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/tables/tests/columns.rs

@@ -0,0 +1,95 @@
+use std::{cell::RefCell, rc::Rc};
+
+use gpui::{
+    Context, IntoElement, KeyUpEvent, Keystroke, Modifiers, Render, Styled, TestAppContext, Window,
+    point, px,
+};
+
+use super::{edit_at, settle};
+use crate::{
+    tables::{Column, DataTable, Row},
+    theme::Theme,
+};
+
+/// Three editable columns 200 wide in a table 280 wide, the first pinned or not; it keeps the column of each edit.
+struct Wide(Rc<RefCell<Vec<String>>>, bool);
+
+impl Render for Wide {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let heard = self.0.clone();
+        let column = |key: &'static str| Column::new(key, key).width(gpui::rems(12.5)).editable();
+        let first = if self.1 {
+            column("a").pinned()
+        } else {
+            column("a")
+        };
+        DataTable::new("wide", [first, column("b"), column("c")])
+            .rows(vec![Row::new("r", ["A".into(), "B".into(), "C".into()])])
+            .on_edit(move |_, column, _, _, _| heard.borrow_mut().push(column.to_string()))
+            .w(px(280.0))
+    }
+}
+
+#[gpui::test]
+fn columns_past_the_table_scroll_sideways_and_a_plain_wheel_leaves_them(cx: &mut TestAppContext) {
+    cx.update(|cx| {
+        Theme::init(cx);
+        crate::forms::bind_keys(cx);
+    });
+    for pinned in [false, true] {
+        let heard = Rc::new(RefCell::new(Vec::new()));
+        let seen = heard.clone();
+        let (_, cx) = cx.add_window_view(|_, _| Wide(seen, pinned));
+        settle(cx);
+        let cell = point(px(250.0), px(54.0));
+        for delta in [point(px(0.0), px(-2000.0)), point(px(-2000.0), px(0.0))] {
+            cx.simulate_event(gpui::ScrollWheelEvent {
+                position: cell,
+                delta: gpui::ScrollDelta::Pixels(delta),
+                modifiers: Modifiers::none(),
+                touch_phase: gpui::TouchPhase::Moved,
+            });
+            settle(cx);
+            edit_at(cell, "x", cx);
+        }
+        assert_eq!(*heard.borrow(), ["b", "c"], "pinned {pinned}");
+    }
+}
+
+/// Two rows under a sortable, editable name; it keeps the row of each edit.
+struct Sorting(Rc<RefCell<Vec<String>>>);
+
+impl Render for Sorting {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let heard = self.0.clone();
+        DataTable::new("sorting", [Column::new("name", "Name").editable()])
+            .rows(vec![
+                Row::new("bea", ["Bea".into()]),
+                Row::new("ada", ["Ada".into()]),
+            ])
+            .on_edit(move |row, _, _, _, _| heard.borrow_mut().push(row.to_string()))
+            .w(px(400.0))
+    }
+}
+
+#[gpui::test]
+fn tab_reaches_a_header_and_enter_sorts_by_it(cx: &mut TestAppContext) {
+    cx.update(|cx| {
+        Theme::init(cx);
+        crate::forms::bind_keys(cx);
+    });
+    let heard = Rc::new(RefCell::new(Vec::new()));
+    let seen = heard.clone();
+    let (_, cx) = cx.add_window_view(|_, _| Sorting(seen));
+    cx.update(|window, _| window.activate_window());
+    settle(cx);
+    cx.update(|window, _| window.focus_next());
+    cx.simulate_keystrokes("enter");
+    settle(cx);
+    cx.simulate_event(KeyUpEvent {
+        keystroke: Keystroke::parse("enter").expect("a key"),
+    });
+    settle(cx);
+    edit_at(point(px(120.0), px(54.0)), "x", cx);
+    assert_eq!(*heard.borrow(), ["ada"], "Ada rises to the top");
+}