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https://github.com/kovidgoyal/calibre.git
synced 2025-07-09 03:04:10 -04:00
Implement update for sfnt metrics tables
Also fix reading of bearings for fonts that have fewer advances than glyphs
This commit is contained in:
Kovid Goyal
parent
01666d4fff
commit
4cbf6ab7fd
@ -6,6 +6,7 @@ __license__ = 'GPL v3'
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__copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
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__docformat__ = 'restructuredtext en'
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import array
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from struct import unpack_from, pack, calcsize
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from calibre.utils.fonts.sfnt import UnknownTable, DateTimeProperty, FixedProperty
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@ -55,93 +56,132 @@ class HeadTable(UnknownTable):
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self.raw = pack(self._fmt, *vals)
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def read_metrics(raw, num_of_metrics, num_of_glyphs, table_name):
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rawsz = 4 * num_of_metrics
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if len(raw) < rawsz:
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raise UnsupportedFont(f'The {table_name} table has insufficient data')
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long_hor_metric = raw[:rawsz]
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a = read_array(long_hor_metric)
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advances = a[0::2]
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a = read_array(long_hor_metric, 'h')
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bearings = a[1::2]
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if num_of_glyphs > num_of_metrics:
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extra = num_of_glyphs - num_of_metrics
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raw = raw[rawsz:]
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rawsz = 2 * extra
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if len(raw) < rawsz:
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raise UnsupportedFont(f'The {table_name} table has insufficient data for trailing bearings')
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bearings += read_array(raw, 'h')
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return advances, bearings
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def update_metrics_table(metrics_map, mtx_table):
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recs, aw, b = [], array.array('H'), array.array('h')
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for glyph_id in sorted(metrics_map):
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adv, bearing = metrics_map[glyph_id]
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aw.append(adv)
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b.append(bearing)
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recs.append(pack('>Hh', adv, bearing))
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mtx_table.raw = b''.join(recs)
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return aw, b
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class HorizontalHeader(UnknownTable):
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version_number = FixedProperty('_version_number')
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field_types = (
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'_version_number' , 'l',
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'ascender', 'h',
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'descender', 'h',
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'line_gap', 'h',
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'advance_width_max', 'H',
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'min_left_side_bearing', 'h',
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'min_right_side_bearing', 'h',
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'x_max_extent', 'h',
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'caret_slope_rise', 'h',
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'caret_slop_run', 'h',
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'caret_offset', 'h',
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'r1', 'h',
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'r2', 'h',
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'r3', 'h',
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'r4', 'h',
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'metric_data_format', 'h',
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'number_of_h_metrics', 'H',
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)
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def read_data(self, hmtx):
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if hasattr(self, 'ascender'):
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return
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field_types = (
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'_version_number' , 'l',
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'ascender', 'h',
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'descender', 'h',
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'line_gap', 'h',
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'advance_width_max', 'H',
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'min_left_side_bearing', 'h',
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'min_right_side_bearing', 'h',
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'x_max_extent', 'h',
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'caret_slope_rise', 'h',
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'caret_slop_run', 'h',
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'caret_offset', 'h',
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'r1', 'h',
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'r2', 'h',
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'r3', 'h',
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'r4', 'h',
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'metric_data_format', 'h',
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'number_of_h_metrics', 'H',
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)
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self._fmt = ('>%s'%(''.join(field_types[1::2]))).encode('ascii')
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self._fields = field_types[0::2]
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def read_data(self, hmtx, num_glyphs):
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self._fmt = ('>%s'%(''.join(self.field_types[1::2]))).encode('ascii')
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self._fields = self.field_types[0::2]
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for f, val in zip(self._fields, unpack_from(self._fmt, self.raw)):
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setattr(self, f, val)
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raw = hmtx.raw
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num = self.number_of_h_metrics
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if len(raw) < 4*num:
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raise UnsupportedFont('The hmtx table has insufficient data')
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long_hor_metric = raw[:4*num]
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a = read_array(long_hor_metric)
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self.advance_widths = a[0::2]
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a = read_array(long_hor_metric, 'h')
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self.left_side_bearings = a[1::2]
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self.advance_widths, self.left_side_bearings = read_metrics(hmtx.raw, self.number_of_h_metrics, num_glyphs, 'hmtx')
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def metrics_for(self, glyph_id):
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lsb = self.left_side_bearings[glyph_id]
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if glyph_id >= len(self.advance_widths):
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glyph_id = -1
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return self.advance_widths[glyph_id], lsb
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def update(self, metrics_map, mtx_table):
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aw, b = update_metrics_table(metrics_map, mtx_table)
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self.advance_widths = aw
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self.left_side_bearings = b
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self.number_of_h_metrics = len(metrics_map)
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self.advance_width_max = max(aw or (0,))
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self.min_left_side_bearing = min(b or (0,))
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data = (getattr(self, x) for x in self._fields)
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self.raw = pack('>' + ''.join(self.field_types[1::2]), *data)
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class VerticalHeader(UnknownTable):
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version_number = FixedProperty('_version_number')
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field_types = (
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'_version_number' , 'l',
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'ascender', 'h',
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'descender', 'h',
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'line_gap', 'h',
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'advance_height_max', 'H',
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'min_top_side_bearing', 'h',
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'min_bottom_side_bearing', 'h',
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'y_max_extent', 'h',
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'caret_slope_rise', 'h',
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'caret_slop_run', 'h',
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'caret_offset', 'h',
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'r1', 'h',
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'r2', 'h',
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'r3', 'h',
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'r4', 'h',
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'metric_data_format', 'h',
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'number_of_v_metrics', 'H',
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)
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def read_data(self, vmtx):
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if hasattr(self, 'ascender'):
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return
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field_types = (
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'_version_number' , 'l',
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'ascender', 'h',
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'descender', 'h',
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'line_gap', 'h',
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'advance_height_max', 'H',
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'min_top_side_bearing', 'h',
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'min_bottom_side_bearing', 'h',
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'y_max_extent', 'h',
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'caret_slope_rise', 'h',
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'caret_slop_run', 'h',
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'caret_offset', 'h',
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'r1', 'h',
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'r2', 'h',
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'r3', 'h',
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'r4', 'h',
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'metric_data_format', 'h',
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'number_of_v_metrics', 'H',
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)
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self._fmt = ('>%s'%(''.join(field_types[1::2]))).encode('ascii')
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self._fields = field_types[0::2]
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def read_data(self, vmtx, num_glyphs):
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self._fmt = ('>%s'%(''.join(self.field_types[1::2]))).encode('ascii')
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self._fields = self.field_types[0::2]
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for f, val in zip(self._fields, unpack_from(self._fmt, self.raw)):
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setattr(self, f, val)
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raw = vmtx.raw
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num = self.number_of_v_metrics
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if len(raw) < 4*num:
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raise UnsupportedFont('The vmtx table has insufficient data')
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long_hor_metric = raw[:4*num]
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long_hor_metric = raw[:4*num]
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a = read_array(long_hor_metric)
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self.advance_heights = a[0::2]
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a = read_array(long_hor_metric, 'h')
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self.top_side_bearings = a[1::2]
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self.advance_heights, self.top_side_bearings = read_metrics(vmtx.raw, self.number_of_v_metrics, num_glyphs, 'vmtx')
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def metrics_for(self, glyph_id):
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tsb = self.top_side_bearings[glyph_id]
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if glyph_id >= len(self.advance_heights):
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glyph_id = -1
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return self.advance_heights[glyph_id], tsb
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def update(self, metrics_map, mtx_table):
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aw, b = update_metrics_table(metrics_map, mtx_table)
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self.advance_heights = aw
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self.top_side_bearings = b
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self.number_of_v_metrics = len(metrics_map)
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self.advance_height_max = max(aw or (0,))
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self.min_top_side_bearing = min(b or (0,))
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data = (getattr(self, x) for x in self._fields)
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self.raw = pack('>' + ''.join(self.field_types[1::2]), *data)
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class OS2Table(UnknownTable):
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@ -21,14 +21,14 @@ class FontMetrics(object):
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def __init__(self, sfnt):
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for table in (b'head', b'hhea', b'hmtx', b'cmap', b'OS/2', b'post',
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b'name'):
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b'name', b'maxp'):
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if table not in sfnt:
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raise UnsupportedFont('This font has no %s table'%table)
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self.sfnt = sfnt
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self.head = self.sfnt[b'head']
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hhea = self.sfnt[b'hhea']
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hhea.read_data(self.sfnt[b'hmtx'])
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hhea.read_data(self.sfnt[b'hmtx'], self.sfnt[b'maxp'].num_glyphs)
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self.ascent = hhea.ascender
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self.descent = hhea.descender
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self.bbox = (self.head.x_min, self.head.y_min, self.head.x_max,
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