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331 lines
13 KiB
Python
331 lines
13 KiB
Python
# coding: utf8
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# WeasyPrint converts web documents (HTML, CSS, ...) to PDF.
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# Copyright (C) 2011 Simon Sapin
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as
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# published by the Free Software Foundation, either version 3 of the
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# License, or (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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#
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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"""
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Functions laying out tables.
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"""
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from __future__ import division
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from ..formatting_structure import boxes
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from .percentages import resolve_percentages, resolve_one_percentage
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def table_layout(document, table, max_position_y, containing_block,
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device_size, page_is_empty):
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"""Layout for a table box.
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For now only the fixed layout and separate border model are supported.
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"""
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# Avoid a circular import
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from .blocks import block_level_height
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column_widths = table.column_widths
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grid_width = len(column_widths)
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border_spacing_x, border_spacing_y = table.style.border_spacing
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# TODO: reverse this for direction: rtl
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column_positions = []
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position_x = table.content_box_x()
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rows_x = position_x + border_spacing_x
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for width in column_widths:
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position_x += border_spacing_x
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column_positions.append(position_x)
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position_x += width
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rows_width = position_x - rows_x
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# Layout for row groups, rows and cells
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position_y = table.content_box_y() + border_spacing_y
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initial_position_y = position_y
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new_table_children = []
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for group in table.children:
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resolve_percentages(group, containing_block=table)
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group.position_x = rows_x
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group.position_y = position_y
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group.width = rows_width
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new_group_children = []
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# For each rows, cells for which this is the last row (with rowspan)
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ending_cells_by_row = [[] for row in group.children]
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for row in group.children:
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resolve_percentages(row, containing_block=table)
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row.position_x = rows_x
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row.position_y = position_y
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row.width = rows_width
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# Place cells at the top of the row and layout their content
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new_row_children = []
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for cell in row.children:
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spanned_widths = column_widths[cell.grid_x:][:cell.colspan]
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# In the fixed layout the grid width is set by cells in
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# the first row and column elements.
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# This may be less than the previous value of cell.colspan
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# if that would bring the cell beyond the grid width.
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cell.colspan = len(spanned_widths)
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if cell.colspan == 0:
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# The cell is entierly beyond the grid width, remove it
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# entierly. Subsequent cells in the same row have greater
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# grid_x, so they are beyond too.
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# TODO warn?
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break
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resolve_percentages(cell, containing_block=table)
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cell.position_x = column_positions[cell.grid_x]
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cell.position_y = row.position_y
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cell.margin_top = 0
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cell.margin_left = 0
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cell.width = 0
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borders_plus_padding = cell.border_width() # with width==0
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cell.width = (
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sum(spanned_widths)
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+ border_spacing_x * (cell.colspan - 1)
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- borders_plus_padding)
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# The computed height is a minimum
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computed_cell_height = cell.height
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cell.height = 'auto'
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cell, _ = block_level_height(
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document, cell,
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max_position_y=float('inf'),
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skip_stack=None,
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device_size=device_size,
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page_is_empty=True)
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if computed_cell_height != 'auto':
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cell.height = max(cell.height, computed_cell_height)
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new_row_children.append(cell)
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row = row.copy_with_children(new_row_children)
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new_group_children.append(row)
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# Table height algorithm
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# http://www.w3.org/TR/CSS21/tables.html#height-layout
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# cells with vertical-align: baseline
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baseline_cells = []
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for cell in row.children:
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vertical_align = cell.style.vertical_align
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if vertical_align in ('top', 'middle', 'bottom'):
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cell.vertical_align = vertical_align
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else:
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# Assume 'baseline' for any other value
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cell.vertical_align = 'baseline'
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cell.baseline = cell_baseline(cell)
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baseline_cells.append(cell)
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if baseline_cells:
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row.baseline = max(cell.baseline for cell in baseline_cells)
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for cell in baseline_cells:
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if cell.baseline != row.baseline:
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add_top_padding(cell, row.baseline - cell.baseline)
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else:
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row.baseline = None
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# row height
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for cell in row.children:
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ending_cells_by_row[cell.rowspan - 1].append(cell)
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ending_cells = ending_cells_by_row.pop(0)
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if ending_cells: # in this row
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row_bottom_y = max(
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cell.position_y + cell.border_height()
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for cell in ending_cells)
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row.height = row_bottom_y - row.position_y
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else:
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row_bottom_y = row.position_y
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row.height = 0
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# Add extra padding to make the cells the same height as the row
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for cell in ending_cells:
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cell_bottom_y = cell.position_y + cell.border_height()
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extra = row_bottom_y - cell_bottom_y
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if cell.vertical_align == 'bottom':
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add_top_padding(cell, extra)
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elif cell.vertical_align == 'middle':
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extra /= 2.
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add_top_padding(cell, extra)
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cell.padding_bottom += extra
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else:
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cell.padding_bottom += extra
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position_y += row.height + border_spacing_y
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group = group.copy_with_children(new_group_children)
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new_table_children.append(group)
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# Set missing baselines in a second loop because of rowspan
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for row in group.children:
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if row.baseline is None:
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if row.children:
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# lowest bottom content edge
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row.baseline = row.position_y - max(
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cell.content_box_y() + cell.height
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for cell in row.children)
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else:
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row.baseline = 0
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group.height = position_y - group.position_y
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if group.children:
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# The last border spacing is outside of the group.
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group.height -= border_spacing_y
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table = table.copy_with_children(new_table_children)
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# If the height property has a bigger value, just add blank space
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# below the last row group.
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table.height = max(
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table.height if table.height != 'auto' else 0,
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position_y - table.content_box_y())
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# Layout for column groups and columns
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columns_height = position_y - initial_position_y
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if table.children:
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# The last border spacing is below the columns.
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columns_height -= border_spacing_y
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for group in table.column_groups:
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for column in group.children:
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column.position_x = column_positions[column.grid_x]
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column.position_y = initial_position_y
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column.width = column_widths[column.grid_x]
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column.height = columns_height
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first = group.children[0]
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last = group.children[-1]
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group.position_x = first.position_x
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group.position_y = initial_position_y
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group.width = last.position_x + last.width - first.position_x
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group.height = columns_height
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if ((table.position_y + table.margin_height()) > max_position_y
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and not page_is_empty):
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# If the table does not fit, put it on the next page.
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# (No page break inside tables yet.)
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return None, None
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else:
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return table, None
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def add_top_padding(box, extra_padding):
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"""Increase the top padding of a box. This also translates the children.
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"""
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box.padding_top += extra_padding
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for child in box.children:
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child.translate(dy=extra_padding)
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def fixed_table_layout(table):
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"""Run the fixed table layout and return a list of column widths
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http://www.w3.org/TR/CSS21/tables.html#fixed-table-layout
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"""
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assert table.width != 'auto'
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all_columns = [column for column_group in table.column_groups
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for column in column_group.children]
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if table.children and table.children[0].children:
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first_rowgroup = table.children[0]
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first_row_cells = first_rowgroup.children[0].children
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else:
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first_row_cells = []
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num_columns = max(
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len(all_columns),
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sum(cell.colspan for cell in first_row_cells)
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)
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# ``None`` means not know yet.
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column_widths = [None] * num_columns
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# `width` on column boxes
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for i, column in enumerate(all_columns):
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resolve_one_percentage(column, 'width', table.width, ['auto'])
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if column.width != 'auto':
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column_widths[i] = column.width
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# `width` on cells of the first row.
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border_spacing_x, border_spacing_y = table.style.border_spacing
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i = 0
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for cell in first_row_cells:
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resolve_percentages(cell, table)
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if cell.width != 'auto':
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width = cell.border_width()
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width -= border_spacing_x * (cell.colspan - 1)
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# In the general case, this width affects several columns (through
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# colspan) some of which already have a width. Subscract these
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# known widths and divide among remaining columns.
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columns_without_width = [] # and occupied by this cell
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for j in xrange(i, i + cell.colspan):
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if column_widths[j] is None:
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columns_without_width.append(j)
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else:
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width -= column_widths[j]
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width_per_column = width / len(columns_without_width)
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for j in columns_without_width:
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column_widths[j] = width_per_column
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i += cell.colspan
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# Distribute the remaining space equally on columns that do not have
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# a width yet.
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all_border_spacing = border_spacing_x * (num_columns + 1)
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min_table_width = (sum(w for w in column_widths if w is not None)
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+ all_border_spacing)
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columns_without_width = [i for i, width in enumerate(column_widths)
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if width is None]
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if columns_without_width and table.width >= min_table_width:
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remaining_width = table.width - min_table_width
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width_per_column = remaining_width / len(columns_without_width)
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for i in columns_without_width:
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column_widths[i] = width_per_column
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else:
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# XXX this is bad, but we were given a broken table to work with...
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for i in columns_without_width:
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column_widths[i] = 0
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# If the sum is less than the table width,
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# distribute the remaining space equally
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extra_width = table.width - sum(column_widths) - all_border_spacing
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if extra_width <= 0:
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# substract a negative: widen the table
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table.width -= extra_width
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elif num_columns:
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extra_per_column = extra_width / num_columns
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column_widths = [w + extra_per_column for w in column_widths]
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# Now we have table.width == sum(column_widths) + all_border_spacing
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# with possible floating point rounding errors.
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# (unless there is zero column)
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table.column_widths = column_widths
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return column_widths
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def cell_baseline(cell):
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"""
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Return the y position of a cell’s baseline from the top of its border box.
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See http://www.w3.org/TR/CSS21/tables.html#height-layout
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"""
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# Do not use cell.descendants() as we do not want to recurse into
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# out-of-flow children.
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stack = [iter(cell.children)] # DIY recursion
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while stack:
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child = next(stack[-1], None)
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if child is None:
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stack.pop()
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continue
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if not child.is_in_normal_flow():
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continue
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if isinstance(child, (boxes.LineBox, boxes.TableRowBox)):
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# First in-flow line or row.
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return child.baseline + child.position_y - cell.position_y
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if isinstance(child, boxes.ParentBox):
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stack.append(iter(child.children))
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# Default to the bottom of the content area.
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return cell.style.border_top_width + cell.padding_top + cell.height
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