# GPS2Audio v2.7.36 — Handoff

Critical bugfix on top of v2.7.35: **the app froze and crashed right after a
backup was successfully created.** No feature/UI redesign; one targeted fix.

## Root cause

`WaypointViewModel.exportBackupZip()` ran the **entire** backup on the **main
(UI) thread**. Its `viewModelScope.launch { … }` block (viewModelScope defaults
to `Dispatchers.Main`) directly performed:

- several `repository.*.first()` / `musicStore.settingsFlow.first()` flow reads, and
- `BackupExportManager.writeBackup(...)` — which opens the destination
  `OutputStream`, builds the ZIP, and copies **every referenced media file** in
  64 KB chunks (`copyMediaToZip`).

For any backup containing media this blocks the UI thread for seconds. Android
raises an **ANR ("Application Not Responding")**, which the user experiences as
"the app no longer responds and crashes." Crucially, the ZIP write itself
completes first — so the backup file is created successfully and *then* the app
hangs, which is exactly the reported symptom.

The import paths (`loadBackupPreview`, the import-confirm flow) already correctly
wrap their heavy work in `withContext(Dispatchers.IO)`. The **export path was the
lone offender** — it never switched dispatchers.

## The fix

In `exportBackupZip()`, the heavy work (flow reads + `writeBackup`) is now wrapped
in `withContext(Dispatchers.IO)`, mirroring the existing import code. The
success/error UI-state updates (`_infoMessage` / `_errorMessage`) stay after the
IO block on the coroutine's resumption. The whole IO section is additionally
guarded by `runCatching { … }.getOrElse { … }` so that any unexpected failure
(e.g. a `SecurityException` on the target URI) surfaces as a **non-fatal error
message** instead of crashing — the file is already written by then, so the user
still keeps their backup.

`BackupExportManager.writeBackup` already had robust internal `runCatching`
handling per-file and overall, so no changes were needed there. The added outer
guard is belt-and-suspenders for anything thrown before/around it.

What was **not** changed: the backup ZIP schema/content, `formatVersion`, the
import logic, and every other feature/fix (v2.7.32 tour ordering + player
auto-open, v2.7.33 Begleitmusik UI, v2.7.34 waypoint-edit UI, v2.7.35 library UI,
Explorer/MapLibre/routing/POI/license/PTT/Atmo/multiclip/background playback).

## Changed files

1. `app/src/main/kotlin/de/waypointaudio/viewmodel/WaypointViewModel.kt`
   - `exportBackupZip()`: heavy IO moved onto `Dispatchers.IO`; added outer
     `runCatching` so post-write failures are reported, not fatal. No signature,
     parameter, or behavior change beyond threading + error safety. Identical
     `BackupInput` / `BackupSelection` are built and the same
     `BackupExportManager.writeBackup(...)` is called.
2. `app/build.gradle.kts`
   - `versionCode 141 → 142`, `versionName 2.7.35 → 2.7.36`, changelog comment.

## Build & test

- Command: `./gradlew :app:assembleRelease --no-daemon`
- Result: **BUILD SUCCESSFUL** (~56s). Only pre-existing deprecation warnings;
  none from the changed function.
- Signed with the release config from `keystore.properties`. Verified:
  `CN=GPS2Audio, OU=NesoHub, O=GPS2Audio, L=Germany, C=DE`,
  SHA-256 `490511f3…d4e5` (same key as prior releases).
- `aapt2 badging`: `versionCode='142' versionName='2.7.36'`.
- No unit/instrumented test suite in the project. Verification was build +
  signature + version + code-path review against the working import path
  (which already used the off-main-thread pattern this fix adopts). The flow was
  **not** exercised on a device/emulator in this environment.

### How to verify on device
Create a backup that **includes media** (waypoint audio and/or Atmo playlists,
i.e. the "Medien/Atmo" section enabled) to a SAF location. Before: the UI freezes
for several seconds after the file appears, then ANR/crash. After: the UI stays
responsive and a "Backup erfolgreich erstellt …" message is shown.

## Artifacts

- `GPS2Audio_v2.7.36_universal-release-signed.apk` — signed universal release
  APK (single APK; no ABI splits configured).
- `GPS2Audio_v2.7.36_src.zip` — clean source. Excludes `.gradle`, `.idea`,
  `.kotlin`, all `build/` dirs, `.git`, and binaries
  (`.apk/.aab/.jks/.keystore/.so` and raster images). Verified: changed files
  present, no excluded artifacts inside.
  **Note:** `keystore.properties` and `local.properties` text files are still
  included. `keystore.properties` carries the signing path/passwords — **strip
  it before distributing the source externally.**