Appearance Utilities## Appearance Guide

Physical geometry (formboard segments, schematic wires, harness overlays) is plotted from an engineering appearance dict:

{
    "base_color": "#000000",
    "parallelstripe": ["#000000", "#000000"],
    "perpstripe": ["#000000", "#000000"],
    "twisted": null
}

The same dict is the optional channel_default_appearance cell, and each value inside signal_default_appearances, on the channel type's channel_types.tsv. See Channel Types. An instance appearance that already includes base_color is the appearance drawn for that trace.

Drafting ink (tables, wirelists, labels, dimension lines) is painted from a style dict: fill_color, stroke_color, text_color. Build that dict at the instance from its parsed appearance.

Arguments

Required - base_color: exactly one value

Optional - parallelstripe: 0+ values (list) - perpstripe: 0+ values (list) - twisted: 0–1 value (null, "RH", or "LH") - outline_color: 0–1 value

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Commands

These functions are already available in build instructions as appearance. Use them as written.

appearance.parse(val)

Use this when a build needs an appearance dict whose colors are #rrggbb.

Parse a dict or dict-string, converting color-like values to #rrggbb.

Runs ast.literal_eval on strings. Nested dicts and lists are walked. Non-color strings are left as-is. Empty or non-dict input returns None.

Args: - val (dict or str): Dictionary, or a string ast.literal_eval can read as a dict.

Returns: - dict: Same keys with colors as #rrggbb, or None.

appearance.to_rgb(val)

Use this when a build needs red, green, and blue from a color name, a hex string, or an appearance dict.

Return (r, g, b) in 0–255 from a color name, hex string, or appearance dict.

Unknown or empty values return (0, 0, 0). Appearance dicts use base_color, then outline_color.

Args: - val (str or dict): Color name, hex, or appearance dictionary.

Returns: - tuple: (r, g, b) each 0–255.

appearance.black_or_white_to_contrast_with_color(color)

Use this when a drawing needs black or white text chosen to contrast with a color.

Return #ffffff or #000000, whichever has higher WCAG contrast against the color.

Args: - color (str or dict): Color name, hex, or appearance dictionary.

Returns: - str: #ffffff or #000000.