Creating an App

Every VyomaOS app is a standard Rust crate that compiles to wasm32-wasip2. Here’s how to create one.

1. Create the App Directory

mkdir apps/my-app
cd apps/my-app

2. Create Cargo.toml

[package]
name    = "my-app"
version = "0.1.0"
edition = "2021"

[[bin]]
name = "my-app"
path = "src/main.rs"

[dependencies]
# Keep minimal for small binary size

3. Write Your App

Create src/main.rs:

fn main() {
    println!("Hello from my-app!");
}

For a GUI app using the VYOMA_DRAW protocol:

const WHITE: u32 = 0xFFFFFFFF;
const BG: u32 = 0x1E1E2EFF;
const PURPLE: u32 = 0x7C3AEDFF;

fn main() {
    // Clear background
    println!("VYOMA_DRAW:fill_rect:0,0,960,700,{BG}");

    // Draw title
    println!("VYOMA_DRAW:draw_text:20,30,{WHITE},m,My App");

    // Draw a colored box
    println!("VYOMA_DRAW:fill_rect:20,60,200,100,{PURPLE}");
    println!("VYOMA_DRAW:draw_text:30,100,{WHITE},m,Hello World!");

    // Commit frame to display
    println!("VYOMA_DRAW:flush");

    // Keep running to receive input
    loop {
        let mut line = String::new();
        if std::io::stdin().read_line(&mut line).is_ok() {
            let input = line.trim();
            if input.starts_with("VYOMA_INPUT:key:") {
                let key = &input[16..];
                eprintln!("[my-app] key pressed: {key}");
            }
        }
    }
}

4. Create the Manifest

Create vyoma.toml:

[app]
name    = "my-app"
version = "0.1.0"
wasm    = "my-app.wasm"

[capabilities]
stdio   = true      # Required for console output
display = true      # Required for VYOMA_DRAW
# filesystem = true # Mount /data for persistent storage
# network = true    # TCP sockets
# shell = true      # @supervisor: commands
# mouse = true      # Mouse input events

Only declare the capabilities your app needs. Undeclared capabilities are never wired up.

5. Build

cargo build --target wasm32-wasip2 --release

The output is at target/wasm32-wasip2/release/my-app.wasm (typically 1-10 KB).

6. Add to Boot

Update base/rootfs.sh to include your app in the initramfs. Follow the pattern used by existing apps like hello-world.

Then rebuild and boot:

make rootfs && make run

Capabilities Reference

Capability	What it enables
stdio = true	stdin/stdout/stderr (console I/O, keyboard input)
filesystem = true	Mount /data (9P, persistent across reboots)
network = true	WASI sockets (TCP, default port 8080)
display = true	Framebuffer access + VYOMA_DRAW protocol
shell = true	Issue @supervisor: process management commands
mouse = true	Receive VYOMA_INPUT:mouse: events
watchdog_secs = N	Supervisor kills app if silent for N seconds

IPC Communication

Apps can send messages to other apps via stdout:

// Send to a specific app
println!("@other-app: hello!");

// Broadcast to all apps
println!("@broadcast: system event");

// Reply to last sender
println!("@reply: got it");

// Supervisor commands
println!("@supervisor: list");
println!("@supervisor: ping");

Tips

• Keep dependencies minimal — every dependency increases binary size
• Use eprintln! for debug logging (goes to supervisor’s stderr log)
• Test with cargo build --target wasm32-wasip2 before integrating
• The 500-line limit applies to all .rs files — split into modules early