Source code for traitsui.null.font_trait

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""" Trait definition for a null-based (i.e., no UI) font.
"""


from traits.api import Trait, TraitHandler, TraitError

# ------------------------------------------------------------------------------
#  Convert a string into a valid 'wxFont' object (if possible):
# ------------------------------------------------------------------------------

# Mapping of strings to valid wxFont families
font_families = ["default", "decorative", "roman", "script", "swiss", "modern"]

# Mapping of strings to wxFont styles
font_styles = ["slant", "italic"]

# Mapping of strings wxFont weights
font_weights = ["light", "bold"]

# Strings to ignore in text representations of fonts
font_noise = ["pt", "point", "family"]


# ------------------------------------------------------------------------------
#  'TraitFont' class'
# ------------------------------------------------------------------------------


class TraitFont(TraitHandler):
    """Ensures that values assigned to a trait attribute are valid font
    descriptor strings; the value actually assigned is the corresponding
    canonical font descriptor string.
    """

    def validate(self, object, name, value):
        """Validates that the value is a valid font descriptor string."""
        try:
            point_size = family = style = weight = underline = ""
            facename = [""]
            for word in value.split():
                lword = word.lower()
                if lword in font_families:
                    family = " " + lword
                elif lword in font_styles:
                    style = " " + lword
                elif lword in font_weights:
                    weight = " " + lword
                elif lword == "underline":
                    underline = " " + lword
                elif lword not in font_noise:
                    try:
                        int(lword)
                        point_size = lword + " pt"
                    except:
                        facename.append(word)
            fontstr = (
                "%s%s%s%s%s%s"
                % (
                    point_size,
                    family,
                    style,
                    weight,
                    underline,
                    " ".join(facename),
                )
            ).strip()
            return fontstr
        except Exception:
            pass
        raise TraitError(object, name, "a font descriptor string", repr(value))

    def info(self):
        return (
            "a string describing a font (e.g. '12 pt bold italic "
            "swiss family Arial' or 'default 12')"
        )


# ------------------------------------------------------------------------------
#  Define a 'null' specific font trait:
# ------------------------------------------------------------------------------

### Note: Declare the editor to be a function which returns the FontEditor
# class from traits ui to avoid circular import issues. For backwards
# compatibility with previous Traits versions, the 'editors' folder in Traits
# project declares 'from api import *' in its __init__.py. The 'api' in turn
# can contain classes that have a Font trait which lead to this file getting
# imported. This leads to a circular import when declaring a Font trait.
def get_font_editor(*args, **traits):
    from ..api import FontEditor

    return FontEditor(*args, **traits)


fh = TraitFont()
NullFont = Trait(
    fh.validate(None, None, "Arial 10"), fh, editor=get_font_editor
)