240 lines
9.2 KiB
Python
240 lines
9.2 KiB
Python
"""Manage background position and size."""
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from collections import namedtuple
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from itertools import cycle
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from tinycss2.color3 import parse_color
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from ..formatting_structure import boxes
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from . import replaced
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from .percent import percentage, resolve_radii_percentages
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Background = namedtuple('Background', 'color, layers, image_rendering')
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BackgroundLayer = namedtuple(
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'BackgroundLayer',
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'image, size, position, repeat, unbounded, '
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'painting_area, positioning_area, clipped_boxes')
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def box_rectangle(box, which_rectangle):
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if which_rectangle == 'border-box':
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return (
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box.border_box_x(), box.border_box_y(),
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box.border_width(), box.border_height())
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elif which_rectangle == 'padding-box':
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return (
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box.padding_box_x(), box.padding_box_y(),
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box.padding_width(), box.padding_height())
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else:
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assert which_rectangle == 'content-box', which_rectangle
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return (
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box.content_box_x(), box.content_box_y(),
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box.width, box.height)
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def layout_box_backgrounds(page, box, get_image_from_uri, layout_children=True,
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style=None):
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"""Fetch and position background images."""
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from ..draw import get_color
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# Resolve percentages in border-radius properties
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resolve_radii_percentages(box)
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if layout_children:
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for child in box.all_children():
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layout_box_backgrounds(page, child, get_image_from_uri)
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if style is None:
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style = box.style
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if style['visibility'] == 'hidden':
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images = []
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color = parse_color('transparent')
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else:
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orientation = style['image_orientation']
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images = [
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get_image_from_uri(url=value, orientation=orientation)
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if type_ == 'url' else value
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for type_, value in style['background_image']]
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color = get_color(style, 'background_color')
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if color.alpha == 0 and not any(images):
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if box != page: # Pages need a background for bleed box
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box.background = None
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return
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layers = [
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layout_background_layer(box, page, style['image_resolution'], *layer)
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for layer in zip(images, *map(cycle, [
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style['background_size'],
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style['background_clip'],
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style['background_repeat'],
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style['background_origin'],
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style['background_position'],
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style['background_attachment']]))]
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box.background = Background(color, layers, style['image_rendering'])
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def layout_background_layer(box, page, resolution, image, size, clip, repeat,
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origin, position, attachment):
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# TODO: respect box-sizing for table cells?
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clipped_boxes = []
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painting_area = 0, 0, 0, 0
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if box is page:
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# [The page’s] background painting area is the bleed area […]
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# regardless of background-clip.
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# https://drafts.csswg.org/css-page-3/#painting
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painting_area = page.bleed_area
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clipped_boxes = []
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elif isinstance(box, boxes.TableRowGroupBox):
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clipped_boxes = []
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total_height = 0
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for row in box.children:
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if row.children:
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clipped_boxes += [
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cell.rounded_border_box() for cell in row.children]
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total_height = max(total_height, max(
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cell.border_height() for cell in row.children))
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painting_area = [
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box.border_box_x(), box.border_box_y(),
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box.border_width(), total_height]
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elif isinstance(box, boxes.TableRowBox):
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if box.children:
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clipped_boxes = [
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cell.rounded_border_box() for cell in box.children]
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height = max(cell.border_height() for cell in box.children)
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painting_area = [
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box.border_box_x(), box.border_box_y(),
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box.border_width(), height]
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elif isinstance(box, (boxes.TableColumnGroupBox, boxes.TableColumnBox)):
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cells = box.get_cells()
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if cells:
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clipped_boxes = [cell.rounded_border_box() for cell in cells]
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min_x = min(cell.border_box_x() for cell in cells)
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max_x = max(
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cell.border_box_x() + cell.border_width() for cell in cells)
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painting_area = [
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min_x, box.border_box_y(), max_x - min_x, box.border_height()]
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else:
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painting_area = box_rectangle(box, clip)
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if clip == 'border-box':
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clipped_boxes = [box.rounded_border_box()]
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elif clip == 'padding-box':
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clipped_boxes = [box.rounded_padding_box()]
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else:
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assert clip == 'content-box', clip
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clipped_boxes = [box.rounded_content_box()]
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if image is not None:
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intrinsic_width, intrinsic_height, ratio = image.get_intrinsic_size(
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resolution, box.style['font_size'])
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if image is None or 0 in (intrinsic_width, intrinsic_height):
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return BackgroundLayer(
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image=None, unbounded=False, painting_area=painting_area,
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size='unused', position='unused', repeat='unused',
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positioning_area='unused', clipped_boxes=clipped_boxes)
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if attachment == 'fixed':
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# Initial containing block
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if isinstance(box, boxes.PageBox):
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# […] if background-attachment is fixed then the image is
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# positioned relative to the page box including its margins […].
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# https://drafts.csswg.org/css-page/#painting
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positioning_area = (0, 0, box.margin_width(), box.margin_height())
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else:
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positioning_area = box_rectangle(page, 'content-box')
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else:
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positioning_area = box_rectangle(box, origin)
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positioning_x, positioning_y, positioning_width, positioning_height = (
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positioning_area)
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painting_x, painting_y, painting_width, painting_height = painting_area
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if size == 'cover':
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image_width, image_height = replaced.cover_constraint_image_sizing(
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positioning_width, positioning_height, ratio)
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elif size == 'contain':
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image_width, image_height = replaced.contain_constraint_image_sizing(
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positioning_width, positioning_height, ratio)
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else:
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size_width, size_height = size
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image_width, image_height = replaced.default_image_sizing(
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intrinsic_width, intrinsic_height, ratio,
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percentage(size_width, positioning_width),
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percentage(size_height, positioning_height),
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positioning_width, positioning_height)
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origin_x, position_x, origin_y, position_y = position
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ref_x = positioning_width - image_width
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ref_y = positioning_height - image_height
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position_x = percentage(position_x, ref_x)
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position_y = percentage(position_y, ref_y)
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if origin_x == 'right':
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position_x = ref_x - position_x
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if origin_y == 'bottom':
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position_y = ref_y - position_y
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repeat_x, repeat_y = repeat
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if repeat_x == 'round':
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n_repeats = max(1, round(positioning_width / image_width))
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new_width = positioning_width / n_repeats
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position_x = 0 # Ignore background-position for this dimension
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if repeat_y != 'round' and size[1] == 'auto':
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image_height *= new_width / image_width
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image_width = new_width
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if repeat_y == 'round':
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n_repeats = max(1, round(positioning_height / image_height))
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new_height = positioning_height / n_repeats
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position_y = 0 # Ignore background-position for this dimension
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if repeat_x != 'round' and size[0] == 'auto':
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image_width *= new_height / image_height
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image_height = new_height
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return BackgroundLayer(
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image=image,
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size=(image_width, image_height),
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position=(position_x, position_y),
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repeat=repeat,
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unbounded=False,
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painting_area=painting_area,
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positioning_area=positioning_area,
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clipped_boxes=clipped_boxes)
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def layout_backgrounds(page, get_image_from_uri):
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"""Layout backgrounds on the page box and on its children.
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This function takes care of the canvas background, taken from the root
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elememt or a <body> child of the root element.
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See https://www.w3.org/TR/CSS21/colors.html#background
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"""
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layout_box_backgrounds(page, page, get_image_from_uri)
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assert not isinstance(page.children[0], boxes.MarginBox)
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root_box = page.children[0]
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chosen_box = root_box
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if root_box.element_tag.lower() == 'html' and root_box.background is None:
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for child in root_box.children:
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if child.element_tag.lower() == 'body':
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chosen_box = child
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break
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if chosen_box.background:
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painting_area = box_rectangle(page, 'border-box')
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original_background = page.background
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layout_box_backgrounds(
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page, page, get_image_from_uri, layout_children=False,
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style=chosen_box.style)
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page.canvas_background = page.background._replace(
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# TODO: background-clip should be updated
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layers=[
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layer._replace(painting_area=painting_area)
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for layer in page.background.layers])
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page.background = original_background
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chosen_box.background = None
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else:
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page.canvas_background = None
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