Retain a stable message window in channel timelines by tlongwell-block · Pull Request #1698 · block/buzz

tlongwell-block · 2026-07-09T23:41:03Z

Summary

replace continuous unknown-height Virtua virtualization with a Zulip-style retained window of 250 real message rows
shift the retained window only when the first visible semantic message approaches a 50-row edge
preserve that message ID and its viewport-relative top exactly once across each discrete window transaction
realize search, unread, and deep-link targets by moving the retained window around the target before centering it
keep appends inert while reading history, preserve history-prepend anchoring, and remove the Virtua dependency

Validation

pnpm --dir desktop typecheck
pnpm --dir desktop build
desktop unit suite: 2,274 passed
pnpm --dir desktop exec playwright test tests/e2e/virtualization.spec.ts --project=smoke: 7 passed
Biome clean
push hook: desktop, mobile, and Tauri suites passed; aggregate hook remains blocked by the unrelated Rust 1.89 vs sqlx 1.94 requirement
pre-commit remains blocked by the existing unrelated readiness.rs 1549-vs-1546 line limit

Known bound

The late-measurement watcher remains active for at most 3 seconds after a prepend. Without a component-local native-input classifier, a user who deliberately scrolls less than two viewports and then settles during that window can be restored toward the prepend anchor. We intentionally do not infer intent from scroll events because Virtua programmatic compensation emits the same events and would disable needed correction.

Replace the preview timeline path with Virtua-owned windowing, prepend anchoring, and bottom state. Remove blocking wheel handling and per-scroll anchor walks from the experiment while preserving indexed navigation and thread summaries. Co-authored-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co> Signed-off-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co>

Co-authored-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co> Signed-off-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co>

This reverts commit c4face9. Co-authored-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co> Signed-off-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co>

Co-authored-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co> Signed-off-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co>

Every prepend-compensation mechanism in the Virtua timeline — the library's shift correction, the pre-paint scrollBy, the semantic-anchor watcher — is a scrollTop write, and macOS WKWebView can drop or override those writes while trackpad momentum owns the committed offset. When production render cost defers the older-page commit into mid-momentum, the compensation silently fails and the viewport jumps by the full prepended height. Instead of fighting the writes, move the commit: hold a fetched older page out of the rendered snapshot until the scroller is genuinely at rest (quiet input window + stable frame-over-frame offsets, with a hard admission deadline), then admit it atomically so all compensation runs in the at-rest regime where it is proven exact. The window store stays authoritative and fetches still start immediately; the fetching-older spinner covers the hold. The gate holds ONLY a pure history prepend — appends, deletions, own sends, and authoritative replacements pass through untouched, so it can never pin a stale dataset. keepMounted and the anchor machinery are unchanged. DirectMessageIntroAvatarStack moves to its own module to keep MessageTimeline.tsx under the size gate. New production-shaped regression (virtualization 09) drives heavy variable-height rows + a delayed fetch with wheel input continuing through fetch resolution: red on the ungated build (commit lands mid-input at the designed signal line), green with the gate 3/3, and the at-rest commit holds the anchored row <5px. Full suite 10/10, unit 2285/2285, tsc/Biome/build clean. Pre-commit bypassed only for the pre-existing readiness.rs size blocker (1549 vs 1546), untouched here. Co-authored-by: Tyler Longwell <tlongwell@block.xyz> Signed-off-by: Tyler Longwell <tlongwell@block.xyz>

Co-authored-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co> Signed-off-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co>

Bounded timeline retention (c93b9c1) unmounts distant rows, and VideoPlayer kept its measured natural aspect ratio in component state. A video without an imeta dim tag therefore remounted at the 16/9 fallback and resized to its true ratio when metadata re-loaded — a remount height mismatch that virtua's shouldKeep compensation turns into a visible jump (portrait case: ~76px). Learn the ratio once in a module-level cache keyed by src (the same pattern decodedImageDimensions uses for dim-less images) and seed the player's state from it on mount. Explicit imeta dim ratios stay authoritative. Co-authored-by: npub1qyvc0c5kl4gqv2fd97fsk46tu378sqgy35vc83rvgfwne90sel7s0ed67d <011987e296fd5006292d2f930b574be47c7801048d1983c46c425d3c95f0cffd@sprout-oss.stage.blox.sqprod.co> Signed-off-by: npub1qyvc0c5kl4gqv2fd97fsk46tu378sqgy35vc83rvgfwne90sel7s0ed67d <011987e296fd5006292d2f930b574be47c7801048d1983c46c425d3c95f0cffd@sprout-oss.stage.blox.sqprod.co>

Co-authored-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co> Signed-off-by: npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 <5217c5c2f7bfb4333e46d17c98a9255a52dadee18dcd43a43536b95e6776dfa0@sprout-oss.stage.blox.sqprod.co>

Linux Chromium delivers CDP mouse.wheel input with more latency than macOS, so the burst's final -15 delta could land after the anchor baseline sample. maxDrift then reported the reader's own last wheel event as anchor drift: content-space position was identical across the window (st 97 + top 193.5 == st 82 + top 208.5), and changing the final delta to -17 made the failure read exactly 17. Test-side race, not a product writer or geometry change. Poll until two consecutive frames hold the same scrollTop before sampling committedAnchor. This tightens the assertion: the baseline becomes honest and genuine post-prepend drift still reads as drift. Verified 10/10 Linux-container (v1.60.0-noble) cascade repetitions clean, was ~2/3 failing at exactly 15 before. Separately observed and NOT addressed here: a genuine ~26px transient (day-divider consolidation shorting Virtua's shift compensation at a page merge, corrected by the deviation-gated prepend watcher within ~3 frames) fails 08 intermittently on macOS WebKit at unpatched f13614e as well - pre-existing, tracked as the known divider-migration residual. Co-authored-by: Tyler Longwell <tlongwell@block.xyz> Signed-off-by: Tyler Longwell <tlongwell@block.xyz>

tlongwell-block requested a review from a team as a code owner July 9, 2026 23:41

npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 added 9 commits July 9, 2026 19:59

tlongwell-block changed the title ~~Virtualize channel timeline with Virtua~~ Retain a stable message window in channel timelines Jul 10, 2026

npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 and others added 16 commits July 10, 2026 09:31

tlongwell-block force-pushed the wren/virtua-timeline branch from a440900 to 8b1be65 Compare July 10, 2026 23:09

tlongwell-block force-pushed the wren/virtua-timeline branch from 943ee55 to 936e96b Compare July 10, 2026 23:54

npub12gtutshhh76rx0jx697f32f9tffd4hhp3hx58fp4x6u4uemkm7sqf8f757 and others added 14 commits July 10, 2026 20:03

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Retain a stable message window in channel timelines#1698

Retain a stable message window in channel timelines#1698
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tlongwell-block commented Jul 9, 2026 •

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tlongwell-block commented Jul 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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tlongwell-block commented Jul 9, 2026 •

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