951 lines
38 KiB
Python
951 lines
38 KiB
Python
"""
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weasyprint.layout.block
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-----------------------
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Page breaking and layout for block-level and block-container boxes.
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"""
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from ..formatting_structure import boxes
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from .absolute import AbsolutePlaceholder, absolute_layout
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from .column import columns_layout
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from .flex import flex_layout
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from .float import avoid_collisions, float_layout, get_clearance
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from .inline import iter_line_boxes
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from .min_max import handle_min_max_width
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from .percent import resolve_percentages, resolve_position_percentages
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from .replaced import block_replaced_box_layout
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from .table import table_layout, table_wrapper_width
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def block_level_layout(context, box, bottom_space, skip_stack,
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containing_block, page_is_empty, absolute_boxes,
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fixed_boxes, adjoining_margins, discard):
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"""Lay out the block-level ``box``."""
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if not isinstance(box, boxes.TableBox):
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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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if context.current_page > 1 and page_is_empty:
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# TODO: this condition is wrong, it only works for blocks whose
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# parent breaks collapsing margins. It should work for blocks whose
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# one of the ancestors breaks collapsing margins.
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# See test_margin_break_clearance.
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collapse_with_page = (
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containing_block.is_for_root_element or
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adjoining_margins)
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if collapse_with_page:
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if box.style['margin_break'] == 'discard':
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box.margin_top = 0
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elif box.style['margin_break'] == 'auto':
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if not context.forced_break:
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box.margin_top = 0
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collapsed_margin = collapse_margin(
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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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return block_level_layout_switch(
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context, box, bottom_space, skip_stack, containing_block,
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page_is_empty, absolute_boxes, fixed_boxes, adjoining_margins, discard)
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def block_level_layout_switch(context, box, bottom_space, skip_stack,
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containing_block, page_is_empty, absolute_boxes,
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fixed_boxes, adjoining_margins, discard):
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"""Call the layout function corresponding to the ``box`` type."""
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if isinstance(box, boxes.TableBox):
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return table_layout(
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context, box, bottom_space, skip_stack, containing_block,
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page_is_empty, absolute_boxes, fixed_boxes)
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elif isinstance(box, boxes.BlockBox):
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return block_box_layout(
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context, box, bottom_space, skip_stack, containing_block,
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page_is_empty, absolute_boxes, fixed_boxes, adjoining_margins,
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discard)
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elif isinstance(box, boxes.BlockReplacedBox):
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return block_replaced_box_layout(context, box, containing_block)
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elif isinstance(box, boxes.FlexBox):
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return flex_layout(
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context, box, bottom_space, skip_stack, containing_block,
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page_is_empty, absolute_boxes, fixed_boxes)
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else: # pragma: no cover
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raise TypeError(f'Layout for {type(box).__name__} not handled yet')
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def block_box_layout(context, box, bottom_space, skip_stack,
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containing_block, page_is_empty, absolute_boxes,
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fixed_boxes, adjoining_margins, discard):
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"""Lay out the block ``box``."""
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if (box.style['column_width'] != 'auto' or
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box.style['column_count'] != 'auto'):
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result = columns_layout(
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context, box, bottom_space, skip_stack, containing_block,
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page_is_empty, absolute_boxes, fixed_boxes, adjoining_margins)
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resume_at = result[1]
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# TODO: this condition and the whole relayout are probably wrong
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if resume_at is None:
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new_box = result[0]
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columns_bottom_space = (
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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 columns_bottom_space:
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bottom_space += columns_bottom_space
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result = columns_layout(
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context, box, bottom_space, skip_stack,
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containing_block, page_is_empty, absolute_boxes,
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fixed_boxes, adjoining_margins)
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return result
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elif 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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result = block_container_layout(
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context, box, bottom_space, skip_stack, page_is_empty,
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absolute_boxes, fixed_boxes, adjoining_margins, discard)
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new_box = result[0]
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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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return result
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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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if isinstance(containing_block, boxes.Box):
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cb_width = containing_block.width
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direction = containing_block.style['direction']
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else:
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cb_width = containing_block[0]
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# TODO: what is the real text direction?
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direction = 'ltr'
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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 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 _out_of_flow_layout(context, box, index, child, new_children,
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page_is_empty, absolute_boxes, fixed_boxes,
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adjoining_margins, bottom_space):
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stop = False
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resume_at = None
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out_of_flow_resume_at = None
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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():
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new_child, out_of_flow_resume_at = float_layout(
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context, child, box, absolute_boxes, fixed_boxes, bottom_space,
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skip_stack=None)
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# New page if overflow
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if (page_is_empty and not new_children) or not (
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new_child.position_y + new_child.height >
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context.page_bottom - bottom_space):
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new_child.index = index
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new_children.append(new_child)
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else:
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last_in_flow_child = find_last_in_flow_child(new_children)
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page_break = block_level_page_break(last_in_flow_child, child)
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resume_at = {index: None}
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if new_children and page_break in ('avoid', 'avoid-page'):
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result = find_earlier_page_break(
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new_children, absolute_boxes, fixed_boxes)
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if result:
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new_children, resume_at = result
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stop = True
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elif child.is_running():
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running_name = child.style['position'][1]
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page = context.current_page
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context.running_elements[running_name][page].append(child)
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return stop, resume_at, out_of_flow_resume_at
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def _break_line(box, new_children, lines_iterator, page_is_empty, index,
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skip_stack, resume_at):
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over_orphans = len(new_children) - box.style['orphans']
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if over_orphans < 0 and not page_is_empty:
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# Reached the bottom of the page before we had
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# enough lines for orphans, cancel the whole box.
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return True, False, resume_at
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# How many lines we need on the next page to satisfy widows
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# -1 for the current line.
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needed = box.style['widows'] - 1
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if needed:
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for _ in lines_iterator:
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needed -= 1
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if needed == 0:
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break
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if needed > over_orphans and not page_is_empty:
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# Total number of lines < orphans + widows
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return True, False, resume_at
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if needed and needed <= over_orphans:
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# Remove lines to keep them for the next page
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del new_children[-needed:]
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# Page break here, resume before this line
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return False, True, {index: skip_stack}
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def _linebox_layout(context, box, index, child, new_children, page_is_empty,
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absolute_boxes, fixed_boxes, adjoining_margins,
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bottom_space, position_y, skip_stack, first_letter_style,
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draw_bottom_decoration):
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abort = stop = False
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resume_at = None
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assert len(box.children) == 1, 'line box with siblings before layout'
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if adjoining_margins:
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position_y += collapse_margin(adjoining_margins)
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new_containing_block = box
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lines_iterator = iter_line_boxes(
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context, child, position_y, bottom_space, skip_stack,
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new_containing_block, absolute_boxes, fixed_boxes, first_letter_style)
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for i, (line, resume_at) in enumerate(lines_iterator):
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line.resume_at = resume_at
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new_position_y = line.position_y + line.height
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# Add bottom padding and border to the bottom position of the
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# box if needed
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draw_bottom_decoration |= resume_at is None
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if draw_bottom_decoration:
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offset_y = box.border_bottom_width + box.padding_bottom
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else:
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offset_y = 0
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# Allow overflow if the first line of the page is higher
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# than the page itself so that we put *something* on this
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# page and can advance in the context.
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overflow = (
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(new_children or not page_is_empty) and
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(new_position_y + offset_y > context.page_bottom - bottom_space))
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if overflow:
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abort, stop, resume_at = _break_line(
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box, new_children, lines_iterator, page_is_empty, index,
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skip_stack, resume_at)
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break
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# TODO: this is incomplete.
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# See http://dev.w3.org/csswg/css3-page/#allowed-pg-brk
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# "When an unforced page break occurs here, both the adjoining
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# ‘margin-top’ and ‘margin-bottom’ are set to zero."
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# See https://github.com/Kozea/WeasyPrint/issues/115
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elif page_is_empty and (
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new_position_y > context.page_bottom - bottom_space):
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# Remove the top border when a page is empty and the box is
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# too high to be drawn in one page
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new_position_y -= box.margin_top
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line.translate(0, -box.margin_top)
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box.margin_top = 0
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if context.footnotes:
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break_linebox = False
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footnotes = (
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descendant.footnote for descendant in line.descendants()
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if descendant.footnote in context.footnotes)
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for footnote in footnotes:
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context.layout_footnote(footnote)
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overflow = context.reported_footnotes or (
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new_position_y + offset_y >
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context.page_bottom - bottom_space)
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if overflow:
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context.report_footnote(footnote)
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if footnote.style['footnote_policy'] == 'line':
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abort, stop, resume_at = _break_line(
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box, new_children, lines_iterator, page_is_empty,
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index, skip_stack, resume_at)
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break_linebox = True
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elif footnote.style['footnote_policy'] == 'block':
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abort = break_linebox = True
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break
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if break_linebox:
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break
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new_children.append(line)
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position_y = new_position_y
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skip_stack = resume_at
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# Break box if we reached max-lines
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if box.style['max_lines'] != 'none':
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if i >= box.style['max_lines'] - 1:
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line.block_ellipsis = box.style['block_ellipsis']
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break
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if new_children:
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resume_at = {index: new_children[-1].resume_at}
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return abort, stop, resume_at, position_y
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def _in_flow_layout(context, box, index, child, new_children, page_is_empty,
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absolute_boxes, fixed_boxes, adjoining_margins,
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bottom_space, position_y, skip_stack, first_letter_style,
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draw_bottom_decoration, collapsing_with_children, discard,
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next_page):
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abort = stop = False
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last_in_flow_child = find_last_in_flow_child(new_children)
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if last_in_flow_child is not None:
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# Between in-flow siblings
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page_break = block_level_page_break(last_in_flow_child, child)
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page_name = block_level_page_name(last_in_flow_child, child)
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if page_name or page_break in (
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'page', 'left', 'right', 'recto', 'verso'):
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page_name = child.page_values()[0]
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next_page = {'break': page_break, 'page': page_name}
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resume_at = {index: None}
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stop = True
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return (
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abort, stop, resume_at, position_y, adjoining_margins,
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next_page, new_children)
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else:
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page_break = 'auto'
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new_containing_block = box
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if not new_containing_block.is_table_wrapper:
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resolve_percentages(child, new_containing_block)
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if (child.is_in_normal_flow() and last_in_flow_child is None and
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collapsing_with_children):
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# TODO: add the adjoining descendants' margin top to
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# [child.margin_top]
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old_collapsed_margin = collapse_margin(adjoining_margins)
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if child.margin_top == 'auto':
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child_margin_top = 0
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else:
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child_margin_top = child.margin_top
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new_collapsed_margin = collapse_margin(
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adjoining_margins + [child_margin_top])
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collapsed_margin_difference = (
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new_collapsed_margin - old_collapsed_margin)
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for previous_new_child in new_children:
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previous_new_child.translate(dy=collapsed_margin_difference)
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clearance = get_clearance(context, child, new_collapsed_margin)
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if clearance is not None:
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for previous_new_child in new_children:
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previous_new_child.translate(
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dy=-collapsed_margin_difference)
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collapsed_margin = collapse_margin(adjoining_margins)
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box.position_y += collapsed_margin - box.margin_top
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# Count box.margin_top as we emptied adjoining_margins
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adjoining_margins = []
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position_y = box.content_box_y()
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if adjoining_margins and box.is_table_wrapper:
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collapsed_margin = collapse_margin(adjoining_margins)
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child.position_y += collapsed_margin
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position_y += collapsed_margin
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adjoining_margins = []
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page_is_empty_with_no_children = page_is_empty and not any(
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child for child in new_children
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if not isinstance(child, AbsolutePlaceholder))
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if not getattr(child, 'first_letter_style', None):
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child.first_letter_style = first_letter_style
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(new_child, resume_at, next_page, next_adjoining_margins,
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collapsing_through) = block_level_layout(
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context, child, bottom_space, skip_stack,
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new_containing_block, page_is_empty_with_no_children, absolute_boxes,
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fixed_boxes, adjoining_margins, discard)
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if new_child is not None:
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# index in its non-laid-out parent, not in future new parent
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# May be used in find_earlier_page_break()
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new_child.index = index
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# We need to do this after the child layout to have the
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# used value for margin_top (eg. it might be a percentage.)
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if not isinstance(new_child, (boxes.BlockBox, boxes.TableBox)):
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adjoining_margins.append(new_child.margin_top)
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offset_y = (
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collapse_margin(adjoining_margins) - new_child.margin_top)
|
||
new_child.translate(0, offset_y)
|
||
# else: blocks handle that themselves.
|
||
|
||
if not collapsing_through:
|
||
new_content_position_y = (
|
||
new_child.content_box_y() + new_child.height)
|
||
new_position_y = (
|
||
new_child.border_box_y() + new_child.border_height())
|
||
|
||
if (new_content_position_y > context.page_bottom - bottom_space and
|
||
not page_is_empty_with_no_children):
|
||
# The child content overflows the page area, display it on the
|
||
# next page.
|
||
remove_placeholders([new_child], absolute_boxes, fixed_boxes)
|
||
new_child = None
|
||
elif (new_position_y > context.page_bottom - bottom_space and
|
||
not page_is_empty_with_no_children):
|
||
# The child border/padding overflows the page area, do the
|
||
# layout again with a higher bottom_space value.
|
||
remove_placeholders([new_child], absolute_boxes, fixed_boxes)
|
||
bottom_space += (
|
||
new_child.padding_bottom + new_child.border_bottom_width)
|
||
(new_child, resume_at, next_page, next_adjoining_margins,
|
||
collapsing_through) = block_level_layout(
|
||
context, child, bottom_space, skip_stack,
|
||
new_containing_block, page_is_empty_with_no_children,
|
||
absolute_boxes, fixed_boxes, adjoining_margins, discard)
|
||
if new_child:
|
||
position_y = (
|
||
new_child.border_box_y() + new_child.border_height())
|
||
else:
|
||
position_y = new_position_y
|
||
|
||
adjoining_margins = next_adjoining_margins
|
||
if new_child:
|
||
adjoining_margins.append(new_child.margin_bottom)
|
||
|
||
if new_child and new_child.clearance:
|
||
position_y = new_child.border_box_y() + new_child.border_height()
|
||
|
||
skip_stack = None
|
||
|
||
if new_child is None:
|
||
# Nothing fits in the remaining space of this page: break
|
||
if page_break in ('avoid', 'avoid-page'):
|
||
# TODO: fill the blank space at the bottom of the page
|
||
result = find_earlier_page_break(
|
||
new_children, absolute_boxes, fixed_boxes)
|
||
if result:
|
||
new_children, resume_at = result
|
||
stop = True
|
||
return (
|
||
abort, stop, resume_at, position_y, adjoining_margins,
|
||
next_page, new_children)
|
||
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.
|
||
abort = True
|
||
return (
|
||
abort, stop, resume_at, position_y, adjoining_margins,
|
||
next_page, new_children)
|
||
# else:
|
||
# ignore this 'avoid' and break anyway.
|
||
|
||
if all(child.is_absolutely_positioned() for child in new_children):
|
||
# This box has only rendered absolute children, keep them
|
||
# for the next page. This is for example useful for list
|
||
# markers.
|
||
remove_placeholders(new_children, absolute_boxes, fixed_boxes)
|
||
new_children = []
|
||
|
||
if new_children:
|
||
resume_at = {index: None}
|
||
stop = True
|
||
else:
|
||
# This was the first child of this box, cancel the box completly
|
||
abort = True
|
||
return (
|
||
abort, stop, resume_at, position_y, adjoining_margins, next_page,
|
||
new_children)
|
||
|
||
new_children.append(new_child)
|
||
if resume_at is not None:
|
||
resume_at = {index: resume_at}
|
||
stop = True
|
||
|
||
return (
|
||
abort, stop, resume_at, position_y, adjoining_margins, next_page,
|
||
new_children)
|
||
|
||
|
||
def block_container_layout(context, box, bottom_space, skip_stack,
|
||
page_is_empty, absolute_boxes, fixed_boxes,
|
||
adjoining_margins, discard):
|
||
"""Set the ``box`` height."""
|
||
# TODO: boxes.FlexBox is allowed here because flex_layout calls
|
||
# block_container_layout, there's probably a better solution.
|
||
assert isinstance(box, (boxes.BlockContainerBox, boxes.FlexBox))
|
||
|
||
if establishes_formatting_context(box):
|
||
context.create_block_formatting_context()
|
||
|
||
is_start = skip_stack is None
|
||
box.remove_decoration(start=not is_start, end=False)
|
||
|
||
discard |= box.style['continue'] == 'discard'
|
||
draw_bottom_decoration = (
|
||
discard or box.style['box_decoration_break'] == 'clone')
|
||
|
||
if adjoining_margins is None:
|
||
adjoining_margins = []
|
||
|
||
if draw_bottom_decoration:
|
||
bottom_space += (
|
||
box.padding_bottom + box.border_bottom_width + box.margin_bottom)
|
||
|
||
adjoining_margins.append(box.margin_top)
|
||
this_box_adjoining_margins = adjoining_margins
|
||
|
||
collapsing_with_children = not (
|
||
box.border_top_width or box.padding_top or box.is_flex_item or
|
||
establishes_formatting_context(box) or box.is_for_root_element)
|
||
if collapsing_with_children:
|
||
# Not counting margins in adjoining_margins, if any
|
||
# (there are not padding or borders, see above)
|
||
position_y = box.position_y
|
||
else:
|
||
box.position_y += collapse_margin(adjoining_margins) - box.margin_top
|
||
adjoining_margins = []
|
||
position_y = box.content_box_y()
|
||
|
||
position_x = box.content_box_x()
|
||
|
||
if box.style['position'] == 'relative':
|
||
# New containing block, use a new absolute list
|
||
absolute_boxes = []
|
||
|
||
new_children = []
|
||
next_page = {'break': 'any', 'page': None}
|
||
|
||
last_in_flow_child = None
|
||
|
||
if is_start:
|
||
skip = 0
|
||
first_letter_style = getattr(box, 'first_letter_style', None)
|
||
else:
|
||
# TODO: handle multiple skip stacks
|
||
(skip, skip_stack), = skip_stack.items()
|
||
first_letter_style = None
|
||
for index, child in enumerate(box.children[skip:], start=(skip or 0)):
|
||
child.position_x = position_x
|
||
child.position_y = position_y # doesn’t count adjoining_margins
|
||
|
||
if not child.is_in_normal_flow():
|
||
abort = False
|
||
stop, resume_at, out_of_flow_resume_at = _out_of_flow_layout(
|
||
context, box, index, child, new_children, page_is_empty,
|
||
absolute_boxes, fixed_boxes, adjoining_margins,
|
||
bottom_space)
|
||
if out_of_flow_resume_at:
|
||
context.broken_out_of_flow.append(
|
||
(child, box, out_of_flow_resume_at))
|
||
|
||
elif isinstance(child, boxes.LineBox):
|
||
abort, stop, resume_at, position_y = _linebox_layout(
|
||
context, box, index, child, new_children, page_is_empty,
|
||
absolute_boxes, fixed_boxes, adjoining_margins, bottom_space,
|
||
position_y, skip_stack, first_letter_style,
|
||
draw_bottom_decoration)
|
||
draw_bottom_decoration |= resume_at is None
|
||
adjoining_margins = []
|
||
|
||
else:
|
||
(abort, stop, resume_at, position_y, adjoining_margins,
|
||
next_page, new_children) = _in_flow_layout(
|
||
context, box, index, child, new_children, page_is_empty,
|
||
absolute_boxes, fixed_boxes, adjoining_margins, bottom_space,
|
||
position_y, skip_stack, first_letter_style,
|
||
draw_bottom_decoration, collapsing_with_children, discard,
|
||
next_page)
|
||
skip_stack = None
|
||
|
||
if abort:
|
||
page = child.page_values()[0]
|
||
return None, None, {'break': 'any', 'page': page}, [], False
|
||
elif stop:
|
||
break
|
||
|
||
else:
|
||
resume_at = None
|
||
|
||
box_is_fragmented = resume_at is not None
|
||
if box.style['continue'] == 'discard':
|
||
resume_at = None
|
||
|
||
if (box_is_fragmented 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)
|
||
|
||
last_in_flow_child = find_last_in_flow_child(new_children)
|
||
collapsing_through = False
|
||
if last_in_flow_child is None:
|
||
collapsed_margin = collapse_margin(adjoining_margins)
|
||
# Top and bottom margins of this box
|
||
if (box.height in ('auto', 0) and
|
||
get_clearance(context, box, collapsed_margin) is None and
|
||
all(value == 0 for value 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 or
|
||
box.is_table_wrapper):
|
||
position_y += collapse_margin(adjoining_margins)
|
||
adjoining_margins = []
|
||
|
||
# Add block ellipsis
|
||
if box_is_fragmented and new_children:
|
||
last_child = new_children[-1]
|
||
if isinstance(last_child, boxes.LineBox):
|
||
last_child.block_ellipsis = box.style['block_ellipsis']
|
||
|
||
new_box = box.copy_with_children(new_children)
|
||
new_box.remove_decoration(
|
||
start=not is_start, end=box_is_fragmented and not discard)
|
||
|
||
# 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':
|
||
if context.excluded_shapes and new_box.style['overflow'] != 'visible':
|
||
max_float_position_y = max(
|
||
float_box.position_y + float_box.margin_height()
|
||
for float_box in context.excluded_shapes)
|
||
position_y = max(max_float_position_y, position_y)
|
||
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, bottom_space,
|
||
skip_stack=None)
|
||
|
||
for child in new_box.children:
|
||
relative_positioning(child, (new_box.width, new_box.height))
|
||
|
||
if establishes_formatting_context(new_box):
|
||
context.finish_block_formatting_context(new_box)
|
||
|
||
if discard or not box_is_fragmented:
|
||
# 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)
|
||
elif bottom_space > -float('inf'):
|
||
# Make the box fill the blank space at the bottom of the page
|
||
# https://www.w3.org/TR/css-break-3/#box-splitting
|
||
new_box.height = (
|
||
context.page_bottom - bottom_space - new_box.position_y -
|
||
(new_box.margin_height() - new_box.height))
|
||
if draw_bottom_decoration:
|
||
new_box.height += (
|
||
box.padding_bottom + box.border_bottom_width +
|
||
box.margin_bottom)
|
||
|
||
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):
|
||
"""Get the amount of collapsed margin for a list of adjoining margins."""
|
||
margins = [0] # add 0 to make sure that max/min don’t get an empty list
|
||
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 whether 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 (
|
||
# TODO: columns shouldn't be block boxes, this condition would then be
|
||
# useless when this is fixed
|
||
box.is_column
|
||
) or (
|
||
isinstance(box, boxes.BlockContainerBox) and
|
||
not isinstance(box, boxes.BlockBox)
|
||
) or (
|
||
isinstance(box, boxes.BlockBox) and box.style['overflow'] != 'visible'
|
||
) or (
|
||
'flow-root' in box.style['display']
|
||
)
|
||
|
||
|
||
def block_level_page_break(sibling_before, sibling_after):
|
||
"""Get the correct page break value between siblings.
|
||
|
||
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 = []
|
||
# https://drafts.csswg.org/css-break-3/#possible-breaks
|
||
block_parallel_box_types = (
|
||
boxes.BlockLevelBox, boxes.TableRowGroupBox, boxes.TableRowBox)
|
||
|
||
box = sibling_before
|
||
while isinstance(box, block_parallel_box_types):
|
||
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, block_parallel_box_types):
|
||
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):
|
||
"""Find the last possible page break in ``children``.
|
||
|
||
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 isinstance(child, boxes.TableRowGroupBox) and (
|
||
child.is_header or child.is_footer):
|
||
# We don’t want to break pages before table headers or footers.
|
||
continue
|
||
elif child.is_column:
|
||
# We don’t want to break pages between columns.
|
||
continue
|
||
|
||
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')):
|
||
breakable_box_types = (
|
||
boxes.BlockBox, boxes.TableBox, boxes.TableRowGroupBox)
|
||
if isinstance(child, breakable_box_types):
|
||
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]
|
||
|
||
# Re-add footer at the end of split table
|
||
# TODO: fix table height and footer position
|
||
if isinstance(child, boxes.TableRowGroupBox):
|
||
for next_child in children[index:]:
|
||
if next_child.is_footer:
|
||
new_children.append(next_child)
|
||
|
||
# Index in the original parent
|
||
resume_at = {new_child.index: resume_at}
|
||
index += 1 # Remove placeholders after child
|
||
break
|
||
else:
|
||
return None
|
||
|
||
# TODO: don’t remove absolute and fixed placeholders found in table footers
|
||
remove_placeholders(children[index:], absolute_boxes, fixed_boxes)
|
||
return new_children, resume_at
|
||
|
||
|
||
def find_last_in_flow_child(children):
|
||
"""Find and return the last in-flow child of given ``children``."""
|
||
for child in reversed(children):
|
||
if child.is_in_normal_flow():
|
||
return child
|
||
|
||
|
||
def reversed_enumerate(seq):
|
||
"""Like reversed(list(enumerate(seq))) without copying the whole seq."""
|
||
return zip(reversed(range(len(seq))), reversed(seq))
|
||
|
||
|
||
def remove_placeholders(box_list, absolute_boxes, fixed_boxes):
|
||
"""Remove placeholders from absolute and fixed lists.
|
||
|
||
For boxes that have been removed in find_earlier_page_break(), 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)
|