calender

A desktop calendar app packaged with Wails v2, using a Go backend and Svelte frontend. Events are stored only on your machine in a single JSON file—no server or account required.

Features

• Month grid view with previous / next month controls.
• Right-click a day to add an event (title via prompt; default color is a yellow tone).
• Right-click an event row to delete that entry.
• Persistent storage; data reloads when you reopen the app.
• Dates use YYYY-MM-DD in the local calendar day—no UTC shift from toISOString().

Tech stack

The frontend lives under frontend/; production assets go to frontend/dist/ and are embedded into the binary via //go:embed in main.go.

Architecture (overview)

1. Startup: main.go runs the Wails app and binds the App struct to the frontend.
2. Frontend: App.svelte renders the calendar; it calls GetEvents, AddEvent, and DeleteEvent through frontend/wailsjs/go/main/App.js (generated by wails generate / wails build—do not edit by hand).
3. Data: An in-memory list in app.go, guarded by sync.Mutex; each add/delete writes JSON to disk.

flowchart LR
  subgraph ui [Frontend]
    Svelte[Svelte / Vite]
  end
  subgraph bridge [Wails]
    IPC[IPC calls]
  end
  subgraph go [Go]
    App[app.go App]
    FS[(events.json)]
  end
  Svelte --> IPC --> App
  App --> FS

Backend API (app.go)

Storage details:

• Path: filepath.Join(os.UserConfigDir(), "calender", "events.json").
• Writes use a temp file (*.tmp) plus rename for atomic replacement (reduces risk of a half-written file on crash).
• If UserConfigDir fails, cfg falls back to ".", so the path becomes ./calender/events.json.

Frontend behavior

• Initial load: onMount uses await loadEvents() so the first paint waits for backend data (where applicable).
• Race handling: If GetEvents is slow and the user adds an event, a loadGeneration counter prevents a late GetEvents response from overwriting the list; successful add/delete bumps the counter.
• Date strings: Local year/month/day are used instead of toISOString() so timezone skew does not move events across calendar days.
• Browser-only dev: When window.go is missing (plain npm run dev), sample events are shown; nothing is persisted.

Requirements

• Go (prefer a version compatible with go.mod)
• Node.js and npm
• Wails CLI v2 (wails on your PATH)

Verify your setup:

go version
node -v
npm -v
wails version

Setup and development

After cloning or extracting the repo:

cd calender

Install frontend dependencies once:

cd frontend && npm install && cd ..

Live development (recommended):

wails dev

Vite provides fast HMR for the frontend. If you change Go code (app.go, main.go), you usually need to restart wails dev. If you change Go method signatures exposed to the frontend, run:

wails generate module

or let the next wails build / wails dev regenerate bindings.

Frontend only (no Wails):

cd frontend && npm run dev

Opens in the browser; the Go API is unavailable and the app uses sample data.

Production build

wails build

Output is typically build/bin/calender (Linux/macOS) or build\bin\calender.exe (Windows). Adjust outputfilename and author metadata in wails.json as needed.

More options: Wails build CLI docs.

Data file

Location

Example payload

[
  {
    "id": "550e8400-e29b-41d4-a716-446655440000",
    "date": "2026-04-05",
    "title": "Meeting",
    "color": "#4ade80"
  }
]

Copy this file to back up your events. To reset or test, delete or edit it (preferably while the app is closed).

UI cheat sheet

Project layout

calender/
├── main.go           # Wails entry, embedded static assets
├── app.go            # Event CRUD and JSON persistence
├── go.mod / go.sum
├── wails.json        # Wails project settings
├── frontend/
│   ├── src/
│   │   ├── App.svelte
│   │   ├── main.js
│   │   └── style.css
│   ├── index.html
│   ├── vite.config.js
│   ├── package.json
│   └── wailsjs/      # Generated Go bindings (do not edit)
└── build/            # wails build output (often gitignored)

Troubleshooting