790 lines
26 KiB
Python
790 lines
26 KiB
Python
"""
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weasyprint.css.computed_values
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------------------------------
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Convert *specified* property values (the result of the cascade and
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inhertance) into *computed* values (that are inherited).
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:copyright: Copyright 2011-2019 Simon Sapin and contributors, see AUTHORS.
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:license: BSD, see LICENSE for details.
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"""
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from collections import OrderedDict
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from urllib.parse import unquote
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from tinycss2.color3 import parse_color
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from .. import text
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from ..logger import LOGGER
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from ..urls import get_link_attribute
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from .properties import (
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INHERITED, INITIAL_NOT_COMPUTED, INITIAL_VALUES, Dimension)
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from .utils import (
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ANGLE_TO_RADIANS, LENGTH_UNITS, LENGTHS_TO_PIXELS, check_var_function,
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safe_urljoin)
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ZERO_PIXELS = Dimension(0, 'px')
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# Value in pixels of font-size for <absolute-size> keywords: 12pt (16px) for
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# medium, and scaling factors given in CSS3 for others:
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# http://www.w3.org/TR/css3-fonts/#font-size-prop
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FONT_SIZE_KEYWORDS = OrderedDict(
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# medium is 16px, others are a ratio of medium
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(name, INITIAL_VALUES['font_size'] * a / b)
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for name, a, b in (
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('xx-small', 3, 5),
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('x-small', 3, 4),
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('small', 8, 9),
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('medium', 1, 1),
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('large', 6, 5),
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('x-large', 3, 2),
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('xx-large', 2, 1),
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)
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)
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# These are unspecified, other than 'thin' <='medium' <= 'thick'.
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# Values are in pixels.
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BORDER_WIDTH_KEYWORDS = {
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'thin': 1,
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'medium': 3,
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'thick': 5,
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}
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assert INITIAL_VALUES['border_top_width'] == BORDER_WIDTH_KEYWORDS['medium']
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# http://www.w3.org/TR/CSS21/fonts.html#propdef-font-weight
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FONT_WEIGHT_RELATIVE = dict(
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bolder={
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100: 400,
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200: 400,
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300: 400,
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400: 700,
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500: 700,
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600: 900,
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700: 900,
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800: 900,
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900: 900,
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},
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lighter={
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100: 100,
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200: 100,
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300: 100,
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400: 100,
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500: 100,
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600: 400,
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700: 400,
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800: 700,
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900: 700,
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},
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)
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# http://www.w3.org/TR/css3-page/#size
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# name=(width in pixels, height in pixels)
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PAGE_SIZES = dict(
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a5=(
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Dimension(148, 'mm'),
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Dimension(210, 'mm'),
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),
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a4=(
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Dimension(210, 'mm'),
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Dimension(297, 'mm'),
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),
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a3=(
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Dimension(297, 'mm'),
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Dimension(420, 'mm'),
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),
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b5=(
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Dimension(176, 'mm'),
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Dimension(250, 'mm'),
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),
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b4=(
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Dimension(250, 'mm'),
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Dimension(353, 'mm'),
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),
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letter=(
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Dimension(8.5, 'in'),
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Dimension(11, 'in'),
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),
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legal=(
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Dimension(8.5, 'in'),
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Dimension(14, 'in'),
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),
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ledger=(
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Dimension(11, 'in'),
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Dimension(17, 'in'),
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),
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)
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# In "portrait" orientation.
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for w, h in PAGE_SIZES.values():
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assert w.value < h.value
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INITIAL_PAGE_SIZE = PAGE_SIZES['a4']
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INITIAL_VALUES['size'] = tuple(
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d.value * LENGTHS_TO_PIXELS[d.unit] for d in INITIAL_PAGE_SIZE)
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def _computing_order():
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"""Some computed values are required by others, so order matters."""
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first = [
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'font_stretch', 'font_weight', 'font_family', 'font_variant',
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'font_style', 'font_size', 'line_height', 'marks']
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order = sorted(INITIAL_VALUES)
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for name in first:
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order.remove(name)
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return tuple(first + order)
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COMPUTING_ORDER = _computing_order()
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# Maps property names to functions returning the computed values
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COMPUTER_FUNCTIONS = {}
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def _resolve_var(computed, variable_name, default):
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known_variable_names = [variable_name]
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computed_value = computed.get(variable_name)
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if computed_value and len(computed_value) == 1:
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value = computed_value[0]
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if value.type == 'ident' and value.value == 'initial':
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return default
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computed_value = computed.get(variable_name, default)
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while (computed_value and
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isinstance(computed_value, tuple)
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and len(computed_value) == 1):
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var_function = check_var_function(computed_value[0])
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if var_function:
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new_variable_name, new_default = var_function[1]
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if new_variable_name in known_variable_names:
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computed_value = default
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break
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known_variable_names.append(new_variable_name)
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computed_value = computed.get(new_variable_name, new_default)
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default = new_default
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else:
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break
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return computed_value
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def register_computer(name):
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"""Decorator registering a property ``name`` for a function."""
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name = name.replace('-', '_')
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def decorator(function):
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"""Register the property ``name`` for ``function``."""
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COMPUTER_FUNCTIONS[name] = function
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return function
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return decorator
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def compute(element, pseudo_type, specified, computed, parent_style,
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root_style, base_url, target_collector):
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"""Create a dict of computed values.
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:param element: The HTML element these style apply to
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:param pseudo_type: The type of pseudo-element, eg 'before', None
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:param specified: A dict of specified values. Should contain
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values for all properties.
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:param computed: A dict of already known computed values.
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Only contains some properties (or none).
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:param parent_style: A dict of computed values of the parent
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element (should contain values for all properties),
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or ``None`` if ``element`` is the root element.
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:param base_url: The base URL used to resolve relative URLs.
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:param target_collector: A target collector used to get computed targets.
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"""
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from .validation.properties import PROPERTIES
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computer = {
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'is_root_element': parent_style is None,
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'element': element,
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'pseudo_type': pseudo_type,
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'specified': specified,
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'computed': computed,
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'parent_style': parent_style or INITIAL_VALUES,
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'root_style': root_style,
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'base_url': base_url,
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'target_collector': target_collector,
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}
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getter = COMPUTER_FUNCTIONS.get
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for name in COMPUTING_ORDER:
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if name in computed:
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# Already computed
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continue
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value = specified[name]
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function = getter(name)
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already_computed_value = False
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if value and isinstance(value, tuple) and value[0] == 'var()':
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variable_name, default = value[1]
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computed_value = _resolve_var(computed, variable_name, default)
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if computed_value is None:
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new_value = None
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else:
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prop = PROPERTIES[name.replace('_', '-')]
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if prop.wants_base_url:
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new_value = prop(computed_value, base_url)
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else:
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new_value = prop(computed_value)
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# See https://drafts.csswg.org/css-variables/#invalid-variables
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if new_value is None:
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try:
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computed_value = ''.join(
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token.serialize() for token in computed_value)
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except BaseException:
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pass
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LOGGER.warning(
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'Unsupported computed value `%s` set in variable `%s` '
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'for property `%s`.', computed_value,
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variable_name.replace('_', '-'), name.replace('_', '-'))
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if name in INHERITED and parent_style:
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already_computed_value = True
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value = parent_style[name]
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else:
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already_computed_value = name not in INITIAL_NOT_COMPUTED
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value = INITIAL_VALUES[name]
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else:
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value = new_value
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if function is not None and not already_computed_value:
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value = function(computer, name, value)
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# else: same as specified
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computed[name] = value
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computed['_weasy_specified_display'] = specified['display']
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return computed
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@register_computer('background-image')
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def background_image(computer, name, values):
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"""Compute lenghts in gradient background-image."""
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for type_, value in values:
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if type_ in ('linear-gradient', 'radial-gradient'):
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value.stop_positions = tuple(
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length(computer, name, pos) if pos is not None else None
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for pos in value.stop_positions)
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if type_ == 'radial-gradient':
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value.center, = compute_position(
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computer, name, (value.center,))
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if value.size_type == 'explicit':
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value.size = length_or_percentage_tuple(
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computer, name, value.size)
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return values
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@register_computer('background-position')
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@register_computer('object-position')
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def compute_position(computer, name, values):
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"""Compute lengths in background-position."""
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return tuple(
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(origin_x, length(computer, name, pos_x),
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origin_y, length(computer, name, pos_y))
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for origin_x, pos_x, origin_y, pos_y in values)
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@register_computer('transform-origin')
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def length_or_percentage_tuple(computer, name, values):
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"""Compute the lists of lengths that can be percentages."""
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return tuple(length(computer, name, value) for value in values)
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@register_computer('border-spacing')
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@register_computer('size')
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@register_computer('clip')
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def length_tuple(computer, name, values):
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"""Compute the properties with a list of lengths."""
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return tuple(length(computer, name, value, pixels_only=True)
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for value in values)
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@register_computer('break-after')
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@register_computer('break-before')
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def break_before_after(computer, name, value):
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"""Compute the ``break-before`` and ``break-after`` properties."""
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# 'always' is defined as an alias to 'page' in multi-column
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# https://www.w3.org/TR/css3-multicol/#column-breaks
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if value == 'always':
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return 'page'
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else:
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return value
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@register_computer('top')
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@register_computer('right')
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@register_computer('left')
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@register_computer('bottom')
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@register_computer('margin-top')
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@register_computer('margin-right')
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@register_computer('margin-bottom')
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@register_computer('margin-left')
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@register_computer('height')
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@register_computer('width')
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@register_computer('min-width')
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@register_computer('min-height')
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@register_computer('max-width')
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@register_computer('max-height')
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@register_computer('padding-top')
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@register_computer('padding-right')
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@register_computer('padding-bottom')
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@register_computer('padding-left')
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@register_computer('text-indent')
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@register_computer('hyphenate-limit-zone')
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@register_computer('flex-basis')
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def length(computer, name, value, font_size=None, pixels_only=False):
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"""Compute a length ``value``."""
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if value in ('auto', 'content'):
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return value
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if value.value == 0:
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return 0 if pixels_only else ZERO_PIXELS
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unit = value.unit
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if unit == 'px':
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return value.value if pixels_only else value
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elif unit in LENGTHS_TO_PIXELS:
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# Convert absolute lengths to pixels
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result = value.value * LENGTHS_TO_PIXELS[unit]
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elif unit in ('em', 'ex', 'ch', 'rem'):
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if font_size is None:
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font_size = computer['computed']['font_size']
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if unit == 'ex':
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# TODO: cache
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result = value.value * font_size * ex_ratio(computer['computed'])
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elif unit == 'ch':
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# TODO: cache
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# TODO: use context to use @font-face fonts
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layout = text.Layout(
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context=None, font_size=font_size,
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style=computer['computed'])
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layout.set_text('0')
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line, _ = layout.get_first_line()
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logical_width, _ = text.get_size(line, computer['computed'])
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result = value.value * logical_width
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elif unit == 'em':
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result = value.value * font_size
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elif unit == 'rem':
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result = value.value * computer['root_style']['font_size']
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else:
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# A percentage or 'auto': no conversion needed.
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return value
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return result if pixels_only else Dimension(result, 'px')
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@register_computer('bleed-left')
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@register_computer('bleed-right')
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@register_computer('bleed-top')
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@register_computer('bleed-bottom')
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def bleed(computer, name, value):
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if value == 'auto':
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if 'crop' in computer['computed']['marks']:
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return Dimension(8, 'px') # 6pt
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else:
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return Dimension(0, 'px')
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else:
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return length(computer, name, value)
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@register_computer('letter-spacing')
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def pixel_length(computer, name, value):
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if value == 'normal':
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return value
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else:
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return length(computer, name, value, pixels_only=True)
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@register_computer('background-size')
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def background_size(computer, name, values):
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"""Compute the ``background-size`` properties."""
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return tuple(
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value if value in ('contain', 'cover') else
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length_or_percentage_tuple(computer, name, value)
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for value in values)
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@register_computer('border-top-width')
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@register_computer('border-right-width')
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@register_computer('border-left-width')
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@register_computer('border-bottom-width')
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@register_computer('column-rule-width')
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@register_computer('outline-width')
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def border_width(computer, name, value):
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"""Compute the ``border-*-width`` properties."""
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style = computer['computed'][name.replace('width', 'style')]
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if style in ('none', 'hidden'):
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return 0
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if value in BORDER_WIDTH_KEYWORDS:
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return BORDER_WIDTH_KEYWORDS[value]
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if isinstance(value, int):
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# The initial value can get here, but length() would fail as
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# it does not have a 'unit' attribute.
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return value
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return length(computer, name, value, pixels_only=True)
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@register_computer('column-width')
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def column_width(computer, name, value):
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"""Compute the ``column-width`` property."""
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return length(computer, name, value, pixels_only=True)
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@register_computer('border-top-left-radius')
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@register_computer('border-top-right-radius')
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@register_computer('border-bottom-left-radius')
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@register_computer('border-bottom-right-radius')
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def border_radius(computer, name, values):
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"""Compute the ``border-*-radius`` properties."""
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return tuple(length(computer, name, value) for value in values)
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@register_computer('column-gap')
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def column_gap(computer, name, value):
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"""Compute the ``column-gap`` property."""
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if value == 'normal':
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value = Dimension(1, 'em')
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return length(computer, name, value, pixels_only=True)
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def compute_attr_function(computer, values):
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# TODO: use real token parsing instead of casting with Python types
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func_name, value = values
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assert func_name == 'attr()'
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attr_name, type_or_unit, fallback = value
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# computer['element'] sometimes is None
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# computer['element'] sometimes is a 'PageType' object without .get()
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# so wrapt the .get() into try and return None instead of crashing
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try:
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attr_value = computer['element'].get(attr_name, fallback)
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if type_or_unit == 'string':
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pass # Keep the string
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elif type_or_unit == 'url':
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if attr_value.startswith('#'):
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attr_value = ('internal', unquote(attr_value[1:]))
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else:
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attr_value = (
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'external', safe_urljoin(computer['base_url'], attr_value))
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elif type_or_unit == 'color':
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attr_value = parse_color(attr_value.strip())
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elif type_or_unit == 'integer':
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attr_value = int(attr_value.strip())
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elif type_or_unit == 'number':
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attr_value = float(attr_value.strip())
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elif type_or_unit == '%':
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attr_value = Dimension(float(attr_value.strip()), '%')
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type_or_unit = 'length'
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elif type_or_unit in LENGTH_UNITS:
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attr_value = Dimension(float(attr_value.strip()), type_or_unit)
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type_or_unit = 'length'
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elif type_or_unit in ANGLE_TO_RADIANS:
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attr_value = Dimension(float(attr_value.strip()), type_or_unit)
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type_or_unit = 'angle'
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except Exception:
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return
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return (type_or_unit, attr_value)
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def _content_list(computer, values):
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computed_values = []
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for value in values:
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if value[0] in ('string', 'content', 'url', 'quote', 'leader()'):
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computed_value = value
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elif value[0] == 'attr()':
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assert value[1][1] == 'string'
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computed_value = compute_attr_function(computer, value)
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elif value[0] in (
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'counter()', 'counters()', 'content()', 'element()',
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'string()',
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):
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# Other values need layout context, their computed value cannot be
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# better than their specified value yet.
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# See build.compute_content_list.
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computed_value = value
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elif value[0] in (
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'target-counter()', 'target-counters()', 'target-text()'):
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anchor_token = value[1][0]
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if anchor_token[0] == 'attr()':
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attr = compute_attr_function(computer, anchor_token)
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if attr is None:
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computed_value = None
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else:
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computed_value = (value[0], (
|
|
(attr,) + value[1][1:]))
|
|
else:
|
|
computed_value = value
|
|
if computer['target_collector'] and computed_value:
|
|
computer['target_collector'].collect_computed_target(
|
|
computed_value[1][0])
|
|
if computed_value is None:
|
|
LOGGER.warning('Unable to compute %s\'s value for content: %s' % (
|
|
computer['element'], ', '.join(str(item) for item in value)))
|
|
else:
|
|
computed_values.append(computed_value)
|
|
|
|
return tuple(computed_values)
|
|
|
|
|
|
@register_computer('bookmark-label')
|
|
def bookmark_label(computer, name, values):
|
|
"""Compute the ``bookmark-label`` property."""
|
|
return _content_list(computer, values)
|
|
|
|
|
|
@register_computer('string-set')
|
|
def string_set(computer, name, values):
|
|
"""Compute the ``string-set`` property."""
|
|
# Spec asks for strings after custom keywords, but we allow content-lists
|
|
return tuple(
|
|
(string_set[0], _content_list(computer, string_set[1]))
|
|
for string_set in values)
|
|
|
|
|
|
@register_computer('content')
|
|
def content(computer, name, values):
|
|
"""Compute the ``content`` property."""
|
|
if len(values) == 1:
|
|
value, = values
|
|
if value == 'normal':
|
|
return 'inhibit' if computer['pseudo_type'] else 'contents'
|
|
elif value == 'none':
|
|
return 'inhibit'
|
|
return _content_list(computer, values)
|
|
|
|
|
|
@register_computer('display')
|
|
def display(computer, name, value):
|
|
"""Compute the ``display`` property.
|
|
|
|
See http://www.w3.org/TR/CSS21/visuren.html#dis-pos-flo
|
|
|
|
"""
|
|
float_ = computer['specified']['float']
|
|
position = computer['specified']['position']
|
|
if position in ('absolute', 'fixed') or float_ != 'none' or \
|
|
computer['is_root_element']:
|
|
if value == 'inline-table':
|
|
return'table'
|
|
elif value in ('inline', 'table-row-group', 'table-column',
|
|
'table-column-group', 'table-header-group',
|
|
'table-footer-group', 'table-row', 'table-cell',
|
|
'table-caption', 'inline-block'):
|
|
return 'block'
|
|
return value
|
|
|
|
|
|
@register_computer('float')
|
|
def compute_float(computer, name, value):
|
|
"""Compute the ``float`` property.
|
|
|
|
See http://www.w3.org/TR/CSS21/visuren.html#dis-pos-flo
|
|
|
|
"""
|
|
if computer['specified']['position'] in ('absolute', 'fixed'):
|
|
return 'none'
|
|
else:
|
|
return value
|
|
|
|
|
|
@register_computer('font-size')
|
|
def font_size(computer, name, value):
|
|
"""Compute the ``font-size`` property."""
|
|
if value in FONT_SIZE_KEYWORDS:
|
|
return FONT_SIZE_KEYWORDS[value]
|
|
|
|
keyword_values = list(FONT_SIZE_KEYWORDS.values())
|
|
parent_font_size = computer['parent_style']['font_size']
|
|
|
|
if value == 'larger':
|
|
for i, keyword_value in enumerate(keyword_values):
|
|
if keyword_value > parent_font_size:
|
|
return keyword_values[i]
|
|
else:
|
|
return parent_font_size * 1.2
|
|
elif value == 'smaller':
|
|
for i, keyword_value in enumerate(keyword_values[::-1]):
|
|
if keyword_value < parent_font_size:
|
|
return keyword_values[-i - 1]
|
|
else:
|
|
return parent_font_size * 0.8
|
|
elif value.unit == '%':
|
|
return value.value * parent_font_size / 100.
|
|
else:
|
|
return length(
|
|
computer, name, value, pixels_only=True,
|
|
font_size=parent_font_size)
|
|
|
|
|
|
@register_computer('font-weight')
|
|
def font_weight(computer, name, value):
|
|
"""Compute the ``font-weight`` property."""
|
|
if value == 'normal':
|
|
return 400
|
|
elif value == 'bold':
|
|
return 700
|
|
elif value in ('bolder', 'lighter'):
|
|
parent_value = computer['parent_style']['font_weight']
|
|
return FONT_WEIGHT_RELATIVE[value][parent_value]
|
|
else:
|
|
return value
|
|
|
|
|
|
@register_computer('line-height')
|
|
def line_height(computer, name, value):
|
|
"""Compute the ``line-height`` property."""
|
|
if value == 'normal':
|
|
return value
|
|
elif not value.unit:
|
|
return ('NUMBER', value.value)
|
|
elif value.unit == '%':
|
|
factor = value.value / 100.
|
|
font_size_value = computer['computed']['font_size']
|
|
pixels = factor * font_size_value
|
|
else:
|
|
pixels = length(computer, name, value, pixels_only=True)
|
|
return ('PIXELS', pixels)
|
|
|
|
|
|
@register_computer('anchor')
|
|
def anchor(computer, name, values):
|
|
"""Compute the ``anchor`` property."""
|
|
if values != 'none':
|
|
_, key = values
|
|
anchor_name = computer['element'].get(key) or None
|
|
computer['target_collector'].collect_anchor(anchor_name)
|
|
return anchor_name
|
|
|
|
|
|
@register_computer('link')
|
|
def link(computer, name, values):
|
|
"""Compute the ``link`` property."""
|
|
if values == 'none':
|
|
return None
|
|
else:
|
|
type_, value = values
|
|
if type_ == 'attr()':
|
|
return get_link_attribute(
|
|
computer['element'], value, computer['base_url'])
|
|
else:
|
|
return values
|
|
|
|
|
|
@register_computer('lang')
|
|
def lang(computer, name, values):
|
|
"""Compute the ``lang`` property."""
|
|
if values == 'none':
|
|
return None
|
|
else:
|
|
type_, key = values
|
|
if type_ == 'attr()':
|
|
return computer['element'].get(key) or None
|
|
elif type_ == 'string':
|
|
return key
|
|
|
|
|
|
@register_computer('tab-size')
|
|
def tab_size(computer, name, value):
|
|
"""Compute the ``tab-size`` property."""
|
|
if isinstance(value, int):
|
|
return value
|
|
else:
|
|
return length(computer, name, value)
|
|
|
|
|
|
@register_computer('transform')
|
|
def transform(computer, name, value):
|
|
"""Compute the ``transform`` property."""
|
|
result = []
|
|
for function, args in value:
|
|
if function == 'translate':
|
|
args = length_or_percentage_tuple(computer, name, args)
|
|
result.append((function, args))
|
|
return tuple(result)
|
|
|
|
|
|
@register_computer('vertical-align')
|
|
def vertical_align(computer, name, value):
|
|
"""Compute the ``vertical-align`` property."""
|
|
# Use +/- half an em for super and sub, same as Pango.
|
|
# (See the SUPERSUB_RISE constant in pango-markup.c)
|
|
if value in ('baseline', 'middle', 'text-top', 'text-bottom',
|
|
'top', 'bottom'):
|
|
return value
|
|
elif value == 'super':
|
|
return computer['computed']['font_size'] * 0.5
|
|
elif value == 'sub':
|
|
return computer['computed']['font_size'] * -0.5
|
|
elif value.unit == '%':
|
|
height, _ = strut_layout(computer['computed'])
|
|
return height * value.value / 100.
|
|
else:
|
|
return length(computer, name, value, pixels_only=True)
|
|
|
|
|
|
@register_computer('word-spacing')
|
|
def word_spacing(computer, name, value):
|
|
"""Compute the ``word-spacing`` property."""
|
|
if value == 'normal':
|
|
return 0
|
|
else:
|
|
return length(computer, name, value, pixels_only=True)
|
|
|
|
|
|
def strut_layout(style, context=None):
|
|
"""Return a tuple of the used value of ``line-height`` and the baseline.
|
|
|
|
The baseline is given from the top edge of line height.
|
|
|
|
"""
|
|
# TODO: always get the real value for `context`? (if we really care…)
|
|
|
|
if style['font_size'] == 0:
|
|
return 0, 0
|
|
|
|
if context:
|
|
key = (
|
|
style['font_size'], style['font_language_override'], style['lang'],
|
|
tuple(style['font_family']), style['font_style'],
|
|
style['font_stretch'], style['font_weight'], style['line_height'])
|
|
if key in context.strut_layouts:
|
|
return context.strut_layouts[key]
|
|
|
|
layout = text.Layout(context, style['font_size'], style)
|
|
layout.set_text(' ')
|
|
line, _ = layout.get_first_line()
|
|
_, _, _, _, text_height, baseline = text.first_line_metrics(
|
|
line, '', layout, resume_at=None, space_collapse=False, style=style)
|
|
if style['line_height'] == 'normal':
|
|
result = text_height, baseline
|
|
if context:
|
|
context.strut_layouts[key] = result
|
|
return result
|
|
type_, line_height = style['line_height']
|
|
if type_ == 'NUMBER':
|
|
line_height *= style['font_size']
|
|
result = line_height, baseline + (line_height - text_height) / 2
|
|
if context:
|
|
context.strut_layouts[key] = result
|
|
return result
|
|
|
|
|
|
def ex_ratio(style):
|
|
"""Return the ratio 1ex/font_size, according to given style."""
|
|
font_size = 1000 # big value
|
|
# TODO: use context to use @font-face fonts
|
|
layout = text.Layout(context=None, font_size=font_size, style=style)
|
|
layout.set_text('x')
|
|
line, _ = layout.get_first_line()
|
|
_, ink_height_above_baseline = text.get_ink_position(line)
|
|
# Zero means some kind of failure, fallback is 0.5.
|
|
# We round to try keeping exact values that were altered by Pango.
|
|
return round(-ink_height_above_baseline / font_size, 5) or 0.5
|