## Summary * **What is the goal of this PR?** Fix KOSync failing with "Network error" on large/complex EPUBs, and simplify the sync navigation flow by removing the callback/result pattern. * **What changes are included?** This PR combines the approaches from #1855 and #1760 into a single, cleaner solution: **Memory fix (from #1855):** - `EpubReaderActivity` pre-computes the local KOReader position and chapter name, then explicitly releases `epub` and `section` before launching `KOReaderSyncActivity`. This frees ~65KB measured on device, giving the TLS handshake sufficient heap. The root cause was `MBEDTLS_ERR_X509_ALLOC_FAILED` (-0x2880) when a 3-cert chain consumed ~48KB during the handshake with only ~50KB available. - `KOReaderSyncActivity` no longer receives a `shared_ptr<Epub>` at construction — it lazy-loads the Epub after TLS only if remote progress is found (`ensureEpubLoaded()`). - Added `MIN_HEAP_FOR_TLS = 55000` guard in `KOReaderSyncClient` — returns `LOW_MEMORY` early if aggregate free heap is too low before attempting a TLS connection. **Navigation simplification (from #1760):** - Replaced `startActivityForResult` + callback with `activityManager.replaceActivity` / `activityManager.goToReader`. Progress is saved to `progress.bin` before the epub is released (cancel/upload paths) and in `saveProgressAndReturn` (apply remote path). The reader re-launches from the saved position naturally via `goToReader`, eliminating the need to reload the epub in a callback. - Extracted `ReaderUtils::saveProgress()` as a shared helper used by both `EpubReaderActivity` and `KOReaderSyncActivity`. - Added `STR_SAVE_PROGRESS_FAILED` to all 22 language files for the case where writing the synced position to SD fails. **Orientation fix (found during device testing):** - `EpubReaderActivity::onExit()` resets the renderer to portrait before destruction. With `replaceActivity` the reader is fully torn down before KOSync starts, so KOSync was always rendering in portrait even when reading in landscape. Fixed by calling `ReaderUtils::applyOrientation` in `KOReaderSyncActivity::onEnter()`. ## Additional Context Heap measurements on device (large EPUB with complex CSS): | Metric | Before | After | |---|---|---| | Heap before Epub release | 88,156 bytes | — | | Heap after Epub release | — | 153,892 bytes (+65,736) | | Heap at TLS handshake | ~50,000 bytes (fails) | ~116,384 bytes (passes) | | Min-free-ever during sync session | 2,600 bytes | 33,052 bytes | | TLS result | `MBEDTLS_ERR_X509_ALLOC_FAILED` | HTTP 200 | Tested on device: sync from inside a large EPUB in both portrait and landscape, cancel, apply remote progress, upload local progress. --- ### AI Usage Did you use AI tools to help write this code? _**YES**_ --------- Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
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