Phase 4: Daemon Mode & gar Integration

Goal

Implement daemon mode with IPC server, integrate with gar window manager for workspace-aware wallpapers.

Tasks

4.1 Daemon Mode

• Daemonize process (fork, setsid, etc.)
• PID file management
• Signal handling (SIGHUP for reload, SIGTERM for shutdown)
• Graceful shutdown with resource cleanup

4.2 IPC Server

• Unix socket at $XDG_RUNTIME_DIR/garbg.sock
• JSON lines protocol
• Command parsing and dispatch
• Response serialization
• Client connection management

4.3 IPC Commands

• set - Set wallpaper
• next / prev - Slideshow navigation
• random - Random wallpaper from source
• reload - Reload configuration
• pause / resume - Animation/slideshow control
• status - Get current state
• subscribe - Event subscription

4.4 gar IPC Client

• Connect to gar's IPC socket
• Subscribe to workspace events
• Subscribe to monitor events
• Parse gar's JSON event format

4.5 Per-Workspace Wallpapers

• Map workspace ID to wallpaper config
• Switch wallpaper on workspace change
• Smooth transition (instant, per design decision)
• Fallback to default wallpaper

4.6 Slideshow/Rotation

• Timer-based rotation
• Configurable interval
• Random or sequential ordering
• Per-source playlist management

Deliverables

• garbg daemon starts background daemon
• garbgctl set /path/to/image.png sends command to daemon
• Changing workspaces in gar changes wallpaper
• Slideshow rotates wallpapers at configured interval

IPC Protocol

Commands (Client -> Server)

{"command": "set", "source": "/path/to/image.png", "mode": "fill"}
{"command": "next"}
{"command": "prev"}
{"command": "random"}
{"command": "reload"}
{"command": "pause"}
{"command": "resume"}
{"command": "status"}
{"command": "subscribe", "events": ["wallpaper_changed", "slideshow_advanced"]}

Responses (Server -> Client)

{"success": true}
{"success": true, "data": {"current": "/path/to/image.png", "mode": "fill", "paused": false}}
{"success": false, "error": "File not found"}

Events (Server -> Subscribed Clients)

{"event": "wallpaper_changed", "source": "/path/to/new.png", "workspace": 1}
{"event": "slideshow_advanced", "current": 5, "total": 20}
{"event": "error", "message": "Failed to fetch remote image"}

gar Event Handling

// Subscribe to gar workspace events
let subscribe_msg = json!({
    "command": "subscribe",
    "events": ["workspace"]
});

// Handle workspace change
fn handle_gar_event(&mut self, event: GarEvent) {
    match event {
        GarEvent::Workspace { current, .. } => {
            if let Some(config) = self.config.workspaces.get(&current) {
                self.set_wallpaper(&config.source, config.mode);
            }
        }
        _ => {}
    }
}

Files Modified/Created

• /garbg/garbg/src/daemon/mod.rs - Daemon module
• /garbg/garbg/src/daemon/state.rs - Daemon state management
• /garbg/garbg/src/daemon/event_loop.rs - Main event loop
• /garbg/garbg/src/daemon/signals.rs - Signal handling
• /garbg/garbg/src/ipc/mod.rs - IPC module
• /garbg/garbg/src/ipc/server.rs - IPC server
• /garbg/garbg/src/ipc/protocol.rs - Command/Response types
• /garbg/garbg/src/ipc/gar_client.rs - gar IPC client