Files
buzz/mobile/lib
Tom Brow 9e40bf5d79 perf(mobile): don't treat a Control Center pull as a resume (#9443)
Pulling down Control Center or Notification Center, answering a system
alert, or glancing at the app switcher moves the app to `inactive` and
straight back to `resumed`. The app never leaves the foreground and the
socket stays connected, but every resume listener treated it as a return
from the background. Each glance re-read the channel list (memberships,
metadata, unread catch-up), the four settings documents (mutes, stars,
sections, sort) and the Me groups, and tore down and rebuilt the
community presence subscription. On a heavy Builderlab account that is
about 2.6 MB per glance.

This adds `appForegroundProvider`, which follows the app lifecycle but
ignores `inactive`. The resume refreshes and both presence providers
watch it instead of the raw lifecycle, so they run only when the app
actually comes back from the background. Camera capture keeps watching
the raw lifecycle, since it has to release the camera while the app is
inactive.

### Validation

Added tests: the channel sync journey test now pulls the app through
`inactive` and back without leaving the foreground and expects no
membership read; it fails without this change (2 reads instead of 1).
The existing resume and background cases in that test still pass
unchanged. A second step lets a failed list read's retry come due while
the app is `inactive`; it is read then, not left for a resume that no
longer comes (it fails without the read gate change, 8 reads instead of
9). Full mobile test suite passes.

On an iPhone 12 mini signed in to Block's Builderlab (instrumented
profile build), pulling Control Center down and dismissing it:

| | Downloaded after dismissing it |
| --- | --- |
| Before | 2.6 MB (rosters 1.5 MB, latest messages 0.7 MB, channel
metadata 183 KB, settings, presence resubscribe) |
| After | 6.5 KB (live typing and presence only) |

The same run covered cold start, 5 minutes idle on Messages, and a
resume after 60 s in the background; the resume still refreshed the
channel list, read state and settings documents as before (2.8 MB HTTP,
2.1 MB WebSocket).

### Regressions

None expected. A real return from the background still goes through
`hidden`/`paused` first, so it triggers every refresh it did before. The
only behavior change is for `inactive` alone: no refetch, and the user's
presence no longer flips through a republish of `online`. A channel-list
read that comes due during `inactive` (a membership notice or a retry)
now runs then instead of waiting for a resume, since the socket is still
connected. A missed live event during a Control Center glance is still
caught by the next real resume or reconnect, as before for any time in
the foreground.

---------

Signed-off-by: Tom Brow <tomb@squareup.com>
Co-authored-by: Tom Brow <tomb@squareup.com>
Co-authored-by: studio <dc2fc481343672df31a689840c09299972e704dac592e0da6f18486646a7ee3e@localhost>
2026-11-13 14:40:00 -08:00
..