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Maurice
0a824cec84
Includes the tab ids the ?tab= parameter takes - they are the historic German names, which is not something anyone would guess. That matters for the people who asked: a shortcut or a browser wrapper can point at a tab without the setting at all.
93 lines
6.4 KiB
Markdown
93 lines
6.4 KiB
Markdown
# Offline Mode and PWA
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TREK can be installed as a Progressive Web App (PWA) and used without an internet connection for previously synced trips.
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## Install as an app (PWA)
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TREK must be served over **HTTPS** — the install prompt does not appear on plain HTTP.
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**iOS (Safari):**
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1. Open TREK in Safari.
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2. Tap the Share button.
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3. Select **Add to Home Screen**.
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**Android (Chrome / Edge):**
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1. Open TREK in the browser.
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2. Tap the browser menu.
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3. Select **Install app** or **Add to Home Screen**.
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Once installed, TREK launches in **standalone** mode (fullscreen, no browser UI) using the TREK icon.
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The installed app starts at the app root, so the **Start page** setting decides what you see when you tap the icon — the dashboard, or straight into your active trip on a tab of your choice. See [Display-Settings](Display-Settings).
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## What works offline
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TREK uses Workbox service-worker caching plus an IndexedDB database (Dexie) for structured trip data. The following content is available offline after the first sync:
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**Service-worker cache (Workbox)**
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| Content | Cache name | Strategy | Duration | Max entries |
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|---------|------------|----------|----------|-------------|
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| CartoDB / OpenStreetMap map tiles | `map-tiles` | CacheFirst | 30 days | 12 288 |
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| Mapbox GL style, glyphs, sprites and vector tiles | `mapbox-tiles` | StaleWhileRevalidate | 30 days | 3 000 |
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| OpenFreeMap MapLibre style and tiles | `openfreemap-tiles` | StaleWhileRevalidate | 30 days | 3 000 |
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| Cover images and avatars (`/uploads/covers`, `/uploads/avatars`) | `user-uploads` | CacheFirst | 7 days | 300 |
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| App shell and every page of the app (HTML / JS / CSS) | precache | Precached | Until next deploy | — |
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> **Note:** API responses are **never** stored in the service-worker cache. Workbox keys its entries by URL and cannot vary them on the session cookie, so on a shared device one account's cached data could be served to the next. Offline reads come from the per-user IndexedDB cache described below instead.
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> **Note:** The precache covers every page, not just the one you happen to open first. A page you have never visited still works after you lose connectivity — at the cost of a larger initial install.
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**IndexedDB (Dexie) — structured trip data**
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On login, after each trip-list refresh, and on WebSocket reconnect, TREK runs a background sync that writes full trip bundles into IndexedDB:
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- Trips, days, places, packing items, to-dos, budget items, reservations, accommodations, trip members, tags, and categories.
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- Non-photo file attachments (PDFs, documents, etc.) are downloaded and stored as blobs in IndexedDB.
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- Map tiles are pre-fetched into the service-worker `map-tiles` cache for zoom levels 10–16 across each trip's bounding box (capped at ~50 MB of tiles per sync).
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**Sync scope and eviction**
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- Only ongoing and future trips are cached (trips whose `end_date` is today or later, or has no end date).
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- Trips that ended more than 7 days ago are automatically evicted from IndexedDB on the next sync.
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## Settings → Offline
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The **Offline** tab gives you control over what is stored on this device and lets you go offline deliberately.
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### Offline mode
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- **Force offline mode** — a switch that first downloads everything you need (see *Prepare for offline* below) and then routes the whole app to the local cache, queueing every change you make. Flip it back off to reconnect: queued changes are replayed and the cache is refreshed. The override is remembered across app restarts, so a session forced offline before a flight stays offline when the PWA relaunches.
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- **Prepare for offline** → **Download for offline use** — a one-tap, progress-tracked download of trip data, documents and map tiles for every trip you keep offline. Unlike a background sync it *waits* for the downloads to finish, so the completion state means you really have everything.
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- **Re-sync now** — refreshes the cache from the server. Disabled while offline.
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### What to store offline
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- **Store map tiles offline** — map tiles use the most storage by far. Turn this off to keep only trip data and documents on the device; the pre-downloaded tile cache is cleared immediately.
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- **Per-trip toggle** — each trip has its own on/off switch. Turning a trip off evicts its cached read data from the device (your unsynced edits are kept and still sync).
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### Sync conflicts
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If a change you made offline collides with a newer change on the server, it is surfaced as a **conflict** instead of silently overwriting anything. The conflict list lets you **keep mine** or **keep theirs** per item. A default rule (*Ask me each time* / *Always keep my version* / *Always keep the server version*) is configurable under **When a conflict happens**. Conflict detection covers places and packing items.
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### Stats & cache
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The stats panel shows cached trips, pending changes, conflicts and failed changes. **Clear cache** removes all offline data from IndexedDB (you can re-sync any time while online). Each cached trip entry shows its date range, place/file count and last successful sync.
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## Limitations
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- Offline **editing** is supported for places and packing items (with conflict detection). Other entities — budget, to-dos, reservations, days — require connectivity to edit; while forced offline those edits still go to the live server when a connection is actually present.
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- A change you made offline that **deletes** an item wins over a concurrent server edit of that same item ("delete wins"); only edit-vs-edit conflicts are surfaced for resolution.
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- The conflict token has one-second resolution, so two edits to the same field within the same second can't be told apart and fall back to last-write-wins (only relevant to sub-second races; normal offline windows are unaffected).
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- New trips created while offline are queued and synced when connectivity is restored.
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- Photo uploads require connectivity; non-photo file attachments are pre-cached automatically during sync.
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- Real-time collaboration features require an active WebSocket connection.
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- Mapbox GL / vector tiles are not pre-downloaded; raster (Leaflet) tiles are. With map-tile storage off, individually viewed tiles may still be cached opportunistically by the service worker.
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## See also
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- [User-Settings](User-Settings)
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- [Display-Settings](Display-Settings)
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