302 lines
11 KiB
Python
302 lines
11 KiB
Python
"""Layout for images and other replaced elements.
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See https://drafts.csswg.org/css-images-3/#sizing
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"""
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from .min_max import handle_min_max_height, handle_min_max_width
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from .percent import percentage
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def default_image_sizing(intrinsic_width, intrinsic_height, intrinsic_ratio,
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specified_width, specified_height,
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default_width, default_height):
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"""Default sizing algorithm for the concrete object size.
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Return a ``(concrete_width, concrete_height)`` tuple.
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See https://drafts.csswg.org/css-images-3/#default-sizing
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"""
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if specified_width == 'auto':
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specified_width = None
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if specified_height == 'auto':
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specified_height = None
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if specified_width is not None and specified_height is not None:
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return specified_width, specified_height
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elif specified_width is not None:
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return specified_width, (
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specified_width / intrinsic_ratio if intrinsic_ratio is not None
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else intrinsic_height if intrinsic_height is not None
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else default_height)
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elif specified_height is not None:
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return (
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specified_height * intrinsic_ratio if intrinsic_ratio is not None
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else intrinsic_width if intrinsic_width is not None
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else default_width
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), specified_height
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else:
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if intrinsic_width is not None or intrinsic_height is not None:
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return default_image_sizing(
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intrinsic_width, intrinsic_height, intrinsic_ratio,
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intrinsic_width, intrinsic_height, default_width,
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default_height)
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else:
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return contain_constraint_image_sizing(
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default_width, default_height, intrinsic_ratio)
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def contain_constraint_image_sizing(constraint_width, constraint_height,
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intrinsic_ratio):
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"""Contain constraint sizing algorithm for the concrete object size.
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Return a ``(concrete_width, concrete_height)`` tuple.
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See https://drafts.csswg.org/css-images-3/#contain-constraint
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"""
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return _constraint_image_sizing(
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constraint_width, constraint_height, intrinsic_ratio, cover=False)
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def cover_constraint_image_sizing(constraint_width, constraint_height,
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intrinsic_ratio):
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"""Cover constraint sizing algorithm for the concrete object size.
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Return a ``(concrete_width, concrete_height)`` tuple.
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See https://drafts.csswg.org/css-images-3/#cover-constraint
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"""
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return _constraint_image_sizing(
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constraint_width, constraint_height, intrinsic_ratio, cover=True)
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def _constraint_image_sizing(constraint_width, constraint_height,
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intrinsic_ratio, cover):
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if intrinsic_ratio is None:
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return constraint_width, constraint_height
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elif cover ^ (constraint_width > constraint_height * intrinsic_ratio):
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return constraint_height * intrinsic_ratio, constraint_height
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else:
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return constraint_width, constraint_width / intrinsic_ratio
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def replacedbox_layout(box):
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# TODO: respect box-sizing ?
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object_fit = box.style['object_fit']
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position = box.style['object_position']
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image = box.replacement
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intrinsic_width, intrinsic_height, intrinsic_ratio = (
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image.get_intrinsic_size(
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box.style['image_resolution'], box.style['font_size']))
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if None in (intrinsic_width, intrinsic_height):
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intrinsic_width, intrinsic_height = contain_constraint_image_sizing(
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box.width, box.height, intrinsic_ratio)
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if object_fit == 'fill':
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draw_width, draw_height = box.width, box.height
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else:
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if object_fit in ('contain', 'scale-down'):
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draw_width, draw_height = contain_constraint_image_sizing(
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box.width, box.height, intrinsic_ratio)
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elif object_fit == 'cover':
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draw_width, draw_height = cover_constraint_image_sizing(
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box.width, box.height, intrinsic_ratio)
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else:
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assert object_fit == 'none', object_fit
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draw_width, draw_height = intrinsic_width, intrinsic_height
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if object_fit == 'scale-down':
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draw_width = min(draw_width, intrinsic_width)
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draw_height = min(draw_height, intrinsic_height)
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origin_x, position_x, origin_y, position_y = position[0]
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ref_x = box.width - draw_width
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ref_y = box.height - draw_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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position_x += box.content_box_x()
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position_y += box.content_box_y()
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return draw_width, draw_height, position_x, position_y
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@handle_min_max_width
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def replaced_box_width(box, containing_block):
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"""Set the used width for replaced boxes."""
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from .block import block_level_width
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width, height, ratio = box.replacement.get_intrinsic_size(
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box.style['image_resolution'], box.style['font_size'])
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# This algorithm simply follows the different points of the specification:
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# https://www.w3.org/TR/CSS21/visudet.html#inline-replaced-width
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if box.height == box.width == 'auto':
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if width is not None:
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# Point #1
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box.width = width
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elif ratio is not None:
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if height is not None:
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# Point #2 first part
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box.width = height * ratio
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else:
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# Point #3
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block_level_width(box, containing_block)
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if box.width == 'auto':
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if ratio is not None:
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# Point #2 second part
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box.width = box.height * ratio
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elif width is not None:
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# Point #4
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box.width = width
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else:
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# Point #5
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# It's pretty useless to rely on device size to set width.
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box.width = 300
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@handle_min_max_height
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def replaced_box_height(box):
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"""Compute and set the used height for replaced boxes."""
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# https://www.w3.org/TR/CSS21/visudet.html#inline-replaced-height
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width, height, ratio = box.replacement.get_intrinsic_size(
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box.style['image_resolution'], box.style['font_size'])
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# Test 'auto' on the computed width, not the used width
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if box.height == box.width == 'auto':
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box.height = height
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elif box.height == 'auto' and ratio:
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box.height = box.width / ratio
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if box.height == box.width == 'auto' and height is not None:
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box.height = height
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elif ratio is not None and box.height == 'auto':
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box.height = box.width / ratio
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elif box.height == 'auto' and height is not None:
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box.height = height
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elif box.height == 'auto':
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# It's pretty useless to rely on device size to set width.
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box.height = 150
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def inline_replaced_box_layout(box, containing_block):
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"""Lay out an inline :class:`boxes.ReplacedBox` ``box``."""
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for side in ('top', 'right', 'bottom', 'left'):
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if getattr(box, f'margin_{side}') == 'auto':
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setattr(box, f'margin_{side}', 0)
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inline_replaced_box_width_height(box, containing_block)
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def inline_replaced_box_width_height(box, containing_block):
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if box.style['width'] == box.style['height'] == 'auto':
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replaced_box_width.without_min_max(box, containing_block)
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replaced_box_height.without_min_max(box)
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min_max_auto_replaced(box)
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else:
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replaced_box_width(box, containing_block)
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replaced_box_height(box)
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def min_max_auto_replaced(box):
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"""Resolve min/max constraints on replaced elements with 'auto' sizes."""
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width = box.width
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height = box.height
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min_width = box.min_width
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min_height = box.min_height
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max_width = max(min_width, box.max_width)
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max_height = max(min_height, box.max_height)
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# (violation_width, violation_height)
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violations = (
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'min' if width < min_width else 'max' if width > max_width else '',
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'min' if height < min_height else 'max' if height > max_height else '')
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# Work around divisions by zero. These are pathological cases anyway.
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# TODO: is there a cleaner way?
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if width == 0:
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width = 1e-6
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if height == 0:
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height = 1e-6
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# ('', ''): nothing to do
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if violations == ('max', ''):
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box.width = max_width
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box.height = max(max_width * height / width, min_height)
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elif violations == ('min', ''):
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box.width = min_width
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box.height = min(min_width * height / width, max_height)
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elif violations == ('', 'max'):
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box.width = max(max_height * width / height, min_width)
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box.height = max_height
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elif violations == ('', 'min'):
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box.width = min(min_height * width / height, max_width)
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box.height = min_height
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elif violations == ('max', 'max'):
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if max_width / width <= max_height / height:
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box.width = max_width
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box.height = max(min_height, max_width * height / width)
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else:
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box.width = max(min_width, max_height * width / height)
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box.height = max_height
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elif violations == ('min', 'min'):
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if min_width / width <= min_height / height:
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box.width = min(max_width, min_height * width / height)
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box.height = min_height
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else:
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box.width = min_width
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box.height = min(max_height, min_width * height / width)
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elif violations == ('min', 'max'):
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box.width = min_width
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box.height = max_height
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elif violations == ('max', 'min'):
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box.width = max_width
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box.height = min_height
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def block_replaced_box_layout(context, box, containing_block):
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"""Lay out the block :class:`boxes.ReplacedBox` ``box``."""
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from .block import block_level_width
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from .float import avoid_collisions
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box = box.copy()
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if box.style['width'] == 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)
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replaced_box_height.without_min_max(box)
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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)
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replaced_box_height(box)
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# Don't collide with floats
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# https://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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@handle_min_max_width
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def block_replaced_width(box, containing_block):
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from .block import block_level_width
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# https://www.w3.org/TR/CSS21/visudet.html#block-replaced-width
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replaced_box_width.without_min_max(box, containing_block)
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block_level_width.without_min_max(box, containing_block)
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