Servo's hit-test silently absorbs notify_input_event on a hidden or
unfocused WebView. Today show()+focus() are called at creation and on
the first-navigate rebuild, but every later sibling-WebView creation
also calls focus() — silently stealing focus from the foreground tab.
load() (later navigates), resize, set_page_zoom, and paint never
re-focus, so a click on the visible tab can land on an unreachable
WebView and disappear.
Move the invariant from a state spread across creation/navigation/
tab-switching into a property of the dispatch path itself: a private
webview_for_input(id) helper re-asserts show()+focus() and returns
the WebView; click/hover/drag/touch_tap/scroll/type_text all go
through it. The cosmetic show/focus calls in create_webview_in_context
and the navigate-rebuild branch stay (first-frame paint), now annotated
to point to webview_for_input as the input-path owner.
Not a complete fix on its own. focus() goes through constellation_proxy
asynchronously (servo crate webview.rs:352), so debug_assert!(focused())
right after focus() would race the constellation — doc comment is the
only guard. Sidecar integration tests pass 9/9 but only exercise
single-WebView sessions; multi-tab focus stealing on Google / YouTube /
Twitter still needs human verification in the live shell. Linus's
critique of the GPUI-side data structure (PerTabSurface Option-as-queue
+ Ensure bundling config+input+frame) is a separate layer untouched
by this change.
Pre-existing tests/software_host.rs::manages_real_servo_webview_lifecycle
already times out on https://servo.org/ with state=Complete but
has_pending_frame=false on b8795bf without this change, so unrelated.
ZacharyZhang-NY
6314e1f777