T24d: Agent, previews

- BrowserPreview: the address with a lock and a spinner while it loads, the
  host's frame shown, and the frames so far along the foot as Tab stops;
  ScreenshotStream is that strip
- ComputerUseViewer: the host's frame, a ring where the agent points that
  rings again at each new point, and what it does there
- LivePreview: the host's page under its address, with reload
- ArtifactPanel: title, versions through chat::BranchNavigator, Preview and
  Source when it has both, copy and download; it fails loud with neither
- gallery: frames cut from the gallery's own pages; one asset! macro in
  main.rs replaces three copies

src/agent/tests/mod.rs

@@ -4,6 +4,7 @@ use gpui::{
 };
 
 mod changes;
+mod previews;
 
 use super::{AgentProgress, Permission, PermissionPrompt, ToolApprovalDialog};
 use crate::{forms, primitives::FocusNext, theme::Theme};

src/agent/tests/previews.rs

@@ -0,0 +1,103 @@
+use std::{cell::Cell, rc::Rc};
+
+use gpui::{
+    Context, IntoElement, KeyBinding, ParentElement, Render, Styled, TestAppContext, Window,
+    canvas, div, point, px,
+};
+
+use super::{press, settle};
+use crate::{
+    agent::{ArtifactPanel, BrowserPreview, ComputerUseViewer},
+    forms,
+    primitives::{FocusNext, IconName},
+    theme::Theme,
+};
+
+fn setup(cx: &mut TestAppContext) {
+    cx.update(|cx| {
+        Theme::init(cx);
+        forms::bind_keys(cx);
+        cx.bind_keys([KeyBinding::new("tab", FocusNext, None)]);
+    });
+}
+
+/// A browser with three frames, and the frames asked for.
+struct Browsing {
+    asked: Vec<usize>,
+}
+
+impl Render for Browsing {
+    fn render(&mut self, _: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        let view = cx.entity();
+        div().w(px(480.0)).child(
+            BrowserPreview::new("browser", "localhost:5173", ["a.png", "b.png", "c.png"], 2)
+                .on_show(move |ix, _, cx| view.update(cx, |browsing, _| browsing.asked.push(ix))),
+        )
+    }
+}
+
+#[gpui::test]
+fn a_frame_shows_from_the_keyboard(cx: &mut TestAppContext) {
+    setup(cx);
+    let (view, cx) = cx.add_window_view(|_, _| Browsing { asked: Vec::new() });
+    cx.update(|window, _| window.activate_window());
+    settle(cx);
+    cx.update(|window, _| window.focus_next());
+    cx.update(|window, _| window.focus_next());
+    press("enter", cx);
+    assert_eq!(
+        view.read_with(cx, |browsing, _| browsing.asked.clone()),
+        [1]
+    );
+}
+
+#[test]
+#[should_panic(expected = "frame 3 of 3")]
+fn a_frame_past_the_last_fails_loud() {
+    let _ = BrowserPreview::new("browser", "localhost", ["a.png", "b.png", "c.png"], 3);
+}
+
+#[test]
+#[should_panic(expected = "a pointer inside the frame")]
+fn a_pointer_off_the_frame_fails_loud() {
+    let _ = ComputerUseViewer::new("screen", "a.png").pointer(point(1.2, 0.5));
+}
+
+/// A panel with a preview and a source, noting which one drew.
+struct Panel {
+    drew_source: Rc<Cell<bool>>,
+}
+
+impl Render for Panel {
+    fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+        let drew = self.drew_source.clone();
+        div().w(px(480.0)).h(px(320.0)).child(
+            ArtifactPanel::new("panel", "Notes", IconName::FileText)
+                .preview(div().h(px(40.0)))
+                .source(
+                    div().relative().h(px(40.0)).child(
+                        canvas(move |_, _, _| drew.set(true), |_, _, _, _| {})
+                            .absolute()
+                            .top_0()
+                            .left_0()
+                            .size_full(),
+                    ),
+                ),
+        )
+    }
+}
+
+#[gpui::test]
+fn the_source_shows_when_asked(cx: &mut TestAppContext) {
+    setup(cx);
+    let drew = Rc::new(Cell::new(false));
+    let seen = drew.clone();
+    let (_, cx) = cx.add_window_view(|_, _| Panel { drew_source: seen });
+    cx.update(|window, _| window.activate_window());
+    settle(cx);
+    assert!(!drew.get(), "the preview shows first");
+    cx.update(|window, _| window.focus_next());
+    cx.update(|window, _| window.focus_next());
+    press("enter", cx);
+    assert!(drew.get(), "the source shows once asked");
+}