mirror of
https://github.com/Kozea/WeasyPrint.git
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215 lines
6.5 KiB
Python
215 lines
6.5 KiB
Python
# coding: utf8
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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 2011-2012 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 os.path
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import logging
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from .formatting_structure import boxes
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from .urls import get_url_attribute
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from .compat import xrange, urljoin
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from .logger import LOGGER
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from . import CSS
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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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HTML5_UA_STYLESHEET = CSS(
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filename=os.path.join(os.path.dirname(__file__), 'css', 'html5_ua.css'))
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LOGGER.setLevel(level)
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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):
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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](element, box, get_image_from_uri)
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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, element.sourceline, box.style, image)
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@handler('img')
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def handle_img(element, box, get_image_from_uri):
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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')
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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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return [box.copy_with_children(
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[boxes.TextBox.anonymous_from(box, alt)])]
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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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return [box.copy_with_children(
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[boxes.TextBox.anonymous_from(box, alt)])]
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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):
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"""Handle ``<embed>`` elements, return either an image or nothing.
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See: http://www.w3.org/TR/html5/the-iframe-element.html#the-embed-element
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"""
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src = get_url_attribute(element, 'src')
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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):
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"""Handle ``<object>`` elements, return either an image or the fallback
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content.
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See: http://www.w3.org/TR/html5/the-iframe-element.html#the-object-element
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"""
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data = get_url_attribute(element, 'data')
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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):
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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):
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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):
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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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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(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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