fix(desktop): stop channel switches jittering and flashing - #6524
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fix(desktop): stop channel switches jittering and flashing#6524Maxwellimus wants to merge 2 commits into
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Entering a channel whose thread-summary facepiles hydrate after first paint (profiles resolving late) visibly shifted the timeline: every row above a summary slid ~3px per summary a beat after content painted. The summary button was inline-flex, so it participated in its wrapper's line box via its baseline — and that baseline moves when the avatar's content resolves (Radix fallback text appearing after its delay, or the avatar image landing). Make the button a block-level flex row so the wrapper height is padding + button height regardless of avatar state, and render the facepile fallback immediately (fallbackDelayMs=0): the participant starts with no image URL, so the default 200ms delay only left a blank hole where the initials belonged. Regression spec pins the wrapper height from first paint through hydration and the root row's position after the facepile renders, with the users-batch response deliberately delayed past first paint. Signed-off-by: Max Lampert <maxwell@squareup.com>
Two skeleton flashes made switching feel clunky: - Every switch: the deferred timeline snapshot lags the live one for a frame or two, and that gap painted the full skeleton to mask the previous channel's rows — a visible skeleton flash on every switch. The gap is a render-pipeline artifact, not a loading state: it now renders plain background (new "blank" body surface). Blank blocks the same behaviors as the skeleton (autoscroll, jumps, unread pill, scrollback), only the visual differs. Cold loads keep the skeleton. - Stale revisits: the loading latch reset on every switch, so re-entering a channel past the messages staleTime refetched on mount with the unsettled skeleton branch active — a skeleton over a fully cached timeline for the whole relay round-trip. Channels that settled once this session now render their cached rows stale-while-revalidate (session registry, reset via resetCommunityState like every other community-scoped singleton). The revisit spec forces staleness by shifting Date.now past the 5-minute window and asserts the skeleton never mounts over cached rows; the switch-gap behavior is covered by the timelineSnapshot unit suite. Signed-off-by: Max Lampert <maxwell@squareup.com>
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Based on
perf/switch-tracing— retarget to main after it merges. (Shares the settle seam in ChannelScreen and the community-reset inventory.)Two visible artifacts made switching feel clunky (diagnosed by frame-by-frame analysis of a 120fps capture):
inline-flex, so it participated in its wrapper's line box via its baseline — which moves when the avatar's content resolves (Radix fallback delay, or the avatar image landing after profiles hydrate). The button is now a block-level flex row (wrapper height = padding + fixed button height regardless of avatar state: 36px constant, was 39→36) and the facepile renders its fallback immediately — the participant starts with no image URL, so the 200ms fallback delay only left a blank hole.resetCommunityState()).Both are pinned by red-first regression specs:
thread-summary-stability.spec.ts(row geometry through delayed profile hydration; failed 39→36px pre-fix) andchannel-revisit-no-skeleton.spec.ts(staleness forced by shiftingDate.now()past the freshness window; skeleton must never mount over cached rows).Measured impact (live community, switch traces)
Recreates #6457, which was accidentally squash-merged into its base branch
perf/switch-tracing(since reverted there). Same content; still stacked on #6455.