KRYON

What is Kryon?

Kryon is a UI cartridge system — portable bytecode for user interfaces. Write UI definitions in a path-based VFS language, compile to portable bytecode, and control properties over the network via CoAP.

A single .krb file runs on ESP32, Plan 9, Linux, Android, and in the browser. Control your entire UI through simple file operations on network paths.

Philosophy

• Everything is a file — UI properties exposed as VFS paths like /0/radius, /env/w
• Path-based by design — All access through absolute (/dev/draw), relative (./value), and parent (../speed) paths
• Network-native by design — CoAP for lightweight, constrained-device control
• Cross-platform runtime — Single .krb runs everywhere with the krbdraw engine

The .kry Language

A path-based, VFS-oriented language for defining UIs with events and animations.

const meta {
    title "Inner Breeze"
    ver   "alpha"
}

var env {
    w 200
    h 400
}

def circle {
    write /dev/draw [ circ %center[0] %center[1] ./radius %color ]
    %logic
}

circle {
    center [ 100 100 ]
    radius 50
    color 0xFF0000

    logic {
        listen /dev/timer {
            tick 50 {
                write ./radius [ + ./radius ./dir ]
            }
        }
    }
}

Language Features

• const — Compile-time constants (metadata, sprites)
• var — Runtime mutable variables
• def — Creates VFS instances (numbered folders)
• fn — Inline helpers (no VFS created)

Paths

• Absolute: /dev/draw, /env/w, /meta/title
• Relative: ./radius, ./color
• Parent: ../speed, ../size

VFS System

UI properties are exposed as network-accessible file paths. const blocks create read-only paths, var blocks create read-write paths, def creates numbered instance folders.

const meta {
    title "MyApp"        // /meta/title (read-only)
}

var env {
    w 200                // /env/w (read-write)
    h 400                // /env/h (read-write)
}

def button { ... }

button { ... }      // Creates /0
button { ... }      // Creates /1

Binary Format (.krb)

The .krb format is a compact bytecode representation of your UI. Compiled by kry2krb, executed by krbdraw. Typical UIs are under 1KB.

CoAP Protocol

CoAP (Constrained Application Protocol) is the default network protocol for Kryon. Designed for constrained devices like ESP32, it offers UDP-based lightweight communication with REST-like semantics.

Example Usage

# Read value
coap-client get coap://192.168.1.100/0/radius

# Set value to 100
echo -n -e "\x00\x64" | coap-client put coap://192.168.1.100/0/radius

Platform Implementations

Getting Started

1. Write a UI

Create a file named example.kry:

const meta {
    title "Demo"
}

var env {
    w 200
    h 300
}

def window {
    write /dev/wctl [ new 0 0 %size[0] %size[1] %title ]
}

def circle {
    write /dev/draw [ circ %center[0] %center[1] ./radius %color ]
}

window {
    title /meta/title
    size [ /env/w /env/h ]

    circle {
        center [ 100 150 ]
        radius 50
        color 0xFF0000
    }
}

2. Compile

kry2krb example.kry -o example.krb

3. Run

krbdraw example.krb

4. Control over Network

coap-client get coap://esp32.local/0/radius
echo -n -e "\x00\x64" | coap-client put coap://esp32.local/0/radius

Install Dependencies

Documentation

Community

Join the Kryon community to ask questions, share projects, and stay updated.