PanelColorManager¶

class PanelColorManager:
    """Assign consistent colours to panel members by name.

    Unlike positional indexing (where the first column always gets
    colour 0), this class maps *member names* to colours.  The same
    name always receives the same colour within a manager instance,
    regardless of the order it appears in different panel groups.

    Parameters
    ----------
    color_palette : list[str] | None, default=None
        Custom colour hex codes.  Any falsy value (``None`` or an empty
        list ``[]``) falls back to the default `palette_yohou` palette.
        Note this differs from `resolve_color_palette`, which raises
        ``ValueError`` for an empty list.

    Examples
    --------
    >>> mgr = PanelColorManager()
    >>> mgr.get_color("a")
    '#2563EB'
    >>> mgr.get_color("b")
    '#DC2626'
    >>> mgr.get_color("a")  # same name -> same colour
    '#2563EB'
    """

    def __init__(self, color_palette: list[str] | None = None) -> None:
        self._palette = color_palette or list(palette_yohou().values())
        self._name_to_color: dict[str, str] = {}
        self._counter = 0

    def get_color(self, member_name: str) -> str:
        """Return the colour assigned to *member_name*."""
        if member_name not in self._name_to_color:
            self._name_to_color[member_name] = self._palette[self._counter % len(self._palette)]
            self._counter += 1
        return self._name_to_color[member_name]

    def get_colors(self, names: list[str]) -> list[str]:
        """Return colours for a list of member names."""
        return [self.get_color(n) for n in names]