Sidebar / window-edge animations emit a new viewport bounds on every
GPUI paint. The previous flow fired `runtime.ensure_tab` synchronously
on every change, which reached down into Servo's surfman backend and
destroyed + reallocated the rendering framebuffer 50+ times per second
— each cycle leaving the NSView with an empty surface until Servo's
next paint completed. The user saw the page strobe blank-then-content
on every gesture, plus a one-time Metal driver warning about an
unloadable texture (the previous framebuffer caught mid-recreate).
Track `viewport_size_changed_at` on `PerTabSurface` and propagate the
debounce on two seams:
- `record_viewport_size` returns `Buffered` for a transition that
arrives inside the 80 ms window of the previous one, so the
synchronous `flush_external_web_surface_tick` from the GPUI paint
callback skips the resize altogether. The very first measurement
and the first transition after a quiet period still return `Applied`
so a single drag step or page-load is not delayed.
- `ensure_surface` skips while the viewport is settling, but only
*after* the initial ensure has installed `last_ensure_key`. The
first ensure must fire even mid-gesture or the page never loads.
- `next_tick_delay` clamps the poll cadence to `ACTIVE_POLL_INTERVAL`
while any visible tab is settling, so the trailing-edge resize
fires within a frame of the gesture stopping instead of waiting
for an 80 ms idle tick.
The synchronous `record + ensure` pattern in
`failed_surface_ensure_waits_for_a_new_key_before_retrying` can't
advance an `Instant`, so it now calls a `#[cfg(test)]`
`clear_viewport_resize_debounce_for_test` to simulate the
trailing edge and exercise the retry-on-new-key business rule in
isolation. Adds `rapid_viewport_changes_buffer_until_gesture_settles`
to lock the new behaviour.
Root cause of the post-tab lag: the GPUI 16 ms timer was calling
`WebSurfaceRuntime::ensure_tab` and `tick` on the UI thread, and each
call did a synchronous `serde_json` write plus `read_line` against the
Servo sidecar over stdin/stdout. With even one visible tab, every
frame stalled on cross-process IPC.
Introduce `web_surface_worker.rs` — a per-profile worker thread that
owns the `ServoLiveClient`, drains a coalescing request queue
(latest Ensure/Poll per tab wins, no unbounded growth), and ships
results back through a `std::sync::mpsc` channel. `WebSurfaceRuntime`
now submits work non-blockingly and drains responses in `tick`; the
UI thread never blocks on the sidecar.
Adjacent in-flight cleanup riding along: hardware IOSurface
rendering-context completion (sidecar `live_protocol`,
`hardware_rendering_context`, GPUI BGRA surface shader), CSS viewport
size + device pixel ratio plumbing into `ServoLiveFrame`, and the
Send opt-ins for `CVPixelBuffer`-bearing types so frames can cross
the thread boundary.
bool returns on the five record_* surface inputs collapsed nine real
outcomes into one bit. The cascade we found in this round — silent
click drop because viewport_bounds wasn't measured yet, then
keyboard_focus stays None, then typing also "fails" — looked like
three independent symptoms but was one root cause hiding inside
that bit. Replace the bool with a #[must_use] WebSurfaceInputOutcome
enum so each rejection names itself at the call site.
Variants map 1:1 to real return points in web_surface.rs:
Applied / NoChange / Buffered — three distinct success-ish states
the controller already needed to disambiguate (only Applied notifies)
DroppedInvalidBounds — geometry rejected zero/NaN viewport
DroppedNoViewportBounds — input arrived before the viewport tracker
DroppedOutOfBounds — window position outside the viewport rect
DroppedZeroDelta — wheel rounded to zero device px
DroppedEmptyText — empty record_typed_text
DroppedNoKeyboardFocus — type without a prior click
DroppedFocusMismatch — focus belongs to another tab/url
Behavior preserved: Applied is the only notify trigger, matching the
old `true` semantics. Three new negative-path tests (no_viewport_bounds,
zero_delta, no_keyboard_focus) lock the named drops so a future
regression surfaces as a wrong variant in tests instead of a missing
repaint. cargo test ely_app --bin ely_app web_surface: 17 passed.
Eleven parallel BTreeMaps (click_points, hover_points,
pending_scroll_deltas, scroll_offsets, typed_texts, viewport_bounds,
viewport_sizes, pending_viewport_sizes, states, etc.) made every
input bug a coordination problem across 11 disjoint maps with no
compile-time guarantee they stayed in sync. Collapse them into
BTreeMap<TabId, PerTabSurface>: one owner per tab, one lookup per
input event. keyboard_focus stays at the store level because only
one tab in the window can hold focus at a time.
Public API and behavior are unchanged; the previously-fixed
"scroll keeps keyboard_focus" semantics are preserved. cargo test
ely_browser_core + cargo test ely_app --bin ely_app green.
Without continuous MouseMove events, Servo never updates hover state:
no cursor changes over links, no :hover CSS effects, no mouseenter
JavaScript events. The web page appears completely non-interactive.
Track mouse position from GPUI on_mouse_move through the full IPC
pipeline to Servo. Hover position is included with each ensure
request so Servo updates hover state at frame rate (~60fps).
ZacharyZhang-NY