Media: the viewer's picture moves; a viewer with no picture takes no Tab

The stage's picture carries an id, so gpui keeps its frame and asks for
the next: an animated picture plays, turned or not. A viewer whose picture
has not loaded or cannot open is no Tab stop. AGENTS.md: img() moves an
animated picture's frames only with an id.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

AGENTS.md

@@ -109,7 +109,7 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - Set an explicit line height on any box that clips text. gpui's default leading is taller than a tight box, and the clip eats descenders.
 - gpui's `img` takes its picture's pixel size for any `Auto` side, and its aspect ratio beats percent heights in flow. `Image` pins it absolute at full size, so an `Image` needs a sized box.
 - Badges, tags and avatars live in `data_display`; forms and shell draw theirs from there, and `data_display` imports neither. Avatars take square pictures.
-- `img()` keeps loading state only with an id. Content masks are rectangles, so rounded corners survive only when the image fills its box without cropping.
+- `img()` keeps loading state, and moves an animated picture's frames, only with an id. Content masks are rectangles, so rounded corners survive only when the image fills its box without cropping.
 - gpui reads a `&str` picture source as a web address. A file goes through `Path` (`documents::source` in the crate, `Path::new` in the gallery).
 - Taffy 0.9's grid rows overgrow tiles that keep a ratio. Tiles in a picture's shape sit in flex rows of `flex_1` cells (`generative::GenerationGrid`).
 - Rise reads green and fall red unless a component's `red_up` swaps them, as markets in East Asia read. `finance::quotes::moves` picks the pair.

TASKS.md

@@ -307,3 +307,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T25e | 2 | PASS | |
 | T25f | 1 | FAIL | a drag on the turned embedding froze past the plot's edge; which version a diff sets against, and its heading, had no test |
 | T25f | 2 | PASS | |
+| T26a | 1 | FAIL | the viewer's picture had no id, so an animated picture never left its first frame |

src/media/tests.rs

@@ -282,6 +282,9 @@ fn a_picture_that_cannot_open_says_so(cx: &mut TestAppContext) {
     let cx = viewing(std::env::temp_dir().join("ely-media-missing.png"), cx);
     assert!(cx.debug_bounds("image-viewer-failed").is_some());
     assert!(cx.debug_bounds("image-viewer-picture").is_none());
+    cx.update(|window, _| window.focus_next());
+    let focused = cx.update(|window, cx| window.focused(cx));
+    assert!(focused.is_none(), "with nothing to show, nothing takes Tab");
 }
 
 /// Two thumbnails, the second with no handler; the opens the first heard.

src/media/viewer.rs

@@ -119,7 +119,6 @@ impl RenderOnce for ImageViewer {
                 }
             });
         }
-        let focus = tab_stop((self.id.clone(), "focus").into(), true, window, cx);
         let decoded = window.use_asset::<ImageAssetLoader>(&self.source, cx);
         let turns = view.read(cx).turns;
         let picture: Option<Arc<RenderImage>> = match decoded {
@@ -143,6 +142,12 @@ impl RenderOnce for ImageViewer {
             let size = image.size(0);
             (size.width.0 as f32, size.height.0 as f32)
         });
+        let focus = tab_stop(
+            (self.id.clone(), "focus").into(),
+            pixels.is_some(),
+            window,
+            cx,
+        );
         let theme = cx.theme();
         let colors = theme.colors.clone();
         let (zoom, offset, stage) = {
@@ -252,6 +257,7 @@ impl RenderOnce for ImageViewer {
         });
         let body = match (picture, shown) {
             (Some(image), Some((size, left, top))) => img(ImageSource::Render(image))
+                .id((self.id.clone(), "picture"))
                 .debug_selector(|| "image-viewer-picture".into())
                 .absolute()
                 .left(Pixels::from(left))
@@ -305,8 +311,9 @@ impl RenderOnce for ImageViewer {
             .bg(colors.sunken)
             .border_1()
             .border_color(transparent_black())
-            .track_focus(&focus)
-            .focus_ring(cx)
+            .when(pixels.is_some(), |stage| {
+                stage.track_focus(&focus).focus_ring(cx)
+            })
             .when(overhangs, |stage| stage.cursor_grab())
             .child(
                 canvas(