Architecture Overview

mdgreet separates UI layout (Slint) from business logic (Rust) while using Tokio for asynchronous operations like inter-process communication (IPC) with greetd.

Module Structure

The project is structured into clear responsibilities:

• src/main.rs: Acts as the pure orchestrator. It parses CLI arguments, initializes logging, sets up the Slint UI instance, and delegates specific features to the app:: modules.
• src/app/: Contains the core UI logic and event handlers.
  • appearance.rs: Resolves themes (builtin, dynamic, custom), parses colors, handles background blur, and configures fonts.
  • auth.rs: Manages the list of valid system users.
  • login.rs: Orchestrates the authentication flow. It handles the on_login callback, bridging the synchronous Slint UI with asynchronous Tokio tasks that talk to greetd.
  • session.rs: Discovers available Wayland/X11 compositors on the system.
  • state.rs: Manages UI state persistence, such as remembering the last selected user and their preferred compositor.
  • power.rs: Executes system commands for shutdown, reboot, etc.
• src/utils/: Helper utilities.
  • client.rs: The GreetdClient which handles Unix socket IPC using the greetd_ipc protocol.
  • cache.rs: Simple LRU-style disk caching for UI state.

Concurrency Model

Slint runs its own event loop on the main thread. We use tokio::spawn within UI callbacks to run blocking or network tasks asynchronously.

When an async task needs to update the UI (e.g., showing an error message after a failed login), we use ui_weak.upgrade_in_event_loop(...) to safely push the update back to the main UI thread without causing deadlocks.