drawlang — Beyond Purdue Editor

A tiny, deterministic drawing language and its reference interpreter and web editor.

Every visible mark on a drawing — every line, arc, symbol, character of text — is a database record. Nothing is drawn by ad-hoc code. Programs in the language are short ASCII strings executed by a pen-state interpreter. Backends translate the interpreter's abstract calls into SVG, PostScript, or PDF.

• Language spec: docs/spec/drawing-language-spec.md — current. Version history in docs/spec/history/.
• Live editor: editor.drawlang.com
• Community: r/drawlang
• License: Apache 2.0 — © 2026 Beyond Purdue contributors

CAD and diagram tools bake geometry into code. That makes drawings unreproducible: change the tool, lose the drawings. This project inverts the model:

1. The language defines all drawing primitives — 7 core opcodes + 4 extensions. Frozen at v0.1.
2. The interpreter is a pure pen-state machine — no output-format knowledge.
3. Backends (SVG / PostScript / PDF) are independent modules that receive abstract drawing calls.
4. The editor is a thin web UI over interpreter + backends. Programs are stored as text; renders are disposable.

Any drawing you make is a plain text program you can commit to git, diff, template, and round-trip through any compliant interpreter forever.

┌─────────────────────────────────────────────────────────────┐
│  docs/spec/                                                 │
│  drawing-language-spec.md — the language, code-free         │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│  src/drawlang/                                              │
│    parser.py       — tokenize + validate                    │
│    interpreter.py  — pen-state machine (spec §9)            │
│    backend.py      — abstract Backend interface             │
│    errors.py       — LexicalError, SemanticError            │
│    backends/                                                │
│      svg.py        — → SVG                                  │
│      ps.py         — → PostScript                           │
│      pdf.py        — → PDF (ps.py + ps2pdf)                 │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│  editor/                                                    │
│    app/main.py     — FastAPI backend                        │
│    static/         — single-page textarea + live SVG        │
│    library-data/   — starter template library               │
│    user_drawings/  — drawings you save (git-friendly text)  │
└─────────────────────────────────────────────────────────────┘

The interpreter never imports a backend. Backends never import the interpreter. drawlang.render(program, backend="svg" | "ps" | "pdf") is a convenience wrapper that wires them.

Requires Python 3.10+.

git clone https://github.com/BeyondPurdue/drawlang-editor.git
cd drawlang-editor

# core interpreter only
pip install -e .

# core + web editor
pip install -e ".[editor]"

PDF backend additionally requires ghostscript (ps2pdf) in PATH.

from drawlang import render

program = """
mr,0,158;
dl,14,0;
mr,0,-1;
dl,-14,0;
tz,8;
tx,0.,A1;
"""

svg = render(program, backend="svg")
ps  = render(program, backend="ps")
pdf = render(program, backend="pdf")   # bytes

uvicorn editor.app.main:app --port 8000

Open http://localhost:8000. Type a program on the left, see live SVG on the right, export PS or PDF, save to user_drawings/.

Seven core opcodes, four extensions. Two-letter mnemonics, comma-separated args, semicolon-terminated.

Modifiers ,f (fill), ,i (invisible), ,d (dashed), ,cn (color) tweak individual statements.

See the language specification for the full grammar, semantics, worked examples, and the reference algorithm.

Drawings are database records. Each table row holds one cmd string:

The schema for these tables is out of scope for the language spec — the language only cares about the cmd strings.

pip install -e ".[dev]"
pytest

Conformance tests live in tests/test_conformance.py and cover every core opcode against the reference algorithm in spec §9.

Contributions welcome — bug reports, new backends, editor features, documentation, additional starter templates.

• Read CONTRIBUTING.md for the workflow.
• Read CODE_OF_CONDUCT.md.
• The language spec is LOCKED at v0.1. Extensions must go through a formal v0.2 event with community review.

• Live editor: editor.drawlang.com — try the language in your browser
• Reddit: r/drawlang — discussions, drawings, questions
• Issues: GitHub issues — bugs and feature requests

Apache License 2.0. Copyright © 2026 Beyond Purdue contributors. See LICENSE.