mirror of
https://github.com/Kozea/WeasyPrint.git
synced 2024-10-05 16:37:47 +03:00
810 lines
35 KiB
Python
810 lines
35 KiB
Python
# coding: utf-8
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"""
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weasyprint.css
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--------------
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This module takes care of steps 3 and 4 of “CSS 2.1 processing model”:
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Retrieve stylesheets associated with a document and annotate every element
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with a value for every CSS property.
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http://www.w3.org/TR/CSS21/intro.html#processing-model
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This module does this in more than two steps. The
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:func:`get_all_computed_styles` function does everything, but it is itsef
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based on other functions in this module.
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:copyright: Copyright 2011-2014 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 __future__ import division, unicode_literals
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import re
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import tinycss
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import cssselect
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import lxml.etree
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from . import properties
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from . import computed_values
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from .descriptors import preprocess_descriptors
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from .validation import preprocess_declarations
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from ..urls import (element_base_url, get_url_attribute, url_join,
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URLFetchingError)
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from ..logger import LOGGER
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from ..compat import iteritems
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from .. import CSS
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PARSER = tinycss.make_parser('page3', 'fonts3')
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# Reject anything not in here:
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PSEUDO_ELEMENTS = (None, 'before', 'after', 'first-line', 'first-letter')
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# Selectors for @page rules can have a pseudo-class, one of :first, :left,
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# :right or :blank. This maps pseudo-classes to lists of "page types" selected.
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PAGE_PSEUDOCLASS_TARGETS = {
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'first': [
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'first_left_page', 'first_right_page',
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'first_blank_left_page', 'first_blank_right_page'],
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'left': [
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'left_page', 'first_left_page',
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'blank_left_page', 'first_blank_left_page'],
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'right': [
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'right_page', 'first_right_page',
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'blank_right_page', 'first_blank_right_page'],
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'blank': [
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'blank_left_page', 'first_blank_left_page',
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'blank_right_page', 'first_blank_right_page'],
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# no pseudo-class: all pages
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None: [
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'left_page', 'right_page', 'first_left_page', 'first_right_page',
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'blank_left_page', 'blank_right_page',
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'first_blank_left_page', 'first_blank_right_page'],
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}
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# A test function that returns True if the given property name has an
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# initial value that is not always the same when computed.
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RE_INITIAL_NOT_COMPUTED = re.compile(
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'^(display|column_gap|'
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'(border_[a-z]+|outline|column_rule)_(width|color))$').match
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class StyleDict(dict):
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"""A mapping (dict-like) that allows attribute access to values.
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Allow eg. ``style.font_size`` instead of ``style['font-size']``.
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"""
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# TODO: We should remove that. Some attributes (eg. "clear") exist as
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# dict methods and can only be accessed with getitem.
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__getattr__ = dict.__getitem__
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def get_color(self, key):
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value = self[key]
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return value if value != 'currentColor' else self['color']
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def copy(self):
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"""Copy the ``StyleDict``."""
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style = type(self)(self)
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style.anonymous = self.anonymous
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return style
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def inherit_from(self):
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"""Return a new StyleDict with inherited properties from this one.
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Non-inherited properties get their initial values.
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This is the method used for an anonymous box.
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"""
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style = computed_from_cascaded(
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cascaded={}, parent_style=self,
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# Only used by non-inherited properties. eg `content: attr(href)`
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element=None)
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style.anonymous = True
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return style
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# Default values, may be overriden on instances
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anonymous = False
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def get_child_text(element):
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"""Return the text directly in the element, not descendants."""
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content = [element.text] if element.text else []
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for child in element:
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if child.tail:
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content.append(child.tail)
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return ''.join(content)
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def find_stylesheets(element_tree, device_media_type, url_fetcher,
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font_config):
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"""Yield the stylesheets in ``element_tree``.
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The output order is the same as the source order.
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"""
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from ..html import element_has_link_type # Work around circular imports.
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for element in element_tree.iter('style', 'link'):
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mime_type = element.get('type', 'text/css').split(';', 1)[0].strip()
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# Only keep 'type/subtype' from 'type/subtype ; param1; param2'.
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if mime_type != 'text/css':
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continue
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media_attr = element.get('media', '').strip() or 'all'
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media = [media_type.strip() for media_type in media_attr.split(',')]
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if not evaluate_media_query(media, device_media_type):
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continue
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if element.tag == 'style':
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# Content is text that is directly in the <style> element, not its
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# descendants
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content = get_child_text(element)
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# lxml should give us either unicode or ASCII-only bytestrings, so
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# we don't need `encoding` here.
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css = CSS(
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string=content, base_url=element_base_url(element),
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url_fetcher=url_fetcher, media_type=device_media_type,
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font_config=font_config)
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yield css
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elif element.tag == 'link' and element.get('href'):
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if not element_has_link_type(element, 'stylesheet') or \
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element_has_link_type(element, 'alternate'):
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continue
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href = get_url_attribute(element, 'href')
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if href is not None:
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try:
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yield CSS(
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url=href, url_fetcher=url_fetcher,
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_check_mime_type=True, media_type=device_media_type,
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font_config=font_config)
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except URLFetchingError as exc:
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LOGGER.warning('Failed to load stylesheet at %s : %s',
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href, exc)
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def check_style_attribute(parser, element, style_attribute):
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declarations, errors = parser.parse_style_attr(style_attribute)
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for error in errors:
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LOGGER.warning(error)
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return element, declarations, element_base_url(element)
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def find_style_attributes(element_tree, presentational_hints=False):
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"""Yield ``specificity, (element, declaration, base_url)`` rules.
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Rules from "style" attribute are returned with specificity
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``(1, 0, 0, 0)``.
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If ``presentational_hints`` is ``True``, rules from presentational hints
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are returned with specificity ``(0, 0, 0, 0)``.
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"""
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parser = PARSER
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for element in element_tree.iter():
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specificity = (1, 0, 0, 0)
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style_attribute = element.get('style')
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if style_attribute:
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if not presentational_hints:
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continue
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specificity = (0, 0, 0, 0)
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if element.tag == 'body':
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# TODO: we should check the container frame element
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for part, position in (
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('height', 'top'), ('height', 'bottom'),
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('width', 'left'), ('width', 'right')):
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style_attribute = None
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for prop in ('margin%s' % part, '%smargin' % position):
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if element.get(prop):
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style_attribute = 'margin-%s:%spx' % (
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position, element.get(prop))
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break
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if style_attribute:
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('background'):
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style_attribute = 'background-image:url(%s)' % (
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element.get('background'))
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('bgcolor'):
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style_attribute = 'background-color:%s' % (
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element.get('bgcolor'))
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('text'):
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style_attribute = 'color:%s' % element.get('text')
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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# TODO: we should support link, vlink, alink
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elif element.tag == 'center':
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yield specificity, check_style_attribute(
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parser, element, 'text-align:center')
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elif element.tag == 'div':
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align = element.get('align', '').lower()
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if align == 'middle':
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yield specificity, check_style_attribute(
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parser, element, 'text-align:center')
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elif align in ('center', 'left', 'right', 'justify'):
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yield specificity, check_style_attribute(
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parser, element, 'text-align:%s' % align)
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elif element.tag == 'font':
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if element.get('color'):
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yield specificity, check_style_attribute(
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parser, element, 'color:%s' % element.get('color'))
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if element.get('face'):
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yield specificity, check_style_attribute(
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parser, element, 'font-family:%s' % element.get('face'))
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if element.get('size'):
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size = element.get('size').strip()
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relative_plus = size.startswith('+')
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relative_minus = size.startswith('-')
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if relative_plus or relative_minus:
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size = size[1:].strip()
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try:
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size = int(size)
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except ValueError:
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LOGGER.warning('Invalid value for size: %s' % size)
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else:
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font_sizes = {
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1: 'x-small',
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2: 'small',
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3: 'medium',
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4: 'large',
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5: 'x-large',
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6: 'xx-large',
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7: '48px', # 1.5 * xx-large
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}
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if relative_plus:
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size += 3
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elif relative_minus:
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size -= 3
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size = max(1, min(7, size))
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yield specificity, check_style_attribute(
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parser, element, 'font-size:%s' % font_sizes[size])
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elif element.tag == 'table':
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# TODO: we should support cellpadding
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if element.get('cellspacing'):
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yield specificity, check_style_attribute(
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parser, element,
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'border-spacing:%spx' % element.get('cellspacing'))
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if element.get('cellpadding'):
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cellpadding = element.get('cellpadding')
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if cellpadding.isdigit():
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cellpadding += 'px'
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# TODO: don't match subtables cells
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for subelement in element.iter():
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if subelement.tag in ('td', 'th'):
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yield specificity, check_style_attribute(
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parser, subelement,
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'padding-left:%s;padding-right:%s;'
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'padding-top:%s;padding-bottom:%s;' % (
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4 * (cellpadding,)))
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if element.get('hspace'):
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hspace = element.get('hspace')
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if hspace.isdigit():
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hspace += 'px'
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yield specificity, check_style_attribute(
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parser, element,
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'margin-left:%s;margin-right:%s' % (hspace, hspace))
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if element.get('vspace'):
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vspace = element.get('vspace')
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if vspace.isdigit():
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vspace += 'px'
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yield specificity, check_style_attribute(
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parser, element,
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'margin-top:%s;margin-bottom:%s' % (vspace, vspace))
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if element.get('width'):
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style_attribute = 'width:%s' % element.get('width')
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if element.get('width').isdigit():
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style_attribute += 'px'
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('height'):
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style_attribute = 'height:%s' % element.get('height')
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if element.get('height').isdigit():
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style_attribute += 'px'
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('background'):
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style_attribute = 'background-image:url(%s)' % (
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element.get('background'))
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('bgcolor'):
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style_attribute = 'background-color:%s' % (
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element.get('bgcolor'))
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('bordercolor'):
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style_attribute = 'border-color:%s' % (
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element.get('bordercolor'))
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('border'):
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style_attribute = 'border-width:%spx' % (
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element.get('border'))
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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elif element.tag in ('tr', 'td', 'th', 'thead', 'tbody', 'tfoot'):
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align = element.get('align', '').lower()
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if align in ('left', 'right', 'justify'):
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# TODO: we should align descendants too
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yield specificity, check_style_attribute(
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parser, element, 'text-align:%s' % align)
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if element.get('background'):
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style_attribute = 'background-image:url(%s)' % (
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element.get('background'))
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('bgcolor'):
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style_attribute = 'background-color:%s' % (
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element.get('bgcolor'))
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.tag in ('tr', 'td', 'th'):
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if element.get('height'):
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style_attribute = 'height:%s' % element.get('height')
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if element.get('height').isdigit():
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style_attribute += 'px'
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.tag in ('td', 'th'):
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if element.get('width'):
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style_attribute = 'width:%s' % element.get('width')
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if element.get('width').isdigit():
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style_attribute += 'px'
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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elif element.tag == 'caption':
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align = element.get('align', '').lower()
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# TODO: we should align descendants too
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if align in ('left', 'right', 'justify'):
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yield specificity, check_style_attribute(
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parser, element, 'text-align:%s' % align)
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elif element.tag == 'col':
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if element.get('width'):
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style_attribute = 'width:%s' % element.get('width')
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if element.get('width').isdigit():
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style_attribute += 'px'
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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elif element.tag == 'hr':
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size = 0
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if element.get('size'):
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try:
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size = int(element.get('size'))
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except ValueError:
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LOGGER.warning('Invalid value for size: %s' % size)
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if (element.get('color'), element.get('noshade')) != (None, None):
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if size >= 1:
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yield specificity, check_style_attribute(
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parser, element, 'border-width:%spx' % (size / 2))
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elif size == 1:
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yield specificity, check_style_attribute(
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parser, element, 'border-bottom-width:0')
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elif size > 1:
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yield specificity, check_style_attribute(
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parser, element, 'height:%spx' % (size - 2))
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if element.get('width'):
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style_attribute = 'width:%s' % element.get('width')
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if element.get('width').isdigit():
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style_attribute += 'px'
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('color'):
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yield specificity, check_style_attribute(
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parser, element, 'color:%s' % element.get('color'))
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elif element.tag in (
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'iframe', 'applet', 'embed', 'img', 'input', 'object'):
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if (element.tag != 'input' or
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element.get('type', '').lower() == 'image'):
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align = element.get('align', '').lower()
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if align in ('middle', 'center'):
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# TODO: middle and center values are wrong
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yield specificity, check_style_attribute(
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parser, element, 'vertical-align:middle')
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if element.get('hspace'):
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hspace = element.get('hspace')
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if hspace.isdigit():
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hspace += 'px'
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yield specificity, check_style_attribute(
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parser, element,
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'margin-left:%s;margin-right:%s' % (hspace, hspace))
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if element.get('vspace'):
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vspace = element.get('vspace')
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if vspace.isdigit():
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vspace += 'px'
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yield specificity, check_style_attribute(
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parser, element,
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'margin-top:%s;margin-bottom:%s' % (vspace, vspace))
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# TODO: img seems to be excluded for width and height, but a
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# lot of W3C tests rely on this attribute being applied to img
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if element.get('width'):
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style_attribute = 'width:%s' % element.get('width')
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if element.get('width').isdigit():
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style_attribute += 'px'
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.get('height'):
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style_attribute = 'height:%s' % element.get('height')
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if element.get('height').isdigit():
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style_attribute += 'px'
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yield specificity, check_style_attribute(
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parser, element, style_attribute)
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if element.tag in ('img', 'object', 'input'):
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if element.get('border'):
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yield specificity, check_style_attribute(
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parser, element,
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'border-width:%spx;border-style:solid' %
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element.get('border'))
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elif element.tag == 'ol':
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# From https://www.w3.org/TR/css-lists-3/
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if element.get('start'):
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yield specificity, check_style_attribute(
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parser, element,
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'counter-reset:list-item %s;'
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'counter-increment:list-item -1' % element.get('start'))
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elif element.tag == 'ul':
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# From https://www.w3.org/TR/css-lists-3/
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if element.get('value'):
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yield specificity, check_style_attribute(
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parser, element,
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'counter-reset:list-item %s;'
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'counter-increment:none' % element.get('value'))
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def evaluate_media_query(query_list, device_media_type):
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"""Return the boolean evaluation of `query_list` for the given
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`device_media_type`.
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:attr query_list: a cssutilts.stlysheets.MediaList
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:attr device_media_type: a media type string (for now)
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"""
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# TODO: actual support for media queries, not just media types
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return 'all' in query_list or device_media_type in query_list
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def declaration_precedence(origin, importance):
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"""Return the precedence for a declaration.
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Precedence values have no meaning unless compared to each other.
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Acceptable values for ``origin`` are the strings ``'author'``, ``'user'``
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and ``'user agent'``.
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"""
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# See http://www.w3.org/TR/CSS21/cascade.html#cascading-order
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if origin == 'user agent':
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return 1
|
||
elif origin == 'user' and not importance:
|
||
return 2
|
||
elif origin == 'author' and not importance:
|
||
return 3
|
||
elif origin == 'author': # and importance
|
||
return 4
|
||
else:
|
||
assert origin == 'user' # and importance
|
||
return 5
|
||
|
||
|
||
def add_declaration(cascaded_styles, prop_name, prop_values, weight, element,
|
||
pseudo_type=None):
|
||
"""Set the value for a property on a given element.
|
||
|
||
The value is only set if there is no value of greater weight defined yet.
|
||
|
||
"""
|
||
style = cascaded_styles.setdefault((element, pseudo_type), {})
|
||
_values, previous_weight = style.get(prop_name, (None, None))
|
||
if previous_weight is None or previous_weight <= weight:
|
||
style[prop_name] = prop_values, weight
|
||
|
||
|
||
def set_computed_styles(cascaded_styles, computed_styles, element, parent,
|
||
root=None, pseudo_type=None):
|
||
"""Set the computed values of styles to ``element``.
|
||
|
||
Take the properties left by ``apply_style_rule`` on an element or
|
||
pseudo-element and assign computed values with respect to the cascade,
|
||
declaration priority (ie. ``!important``) and selector specificity.
|
||
|
||
"""
|
||
parent_style = computed_styles[parent, None] \
|
||
if parent is not None else None
|
||
# When specified on the font-size property of the root element, the rem
|
||
# units refer to the property’s initial value.
|
||
root_style = {'font_size': properties.INITIAL_VALUES['font_size']} \
|
||
if element is root else computed_styles[root, None]
|
||
cascaded = cascaded_styles.get((element, pseudo_type), {})
|
||
|
||
computed_styles[element, pseudo_type] = computed_from_cascaded(
|
||
element, cascaded, parent_style, pseudo_type, root_style
|
||
)
|
||
|
||
|
||
def computed_from_cascaded(element, cascaded, parent_style, pseudo_type=None,
|
||
root_style=None):
|
||
"""Get a dict of computed style mixed from parent and cascaded styles."""
|
||
if not cascaded and parent_style is not None:
|
||
# Fast path for anonymous boxes:
|
||
# no cascaded style, only implicitly initial or inherited values.
|
||
computed = StyleDict(properties.INITIAL_VALUES)
|
||
for name in properties.INHERITED:
|
||
computed[name] = parent_style[name]
|
||
# border-*-style is none, so border-width computes to zero.
|
||
# Other than that, properties that would need computing are
|
||
# border-*-color, but they do not apply.
|
||
for side in ('top', 'bottom', 'left', 'right'):
|
||
computed['border_%s_width' % side] = 0
|
||
computed['outline_width'] = 0
|
||
return computed
|
||
|
||
# Handle inheritance and initial values
|
||
specified = StyleDict()
|
||
computed = StyleDict()
|
||
for name, initial in iteritems(properties.INITIAL_VALUES):
|
||
if name in cascaded:
|
||
value, _precedence = cascaded[name]
|
||
keyword = value
|
||
else:
|
||
if name in properties.INHERITED:
|
||
keyword = 'inherit'
|
||
else:
|
||
keyword = 'initial'
|
||
|
||
if keyword == 'inherit' and parent_style is None:
|
||
# On the root element, 'inherit' from initial values
|
||
keyword = 'initial'
|
||
|
||
if keyword == 'initial':
|
||
value = initial
|
||
if not RE_INITIAL_NOT_COMPUTED(name):
|
||
# The value is the same as when computed
|
||
computed[name] = value
|
||
elif keyword == 'inherit':
|
||
value = parent_style[name]
|
||
# Values in parent_style are already computed.
|
||
computed[name] = value
|
||
|
||
specified[name] = value
|
||
|
||
return computed_values.compute(
|
||
element, pseudo_type, specified, computed, parent_style, root_style
|
||
)
|
||
|
||
|
||
class Selector(object):
|
||
def __init__(self, specificity, pseudo_element, match):
|
||
self.specificity = specificity
|
||
self.pseudo_element = pseudo_element
|
||
self.match = match
|
||
|
||
|
||
def preprocess_stylesheet(device_media_type, base_url, stylesheet_rules,
|
||
url_fetcher, rules, fonts, font_config):
|
||
"""Do the work that can be done early on stylesheet, before they are
|
||
in a document.
|
||
|
||
"""
|
||
selector_to_xpath = cssselect.HTMLTranslator().selector_to_xpath
|
||
for rule in stylesheet_rules:
|
||
if not rule.at_keyword:
|
||
declarations = list(preprocess_declarations(
|
||
base_url, rule.declarations))
|
||
if declarations:
|
||
selector_string = rule.selector.as_css()
|
||
try:
|
||
selector_list = []
|
||
for selector in cssselect.parse(selector_string):
|
||
xpath = selector_to_xpath(selector)
|
||
try:
|
||
lxml_xpath = lxml.etree.XPath(xpath)
|
||
except ValueError as exc:
|
||
# TODO: Some characters are not supported by lxml's
|
||
# XPath implementation (including control
|
||
# characters), but these characters are valid in
|
||
# the CSS2.1 specification.
|
||
raise cssselect.SelectorError(str(exc))
|
||
selector_list.append(Selector(
|
||
(0,) + selector.specificity(),
|
||
selector.pseudo_element, lxml_xpath))
|
||
for selector in selector_list:
|
||
if selector.pseudo_element not in PSEUDO_ELEMENTS:
|
||
raise cssselect.ExpressionError(
|
||
'Unknown pseudo-element: %s'
|
||
% selector.pseudo_element)
|
||
except cssselect.SelectorError as exc:
|
||
LOGGER.warning("Invalid or unsupported selector '%s', %s",
|
||
selector_string, exc)
|
||
continue
|
||
rules.append((rule, selector_list, declarations))
|
||
|
||
elif rule.at_keyword == '@import':
|
||
if not evaluate_media_query(rule.media, device_media_type):
|
||
continue
|
||
url = url_join(base_url, rule.uri, '@import at %s:%s',
|
||
rule.line, rule.column)
|
||
if url is not None:
|
||
try:
|
||
stylesheet = CSS(
|
||
url=url, url_fetcher=url_fetcher,
|
||
media_type=device_media_type, font_config=font_config)
|
||
except URLFetchingError as exc:
|
||
LOGGER.warning('Failed to load stylesheet at %s : %s',
|
||
url, exc)
|
||
else:
|
||
for result in stylesheet.rules:
|
||
rules.append(result)
|
||
|
||
elif rule.at_keyword == '@media':
|
||
if not evaluate_media_query(rule.media, device_media_type):
|
||
continue
|
||
preprocess_stylesheet(
|
||
device_media_type, base_url, rule.rules, url_fetcher, rules,
|
||
fonts, font_config)
|
||
|
||
elif rule.at_keyword == '@page':
|
||
page_name, pseudo_class = rule.selector
|
||
# TODO: support named pages (see CSS3 Paged Media)
|
||
if page_name is not None:
|
||
LOGGER.warning('Named pages are not supported yet, the whole '
|
||
'@page %s rule was ignored.', page_name + (
|
||
':' + pseudo_class if pseudo_class else ''))
|
||
continue
|
||
declarations = list(preprocess_declarations(
|
||
base_url, rule.declarations))
|
||
|
||
# Use a double lambda to have a closure that holds page_types
|
||
match = (lambda page_types: lambda _document: page_types)(
|
||
PAGE_PSEUDOCLASS_TARGETS[pseudo_class])
|
||
specificity = rule.specificity
|
||
|
||
if declarations:
|
||
selector_list = [Selector(specificity, None, match)]
|
||
rules.append((rule, selector_list, declarations))
|
||
|
||
for margin_rule in rule.at_rules:
|
||
declarations = list(preprocess_declarations(
|
||
base_url, margin_rule.declarations))
|
||
if declarations:
|
||
selector_list = [Selector(
|
||
specificity, margin_rule.at_keyword, match)]
|
||
rules.append((margin_rule, selector_list, declarations))
|
||
|
||
elif rule.at_keyword == '@font-face':
|
||
rule_descriptors = dict(list(preprocess_descriptors(
|
||
base_url, rule.declarations)))
|
||
for key in ('src', 'font_family'):
|
||
if key not in rule_descriptors:
|
||
LOGGER.warning(
|
||
"Missing %s descriptor in '@font-face' rule at %s:%s",
|
||
key.replace('_', '-'), rule.line, rule.column)
|
||
break
|
||
else:
|
||
if font_config is not None:
|
||
font_filename = font_config.add_font_face(
|
||
rule_descriptors, url_fetcher)
|
||
if font_filename:
|
||
fonts.append(font_filename)
|
||
|
||
|
||
def get_all_computed_styles(html, user_stylesheets=None,
|
||
presentational_hints=False, font_config=None):
|
||
"""Compute all the computed styles of all elements in ``html`` document.
|
||
|
||
Do everything from finding author stylesheets to parsing and applying them.
|
||
|
||
Return a ``style_for`` function that takes an element and an optional
|
||
pseudo-element type, and return a StyleDict object.
|
||
|
||
"""
|
||
element_tree = html.root_element
|
||
device_media_type = html.media_type
|
||
url_fetcher = html.url_fetcher
|
||
ua_stylesheets = html._ua_stylesheets()
|
||
author_stylesheets = list(find_stylesheets(
|
||
element_tree, device_media_type, url_fetcher, font_config))
|
||
if presentational_hints:
|
||
ph_stylesheets = html._ph_stylesheets()
|
||
else:
|
||
ph_stylesheets = []
|
||
|
||
# keys: (element, pseudo_element_type)
|
||
# element: a lxml element object or the '@page' string for @page styles
|
||
# pseudo_element_type: a string such as 'first' (for @page) or 'after',
|
||
# or None for normal elements
|
||
# values: dicts of
|
||
# keys: property name as a string
|
||
# values: (values, weight)
|
||
# values: a PropertyValue-like object
|
||
# weight: values with a greater weight take precedence, see
|
||
# http://www.w3.org/TR/CSS21/cascade.html#cascading-order
|
||
cascaded_styles = {}
|
||
|
||
for specificity, attributes in find_style_attributes(
|
||
element_tree, presentational_hints):
|
||
element, declarations, base_url = attributes
|
||
for name, values, importance in preprocess_declarations(
|
||
base_url, declarations):
|
||
precedence = declaration_precedence('author', importance)
|
||
weight = (precedence, specificity)
|
||
add_declaration(cascaded_styles, name, values, weight, element)
|
||
|
||
for sheets, origin, sheet_specificity in (
|
||
# Order here is not important ('origin' is).
|
||
# Use this order for a regression test
|
||
(ua_stylesheets or [], 'user agent', None),
|
||
(ph_stylesheets, 'author', (0, 0, 0, 0)),
|
||
(author_stylesheets, 'author', None),
|
||
(user_stylesheets or [], 'user', None),
|
||
):
|
||
for sheet in sheets:
|
||
for _rule, selector_list, declarations in sheet.rules:
|
||
for selector in selector_list:
|
||
specificity = sheet_specificity or selector.specificity
|
||
pseudo_type = selector.pseudo_element
|
||
for element in selector.match(element_tree):
|
||
for name, values, importance in declarations:
|
||
precedence = declaration_precedence(
|
||
origin, importance)
|
||
weight = (precedence, specificity)
|
||
add_declaration(
|
||
cascaded_styles, name, values, weight,
|
||
element, pseudo_type)
|
||
|
||
# keys: (element, pseudo_element_type), like cascaded_styles
|
||
# values: StyleDict objects:
|
||
# keys: property name as a string
|
||
# values: a PropertyValue-like object
|
||
computed_styles = {}
|
||
|
||
# First, computed styles for "real" elements *in tree order*
|
||
# Tree order is important so that parents have computed styles before
|
||
# their children, for inheritance.
|
||
|
||
# Iterate on all elements, even if there is no cascaded style for them.
|
||
for element in element_tree.iter():
|
||
set_computed_styles(cascaded_styles, computed_styles, element,
|
||
root=element_tree, parent=element.getparent())
|
||
|
||
# Then computed styles for @page.
|
||
|
||
# Iterate on all possible page types, even if there is no cascaded style
|
||
# for them.
|
||
for page_type in PAGE_PSEUDOCLASS_TARGETS[None]:
|
||
set_computed_styles(
|
||
cascaded_styles, computed_styles, page_type,
|
||
# @page inherits from the root element:
|
||
# http://lists.w3.org/Archives/Public/www-style/2012Jan/1164.html
|
||
root=element_tree, parent=element_tree)
|
||
|
||
# Then computed styles for pseudo elements, in any order.
|
||
# Pseudo-elements inherit from their associated element so they come
|
||
# last. Do them in a second pass as there is no easy way to iterate
|
||
# on the pseudo-elements for a given element with the current structure
|
||
# of cascaded_styles. (Keys are (element, pseudo_type) tuples.)
|
||
|
||
# Only iterate on pseudo-elements that have cascaded styles. (Others
|
||
# might as well not exist.)
|
||
for element, pseudo_type in cascaded_styles:
|
||
if pseudo_type:
|
||
set_computed_styles(cascaded_styles, computed_styles,
|
||
element, pseudo_type=pseudo_type,
|
||
# The pseudo-element inherits from the element.
|
||
root=element_tree, parent=element)
|
||
|
||
# This is mostly useful to make pseudo_type optional.
|
||
def style_for(element, pseudo_type=None, __get=computed_styles.get):
|
||
"""
|
||
Convenience function to get the computed styles for an element.
|
||
"""
|
||
return __get((element, pseudo_type))
|
||
|
||
return style_for
|