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