950 lines
39 KiB
Python
950 lines
39 KiB
Python
# coding: utf-8
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"""
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weasyprint.layout.blocks
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------------------------
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Page breaking and layout for block-level and block-container boxes.
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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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from math import floor
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from ..compat import izip, xrange
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from ..formatting_structure import boxes
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from .absolute import AbsolutePlaceholder, absolute_layout
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from .float import avoid_collisions, float_layout, get_clearance
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from .inlines import (
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iter_line_boxes, min_max_auto_replaced, replaced_box_height,
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replaced_box_width)
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from .markers import list_marker_layout
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from .min_max import handle_min_max_width
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from .percentages import resolve_percentages, resolve_position_percentages
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from .tables import table_layout, table_wrapper_width
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def block_level_layout(context, box, max_position_y, skip_stack,
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containing_block, device_size, page_is_empty,
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absolute_boxes, fixed_boxes, adjoining_margins):
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"""Lay out the block-level ``box``.
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:param max_position_y: the absolute vertical position (as in
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``some_box.position_y``) of the bottom of the
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content box of the current page area.
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"""
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if isinstance(box, boxes.TableBox):
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return table_layout(
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context, box, max_position_y, skip_stack, containing_block,
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device_size, page_is_empty, absolute_boxes, fixed_boxes)
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resolve_percentages(box, containing_block)
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if box.margin_top == 'auto':
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box.margin_top = 0
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if box.margin_bottom == 'auto':
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box.margin_bottom = 0
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collapsed_margin = collapse_margin(adjoining_margins + [box.margin_top])
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box.clearance = get_clearance(context, box, collapsed_margin)
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if box.clearance is not None:
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top_border_edge = box.position_y + collapsed_margin + box.clearance
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box.position_y = top_border_edge - box.margin_top
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adjoining_margins = []
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if isinstance(box, boxes.BlockBox):
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style = box.style
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if style.column_width != 'auto' or style.column_count != 'auto':
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result = columns_layout(
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context, box, max_position_y, skip_stack, containing_block,
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device_size, page_is_empty, absolute_boxes, fixed_boxes,
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adjoining_margins)
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resume_at = result[1]
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if resume_at is None:
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new_box = result[0]
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bottom_spacing = (
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new_box.margin_bottom + new_box.padding_bottom +
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new_box.border_bottom_width)
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if bottom_spacing:
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max_position_y -= bottom_spacing
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result = columns_layout(
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context, box, max_position_y, skip_stack,
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containing_block, device_size, page_is_empty,
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absolute_boxes, fixed_boxes, adjoining_margins)
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return result
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else:
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return block_box_layout(
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context, box, max_position_y, skip_stack, containing_block,
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device_size, page_is_empty, absolute_boxes, fixed_boxes,
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adjoining_margins)
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elif isinstance(box, boxes.BlockReplacedBox):
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box = block_replaced_box_layout(box, containing_block, device_size)
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# Don't collide with floats
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# http://www.w3.org/TR/CSS21/visuren.html#floats
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box.position_x, box.position_y, _ = avoid_collisions(
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context, box, containing_block, outer=False)
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resume_at = None
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next_page = {'break': 'any', 'page': None}
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adjoining_margins = []
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collapsing_through = False
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return box, resume_at, next_page, adjoining_margins, collapsing_through
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else: # pragma: no cover
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raise TypeError('Layout for %s not handled yet' % type(box).__name__)
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def block_box_layout(context, box, max_position_y, skip_stack,
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containing_block, device_size, page_is_empty,
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absolute_boxes, fixed_boxes, adjoining_margins):
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"""Lay out the block ``box``."""
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if box.is_table_wrapper:
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table_wrapper_width(
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context, box, (containing_block.width, containing_block.height))
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block_level_width(box, containing_block)
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new_box, resume_at, next_page, adjoining_margins, collapsing_through = \
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block_container_layout(
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context, box, max_position_y, skip_stack, device_size,
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page_is_empty, absolute_boxes, fixed_boxes, adjoining_margins)
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if new_box and new_box.is_table_wrapper:
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# Don't collide with floats
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# http://www.w3.org/TR/CSS21/visuren.html#floats
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position_x, position_y, _ = avoid_collisions(
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context, new_box, containing_block, outer=False)
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new_box.translate(
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position_x - new_box.position_x, position_y - new_box.position_y)
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list_marker_layout(context, new_box)
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return new_box, resume_at, next_page, adjoining_margins, collapsing_through
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def columns_layout(context, box, max_position_y, skip_stack, containing_block,
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device_size, page_is_empty, absolute_boxes, fixed_boxes,
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adjoining_margins):
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"""Lay out a multi-column ``box``."""
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# Implementation of the multi-column pseudo-algorithm:
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# https://www.w3.org/TR/css3-multicol/#pseudo-algorithm
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count = None
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width = None
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style = box.style
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if box.style.position == 'relative':
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# New containing block, use a new absolute list
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absolute_boxes = []
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box = box.copy_with_children(box.children)
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height = box.style.height
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if height != 'auto' and height.unit != '%':
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assert height.unit == 'px'
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known_height = True
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max_position_y = min(
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max_position_y, box.content_box_y() + height.value)
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else:
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known_height = False
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# TODO: the available width can be unknown if the containing block needs
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# the size of this block to know its own size.
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block_level_width(box, containing_block)
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available_width = box.width
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if count is None:
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if style.column_width == 'auto' and style.column_count != 'auto':
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count = style.column_count
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width = max(
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0, available_width - (count - 1) * style.column_gap) / count
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elif style.column_width != 'auto' and style.column_count == 'auto':
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count = max(1, int(floor(
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(available_width + style.column_gap) /
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(style.column_width + style.column_gap))))
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width = (
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(available_width + style.column_gap) / count -
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style.column_gap)
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else:
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count = min(style.column_count, int(floor(
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(available_width + style.column_gap) /
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(style.column_width + style.column_gap))))
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width = (
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(available_width + style.column_gap) / count -
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style.column_gap)
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def create_column_box():
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column_box = box.anonymous_from(box, children=[
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child.copy() for child in box.children])
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resolve_percentages(column_box, containing_block)
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column_box.is_column = True
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column_box.width = width
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column_box.position_x = box.content_box_x()
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column_box.position_y = box.content_box_y()
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return column_box
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def column_descendants(box):
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# TODO: this filtering condition is probably wrong
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if isinstance(box, (boxes.TableBox, boxes.LineBox, boxes.ReplacedBox)):
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yield box
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if hasattr(box, 'descendants') and box.is_in_normal_flow():
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for child in box.children:
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for grand_child in column_descendants(child):
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yield grand_child
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# Balance.
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#
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# The current algorithm starts from the ideal height (the total height
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# divided by the number of columns). We then iterate until the last column
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# is not the highest one. At the end of each loop, we add the minimal
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# height needed to make one direct child at the top of one column go to the
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# end of the previous column.
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#
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# We must probably rely on a real rendering for each loop, but with a
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# stupid algorithm like this it can last minutes.
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#
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# TODO: Rewrite this!
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# - We assume that the children are normal lines or blocks.
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# - We ignore the forced and avoided column breaks.
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# Find the total height of the content
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original_max_position_y = max_position_y
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column_box = create_column_box()
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new_child, _, _, _, _ = block_box_layout(
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context, column_box, float('inf'), skip_stack, containing_block,
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device_size, page_is_empty, [], [], [])
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height = new_child.margin_height()
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if style.column_fill == 'balance':
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height /= count
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box_column_descendants = list(column_descendants(new_child))
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# Increase the column height step by step.
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while True:
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i = 0
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lost_spaces = []
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column_top = new_child.content_box_y()
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for child in box_column_descendants:
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child_height = child.margin_height()
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child_bottom = child.position_y + child_height - column_top
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if child_bottom > height:
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if i < count - 1:
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lost_spaces.append(child_bottom - height)
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i += 1
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column_top = child.position_y
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else:
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break
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else:
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break
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height += min(lost_spaces)
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# TODO: check box.style.max-height
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max_position_y = min(max_position_y, box.content_box_y() + height)
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# Replace the current box children with columns
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children = []
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if box.children:
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i = 0
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while True:
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if i == count - 1:
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max_position_y = original_max_position_y
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column_box = create_column_box()
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if style['direction'] == 'rtl':
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column_box.position_x += (
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box.width - (i + 1) * width - i * style['column_gap'])
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else:
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column_box.position_x += i * (width + style['column_gap'])
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new_child, skip_stack, next_page, _, _ = block_box_layout(
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context, column_box, max_position_y, skip_stack,
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containing_block, device_size, page_is_empty, absolute_boxes,
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fixed_boxes, None)
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if new_child is None:
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break
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children.append(new_child)
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if skip_stack is None:
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break
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i += 1
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if i == count and not known_height:
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# [If] a declaration that constrains the column height (e.g.,
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# using height or max-height). In this case, additional column
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# boxes are created in the inline direction.
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break
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else:
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next_page = {'break': 'any', 'page': None}
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skip_stack = None
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# Set the height of box and the columns
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box.children = children
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if box.children:
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heights = [child.margin_height() for child in box.children]
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if box.height != 'auto':
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heights.append(box.height)
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if box.min_height != 'auto':
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heights.append(box.min_height)
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box.height = max(heights)
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for child in box.children:
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child.height = box.margin_height()
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else:
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box.height = 0
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if box.style.position == 'relative':
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# New containing block, resolve the layout of the absolute descendants
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for absolute_box in absolute_boxes:
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absolute_layout(context, absolute_box, box, fixed_boxes)
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return box, skip_stack, next_page, [0], False
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@handle_min_max_width
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def block_replaced_width(box, containing_block, device_size):
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# http://www.w3.org/TR/CSS21/visudet.html#block-replaced-width
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replaced_box_width.without_min_max(box, device_size)
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block_level_width.without_min_max(box, containing_block)
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def block_replaced_box_layout(box, containing_block, device_size):
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"""Lay out the block :class:`boxes.ReplacedBox` ``box``."""
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if box.style.width == 'auto' and box.style.height == 'auto':
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computed_margins = box.margin_left, box.margin_right
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block_replaced_width.without_min_max(
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box, containing_block, device_size)
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replaced_box_height.without_min_max(box, device_size)
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min_max_auto_replaced(box)
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box.margin_left, box.margin_right = computed_margins
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block_level_width.without_min_max(box, containing_block)
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else:
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block_replaced_width(box, containing_block, device_size)
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replaced_box_height(box, device_size)
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return box
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@handle_min_max_width
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def block_level_width(box, containing_block):
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"""Set the ``box`` width."""
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# 'cb' stands for 'containing block'
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cb_width = containing_block.width
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# http://www.w3.org/TR/CSS21/visudet.html#blockwidth
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# These names are waaay too long
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margin_l = box.margin_left
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margin_r = box.margin_right
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padding_l = box.padding_left
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padding_r = box.padding_right
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border_l = box.border_left_width
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border_r = box.border_right_width
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width = box.width
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# Only margin-left, margin-right and width can be 'auto'.
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# We want: width of containing block ==
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# margin-left + border-left-width + padding-left + width
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# + padding-right + border-right-width + margin-right
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paddings_plus_borders = padding_l + padding_r + border_l + border_r
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if box.width != 'auto':
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total = paddings_plus_borders + width
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if margin_l != 'auto':
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total += margin_l
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if margin_r != 'auto':
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total += margin_r
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if total > cb_width:
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if margin_l == 'auto':
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margin_l = box.margin_left = 0
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if margin_r == 'auto':
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margin_r = box.margin_right = 0
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if width != 'auto' and margin_l != 'auto' and margin_r != 'auto':
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# The equation is over-constrained.
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if containing_block.style['direction'] == 'rtl' and not box.is_column:
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box.position_x += (
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cb_width - paddings_plus_borders - width - margin_r - margin_l)
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# Do nothing in ltr.
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if width == 'auto':
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if margin_l == 'auto':
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margin_l = box.margin_left = 0
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if margin_r == 'auto':
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margin_r = box.margin_right = 0
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width = box.width = cb_width - (
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paddings_plus_borders + margin_l + margin_r)
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margin_sum = cb_width - paddings_plus_borders - width
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if margin_l == 'auto' and margin_r == 'auto':
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box.margin_left = margin_sum / 2.
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box.margin_right = margin_sum / 2.
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elif margin_l == 'auto' and margin_r != 'auto':
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box.margin_left = margin_sum - margin_r
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elif margin_l != 'auto' and margin_r == 'auto':
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box.margin_right = margin_sum - margin_l
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def relative_positioning(box, containing_block):
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"""Translate the ``box`` if it is relatively positioned."""
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if box.style.position == 'relative':
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resolve_position_percentages(box, containing_block)
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if box.left != 'auto' and box.right != 'auto':
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if box.style.direction == 'ltr':
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translate_x = box.left
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else:
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translate_x = -box.right
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elif box.left != 'auto':
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translate_x = box.left
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elif box.right != 'auto':
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translate_x = -box.right
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else:
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translate_x = 0
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if box.top != 'auto':
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translate_y = box.top
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elif box.style.bottom != 'auto':
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translate_y = -box.bottom
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else:
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translate_y = 0
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box.translate(translate_x, translate_y)
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if isinstance(box, (boxes.InlineBox, boxes.LineBox)):
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for child in box.children:
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relative_positioning(child, containing_block)
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def block_container_layout(context, box, max_position_y, skip_stack,
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device_size, page_is_empty, absolute_boxes,
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fixed_boxes, adjoining_margins=None):
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"""Set the ``box`` height."""
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assert isinstance(box, boxes.BlockContainerBox)
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# TODO: this should make a difference, but that is currently neglected.
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# See http://www.w3.org/TR/CSS21/visudet.html#normal-block
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# http://www.w3.org/TR/CSS21/visudet.html#root-height
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# if box.style.overflow != 'visible':
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# ...
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# See http://www.w3.org/TR/CSS21/visuren.html#block-formatting
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if not isinstance(box, boxes.BlockBox):
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context.create_block_formatting_context()
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is_start = skip_stack is None
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if not is_start:
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# Remove top margin, border and padding:
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box._remove_decoration(start=True, end=False)
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if adjoining_margins is None:
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adjoining_margins = []
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adjoining_margins.append(box.margin_top)
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this_box_adjoining_margins = adjoining_margins
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collapsing_with_children = not (
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box.border_top_width or box.padding_top or
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establishes_formatting_context(box) or box.is_for_root_element)
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if collapsing_with_children:
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# XXX not counting margins in adjoining_margins, if any
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# (There are not padding or borders, see above.)
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position_y = box.position_y
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else:
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box.position_y += collapse_margin(adjoining_margins) - box.margin_top
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adjoining_margins = []
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position_y = box.content_box_y()
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position_x = box.content_box_x()
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if box.style.position == 'relative':
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# New containing block, use a new absolute list
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absolute_boxes = []
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new_children = []
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next_page = {'break': 'any', 'page': None}
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last_in_flow_child = None
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if is_start:
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skip = 0
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first_letter_style = getattr(box, 'first_letter_style', None)
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else:
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skip, skip_stack = skip_stack
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first_letter_style = None
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for index, child in box.enumerate_skip(skip):
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child.position_x = position_x
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# XXX does not count margins in adjoining_margins:
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child.position_y = position_y
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if not child.is_in_normal_flow():
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child.position_y += collapse_margin(adjoining_margins)
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if child.is_absolutely_positioned():
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placeholder = AbsolutePlaceholder(child)
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placeholder.index = index
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new_children.append(placeholder)
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if child.style.position == 'absolute':
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absolute_boxes.append(placeholder)
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else:
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fixed_boxes.append(placeholder)
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elif child.is_floated():
|
||
new_child = float_layout(
|
||
context, child, box, device_size, absolute_boxes,
|
||
fixed_boxes)
|
||
# New page if overflow
|
||
if (page_is_empty and not new_children) or not (
|
||
new_child.position_y + new_child.height >
|
||
max_position_y):
|
||
new_child.index = index
|
||
new_children.append(new_child)
|
||
else:
|
||
|
||
for previous_child in reversed(new_children):
|
||
if previous_child.is_in_normal_flow():
|
||
last_in_flow_child = previous_child
|
||
break
|
||
page_break = block_level_page_break(
|
||
last_in_flow_child, child)
|
||
if new_children and page_break in ('avoid', 'avoid-page'):
|
||
result = find_earlier_page_break(
|
||
new_children, absolute_boxes, fixed_boxes)
|
||
if result:
|
||
new_children, resume_at = result
|
||
break
|
||
resume_at = (index, None)
|
||
break
|
||
continue
|
||
|
||
if isinstance(child, boxes.LineBox):
|
||
assert len(box.children) == 1, (
|
||
'line box with siblings before layout')
|
||
if adjoining_margins:
|
||
position_y += collapse_margin(adjoining_margins)
|
||
adjoining_margins = []
|
||
new_containing_block = box
|
||
lines_iterator = iter_line_boxes(
|
||
context, child, position_y, skip_stack,
|
||
new_containing_block, device_size, absolute_boxes, fixed_boxes,
|
||
first_letter_style)
|
||
is_page_break = False
|
||
for line, resume_at in lines_iterator:
|
||
line.resume_at = resume_at
|
||
new_position_y = line.position_y + line.height
|
||
# Allow overflow if the first line of the page is higher
|
||
# than the page itself so that we put *something* on this
|
||
# page and can advance in the context.
|
||
if new_position_y > max_position_y and (
|
||
new_children or not page_is_empty):
|
||
over_orphans = len(new_children) - box.style.orphans
|
||
if over_orphans < 0 and not page_is_empty:
|
||
# Reached the bottom of the page before we had
|
||
# enough lines for orphans, cancel the whole box.
|
||
page = child.page_values()[0]
|
||
return (
|
||
None, None, {'break': 'any', 'page': page}, [],
|
||
False)
|
||
# How many lines we need on the next page to satisfy widows
|
||
# -1 for the current line.
|
||
needed = box.style.widows - 1
|
||
if needed:
|
||
for _ in lines_iterator:
|
||
needed -= 1
|
||
if needed == 0:
|
||
break
|
||
if needed > over_orphans and not page_is_empty:
|
||
# Total number of lines < orphans + widows
|
||
page = child.page_values()[0]
|
||
return (
|
||
None, None, {'break': 'any', 'page': page}, [],
|
||
False)
|
||
if needed and needed <= over_orphans:
|
||
# Remove lines to keep them for the next page
|
||
del new_children[-needed:]
|
||
# Page break here, resume before this line
|
||
resume_at = (index, skip_stack)
|
||
is_page_break = True
|
||
break
|
||
# TODO: this is incomplete.
|
||
# See http://dev.w3.org/csswg/css3-page/#allowed-pg-brk
|
||
# "When an unforced page break occurs here, both the adjoining
|
||
# ‘margin-top’ and ‘margin-bottom’ are set to zero."
|
||
elif page_is_empty and new_position_y > max_position_y:
|
||
# Remove the top border when a page is empty and the box is
|
||
# too high to be drawn in one page
|
||
new_position_y -= box.margin_top
|
||
line.translate(0, -box.margin_top)
|
||
box.margin_top = 0
|
||
new_children.append(line)
|
||
position_y = new_position_y
|
||
skip_stack = resume_at
|
||
if new_children:
|
||
resume_at = (index, new_children[-1].resume_at)
|
||
if is_page_break:
|
||
break
|
||
else:
|
||
for previous_child in reversed(new_children):
|
||
if previous_child.is_in_normal_flow():
|
||
last_in_flow_child = previous_child
|
||
break
|
||
else:
|
||
last_in_flow_child = None
|
||
if last_in_flow_child is not None:
|
||
# Between in-flow siblings
|
||
page_break = block_level_page_break(last_in_flow_child, child)
|
||
page_name = block_level_page_name(last_in_flow_child, child)
|
||
if page_name or page_break in (
|
||
'page', 'left', 'right', 'recto', 'verso'):
|
||
if page_break == 'page':
|
||
page_break = 'any'
|
||
elif page_break not in ('left', 'right', 'recto', 'verso'):
|
||
assert page_name
|
||
page_break = 'any'
|
||
page_name = child.page_values()[0]
|
||
next_page = {'break': page_break, 'page': page_name}
|
||
resume_at = (index, None)
|
||
break
|
||
else:
|
||
page_break = 'auto'
|
||
|
||
new_containing_block = box
|
||
|
||
if not new_containing_block.is_table_wrapper:
|
||
# TODO: there's no collapsing margins inside tables, right?
|
||
resolve_percentages(child, new_containing_block)
|
||
if (child.is_in_normal_flow() and
|
||
last_in_flow_child is None and
|
||
collapsing_with_children):
|
||
# TODO: add the adjoining descendants' margin top to
|
||
# [child.margin_top]
|
||
old_collapsed_margin = collapse_margin(adjoining_margins)
|
||
if child.margin_top == 'auto':
|
||
child_margin_top = 0
|
||
else:
|
||
child_margin_top = child.margin_top
|
||
new_collapsed_margin = collapse_margin(
|
||
adjoining_margins + [child_margin_top])
|
||
collapsed_margin_difference = (
|
||
new_collapsed_margin - old_collapsed_margin)
|
||
for previous_new_child in new_children:
|
||
previous_new_child.translate(
|
||
dy=collapsed_margin_difference)
|
||
clearance = get_clearance(
|
||
context, child, new_collapsed_margin)
|
||
if clearance is not None:
|
||
for previous_new_child in new_children:
|
||
previous_new_child.translate(
|
||
dy=-collapsed_margin_difference)
|
||
|
||
collapsed_margin = collapse_margin(adjoining_margins)
|
||
box.position_y += collapsed_margin - box.margin_top
|
||
# Count box.margin_top as we emptied adjoining_margins
|
||
adjoining_margins = []
|
||
position_y = box.content_box_y()
|
||
|
||
if adjoining_margins and isinstance(child, boxes.TableBox):
|
||
collapsed_margin = collapse_margin(adjoining_margins)
|
||
child.position_y += collapsed_margin
|
||
position_y += collapsed_margin
|
||
adjoining_margins = []
|
||
|
||
if not getattr(child, 'first_letter_style', None):
|
||
child.first_letter_style = first_letter_style
|
||
(new_child, resume_at, next_page, next_adjoining_margins,
|
||
collapsing_through) = block_level_layout(
|
||
context, child, max_position_y, skip_stack,
|
||
new_containing_block, device_size,
|
||
page_is_empty and not new_children,
|
||
absolute_boxes, fixed_boxes,
|
||
adjoining_margins)
|
||
skip_stack = None
|
||
|
||
if new_child is not None:
|
||
# index in its non-laid-out parent, not in future new parent
|
||
# May be used in find_earlier_page_break()
|
||
new_child.index = index
|
||
|
||
# We need to do this after the child layout to have the
|
||
# used value for margin_top (eg. it might be a percentage.)
|
||
if not isinstance(
|
||
new_child, (boxes.BlockBox, boxes.TableBox)):
|
||
adjoining_margins.append(new_child.margin_top)
|
||
offset_y = (
|
||
collapse_margin(adjoining_margins) -
|
||
new_child.margin_top)
|
||
new_child.translate(0, offset_y)
|
||
adjoining_margins = []
|
||
# else: blocks handle that themselves.
|
||
|
||
adjoining_margins = next_adjoining_margins
|
||
adjoining_margins.append(new_child.margin_bottom)
|
||
|
||
if not collapsing_through:
|
||
new_position_y = (
|
||
new_child.border_box_y() + new_child.border_height())
|
||
|
||
if (new_position_y > max_position_y and
|
||
(new_children or not page_is_empty) and
|
||
not (isinstance(child, boxes.TableBox) or (
|
||
# For blocks with children do this per child.
|
||
isinstance(child, boxes.BlockBox) and
|
||
child.children))):
|
||
# The child overflows the page area, put it on the
|
||
# next page. (But don’t delay whole blocks if eg.
|
||
# only the bottom border overflows.)
|
||
new_child = None
|
||
else:
|
||
position_y = new_position_y
|
||
|
||
if new_child is not None and new_child.clearance is not None:
|
||
position_y = (
|
||
new_child.border_box_y() + new_child.border_height())
|
||
|
||
if new_child is None:
|
||
# Nothing fits in the remaining space of this page: break
|
||
if page_break in ('avoid', 'avoid-page'):
|
||
result = find_earlier_page_break(
|
||
new_children, absolute_boxes, fixed_boxes)
|
||
if result:
|
||
new_children, resume_at = result
|
||
break
|
||
else:
|
||
# We did not find any page break opportunity
|
||
if not page_is_empty:
|
||
# The page has content *before* this block:
|
||
# cancel the block and try to find a break
|
||
# in the parent.
|
||
page = child.page_values()[0]
|
||
return (
|
||
None, None, {'break': 'any', 'page': page}, [],
|
||
False)
|
||
# else:
|
||
# ignore this 'avoid' and break anyway.
|
||
|
||
if new_children:
|
||
resume_at = (index, None)
|
||
break
|
||
else:
|
||
# This was the first child of this box, cancel the box
|
||
# completly
|
||
page = child.page_values()[0]
|
||
return (
|
||
None, None, {'break': 'any', 'page': page}, [], False)
|
||
|
||
# Bottom borders may overflow here
|
||
# TODO: back-track somehow when all lines fit but not borders
|
||
new_children.append(new_child)
|
||
if resume_at is not None:
|
||
resume_at = (index, resume_at)
|
||
break
|
||
else:
|
||
resume_at = None
|
||
|
||
if (resume_at is not None and
|
||
box.style.break_inside in ('avoid', 'avoid-page') and
|
||
not page_is_empty):
|
||
return (
|
||
None, None, {'break': 'any', 'page': None}, [], False)
|
||
|
||
if collapsing_with_children:
|
||
box.position_y += (
|
||
collapse_margin(this_box_adjoining_margins) - box.margin_top)
|
||
|
||
for previous_child in reversed(new_children):
|
||
if previous_child.is_in_normal_flow():
|
||
last_in_flow_child = previous_child
|
||
break
|
||
else:
|
||
last_in_flow_child = None
|
||
collapsing_through = False
|
||
if last_in_flow_child is None:
|
||
collapsed_margin = collapse_margin(adjoining_margins)
|
||
# top and bottom margin of this box
|
||
if (box.height in ('auto', 0) and
|
||
get_clearance(context, box, collapsed_margin) is None and
|
||
all(v == 0 for v in [
|
||
box.min_height, box.border_top_width, box.padding_top,
|
||
box.border_bottom_width, box.padding_bottom])):
|
||
collapsing_through = True
|
||
else:
|
||
position_y += collapsed_margin
|
||
adjoining_margins = []
|
||
else:
|
||
# bottom margin of the last child and bottom margin of this box ...
|
||
if box.height != 'auto':
|
||
# not adjoining. (position_y is not used afterwards.)
|
||
adjoining_margins = []
|
||
|
||
if box.border_bottom_width or box.padding_bottom or (
|
||
establishes_formatting_context(box) or box.is_for_root_element):
|
||
position_y += collapse_margin(adjoining_margins)
|
||
adjoining_margins = []
|
||
|
||
new_box = box.copy_with_children(
|
||
new_children, is_start=is_start, is_end=resume_at is None)
|
||
|
||
# TODO: See corner cases in
|
||
# http://www.w3.org/TR/CSS21/visudet.html#normal-block
|
||
# TODO: See float.float_layout
|
||
if new_box.height == 'auto':
|
||
new_box.height = position_y - new_box.content_box_y()
|
||
|
||
if new_box.style.position == 'relative':
|
||
# New containing block, resolve the layout of the absolute descendants
|
||
for absolute_box in absolute_boxes:
|
||
absolute_layout(context, absolute_box, new_box, fixed_boxes)
|
||
|
||
for child in new_box.children:
|
||
relative_positioning(child, (new_box.width, new_box.height))
|
||
|
||
if not isinstance(new_box, boxes.BlockBox):
|
||
context.finish_block_formatting_context(new_box)
|
||
|
||
# After finish_block_formatting_context which may increment new_box.height
|
||
new_box.height = max(
|
||
min(new_box.height, new_box.max_height),
|
||
new_box.min_height)
|
||
|
||
if next_page['page'] is None:
|
||
next_page['page'] = new_box.page_values()[1]
|
||
|
||
return new_box, resume_at, next_page, adjoining_margins, collapsing_through
|
||
|
||
|
||
def collapse_margin(adjoining_margins):
|
||
"""Return the amount of collapsed margin for a list of adjoining margins.
|
||
"""
|
||
# Add 0 to make sure that neither max() or min() get an empty list
|
||
margins = [0]
|
||
margins.extend(adjoining_margins)
|
||
positives = (m for m in margins if m >= 0)
|
||
negatives = (m for m in margins if m <= 0)
|
||
return max(positives) + min(negatives)
|
||
|
||
|
||
def establishes_formatting_context(box):
|
||
"""Return wether a box establishes a block formatting context.
|
||
|
||
See http://www.w3.org/TR/CSS2/visuren.html#block-formatting
|
||
|
||
"""
|
||
return box.is_floated() or box.is_absolutely_positioned() or (
|
||
isinstance(box, boxes.BlockContainerBox) and
|
||
not isinstance(box, boxes.BlockBox)
|
||
) or (
|
||
isinstance(box, boxes.BlockBox) and box.style.overflow != 'visible'
|
||
)
|
||
|
||
|
||
def block_level_page_break(sibling_before, sibling_after):
|
||
"""Return the value of ``page-break-before`` or ``page-break-after``
|
||
that "wins" for boxes that meet at the margin between two sibling boxes.
|
||
|
||
For boxes before the margin, the 'page-break-after' value is considered;
|
||
for boxes after the margin the 'page-break-before' value is considered.
|
||
|
||
* 'avoid' takes priority over 'auto'
|
||
* 'page' takes priority over 'avoid' or 'auto'
|
||
* 'left' or 'right' take priority over 'always', 'avoid' or 'auto'
|
||
* Among 'left' and 'right', later values in the tree take priority.
|
||
|
||
See http://dev.w3.org/csswg/css3-page/#allowed-pg-brk
|
||
|
||
"""
|
||
values = []
|
||
box = sibling_before
|
||
while isinstance(box, boxes.BlockLevelBox):
|
||
values.append(box.style.break_after)
|
||
if not (isinstance(box, boxes.ParentBox) and box.children):
|
||
break
|
||
box = box.children[-1]
|
||
values.reverse() # Have them in tree order
|
||
|
||
box = sibling_after
|
||
while isinstance(box, boxes.BlockLevelBox):
|
||
values.append(box.style.break_before)
|
||
if not (isinstance(box, boxes.ParentBox) and box.children):
|
||
break
|
||
box = box.children[0]
|
||
|
||
result = 'auto'
|
||
for value in values:
|
||
if value in ('left', 'right', 'recto', 'verso') or (value, result) in (
|
||
('page', 'auto'),
|
||
('page', 'avoid'),
|
||
('avoid', 'auto'),
|
||
('page', 'avoid-page'),
|
||
('avoid-page', 'auto')):
|
||
result = value
|
||
|
||
return result
|
||
|
||
|
||
def block_level_page_name(sibling_before, sibling_after):
|
||
"""Return the next page name when siblings don't have the same names."""
|
||
before_page = sibling_before.page_values()[1]
|
||
after_page = sibling_after.page_values()[0]
|
||
if before_page != after_page:
|
||
return after_page
|
||
|
||
|
||
def find_earlier_page_break(children, absolute_boxes, fixed_boxes):
|
||
"""Because of a `page-break-before: avoid` or a `page-break-after: avoid`
|
||
we need to find an earlier page break opportunity inside `children`.
|
||
|
||
Absolute or fixed placeholders removed from children should also be
|
||
removed from `absolute_boxes` or `fixed_boxes`.
|
||
|
||
Return (new_children, resume_at)
|
||
|
||
"""
|
||
if children and isinstance(children[0], boxes.LineBox):
|
||
# Normally `orphans` and `widows` apply to the block container, but
|
||
# line boxes inherit them.
|
||
orphans = children[0].style.orphans
|
||
widows = children[0].style.widows
|
||
index = len(children) - widows # how many lines we keep
|
||
if index < orphans:
|
||
return None
|
||
new_children = children[:index]
|
||
resume_at = (0, new_children[-1].resume_at)
|
||
remove_placeholders(children[index:], absolute_boxes, fixed_boxes)
|
||
return new_children, resume_at
|
||
|
||
previous_in_flow = None
|
||
for index, child in reversed_enumerate(children):
|
||
if child.is_in_normal_flow():
|
||
if previous_in_flow is not None and (
|
||
block_level_page_break(child, previous_in_flow) not in
|
||
('avoid', 'avoid-page')):
|
||
index += 1 # break after child
|
||
new_children = children[:index]
|
||
# Get the index in the original parent
|
||
resume_at = (children[index].index, None)
|
||
break
|
||
previous_in_flow = child
|
||
if child.is_in_normal_flow() and (
|
||
child.style.break_inside not in ('avoid', 'avoid-page')):
|
||
if isinstance(child, boxes.BlockBox):
|
||
result = find_earlier_page_break(
|
||
child.children, absolute_boxes, fixed_boxes)
|
||
if result:
|
||
new_grand_children, resume_at = result
|
||
new_child = child.copy_with_children(new_grand_children)
|
||
new_children = list(children[:index]) + [new_child]
|
||
# Index in the original parent
|
||
resume_at = (new_child.index, resume_at)
|
||
index += 1 # Remove placeholders after child
|
||
break
|
||
elif isinstance(child, boxes.TableBox):
|
||
pass # TODO: find an earlier break between table rows.
|
||
else:
|
||
return None
|
||
|
||
remove_placeholders(children[index:], absolute_boxes, fixed_boxes)
|
||
return new_children, resume_at
|
||
|
||
|
||
def reversed_enumerate(seq):
|
||
"""Like reversed(list(enumerate(seq))) without copying the whole seq."""
|
||
return izip(reversed(xrange(len(seq))), reversed(seq))
|
||
|
||
|
||
def remove_placeholders(box_list, absolute_boxes, fixed_boxes):
|
||
"""For boxes that have been removed in find_earlier_page_break(),
|
||
also remove the matching placeholders in absolute_boxes and fixed_boxes.
|
||
|
||
"""
|
||
for box in box_list:
|
||
if isinstance(box, boxes.ParentBox):
|
||
remove_placeholders(box.children, absolute_boxes, fixed_boxes)
|
||
if box.style.position == 'absolute' and box in absolute_boxes:
|
||
# box is not in absolute_boxes if its parent has position: relative
|
||
absolute_boxes.remove(box)
|
||
elif box.style.position == 'fixed':
|
||
fixed_boxes.remove(box)
|