Architecture
Userland And Windowing
Runtime, apps, compositor, and GUI protocol crates
Userland is a mix of low-level syscall wrappers, a libc layer, async runtime, protocol crates, and apps.
Runtime Layers
| Layer | Source | Role |
|---|---|---|
| Raw syscalls | Userland syscall layer | Thin register-level wrappers |
| libc | libc layer | std PAL shims, malloc, stdio, process, thread, signal, net |
| SlopRing runtime | Runtime crate | Safe userland ring wrapper |
slopfut | Runtime crate | Futures executor, reactor, I/O, time, signals, process waits |
| Protocol | Protocol crate | Display protocol v2 typed wire format |
| Windowing | Windowing runtime | Surfaces, buffers, event loop, raw drawing apps |
| AppKit | App toolkit | Retained widget toolkit and controls |
Apps
The root image currently builds apps and tools such as:
init shell terminal compositor roulette file_manager image_viewer
sysmon nmap ifconfig nc curl pingThe test image adds userland test binaries for fork, heap, image, ring, pidfd,
signalfd, slopfut, terminal grid, clipboard, signal behavior, and more.
Display Protocol
The compositor protocol is versioned in slop-protocol. It includes:
- Version handshake and capability discovery.
- Surface create, attach, damage, commit, frame callbacks, and destroy.
- Toplevel creation, title, app-id, configure/ack, and destroy.
- Cursor shape requests.
- Clipboard copy/paste using memfd buffers and SCM_RIGHTS where needed.
- Interactive move/resize authorization through input serials.
Pixel buffers are memfd-backed and shared with the compositor. The windowing runtime provides raw window and surface APIs; AppKit builds widget trees and retained UI behavior on top.