How it works

Python                         Rust (pyzed._core, PyO3)                 Iced 0.14
App.view() ──► Widget tree ──────► render.rs: Widget → iced::Element ──► layout + wgpu/tiny-skia
App.update() ◄── messages ◄────── app.rs: Message, Command → Task ◄──── events (mouse, keyboard)

Pieces

flowchart TB
    subgraph PY["Python (your code)"]
        A["App / Window"] --> W["view() → pz.* / ui.*"]
        U["update()"]
        L["asyncio loop + threads"]
    end
    subgraph RS["Rust (native extension, PyO3)"]
        B["build Iced elements"] --> I["Iced 0.14"]
        I --> G["wgpu / tiny-skia"]
    end
    W -->|"_core.Widget"| B
    I -->|"events → messages"| U
    L -->|"pz.post / results"| U
    U --> W

File	Responsibility
src/widget.rs	The (immutable) Widget class and the functions that build it (text, row…).
src/render.rs	Turns the Widget tree into an iced::Element every frame.
src/app.rs	The runtime: Message, Command, dispatch to Python, keyboard, post, run and screenshot.
src/style.rs	Conversion of colors, sizes, padding and fonts from Python values.
src/highlighter.rs	Syntax highlighting with syntect (two-face grammars) and theme colors.
src/fonts.rs	Bundled fonts (IBM Plex, Lucide) and load_font.
python/pyzed/	The App class, themes, icons, CLI and the pyzed.ui components.

Performance

• Widgets are Rust data. Building the tree from Python creates small, immutable objects; no live Iced objects exist in Python.
• The heavy lifting is in Rust. Layout, text measurement, highlighting, scrolling and drawing happen in Rust; Python only runs when there is a message.
• The GIL is released while Iced waits for events, so Python threads keep running.
• Native state for the editor. Each editor’s buffer (text, cursor, history) lives in Rust and is identified by id, so typing doesn’t rebuild the text in Python.

Messages

Every interactive widget keeps a reference to the Python value you gave it. When Iced produces an event, app.rs turns it into a call:

1. If it is a callable, it calls it (with the control’s value, if any).
2. If it returns a Command, it translates it into an Iced Task.
3. If it returns any other value (or the message was not callable), it calls app.update(value).
4. It asks for view() again and Iced draws the difference.

Contributing

maturin develop --release
pytest tests
cargo fmt --check && cargo clippy -- -D warnings

The documentation lives in docs/. See editing the documentation.