File: //home/arjun/projects/env/lib/python3.10/site-packages/weasyprint/text/line_break.py
"""Decide where to break text lines."""
import re
from math import inf
import pyphen
from .constants import LST_TO_ISO, PANGO_WRAP_MODE
from .ffi import (
ffi, gobject, pango, pangoft2, unicode_to_char_p, units_from_double,
units_to_double)
from .fonts import font_features, get_font_description
def line_size(line, style):
"""Get logical width and height of the given ``line``.
``style`` is used to add letter spacing (if needed).
"""
logical_extents = ffi.new('PangoRectangle *')
pango.pango_layout_line_get_extents(line, ffi.NULL, logical_extents)
width = units_to_double(logical_extents.width)
height = units_to_double(logical_extents.height)
ffi.release(logical_extents)
if style['letter_spacing'] != 'normal':
width += style['letter_spacing']
return width, height
def first_line_metrics(first_line, text, layout, resume_at, space_collapse,
style, hyphenated=False, hyphenation_character=None):
length = first_line.length
if hyphenated:
length -= len(hyphenation_character.encode())
elif resume_at:
# Set an infinite width as we don't want to break lines when drawing,
# the lines have already been split and the size may differ. Rendering
# is also much faster when no width is set.
pango.pango_layout_set_width(layout.layout, -1)
# Create layout with final text
first_line_text = text.encode()[:length].decode()
# Remove trailing spaces if spaces collapse
if space_collapse:
first_line_text = first_line_text.rstrip(' ')
layout.set_text(first_line_text)
first_line, _ = layout.get_first_line()
length = first_line.length if first_line is not None else 0
width, height = line_size(first_line, style)
baseline = units_to_double(pango.pango_layout_get_baseline(layout.layout))
layout.deactivate()
return layout, length, resume_at, width, height, baseline
class Layout:
"""Object holding PangoLayout-related cdata pointers."""
def __init__(self, context, style, justification_spacing=0,
max_width=None):
self.justification_spacing = justification_spacing
self.setup(context, style)
self.max_width = max_width
def setup(self, context, style):
self.context = context
self.style = style
self.first_line_direction = 0
if context is None:
font_map = ffi.gc(
pangoft2.pango_ft2_font_map_new(), gobject.g_object_unref)
else:
font_map = context.font_config.font_map
pango_context = ffi.gc(
pango.pango_font_map_create_context(font_map),
gobject.g_object_unref)
pango.pango_context_set_round_glyph_positions(pango_context, False)
if style['font_language_override'] != 'normal':
lang_p, lang = unicode_to_char_p(LST_TO_ISO.get(
style['font_language_override'].lower(),
style['font_language_override']))
elif style['lang']:
lang_p, lang = unicode_to_char_p(style['lang'])
else:
lang = None
self.language = pango.pango_language_get_default()
if lang:
self.language = pango.pango_language_from_string(lang_p)
pango.pango_context_set_language(pango_context, self.language)
assert not isinstance(style['font_family'], str), (
'font_family should be a list')
font_description = get_font_description(style)
self.layout = ffi.gc(
pango.pango_layout_new(pango_context),
gobject.g_object_unref)
pango.pango_layout_set_font_description(self.layout, font_description)
text_decoration = style['text_decoration_line']
if text_decoration != 'none':
metrics = ffi.gc(
pango.pango_context_get_metrics(
pango_context, font_description, self.language),
pango.pango_font_metrics_unref)
self.ascent = units_to_double(
pango.pango_font_metrics_get_ascent(metrics))
self.underline_position = units_to_double(
pango.pango_font_metrics_get_underline_position(metrics))
self.strikethrough_position = units_to_double(
pango.pango_font_metrics_get_strikethrough_position(metrics))
self.underline_thickness = units_to_double(
pango.pango_font_metrics_get_underline_thickness(metrics))
self.strikethrough_thickness = units_to_double(
pango.pango_font_metrics_get_strikethrough_thickness(metrics))
else:
self.ascent = None
self.underline_position = None
self.strikethrough_position = None
features = font_features(
style['font_kerning'], style['font_variant_ligatures'],
style['font_variant_position'], style['font_variant_caps'],
style['font_variant_numeric'], style['font_variant_alternates'],
style['font_variant_east_asian'], style['font_feature_settings'])
if features and context:
features = ','.join(
f'{key} {value}' for key, value in features.items()).encode()
# In the meantime, keep a cache to avoid leaking too many of them.
attr = context.font_features.setdefault(
features, pango.pango_attr_font_features_new(features))
attr_list = pango.pango_attr_list_new()
pango.pango_attr_list_insert(attr_list, attr)
pango.pango_layout_set_attributes(self.layout, attr_list)
def get_first_line(self):
first_line = pango.pango_layout_get_line_readonly(self.layout, 0)
second_line = pango.pango_layout_get_line_readonly(self.layout, 1)
index = None if second_line == ffi.NULL else second_line.start_index
self.first_line_direction = first_line.resolved_dir
return first_line, index
def set_text(self, text, justify=False):
index = text.find('\n')
if index != -1:
# Keep only the first line plus one character, we don't need more
text = text[:index+2]
self.text = text
text, bytestring = unicode_to_char_p(text)
pango.pango_layout_set_text(self.layout, text, -1)
word_spacing = self.style['word_spacing']
if justify:
# Justification is needed when drawing text but is useless during
# layout, when it can be ignored.
word_spacing += self.justification_spacing
letter_spacing = self.style['letter_spacing']
if letter_spacing == 'normal':
letter_spacing = 0
word_breaking = (
self.style['overflow_wrap'] in ('anywhere', 'break-word'))
if self.text and (word_spacing or letter_spacing or word_breaking):
attr_list = pango.pango_layout_get_attributes(self.layout)
if attr_list == ffi.NULL:
attr_list = ffi.gc(
pango.pango_attr_list_new(),
pango.pango_attr_list_unref)
def add_attr(start, end, spacing):
attr = pango.pango_attr_letter_spacing_new(spacing)
attr.start_index, attr.end_index = start, end
pango.pango_attr_list_change(attr_list, attr)
if letter_spacing:
letter_spacing = units_from_double(letter_spacing)
add_attr(0, len(bytestring), letter_spacing)
if word_spacing:
if bytestring == b' ':
# We need more than one space to set word spacing
self.text = ' \u200b' # Space + zero-width space
text, bytestring = unicode_to_char_p(self.text)
pango.pango_layout_set_text(self.layout, text, -1)
space_spacing = (
units_from_double(word_spacing) + letter_spacing)
position = bytestring.find(b' ')
# Pango gives only half of word-spacing on boundaries
boundary_positions = (0, len(bytestring) - 1)
while position != -1:
factor = 1 + (position in boundary_positions)
add_attr(position, position + 1, factor * space_spacing)
position = bytestring.find(b' ', position + 1)
if word_breaking:
attr = pango.pango_attr_insert_hyphens_new(False)
attr.start_index, attr.end_index = 0, len(bytestring)
pango.pango_attr_list_change(attr_list, attr)
pango.pango_layout_set_attributes(self.layout, attr_list)
# Tabs width
if b'\t' in bytestring:
self.set_tabs()
def set_tabs(self):
if isinstance(self.style['tab_size'], int):
layout = Layout(
self.context, self.style, self.justification_spacing)
layout.set_text(' ' * self.style['tab_size'])
line, _ = layout.get_first_line()
width, _ = line_size(line, self.style)
width = int(round(width))
else:
width = int(self.style['tab_size'].value)
# 0 is not handled correctly by Pango
array = ffi.gc(
pango.pango_tab_array_new_with_positions(
1, True, pango.PANGO_TAB_LEFT, width or 1),
pango.pango_tab_array_free)
pango.pango_layout_set_tabs(self.layout, array)
def deactivate(self):
del self.layout, self.language, self.style
def reactivate(self, style):
self.setup(self.context, style)
self.set_text(self.text, justify=True)
def create_layout(text, style, context, max_width, justification_spacing):
"""Return an opaque Pango layout with default Pango line-breaks."""
layout = Layout(context, style, justification_spacing, max_width)
# Make sure that max_width * Pango.SCALE == max_width * 1024 fits in a
# signed integer. Treat bigger values same as None: unconstrained width.
text_wrap = style['white_space'] in ('normal', 'pre-wrap', 'pre-line')
if max_width is not None and text_wrap and max_width < 2 ** 21:
pango.pango_layout_set_width(
layout.layout, units_from_double(max(0, max_width)))
layout.set_text(text)
return layout
def split_first_line(text, style, context, max_width, justification_spacing,
is_line_start=True, minimum=False):
"""Fit as much as possible in the available width for one line of text.
Return ``(layout, length, resume_index, width, height, baseline)``.
``layout``: a pango Layout with the first line
``length``: length in UTF-8 bytes of the first line
``resume_index``: The number of UTF-8 bytes to skip for the next line.
May be ``None`` if the whole text fits in one line.
This may be greater than ``length`` in case of preserved
newline characters.
``width``: width in pixels of the first line
``height``: height in pixels of the first line
``baseline``: baseline in pixels of the first line
"""
# See https://www.w3.org/TR/css-text-3/#white-space-property
text_wrap = style['white_space'] in ('normal', 'pre-wrap', 'pre-line')
space_collapse = style['white_space'] in ('normal', 'nowrap', 'pre-line')
original_max_width = max_width
if not text_wrap:
max_width = None
# Step #1: Get a draft layout with the first line
if max_width is not None and max_width != inf and style['font_size']:
short_text = text
if max_width == 0:
# Trying to find minimum size, let's naively split on spaces and
# keep one word + one letter
space_index = text.find(' ')
if space_index != -1:
short_text = text[:space_index+2] # index + space + one letter
else:
short_text = text[:int(max_width / style['font_size'] * 2.5)]
# Try to use a small amount of text instead of the whole text
layout = create_layout(
short_text, style, context, max_width, justification_spacing)
first_line, resume_index = layout.get_first_line()
if resume_index is None and short_text != text:
# The small amount of text fits in one line, give up and use
# the whole text
layout.set_text(text)
first_line, resume_index = layout.get_first_line()
else:
layout = create_layout(
text, style, context, original_max_width, justification_spacing)
first_line, resume_index = layout.get_first_line()
# Step #2: Don't split lines when it's not needed
if max_width is None:
# The first line can take all the place needed
return first_line_metrics(
first_line, text, layout, resume_index, space_collapse, style)
first_line_width, _ = line_size(first_line, style)
if resume_index is None and first_line_width <= max_width:
# The first line fits in the available width
return first_line_metrics(
first_line, text, layout, resume_index, space_collapse, style)
# Step #3: Try to put the first word of the second line on the first line
# https://mail.gnome.org/archives/gtk-i18n-list/2013-September/msg00006
# is a good thread related to this problem.
first_line_text = text.encode()[:resume_index].decode()
first_line_fits = (
first_line_width <= max_width or
' ' in first_line_text.strip() or
can_break_text(first_line_text.strip(), style['lang']))
if first_line_fits:
# The first line fits but may have been cut too early by Pango
second_line_text = text.encode()[resume_index:].decode()
else:
# The line can't be split earlier, try to hyphenate the first word.
first_line_text = ''
second_line_text = text
next_word = second_line_text.split(' ', 1)[0]
if next_word:
if space_collapse:
# next_word might fit without a space afterwards
# only try when space collapsing is allowed
new_first_line_text = first_line_text + next_word
layout.set_text(new_first_line_text)
first_line, resume_index = layout.get_first_line()
if resume_index is None:
if first_line_text:
# The next word fits in the first line, keep the layout
resume_index = len(new_first_line_text.encode()) + 1
return first_line_metrics(
first_line, text, layout, resume_index, space_collapse,
style)
else:
# Second line is None
resume_index = first_line.length + 1
if resume_index >= len(text.encode()):
resume_index = None
elif first_line_text:
# We found something on the first line but we did not find a word on
# the next line, no need to hyphenate, we can keep the current layout
return first_line_metrics(
first_line, text, layout, resume_index, space_collapse, style)
# Step #4: Try to hyphenate
hyphens = style['hyphens']
lang = style['lang'] and pyphen.language_fallback(style['lang'])
total, left, right = style['hyphenate_limit_chars']
hyphenated = False
soft_hyphen = '\xad'
auto_hyphenation = manual_hyphenation = False
if hyphens != 'none':
manual_hyphenation = soft_hyphen in first_line_text + next_word
if hyphens == 'auto' and lang:
next_word_boundaries = get_next_word_boundaries(second_line_text, lang)
if next_word_boundaries:
# We have a word to hyphenate
start_word, stop_word = next_word_boundaries
next_word = second_line_text[start_word:stop_word]
if stop_word - start_word >= total:
# This word is long enough
first_line_width, _ = line_size(first_line, style)
space = max_width - first_line_width
if style['hyphenate_limit_zone'].unit == '%':
limit_zone = (
max_width * style['hyphenate_limit_zone'].value / 100)
else:
limit_zone = style['hyphenate_limit_zone'].value
if space > limit_zone or space < 0:
# Available space is worth the try, or the line is even too
# long to fit: try to hyphenate
auto_hyphenation = True
# Automatic hyphenation opportunities within a word must be ignored if the
# word contains a conditional hyphen, in favor of the conditional
# hyphen(s).
# See https://drafts.csswg.org/css-text-3/#valdef-hyphens-auto
if manual_hyphenation:
# Manual hyphenation: check that the line ends with a soft
# hyphen and add the missing hyphen
if first_line_text.endswith(soft_hyphen):
# The first line has been split on a soft hyphen
if ' ' in first_line_text:
first_line_text, next_word = first_line_text.rsplit(' ', 1)
next_word = f' {next_word}'
layout.set_text(first_line_text)
first_line, _ = layout.get_first_line()
resume_index = len((f'{first_line_text} ').encode())
else:
first_line_text, next_word = '', first_line_text
soft_hyphen_indexes = [
match.start() for match in re.finditer(soft_hyphen, next_word)]
soft_hyphen_indexes.reverse()
dictionary_iterations = [next_word[:i+1] for i in soft_hyphen_indexes]
start_word = 0
elif auto_hyphenation:
dictionary_key = (lang, left, right, total)
dictionary = context.dictionaries.get(dictionary_key)
if dictionary is None:
dictionary = pyphen.Pyphen(lang=lang, left=left, right=right)
context.dictionaries[dictionary_key] = dictionary
dictionary_iterations = [
start for start, end in dictionary.iterate(next_word)]
else:
dictionary_iterations = []
if dictionary_iterations:
for first_word_part in dictionary_iterations:
new_first_line_text = (
first_line_text +
second_line_text[:start_word] +
first_word_part)
hyphenated_first_line_text = (
new_first_line_text + style['hyphenate_character'])
new_layout = create_layout(
hyphenated_first_line_text, style, context, max_width,
justification_spacing)
new_first_line, index = new_layout.get_first_line()
new_first_line_width, _ = line_size(new_first_line, style)
new_space = max_width - new_first_line_width
hyphenated = index is None and (
new_space >= 0 or first_word_part == dictionary_iterations[-1])
if hyphenated:
layout = new_layout
first_line = new_first_line
resume_index = len(new_first_line_text.encode())
break
if not hyphenated and not first_line_text:
# Recreate the layout with no max_width to be sure that
# we don't break before or inside the hyphenate character
hyphenated = True
layout.set_text(hyphenated_first_line_text)
pango.pango_layout_set_width(layout.layout, -1)
first_line, _ = layout.get_first_line()
resume_index = len(new_first_line_text.encode())
if text[len(first_line_text)] == soft_hyphen:
resume_index += len(soft_hyphen.encode())
if not hyphenated and first_line_text.endswith(soft_hyphen):
# Recreate the layout with no max_width to be sure that
# we don't break inside the hyphenate-character string
hyphenated = True
hyphenated_first_line_text = (
first_line_text + style['hyphenate_character'])
layout.set_text(hyphenated_first_line_text)
pango.pango_layout_set_width(layout.layout, -1)
first_line, _ = layout.get_first_line()
resume_index = len(first_line_text.encode())
# Step 5: Try to break word if it's too long for the line
overflow_wrap = style['overflow_wrap']
first_line_width, _ = line_size(first_line, style)
space = max_width - first_line_width
# If we can break words and the first line is too long
can_break = (
style['word_break'] == 'break-all' or (
is_line_start and (
overflow_wrap == 'anywhere' or
(overflow_wrap == 'break-word' and not minimum))))
if space < 0 and can_break:
# Is it really OK to remove hyphenation for word-break ?
hyphenated = False
# TODO: Modify code to preserve W3C condition:
# "Shaping characters are still shaped as if the word were not broken"
# The way new lines are processed in this function (one by one with no
# memory of the last) prevents shaping characters (arabic, for
# instance) from keeping their shape when wrapped on the next line with
# pango layout. Maybe insert Unicode shaping characters in text?
layout.set_text(text)
pango.pango_layout_set_width(
layout.layout, units_from_double(max_width))
pango.pango_layout_set_wrap(
layout.layout, PANGO_WRAP_MODE['WRAP_CHAR'])
first_line, index = layout.get_first_line()
resume_index = index or first_line.length
if resume_index >= len(text.encode()):
resume_index = None
return first_line_metrics(
first_line, text, layout, resume_index, space_collapse, style,
hyphenated, style['hyphenate_character'])
def get_log_attrs(text, lang):
if lang:
lang_p, lang = unicode_to_char_p(lang)
else:
lang = None
language = pango.pango_language_get_default()
if lang:
language = pango.pango_language_from_string(lang_p)
# TODO: this should be removed when bidi is supported
for char in ('\u202a', '\u202b', '\u202c', '\u202d', '\u202e'):
text = text.replace(char, '\u200b')
text_p, bytestring = unicode_to_char_p(text)
length = len(text) + 1
log_attrs = ffi.new('PangoLogAttr[]', length)
pango.pango_get_log_attrs(
text_p, len(bytestring), -1, language, log_attrs, length)
return bytestring, log_attrs
def can_break_text(text, lang):
if not text or len(text) < 2:
return None
bytestring, log_attrs = get_log_attrs(text, lang)
length = len(text) + 1
return any(attr.is_line_break for attr in log_attrs[1:length - 1])
def get_next_word_boundaries(text, lang):
if not text or len(text) < 2:
return None
bytestring, log_attrs = get_log_attrs(text, lang)
for i, attr in enumerate(log_attrs):
if attr.is_word_end:
word_end = i
break
if attr.is_word_boundary:
word_start = i
else:
return None
return word_start, word_end
def get_last_word_end(text, lang):
if not text or len(text) < 2:
return None
bytestring, log_attrs = get_log_attrs(text, lang)
for i, attr in enumerate(list(log_attrs)[::-1]):
if i and attr.is_word_end:
return len(text) - i