146 lines
5.9 KiB
Python
146 lines
5.9 KiB
Python
"""
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weasyprint.stacking
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-------------------
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:copyright: Copyright 2011-2019 Simon Sapin and contributors, see AUTHORS.
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:license: BSD, see LICENSE for details.
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"""
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import operator
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from .formatting_structure import boxes
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from .layout.absolute import AbsolutePlaceholder
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_Z_INDEX_GETTER = operator.attrgetter('z_index')
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class StackingContext(object):
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"""Stacking contexts define the paint order of all pieces of a document.
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http://www.w3.org/TR/CSS21/visuren.html#x43
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http://www.w3.org/TR/CSS21/zindex.html
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"""
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def __init__(self, box, child_contexts, blocks, floats, blocks_and_cells,
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page):
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self.box = box
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self.page = page
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self.block_level_boxes = blocks # 4: In flow, non positioned
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self.float_contexts = floats # 5: Non positioned
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self.negative_z_contexts = [] # 3: Child contexts, z-index < 0
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self.zero_z_contexts = [] # 8: Child contexts, z-index = 0
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self.positive_z_contexts = [] # 9: Child contexts, z-index > 0
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self.blocks_and_cells = blocks_and_cells # 7: Non positioned
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for context in child_contexts:
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if context.z_index < 0:
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self.negative_z_contexts.append(context)
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elif context.z_index == 0:
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self.zero_z_contexts.append(context)
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else: # context.z_index > 0
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self.positive_z_contexts.append(context)
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self.negative_z_contexts.sort(key=_Z_INDEX_GETTER)
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self.positive_z_contexts.sort(key=_Z_INDEX_GETTER)
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# sort() is stable, so the lists are now storted
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# by z-index, then tree order.
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self.z_index = box.style['z_index']
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if self.z_index == 'auto':
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self.z_index = 0
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@classmethod
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def from_page(cls, page):
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# Page children (the box for the root element and margin boxes)
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# as well as the page box itself are unconditionally stacking contexts.
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child_contexts = [cls.from_box(child, page) for child in page.children]
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# Children are sub-contexts, remove them from the "normal" tree.
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page = page.copy_with_children([])
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return cls(page, child_contexts, [], [], [], page)
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@classmethod
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def from_box(cls, box, page, child_contexts=None):
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children = [] # What will be passed to this box
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if child_contexts is None:
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child_contexts = children
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# child_contexts: where to put sub-contexts that we find here.
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# May not be the same as children for:
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# "treat the element as if it created a new stacking context,
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# but any positioned descendants and descendants which actually
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# create a new stacking context should be considered part of the
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# parent stacking context, not this new one."
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blocks = []
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floats = []
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blocks_and_cells = []
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def dispatch(box):
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if isinstance(box, AbsolutePlaceholder):
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box = box._box
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style = box.style
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absolute_and_z_index = (
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style['position'] != 'static' and style['z_index'] != 'auto')
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if (absolute_and_z_index or
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style['opacity'] < 1 or
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# 'transform: none' gives a "falsy" empty list here
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style['transform'] or
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style['overflow'] != 'visible'):
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# This box defines a new stacking context, remove it
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# from the "normal" children list.
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child_contexts.append(
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StackingContext.from_box(box, page))
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else:
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if style['position'] != 'static':
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assert style['z_index'] == 'auto'
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# "Fake" context: sub-contexts will go in this
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# `child_contexts` list.
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# Insert at the position before creating the sub-context.
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index = len(child_contexts)
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child_contexts.insert(
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index,
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StackingContext.from_box(box, page, child_contexts))
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elif box.is_floated():
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floats.append(StackingContext.from_box(
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box, page, child_contexts))
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elif isinstance(
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box, (boxes.InlineBlockBox, boxes.InlineFlexBox)):
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# Have this fake stacking context be part of the "normal"
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# box tree, because we need its position in the middle
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# of a tree of inline boxes.
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return StackingContext.from_box(box, page, child_contexts)
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else:
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if isinstance(box, boxes.BlockLevelBox):
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blocks_index = len(blocks)
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blocks_and_cells_index = len(blocks_and_cells)
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elif isinstance(box, boxes.TableCellBox):
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blocks_index = None
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blocks_and_cells_index = len(blocks_and_cells)
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else:
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blocks_index = None
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blocks_and_cells_index = None
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box = dispatch_children(box)
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# Insert at the positions before dispatch the children.
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if blocks_index is not None:
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blocks.insert(blocks_index, box)
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if blocks_and_cells_index is not None:
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blocks_and_cells.insert(blocks_and_cells_index, box)
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return box
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def dispatch_children(box):
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if not isinstance(box, boxes.ParentBox):
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return box
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new_children = []
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for child in box.children:
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result = dispatch(child)
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if result is not None:
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new_children.append(result)
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box.children = new_children
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return box
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box = dispatch_children(box)
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return cls(box, children, blocks, floats, blocks_and_cells, page)
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