panelmark 0.2.0

A markup language for UI layouts — define panels once, render anywhere.

panelmark

panelmark is a zero-dependency Python library for defining terminal UI layouts using a readable ASCII-art shell language, and for implementing the interaction logic that runs inside them.

panelmark is the core library in the panelmark ecosystem. It has no runtime dependencies on any terminal library. It defines:

---

What is real today

Feature	Status
Shell definition language (ASCII-art DSL)	✅ Fully working
# line comments and /* */ block comments	✅ Fully working
Horizontal splits (= / - border rows)	✅ Fully working
Vertical splits — single-line divider (|)	✅ Fully working
Vertical splits — double-line divider (||)	✅ Fully working
Equal-width fill splits (all columns fill-width)	✅ Columns share space equally (differ by at most 1 char)
Panel headings (__text__ syntax)	⚠️ Parsed and stored; renderers must implement display
Shell state machine (focus, dirty tracking, key dispatch, on_change, bind)	✅ Fully working
Draw command abstraction (DrawCommand, RenderContext, WriteCmd, FillCmd, CursorCmd)	✅ Fully working
Interaction base class	✅ Fully working

See panelmark-tui limitations for the combined limitations list.

---

• The shell definition language — an ASCII-art syntax for describing layouts
• The layout model — resolved geometry (row, col, width, height) for each named region
• The draw command abstraction — renderer-agnostic DrawCommand types returned by interactions
• The Interaction base class — the protocol all interactive widgets implement
• The Shell state machine — focus, dirty tracking, key dispatch, and value observation

To actually display a shell in a terminal, pair panelmark with panelmark-tui, which wraps blessed and provides a full event loop, built-in interactions, and renderer-specific convenience widgets.

---

Installation

pip install panelmark

---

Quick start

from panelmark import Shell, Interaction
from panelmark.draw import DrawCommand, RenderContext, WriteCmd, FillCmd

# 1. Define a layout
LAYOUT = """
|=== <bold>My App</> ===|
|{10R $sidebar$  }|{$main$        }|
|==================|
|{2R  $status$              }|
|==================|
"""

# 2. Implement an interaction
class Label(Interaction):
    def __init__(self, text: str):
        self._text = text

    @property
    def is_focusable(self) -> bool:
        return False

    def render(self, context: RenderContext, focused: bool = False) -> list[DrawCommand]:
        line = self._text[:context.width].ljust(context.width)
        return [WriteCmd(row=0, col=0, text=line)]

    def handle_key(self, key) -> tuple:
        return False, self.get_value()

    def get_value(self):
        return self._text

    def set_value(self, value) -> None:
        self._text = str(value)

# 3. Assign interactions to regions
shell = Shell(LAYOUT)
shell.assign("sidebar", Label("Navigation"))
shell.assign("main", Label("Content area"))
shell.assign("status", Label("Ready"))

# 4. Drive with a renderer (e.g. panelmark-tui)
# result = shell.run()   ← panelmark_tui.Shell adds run()

---

Documentation

Document	Description
Shell Language	Shell, region, and panel concepts; state machine methods
Shell Language Syntax	Full grammar reference for the ASCII-art layout DSL
Shell Language Examples	Annotated examples; custom interactions; portable rendering patterns
Draw Commands	DrawCommand types, RenderContext, and the style dict
Custom Interactions	Implementing the Interaction ABC
Renderer Spec	Renderer compatibility contract, portable library layer, and extension policy
Ecosystem Overview	Layered design; package responsibilities; dependency direction
Choosing a Renderer	Decision tree for selecting the right package

---

Ecosystem

panelmark follows a layered design. The core library is renderer-agnostic; renderer-specific packages extend it.

Package	Role
panelmark (this package)	Zero-dependency core: shell language, layout, draw commands, interaction protocol
panelmark-tui	Terminal renderer (blessed); portable-library-compatible
panelmark-html	Static HTML/CSS renderer; pre-alpha; foundation for panelmark-web
panelmark-web	Live web runtime via WebSockets; portable-library-compatible

See ecosystem overview for the full design rationale and dependency diagram.

---

License

MIT