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WeasyPrint/weasy/layout/preferred.py

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# coding: utf8
# WeasyPrint converts web documents (HTML, CSS, ...) to PDF.
# Copyright (C) 2011 Simon Sapin
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Preferred minimum width and preferred width, also know as shrink-to-fit.
"""
import cairo
from ..formatting_structure import boxes
from ..text import TextFragment
from .inlines import replaced_box_width
def inline_preferred_minimum_width(box):
"""Return the preferred minimum width for an ``InlineBox``.
This is the width by breaking at every line-break opportunity.
*Warning:* only TextBox and InlineReplacedBox children are supported
for now. (No recursive InlineBox childdren.)
"""
widest_line = 0
for child in box.children:
if isinstance(child, boxes.AtomicInlineLevelBox):
# Images are on their own line
current_line = replaced_preferred_width(child)
else:
assert isinstance(child, boxes.TextBox)
current_line = max(text_lines_width(child, width=0))
widest_line = max(widest_line, current_line)
return widest_line
def inline_preferred_width(box):
"""Return the preferred width for an ``InlineBox``.
This is the width by only breaking at forced line breaks.
*Warning:* only TextBox and InlineReplacedBox children are supported
for now. (No recursive InlineBox childdren.)
"""
widest_line = 0
current_line = 0
for child in box.children:
if isinstance(child, boxes.InlineReplacedBox):
# No line break around images
current_line += replaced_preferred_width(child)
else:
assert isinstance(child, boxes.TextBox)
lines = list(text_lines_width(child, width=None))
assert lines
# The first text line goes on the current line
current_line += lines[0]
if len(lines) > 1:
# Forced line break
widest_line = max(widest_line, current_line)
if len(lines) > 2:
widest_line = max(widest_line, max(lines[1:-1]))
current_line = lines[-1]
widest_line = max(widest_line, current_line)
return widest_line
def text_lines_width(box, width):
"""Return the list of line widths for a ``TextBox``."""
# TODO: find the real surface, to have correct hinting
context = cairo.Context(cairo.PDFSurface(None, 1, 1))
fragment = TextFragment(box.text, box.style, context, width=width)
return fragment.line_widths()
def replaced_preferred_width(box):
"""Return the preferred (minimum) width for an ``InlineReplacedBox``."""
# TODO: what about percentage widths?
# TODO: get the actual device size. Or do we really care?
replaced_box_width(box, device_size=None)
return box.width