Calendula Desktop

A native Linux calendar.
A desktop fork of Calendula — the Material 3 calendar — rebuilt with Compose Multiplatform to talk directly to a CalDAV server.

About

This is a fork/port of upstream Calendula, an Android calendar app. The original reads and writes Android's CalendarContract (any calendar already synced to the device); this desktop version replaces that data layer with a small CalDAV client, so it connects straight to a CalDAV server (Nextcloud, Radicale, Baikal, Fastmail, …) and needs no Android stack.

What carries over from upstream:

• The domain model, recurrence engine, and ICS codec (ported faithfully and JVM-tested).
• The Calendula identity: seed-derived slate palette, light/dark theme, and the real launcher icon.

What is different, because it's a PC:

• A sidebar (Month / Week / Day / Agenda / Settings) instead of the Android drawer.
• Settings live in-app and cover appearance, view layout, and new-event defaults — plus the CalDAV server connection.
• Reminder notifications are fired with notify-send.
• The password is stored in the OS keyring (Secret Service) when available.

✨ Features

• Month, week, day, and agenda views with a sidebar switcher
• Week/day time-grid timelines (all-day strip, timed blocks, a "now" line, tap-an-empty-slot to create)
• Full event details — times, location, description, reminders, recurrence
• Create, edit, and delete events; delete a single occurrence (EXDATE) or a series from an occurrence onwards (RRULE truncation)
• Recurrence expansion for DAILY/WEEKLY/MONTHLY/YEARLY, INTERVAL, COUNT, UNTIL, BYDAY, BYMONTH, BYMONTHDAY, BYSETPOS, WKST
• Per-event colors from the ICS COLOR / X-APPLE-CALENDAR-COLOR properties (hex and CSS color names), falling back to the calendar's color
• Reminder notifications (notify-send) for events with a VALARM
• Settings — theme (system/light/dark), dynamic colour (matugen), week start, 12/24-hour time, default view, hour lines, dim-past, default event duration & reminders, and change server
• In-app CalDAV setup — paste server URL, username, and password; no file editing required
• AI assistant (MCP) server — expose your calendars to Claude, Gemini, and other MCP clients as callable tools (opt-in)

🔧 Configuration

On first launch (or via Settings → Server → Change server) you connect with a server URL, username, and password. This writes ~/.config/calendula/config.properties:

caldav.url=https://cloud.example.com/remote.php/dav/
caldav.username=your-user

The password is stored in the OS keyring (via secret-tool / Secret Service); it only falls back to caldav.password in the config file on systems without a keyring. Environment variables CALDAV_URL, CALDAV_USERNAME, and CALDAV_PASSWORD take precedence over the file.

User preferences live in ~/.config/calendula/settings.properties.

🎨 Dynamic colour (matugen)

Calendula can take its whole Material colour scheme from matugen instead of the built-in slate palette. Enable it under Settings → Appearance → Dynamic → Matugen.

The repo ships a ready-made template at packaging/matugen/calendula.template. Point a matugen template at it and write the output to ~/.cache/matugen/calendula.colors:

# ~/.config/matugen/config.toml
[templates.calendula]
input_path = '~/.../calendula-desktop/packaging/matugen/calendula.template'
output_path = '~/.cache/matugen/calendula.colors'

Then run matugen once (e.g. matugen image ~/wallpaper.png) so the file exists. Calendula reads it at launch and whenever the Dynamic setting changes; the output path can be overridden with the CALENDULA_MATUGEN_COLORS environment variable. If the file is missing or malformed, the app silently falls back to the built-in palette.

🤖 AI assistants (MCP)

Calendula can expose your calendars to AI assistants (Claude, Gemini, Cursor, …) as a set of tools over the Model Context Protocol. Enable it under Settings → Integrations → AI assistants, then point your assistant at calendula --mcp. See docs/mcp.md for the config JSON and file locations.

📦 Install

Two ways to run it on Linux (x86_64):

AppImage

Download (or build) Calendula-<version>-x86_64.AppImage, make it executable, and run it. The AppImage bundles its own JRE — no Java required on the target system.

Arch Linux (pacman)

./build.sh also builds the Arch package (calendula-desktop-<version>-1-x86_64.pkg.tar.zst) into dist/. Install it with:

sudo pacman -U dist/calendula-desktop-<version>-1-x86_64.pkg.tar.zst

The package depends on java-runtime>=17 and installs the calendula launcher, desktop entry, and hicolor icon. (You can also run makepkg -si manually inside packaging/arch/, but build.sh is the supported path.)

🛠 Build from source

Requires JDK 17 (set JAVA_HOME, e.g. /usr/lib/jvm/java-17-openjdk):

./gradlew run                       # launch the app (needs a display)
./gradlew build                     # compile + run tests
./build.sh                          # build AppImage + Arch package into dist/

build.sh additionally needs jpackage (bundled with JDK 17), appimagetool for the AppImage, and makepkg + fakeroot for the Arch package.

📁 Project layout

src/jvmMain/kotlin/de/jeanlucmakiola/calendula/
  domain/      — models, recurrence rules, event form (ported from upstream)
  data/
    caldav/    — CalDavClient (WebDAV/HTTP+XML), IcsCodec, Recurrence, Keyring
    prefs/     — settings store
    reminders/ — ReminderNotifier + notify-send backend
    CalendarDataSource.kt / CalDavDataSource.kt — the calendar seam + impl
  ui/          — AppState, sidebar, month/week/day/agenda views, settings, editor
  Main.kt      — desktop entry point + setup screen
packaging/
  arch/        — PKGBUILD, launcher, desktop entry, icon
  icon/        — the launcher SVG (single source of truth for the icon)
  matugen/     — the matugen template for dynamic colour
build.sh       — builds the AppImage + Arch package into dist/

⚖️ Differences from upstream

• Data layer: CalDAV client instead of Android CalendarContract.
• Theme: upstream uses Material 3 Expressive via the Android-only floret-kit; this port uses stable Compose MaterialTheme with the same slate palette (the MaterialExpressiveTheme API is only public in Compose Multiplatform's alpha material3 line).
• Not ported (Android-specific): widgets, per-app language, contact special-dates, launcher-name/font choices, and multi-account UI. (Android's wallpaper dynamic colour is replaced by the matugen integration above.)

📜 License

MIT — Jean-Luc Makiola. This is a fork of Calendula, also MIT.