Fix(reader): preserve reading progress across library round-trips#77
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uiState restore anchors (index, element key, offset fraction) are frozen at chapter-open and never updated during scrolling — scrolling only updates the controller's live progressState. Opening the full library route disposes the reader composition; returning recomposes it and re-runs runScrollRestore, which replayed the stale anchor: it snapped back and then persisted the stale position over the good one. The in-reader drawer never hit this (it keeps the reader composed), and a seek never did (it syncs uiState), which made it intermittent. Gate restore on a monotonic restoreRequestId bumped only at genuine restore points (calculateInitialPosition, seekToProgress). runScrollRestore resolves its anchor via consumeRestoreAnchor(): a genuine load/seek replays the uiState anchor unchanged, a bare recomposition re-applies the live progressState position with the from-bottom one-shot hard-nulled. Also covers rotation and other route pushes, same recomposition surface. Also harden healLibraryItemForChapterList: it wrote a whole row via updateItem (REPLACE outside progressMutex), a lost-update window against a concurrent progress write. It now writes only totalChapters/currentChapter/ hasUpdates via targeted column UPDATEs (healChapterMetadata).
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Problem
Reading progress was lost when scrolling in a chapter, opening the full library screen, then returning to the reader. Intermittent, because it only triggered via the full library route (which disposes the reader composition), not the in-reader drawer, and never after a seek.
Root cause
uiState's restore anchors (scrollIndex,restoreElementKey,restoreOffsetFraction) are set at chapter-open/seek and never updated during scrolling — scrolling updates only the controller's liveprogressState. On return, the reader composition is recreated andrunScrollRestorere-fires, replaying the frozen anchor: it snapped the view back and a post-restore emission then persisted the stale position over the good one.Fix
restoreRequestId, bumped only at genuine restore points (calculateInitialPosition,seekToProgress).runScrollRestoreresolves its anchor viaconsumeRestoreAnchor():uiStateanchor (behavior unchanged);progressStateposition, with the from-bottom one-shot hard-nulled.Secondary hardening
healLibraryItemForChapterListwrote a whole row viaupdateItem(REPLACE) outsideprogressMutex— a lost-update window against a concurrent progress write. It now writes onlytotalChapters/currentChapter/hasUpdatesvia targeted column UPDATEs (healChapterMetadata), matching the refresh-path pattern from #71.Tests
./gradlew testStandardDebugUnitTest detekt→ 487 tests, 0 failures, detekt clean. Adds 7 tests (anchor-resolution branches, the counter increment, the targeted metadata write); retargets one existing test fromupdateItemtohealChapterMetadata.The unit suite covers the decision logic; the composable's dispose→recompose replay still warrants an on-device text-chapter round-trip check.