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"""
Utilities for interpreting CSS from Stylers for formatting non-HTML outputs.
"""
from __future__ import annotations
import re
from typing import (
TYPE_CHECKING,
Callable,
)
import warnings
from pandas.errors import CSSWarning
from pandas.util._exceptions import find_stack_level
if TYPE_CHECKING:
from collections.abc import (
Generator,
Iterable,
Iterator,
)
def _side_expander(prop_fmt: str) -> Callable:
"""
Wrapper to expand shorthand property into top, right, bottom, left properties
Parameters
----------
side : str
The border side to expand into properties
Returns
-------
function: Return to call when a 'border(-{side}): {value}' string is encountered
"""
def expand(self, prop, value: str) -> Generator[tuple[str, str], None, None]:
"""
Expand shorthand property into side-specific property (top, right, bottom, left)
Parameters
----------
prop (str): CSS property name
value (str): String token for property
Yields
------
Tuple (str, str): Expanded property, value
"""
tokens = value.split()
try:
mapping = self.SIDE_SHORTHANDS[len(tokens)]
except KeyError:
warnings.warn(
f'Could not expand "{prop}: {value}"',
CSSWarning,
stacklevel=find_stack_level(),
)
return
for key, idx in zip(self.SIDES, mapping):
yield prop_fmt.format(key), tokens[idx]
return expand
def _border_expander(side: str = "") -> Callable:
"""
Wrapper to expand 'border' property into border color, style, and width properties
Parameters
----------
side : str
The border side to expand into properties
Returns
-------
function: Return to call when a 'border(-{side}): {value}' string is encountered
"""
if side != "":
side = f"-{side}"
def expand(self, prop, value: str) -> Generator[tuple[str, str], None, None]:
"""
Expand border into color, style, and width tuples
Parameters
----------
prop : str
CSS property name passed to styler
value : str
Value passed to styler for property
Yields
------
Tuple (str, str): Expanded property, value
"""
tokens = value.split()
if len(tokens) == 0 or len(tokens) > 3:
warnings.warn(
f'Too many tokens provided to "{prop}" (expected 1-3)',
CSSWarning,
stacklevel=find_stack_level(),
)
# TODO: Can we use current color as initial value to comply with CSS standards?
border_declarations = {
f"border{side}-color": "black",
f"border{side}-style": "none",
f"border{side}-width": "medium",
}
for token in tokens:
if token.lower() in self.BORDER_STYLES:
border_declarations[f"border{side}-style"] = token
elif any(ratio in token.lower() for ratio in self.BORDER_WIDTH_RATIOS):
border_declarations[f"border{side}-width"] = token
else:
border_declarations[f"border{side}-color"] = token
# TODO: Warn user if item entered more than once (e.g. "border: red green")
# Per CSS, "border" will reset previous "border-*" definitions
yield from self.atomize(border_declarations.items())
return expand
class CSSResolver:
"""
A callable for parsing and resolving CSS to atomic properties.
"""
UNIT_RATIOS = {
"pt": ("pt", 1),
"em": ("em", 1),
"rem": ("pt", 12),
"ex": ("em", 0.5),
# 'ch':
"px": ("pt", 0.75),
"pc": ("pt", 12),
"in": ("pt", 72),
"cm": ("in", 1 / 2.54),
"mm": ("in", 1 / 25.4),
"q": ("mm", 0.25),
"!!default": ("em", 0),
}
FONT_SIZE_RATIOS = UNIT_RATIOS.copy()
FONT_SIZE_RATIOS.update(
{
"%": ("em", 0.01),
"xx-small": ("rem", 0.5),
"x-small": ("rem", 0.625),
"small": ("rem", 0.8),
"medium": ("rem", 1),
"large": ("rem", 1.125),
"x-large": ("rem", 1.5),
"xx-large": ("rem", 2),
"smaller": ("em", 1 / 1.2),
"larger": ("em", 1.2),
"!!default": ("em", 1),
}
)
MARGIN_RATIOS = UNIT_RATIOS.copy()
MARGIN_RATIOS.update({"none": ("pt", 0)})
BORDER_WIDTH_RATIOS = UNIT_RATIOS.copy()
BORDER_WIDTH_RATIOS.update(
{
"none": ("pt", 0),
"thick": ("px", 4),
"medium": ("px", 2),
"thin": ("px", 1),
# Default: medium only if solid
}
)
BORDER_STYLES = [
"none",
"hidden",
"dotted",
"dashed",
"solid",
"double",
"groove",
"ridge",
"inset",
"outset",
"mediumdashdot",
"dashdotdot",
"hair",
"mediumdashdotdot",
"dashdot",
"slantdashdot",
"mediumdashed",
]
SIDE_SHORTHANDS = {
1: [0, 0, 0, 0],
2: [0, 1, 0, 1],
3: [0, 1, 2, 1],
4: [0, 1, 2, 3],
}
SIDES = ("top", "right", "bottom", "left")
CSS_EXPANSIONS = {
**{
(f"border-{prop}" if prop else "border"): _border_expander(prop)
for prop in ["", "top", "right", "bottom", "left"]
},
**{
f"border-{prop}": _side_expander(f"border-{{:s}}-{prop}")
for prop in ["color", "style", "width"]
},
"margin": _side_expander("margin-{:s}"),
"padding": _side_expander("padding-{:s}"),
}
def __call__(
self,
declarations: str | Iterable[tuple[str, str]],
inherited: dict[str, str] | None = None,
) -> dict[str, str]:
"""
The given declarations to atomic properties.
Parameters
----------
declarations_str : str | Iterable[tuple[str, str]]
A CSS string or set of CSS declaration tuples
e.g. "font-weight: bold; background: blue" or
{("font-weight", "bold"), ("background", "blue")}
inherited : dict, optional
Atomic properties indicating the inherited style context in which
declarations_str is to be resolved. ``inherited`` should already
be resolved, i.e. valid output of this method.
Returns
-------
dict
Atomic CSS 2.2 properties.
Examples
--------
>>> resolve = CSSResolver()
>>> inherited = {'font-family': 'serif', 'font-weight': 'bold'}
>>> out = resolve('''
... border-color: BLUE RED;
... font-size: 1em;
... font-size: 2em;
... font-weight: normal;
... font-weight: inherit;
... ''', inherited)
>>> sorted(out.items()) # doctest: +NORMALIZE_WHITESPACE
[('border-bottom-color', 'blue'),
('border-left-color', 'red'),
('border-right-color', 'red'),
('border-top-color', 'blue'),
('font-family', 'serif'),
('font-size', '24pt'),
('font-weight', 'bold')]
"""
if isinstance(declarations, str):
declarations = self.parse(declarations)
props = dict(self.atomize(declarations))
if inherited is None:
inherited = {}
props = self._update_initial(props, inherited)
props = self._update_font_size(props, inherited)
return self._update_other_units(props)
def _update_initial(
self,
props: dict[str, str],
inherited: dict[str, str],
) -> dict[str, str]:
# 1. resolve inherited, initial
for prop, val in inherited.items():
if prop not in props:
props[prop] = val
new_props = props.copy()
for prop, val in props.items():
if val == "inherit":
val = inherited.get(prop, "initial")
if val in ("initial", None):
# we do not define a complete initial stylesheet
del new_props[prop]
else:
new_props[prop] = val
return new_props
def _update_font_size(
self,
props: dict[str, str],
inherited: dict[str, str],
) -> dict[str, str]:
# 2. resolve relative font size
if props.get("font-size"):
props["font-size"] = self.size_to_pt(
props["font-size"],
self._get_font_size(inherited),
conversions=self.FONT_SIZE_RATIOS,
)
return props
def _get_font_size(self, props: dict[str, str]) -> float | None:
if props.get("font-size"):
font_size_string = props["font-size"]
return self._get_float_font_size_from_pt(font_size_string)
return None
def _get_float_font_size_from_pt(self, font_size_string: str) -> float:
assert font_size_string.endswith("pt")
return float(font_size_string.rstrip("pt"))
def _update_other_units(self, props: dict[str, str]) -> dict[str, str]:
font_size = self._get_font_size(props)
# 3. TODO: resolve other font-relative units
for side in self.SIDES:
prop = f"border-{side}-width"
if prop in props:
props[prop] = self.size_to_pt(
props[prop],
em_pt=font_size,
conversions=self.BORDER_WIDTH_RATIOS,
)
for prop in [f"margin-{side}", f"padding-{side}"]:
if prop in props:
# TODO: support %
props[prop] = self.size_to_pt(
props[prop],
em_pt=font_size,
conversions=self.MARGIN_RATIOS,
)
return props
def size_to_pt(self, in_val, em_pt=None, conversions=UNIT_RATIOS) -> str:
def _error():
warnings.warn(
f"Unhandled size: {repr(in_val)}",
CSSWarning,
stacklevel=find_stack_level(),
)
return self.size_to_pt("1!!default", conversions=conversions)
match = re.match(r"^(\S*?)([a-zA-Z%!].*)", in_val)
if match is None:
return _error()
val, unit = match.groups()
if val == "":
# hack for 'large' etc.
val = 1
else:
try:
val = float(val)
except ValueError:
return _error()
while unit != "pt":
if unit == "em":
if em_pt is None:
unit = "rem"
else:
val *= em_pt
unit = "pt"
continue
try:
unit, mul = conversions[unit]
except KeyError:
return _error()
val *= mul
val = round(val, 5)
if int(val) == val:
size_fmt = f"{int(val):d}pt"
else:
size_fmt = f"{val:f}pt"
return size_fmt
def atomize(self, declarations: Iterable) -> Generator[tuple[str, str], None, None]:
for prop, value in declarations:
prop = prop.lower()
value = value.lower()
if prop in self.CSS_EXPANSIONS:
expand = self.CSS_EXPANSIONS[prop]
yield from expand(self, prop, value)
else:
yield prop, value
def parse(self, declarations_str: str) -> Iterator[tuple[str, str]]:
"""
Generates (prop, value) pairs from declarations.
In a future version may generate parsed tokens from tinycss/tinycss2
Parameters
----------
declarations_str : str
"""
for decl in declarations_str.split(";"):
if not decl.strip():
continue
prop, sep, val = decl.partition(":")
prop = prop.strip().lower()
# TODO: don't lowercase case sensitive parts of values (strings)
val = val.strip().lower()
if sep:
yield prop, val
else:
warnings.warn(
f"Ill-formatted attribute: expected a colon in {repr(decl)}",
CSSWarning,
stacklevel=find_stack_level(),
)
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