super::{press, settle};
+use crate::{
+    agent::{CostBreakdown, HumanInputRequest},
+    forms::{self, TextInput},
+    primitives::FocusNext,
+    theme::Theme,
+};
+
+/// A question with two answers to pick, and the answers given.
+struct Asked {
+    field: Entity<TextInput>,
+    answers: Vec<String>,
+}
+
+impl Render for Asked {
+    fn render(&mut self, _: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        let view = cx.entity();
+        div().w(px(420.0)).child(
+            HumanInputRequest::new(
+                "asked",
+                "Keep the accents?",
+                &self.field,
+                move |answer, _, cx| {
+                    view.update(cx, |asked, _| asked.answers.push(answer.to_string()))
+                },
+            )
+            .choices(["Keep them", "Lift further"]),
+        )
+    }
+}
+
+fn asked(cx: &mut TestAppContext) -> (Entity<Asked>, &mut VisualTestContext) {
+    cx.update(|cx| {
+        Theme::init(cx);
+        forms::bind_keys(cx);
+        cx.bind_keys([KeyBinding::new("tab", FocusNext, None)]);
+    });
+    let (view, cx) = cx.add_window_view(|window, cx| Asked {
+        field: cx.new(|cx| TextInput::new(window, cx)),
+        answers: Vec::new(),
+    });
+    cx.update(|window, _| window.activate_window());
+    settle(cx);
+    (view, cx)
+}
+
+#[gpui::test]
+fn a_pick_answers_the_question(cx: &mut TestAppContext) {
+    let (view, cx) = asked(cx);
+    cx.update(|window, _| window.focus_next());
+    cx.update(|window, _| window.focus_next());
+    press("enter", cx);
+    assert_eq!(
+        view.read_with(cx, |asked, _| asked.answers.clone()),
+        ["Lift further"]
+    );
+}
+
+#[gpui::test]
+fn enter_sends_a_written_answer_and_skips_a_blank_one(cx: &mut TestAppContext) {
+    let (view, cx) = asked(cx);
+    for _ in 0..3 {
+        cx.update(|window, _| window.focus_next());
+    }
+    cx.simulate_input(" ");
+    press("enter", cx);
+    cx.simulate_input("Lift them to 18%");
+    press("enter", cx);
+    view.read_with(cx, |asked, cx| {
+        assert_eq!(asked.answers, ["Lift them to 18%"]);
+        assert_eq!(asked.field.read(cx).text(), "");
+    });
+}
+
+/// A breakdown of a session that has cost nothing yet.
+struct Nothing;
+
+impl Render for Nothing {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        div()
+            .w(px(320.0))
+            .child(CostBreakdown::new("This session", "USD"))
+    }
+}
+
+#[gpui::test]
+fn a_session_that_cost_nothing_draws_its_total(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let (_, cx) = cx.add_window_view(|_, _| Nothing);
+    settle(cx);
+}

src/agent/tests/mod.rs

@@ -4,6 +4,7 @@ use gpui::{
 };
 
 mod changes;
+mod control;
 mod environment;
 mod previews;