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diff --git a/share/extensions/inkex/units.py b/share/extensions/inkex/units.py
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+# -*- coding: utf-8 -*-
+#
+# Copyright (c) Aaron Spike <aaron@ekips.org>
+# Aurélio A. Heckert <aurium(a)gmail.com>
+# Bulia Byak <buliabyak@users.sf.net>
+# Nicolas Dufour, nicoduf@yahoo.fr
+# Peter J. R. Moulder <pjrm@users.sourceforge.net>
+# Martin Owens <doctormo@gmail.com>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+"""
+Convert to and from various units and find the closest matching unit.
+"""
+
+import re
+
+# a dictionary of unit to user unit conversion factors
+CONVERSIONS = {
+ 'in': 96.0,
+ 'pt': 1.3333333333333333,
+ 'px': 1.0,
+ 'mm': 3.779527559055118,
+ 'cm': 37.79527559055118,
+ 'm': 3779.527559055118,
+ 'km': 3779527.559055118,
+ 'Q': 0.94488188976378,
+ 'pc': 16.0,
+ 'yd': 3456.0,
+ 'ft': 1152.0,
+ '': 1.0, # Default px
+}
+
+# allowed unit types, including percentages, relative units, and others
+# that are not suitable for direct conversion to a length.
+# Note that this is _not_ an exhaustive list of allowed unit types.
+UNITS = ['in', 'pt', 'px', 'mm', 'cm', 'm', 'km', 'Q', 'pc', 'yd', 'ft', '',\
+ '%', 'em', 'ex', 'ch', 'rem', 'vw', 'vh', 'vmin', 'vmax',\
+ 'deg', 'grad', 'rad', 'turn', 's', 'ms', 'Hz', 'kHz',\
+ 'dpi', 'dpcm', 'dppx']
+
+UNIT_MATCH = re.compile(r'({})'.format('|'.join(UNITS)))
+NUMBER_MATCH = re.compile(r'(([-+]?[0-9]+(\.[0-9]*)?|[-+]?\.[0-9]+)([eE][-+]?[0-9]+)?)')
+BOTH_MATCH = re.compile(r'^\s*{}\s*{}\s*$'.format(NUMBER_MATCH.pattern, UNIT_MATCH.pattern))
+
+
+def parse_unit(value, default_unit='px', default_value=None):
+ """
+ Takes a value such as 55.32px and returns (55.32, 'px')
+ Returns default (None) if no match can be found
+ """
+ ret = BOTH_MATCH.match(str(value))
+ if ret:
+ return float(ret.groups()[0]), ret.groups()[-1] or default_unit
+ return (default_value, default_unit) if default_value is not None else None
+
+
+def are_near_relative(point_a, point_b, eps=0.01):
+ """Return true if the points are near to eps"""
+ return (point_a - point_b <= point_a * eps) and (point_a - point_b >= -point_a * eps)
+
+
+def discover_unit(value, viewbox, default='px'):
+ """Attempt to detect the unit being used based on the viewbox"""
+ # Default 100px when width can't be parsed
+ (value, unit) = parse_unit(value, default_value=100.0)
+ if unit not in CONVERSIONS:
+ return default
+ this_factor = CONVERSIONS[unit] * value / viewbox
+
+ # try to find the svgunitfactor in the list of units known. If we don't find something, ...
+ for unit, unit_factor in CONVERSIONS.items():
+ if unit != '':
+ # allow 1% error in factor
+ if are_near_relative(this_factor, unit_factor, eps=0.01):
+ return unit
+ return default
+
+
+def convert_unit(value, to_unit):
+ """Returns userunits given a string representation of units in another system"""
+ value, from_unit = parse_unit(value, default_value=0.0)
+ if from_unit in CONVERSIONS and to_unit in CONVERSIONS:
+ return value * CONVERSIONS[from_unit] / CONVERSIONS.get(to_unit, CONVERSIONS['px'])
+ return 0.0
+
+
+def render_unit(value, unit):
+ """Checks and then renders a number with its unit"""
+ try:
+ if isinstance(value, str):
+ (value, unit) = parse_unit(value, default_unit=unit)
+ return "{:.6g}{:s}".format(value, unit)
+ except TypeError:
+ return ''