Chromium focuses a clicked <button>, so the shared controls bar treated every
mouse click on a control (fullscreen, mute, ...) as keyboard navigation and
pinned itself open until a click on the viewport took focus away — a click
that also paused playback. Most visible on Embedded MPV frame-copy after
entering fullscreen; reproduces on HTML5, Video.js and ArtPlayer too.
Only keyboard-originated focus pins the bar now: pointer-attributed focus
reveals without a pin, the press record is discarded on the first bar focus
event or any keydown, a pointerdown inside the bar releases a keyboard pin,
and a keydown bubbling out of a bar control re-pins it.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>