385 lines
12 KiB
Python
385 lines
12 KiB
Python
# coding: utf-8
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"""
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weasyprint.html
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---------------
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Specific handling for some HTML elements, especially replaced elements.
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Replaced elements (eg. <img> elements) are rendered externally and
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behave as an atomic opaque box in CSS. In general, they may or may not
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have intrinsic dimensions. But the only replaced elements currently
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supported in WeasyPrint are images with intrinsic dimensions.
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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 logging
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import os.path
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import re
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import sys
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from . import CSS
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from .compat import urljoin, xrange
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from .css import get_child_text
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from .formatting_structure import boxes
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from .logger import LOGGER
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from .urls import get_url_attribute
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# XXX temporarily disable logging for user-agent stylesheet
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level = LOGGER.level
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LOGGER.setLevel(logging.ERROR)
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if hasattr(sys, 'frozen'):
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if hasattr(sys, '_MEIPASS'):
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# Frozen with PyInstaller
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# See https://github.com/Kozea/WeasyPrint/pull/540
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root = sys._MEIPASS
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else:
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# Frozen with something else (py2exe, etc.)
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# See https://github.com/Kozea/WeasyPrint/pull/269
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root = os.path.dirname(sys.executable)
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else:
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root = os.path.dirname(__file__)
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HTML5_UA_STYLESHEET = CSS(filename=os.path.join(root, 'css', 'html5_ua.css'))
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HTML5_PH_STYLESHEET = CSS(filename=os.path.join(root, 'css', 'html5_ph.css'))
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LOGGER.setLevel(level)
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# http://whatwg.org/C#space-character
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HTML_WHITESPACE = ' \t\n\f\r'
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HTML_SPACE_SEPARATED_TOKENS_RE = re.compile('[^%s]+' % HTML_WHITESPACE)
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def ascii_lower(string):
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r"""Transform (only) ASCII letters to lower case: A-Z is mapped to a-z.
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:param string: An Unicode string.
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:returns: A new Unicode string.
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This is used for `ASCII case-insensitive
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<http://whatwg.org/C#ascii-case-insensitive>`_ matching.
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This is different from the :meth:`~py:str.lower` method of Unicode strings
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which also affect non-ASCII characters,
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sometimes mapping them into the ASCII range:
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>>> keyword = u'Bac\N{KELVIN SIGN}ground'
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>>> assert keyword.lower() == u'background'
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>>> assert ascii_lower(keyword) != keyword.lower()
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>>> assert ascii_lower(keyword) == u'bac\N{KELVIN SIGN}ground'
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"""
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# This turns out to be faster than unicode.translate()
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return string.encode('utf8').lower().decode('utf8')
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def element_has_link_type(element, link_type):
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"""
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Return whether the given element has a ``rel`` attribute with the
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given link type.
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:param link_type: Must be a lower-case string.
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"""
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return any(ascii_lower(token) == link_type for token in
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HTML_SPACE_SEPARATED_TOKENS_RE.findall(element.get('rel', '')))
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# Maps HTML tag names to function taking an HTML element and returning a Box.
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HTML_HANDLERS = {}
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def handle_element(element, box, get_image_from_uri, base_url):
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"""Handle HTML elements that need special care.
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:returns: a (possibly empty) list of boxes.
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"""
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if box.element_tag in HTML_HANDLERS:
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return HTML_HANDLERS[element.tag](
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element, box, get_image_from_uri, base_url)
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else:
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return [box]
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def handler(tag):
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"""Return a decorator registering a function handling ``tag`` elements."""
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def decorator(function):
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"""Decorator registering a function handling ``tag`` elements."""
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HTML_HANDLERS[tag] = function
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return function
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return decorator
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def make_replaced_box(element, box, image):
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"""Wrap an image in a replaced box.
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That box is either block-level or inline-level, depending on what the
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element should be.
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"""
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if box.style.display in ('block', 'list-item', 'table'):
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type_ = boxes.BlockReplacedBox
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else:
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# TODO: support images with 'display: table-cell'?
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type_ = boxes.InlineReplacedBox
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return type_(element.tag, box.style, image)
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@handler('img')
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def handle_img(element, box, get_image_from_uri, base_url):
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"""Handle ``<img>`` elements, return either an image or the alt-text.
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See: http://www.w3.org/TR/html5/embedded-content-1.html#the-img-element
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"""
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src = get_url_attribute(element, 'src', base_url)
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alt = element.get('alt')
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if src:
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image = get_image_from_uri(src)
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if image is not None:
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return [make_replaced_box(element, box, image)]
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else:
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# Invalid image, use the alt-text.
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if alt:
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box.children = [boxes.TextBox.anonymous_from(box, alt)]
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return [box]
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elif alt == '':
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# The element represents nothing
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return []
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else:
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assert alt is None
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# TODO: find some indicator that an image is missing.
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# For now, just remove the image.
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return []
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else:
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if alt:
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box.children = [boxes.TextBox.anonymous_from(box, alt)]
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return [box]
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else:
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return []
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@handler('embed')
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def handle_embed(element, box, get_image_from_uri, base_url):
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"""Handle ``<embed>`` elements, return either an image or nothing.
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See: https://www.w3.org/TR/html5/embedded-content-0.html#the-embed-element
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"""
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src = get_url_attribute(element, 'src', base_url)
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type_ = element.get('type', '').strip()
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if src:
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image = get_image_from_uri(src, type_)
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if image is not None:
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return [make_replaced_box(element, box, image)]
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# No fallback.
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return []
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@handler('object')
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def handle_object(element, box, get_image_from_uri, base_url):
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"""Handle ``<object>`` elements, return either an image or the fallback
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content.
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See: https://www.w3.org/TR/html5/embedded-content-0.html#the-object-element
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"""
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data = get_url_attribute(element, 'data', base_url)
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type_ = element.get('type', '').strip()
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if data:
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image = get_image_from_uri(data, type_)
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if image is not None:
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return [make_replaced_box(element, box, image)]
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# The element’s children are the fallback.
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return [box]
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def integer_attribute(element, box, name, minimum=1):
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"""Read an integer attribute from the HTML element and set it on the box.
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"""
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value = element.get(name, '').strip()
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if value:
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try:
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value = int(value)
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except ValueError:
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pass
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else:
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if value >= minimum:
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setattr(box, name, value)
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@handler('colgroup')
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def handle_colgroup(element, box, _get_image_from_uri, _base_url):
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"""Handle the ``span`` attribute."""
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if isinstance(box, boxes.TableColumnGroupBox):
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if any(child.tag == 'col' for child in element):
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box.span = None # sum of the children’s spans
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else:
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integer_attribute(element, box, 'span')
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box.children = (
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boxes.TableColumnBox.anonymous_from(box, [])
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for _i in xrange(box.span))
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return [box]
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@handler('col')
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def handle_col(element, box, _get_image_from_uri, _base_url):
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"""Handle the ``span`` attribute."""
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if isinstance(box, boxes.TableColumnBox):
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integer_attribute(element, box, 'span')
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if box.span > 1:
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# Generate multiple boxes
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# http://lists.w3.org/Archives/Public/www-style/2011Nov/0293.html
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return [box.copy() for _i in xrange(box.span)]
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return [box]
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@handler('th')
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@handler('td')
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def handle_td(element, box, _get_image_from_uri, _base_url):
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"""Handle the ``colspan``, ``rowspan`` attributes."""
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if isinstance(box, boxes.TableCellBox):
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# HTML 4.01 gives special meaning to colspan=0
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# http://www.w3.org/TR/html401/struct/tables.html#adef-rowspan
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# but HTML 5 removed it
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# http://www.w3.org/TR/html5/tabular-data.html#attr-tdth-colspan
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# rowspan=0 is still there though.
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integer_attribute(element, box, 'colspan')
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integer_attribute(element, box, 'rowspan', minimum=0)
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return [box]
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@handler('a')
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def handle_a(element, box, _get_image_from_uri, base_url):
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"""Handle the ``rel`` attribute."""
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box.is_attachment = element_has_link_type(element, 'attachment')
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return [box]
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def find_base_url(html_document, fallback_base_url):
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"""Return the base URL for the document.
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See http://www.w3.org/TR/html5/urls.html#document-base-url
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"""
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first_base_element = next(iter(html_document.iter('base')), None)
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if first_base_element is not None:
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href = first_base_element.get('href', '').strip()
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if href:
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return urljoin(fallback_base_url, href)
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return fallback_base_url
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def get_html_metadata(wrapper_element, base_url):
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"""
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Relevant specs:
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http://www.whatwg.org/html#the-title-element
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http://www.whatwg.org/html#standard-metadata-names
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http://wiki.whatwg.org/wiki/MetaExtensions
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http://microformats.org/wiki/existing-rel-values#HTML5_link_type_extensions
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"""
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title = None
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description = None
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generator = None
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keywords = []
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authors = []
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created = None
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modified = None
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attachments = []
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for element in wrapper_element.query_all('title', 'meta', 'link'):
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element = element.etree_element
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if element.tag == 'title' and title is None:
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title = get_child_text(element)
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elif element.tag == 'meta':
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name = ascii_lower(element.get('name', ''))
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content = element.get('content', '')
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if name == 'keywords':
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for keyword in map(strip_whitespace, content.split(',')):
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if keyword not in keywords:
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keywords.append(keyword)
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elif name == 'author':
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authors.append(content)
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elif name == 'description' and description is None:
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description = content
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elif name == 'generator' and generator is None:
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generator = content
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elif name == 'dcterms.created' and created is None:
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created = parse_w3c_date(name, content)
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elif name == 'dcterms.modified' and modified is None:
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modified = parse_w3c_date(name, content)
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elif element.tag == 'link' and element_has_link_type(
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element, 'attachment'):
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url = get_url_attribute(element, 'href', base_url)
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title = element.get('title', None)
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if url is None:
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LOGGER.error('Missing href in <link rel="attachment">')
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else:
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attachments.append((url, title))
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return dict(title=title, description=description, generator=generator,
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keywords=keywords, authors=authors,
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created=created, modified=modified,
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attachments=attachments)
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def strip_whitespace(string):
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"""Use the HTML definition of "space character",
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not all Unicode Whitespace.
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http://www.whatwg.org/html#strip-leading-and-trailing-whitespace
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http://www.whatwg.org/html#space-character
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"""
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return string.strip(HTML_WHITESPACE)
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# YYYY (eg 1997)
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# YYYY-MM (eg 1997-07)
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# YYYY-MM-DD (eg 1997-07-16)
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# YYYY-MM-DDThh:mmTZD (eg 1997-07-16T19:20+01:00)
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# YYYY-MM-DDThh:mm:ssTZD (eg 1997-07-16T19:20:30+01:00)
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# YYYY-MM-DDThh:mm:ss.sTZD (eg 1997-07-16T19:20:30.45+01:00)
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W3C_DATE_RE = re.compile('''
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^
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[ \t\n\f\r]*
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(?P<year>\\d\\d\\d\\d)
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(?:
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-(?P<month>0\\d|1[012])
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(?:
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-(?P<day>[012]\\d|3[01])
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(?:
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T(?P<hour>[01]\\d|2[0-3])
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:(?P<minute>[0-5]\\d)
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(?:
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:(?P<second>[0-5]\\d)
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(?:\\.\\d+)? # Second fraction, ignored
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)?
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(?:
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Z | # UTC
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(?P<tz_hour>[+-](?:[01]\\d|2[0-3]))
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:(?P<tz_minute>[0-5]\\d)
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)
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)?
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)?
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)?
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[ \t\n\f\r]*
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$
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''', re.VERBOSE)
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def parse_w3c_date(meta_name, string):
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"""http://www.w3.org/TR/NOTE-datetime"""
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if W3C_DATE_RE.match(string):
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return string
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else:
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LOGGER.warning(
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'Invalid date in <meta name="%s"> %r', meta_name, string)
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