T23a: AI chat, messages

- messages: yours in a quiet bubble, the assistant's as prose beside its mark,
  system notes, errors; avatars, headers with model and time, footers
- MessageList over gpui's bottom-aligned list: drawn near the view, held at the
  newest, counting arrivals while away; a way back down; day separators
- streaming text and markdown reveal toward the text as it grows, with a caret;
  a blinking cursor before the first words
- CodeBlock with language, copy, run, apply, download and folding;
  MarkdownRenderer::code lets messages draw fences with it
- pictures, grids, files, voice notes, video over host frames, link previews
- quotes, actions, an editor that takes focus, versions, regenerate, stop and
  continue
- errors with retry, a rate limit counting down, feedback, thinking blocks
- gallery: the AI Chat page with scripted states

src/chat/tests.rs

@@ -0,0 +1,164 @@
+use std::{cell::RefCell, rc::Rc};
+
+use gpui::{
+    AppContext as _, Context, Entity, Focusable, IntoElement, Modifiers, ParentElement, Render,
+    ScrollDelta, ScrollWheelEvent, Styled, TestAppContext, TouchPhase, VisualTestContext, Window,
+    div, point, px,
+};
+
+use super::{MessageEditor, MessageList};
+use crate::{forms, forms::TextInput, theme::Theme};
+
+type Seen = Rc<RefCell<Vec<usize>>>;
+
+/// A conversation of tall messages, noting which ones each frame drew.
+struct Talk {
+    count: usize,
+    seen: Seen,
+}
+
+impl Render for Talk {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let seen = self.seen.clone();
+        seen.borrow_mut().clear();
+        div()
+            .size_full()
+            .child(MessageList::new("talk", self.count, move |ix, _, _| {
+                seen.borrow_mut().push(ix);
+                div().h(px(80.0)).w_full().into_any_element()
+            }))
+    }
+}
+
+fn settle(cx: &mut VisualTestContext) {
+    cx.run_until_parked();
+    cx.update(|window, _| window.refresh());
+    cx.run_until_parked();
+}
+
+fn newest(seen: &Seen) -> usize {
+    *seen.borrow().iter().max().expect("a frame draws messages")
+}
+
+#[gpui::test]
+fn the_list_follows_the_newest_until_the_reader_scrolls_away(cx: &mut TestAppContext) {
+    cx.update(Theme::init);
+    let seen = Seen::default();
+    let noted = seen.clone();
+    let (talk, cx) = cx.add_window_view(move |_, _| Talk {
+        count: 40,
+        seen: noted,
+    });
+    settle(cx);
+    assert_eq!(newest(&seen), 39, "it opens at the newest");
+    talk.update(cx, |talk, cx| {
+        talk.count = 42;
+        cx.notify();
+    });
+    settle(cx);
+    assert_eq!(newest(&seen), 41, "at the newest, it follows");
+    let middle = cx.update(|window, _| {
+        let size = window.viewport_size();
+        point(size.width / 2.0, size.height / 2.0)
+    });
+    cx.simulate_event(ScrollWheelEvent {
+        position: middle,
+        delta: ScrollDelta::Pixels(point(px(0.0), px(1200.0))),
+        modifiers: Modifiers::none(),
+        touch_phase: TouchPhase::Moved,
+    });
+    settle(cx);
+    let away = newest(&seen);
+    assert!(away < 41, "scrolled up to {away}");
+    talk.update(cx, |talk, cx| {
+        talk.count = 45;
+        cx.notify();
+    });
+    settle(cx);
+    assert_eq!(newest(&seen), away, "away, it holds its place");
+    let button = cx.update(|window, _| {
+        let size = window.viewport_size();
+        point(size.width / 2.0, size.height - px(28.0))
+    });
+    cx.simulate_click(button, Modifiers::none());
+    settle(cx);
+    assert_eq!(newest(&seen), 44, "the button goes back to the newest");
+}
+
+/// A sent message open to change, and what the reader asked.
+struct Edit {
+    field: Entity<TextInput>,
+    saved: usize,
+    cancelled: usize,
+}
+
+impl Render for Edit {
+    fn render(&mut self, _: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        let (save, cancel) = (cx.entity(), cx.entity());
+        div().size_full().child(MessageEditor::new(
+            "edit",
+            &self.field,
+            "Lift blends toward white.",
+            move |_, cx| save.update(cx, |edit, _| edit.saved += 1),
+            move |_, cx| cancel.update(cx, |edit, _| edit.cancelled += 1),
+        ))
+    }
+}
+
+#[gpui::test]
+fn an_edit_saves_only_a_change_and_escape_cancels(cx: &mut TestAppContext) {
+    cx.update(|cx| {
+        Theme::init(cx);
+        forms::bind_keys(cx);
+    });
+    let (edit, cx) = cx.add_window_view(|window, cx| Edit {
+        field: cx.new(|cx| {
+            let mut input = TextInput::new(window, cx);
+            input.set_text("Lift blends toward white.", cx);
+            input
+        }),
+        saved: 0,
+        cancelled: 0,
+    });
+    cx.update(|window, cx| {
+        window.activate_window();
+        let field = edit.read(cx).field.focus_handle(cx);
+        window.focus(&field);
+    });
+    settle(cx);
+    cx.simulate_keystrokes("cmd-enter");
+    settle(cx);
+    assert_eq!(
+        edit.read_with(cx, |edit, _| edit.saved),
+        0,
+        "nothing changed"
+    );
+    cx.simulate_input(" Gently.");
+    settle(cx);
+    cx.simulate_keystrokes("cmd-enter");
+    settle(cx);
+    assert_eq!(edit.read_with(cx, |edit, _| edit.saved), 1);
+    cx.simulate_keystrokes("escape");
+    assert_eq!(edit.read_with(cx, |edit, _| edit.cancelled), 1);
+}
+
+#[gpui::test]
+fn the_editor_takes_focus_as_it_opens(cx: &mut TestAppContext) {
+    cx.update(|cx| {
+        Theme::init(cx);
+        forms::bind_keys(cx);
+    });
+    let (edit, cx) = cx.add_window_view(|window, cx| Edit {
+        field: cx.new(|cx| TextInput::new(window, cx)),
+        saved: 0,
+        cancelled: 0,
+    });
+    cx.update(|window, _| window.activate_window());
+    settle(cx);
+    cx.simulate_keystrokes("escape");
+    assert_eq!(
+        edit.read_with(cx, |edit, _| edit.cancelled),
+        1,
+        "Escape reaches the editor"
+    );
+}