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# SVG Path specification parser.
# This is an adaptation from 'svg.path' by Lennart Regebro (@regebro),
# modified so that the parser takes a FontTools Pen object instead of
# returning a list of svg.path Path objects.
# The original code can be found at:
# https://github.com/regebro/svg.path/blob/4f9b6e3/src/svg/path/parser.py
# Copyright (c) 2013-2014 Lennart Regebro
# License: MIT
from .arc import EllipticalArc
import re
COMMANDS = set("MmZzLlHhVvCcSsQqTtAa")
ARC_COMMANDS = set("Aa")
UPPERCASE = set("MZLHVCSQTA")
COMMAND_RE = re.compile("([MmZzLlHhVvCcSsQqTtAa])")
# https://www.w3.org/TR/css-syntax-3/#number-token-diagram
# but -6.e-5 will be tokenized as "-6" then "-5" and confuse parsing
FLOAT_RE = re.compile(
r"[-+]?" # optional sign
r"(?:"
r"(?:0|[1-9][0-9]*)(?:\.[0-9]+)?(?:[eE][-+]?[0-9]+)?" # int/float
r"|"
r"(?:\.[0-9]+(?:[eE][-+]?[0-9]+)?)" # float with leading dot (e.g. '.42')
r")"
)
BOOL_RE = re.compile("^[01]")
SEPARATOR_RE = re.compile(f"[, \t]")
def _tokenize_path(pathdef):
arc_cmd = None
for x in COMMAND_RE.split(pathdef):
if x in COMMANDS:
arc_cmd = x if x in ARC_COMMANDS else None
yield x
continue
if arc_cmd:
try:
yield from _tokenize_arc_arguments(x)
except ValueError as e:
raise ValueError(f"Invalid arc command: '{arc_cmd}{x}'") from e
else:
for token in FLOAT_RE.findall(x):
yield token
ARC_ARGUMENT_TYPES = (
("rx", FLOAT_RE),
("ry", FLOAT_RE),
("x-axis-rotation", FLOAT_RE),
("large-arc-flag", BOOL_RE),
("sweep-flag", BOOL_RE),
("x", FLOAT_RE),
("y", FLOAT_RE),
)
def _tokenize_arc_arguments(arcdef):
raw_args = [s for s in SEPARATOR_RE.split(arcdef) if s]
if not raw_args:
raise ValueError(f"Not enough arguments: '{arcdef}'")
raw_args.reverse()
i = 0
while raw_args:
arg = raw_args.pop()
name, pattern = ARC_ARGUMENT_TYPES[i]
match = pattern.search(arg)
if not match:
raise ValueError(f"Invalid argument for '{name}' parameter: {arg!r}")
j, k = match.span()
yield arg[j:k]
arg = arg[k:]
if arg:
raw_args.append(arg)
# wrap around every 7 consecutive arguments
if i == 6:
i = 0
else:
i += 1
if i != 0:
raise ValueError(f"Not enough arguments: '{arcdef}'")
def parse_path(pathdef, pen, current_pos=(0, 0), arc_class=EllipticalArc):
"""Parse SVG path definition (i.e. "d" attribute of <path> elements)
and call a 'pen' object's moveTo, lineTo, curveTo, qCurveTo and closePath
methods.
If 'current_pos' (2-float tuple) is provided, the initial moveTo will
be relative to that instead being absolute.
If the pen has an "arcTo" method, it is called with the original values
of the elliptical arc curve commands:
pen.arcTo(rx, ry, rotation, arc_large, arc_sweep, (x, y))
Otherwise, the arcs are approximated by series of cubic Bezier segments
("curveTo"), one every 90 degrees.
"""
# In the SVG specs, initial movetos are absolute, even if
# specified as 'm'. This is the default behavior here as well.
# But if you pass in a current_pos variable, the initial moveto
# will be relative to that current_pos. This is useful.
current_pos = complex(*current_pos)
elements = list(_tokenize_path(pathdef))
# Reverse for easy use of .pop()
elements.reverse()
start_pos = None
command = None
last_control = None
have_arcTo = hasattr(pen, "arcTo")
while elements:
if elements[-1] in COMMANDS:
# New command.
last_command = command # Used by S and T
command = elements.pop()
absolute = command in UPPERCASE
command = command.upper()
else:
# If this element starts with numbers, it is an implicit command
# and we don't change the command. Check that it's allowed:
if command is None:
raise ValueError(
"Unallowed implicit command in %s, position %s"
% (pathdef, len(pathdef.split()) - len(elements))
)
last_command = command # Used by S and T
if command == "M":
# Moveto command.
x = elements.pop()
y = elements.pop()
pos = float(x) + float(y) * 1j
if absolute:
current_pos = pos
else:
current_pos += pos
# M is not preceded by Z; it's an open subpath
if start_pos is not None:
pen.endPath()
pen.moveTo((current_pos.real, current_pos.imag))
# when M is called, reset start_pos
# This behavior of Z is defined in svg spec:
# http://www.w3.org/TR/SVG/paths.html#PathDataClosePathCommand
start_pos = current_pos
# Implicit moveto commands are treated as lineto commands.
# So we set command to lineto here, in case there are
# further implicit commands after this moveto.
command = "L"
elif command == "Z":
# Close path
if current_pos != start_pos:
pen.lineTo((start_pos.real, start_pos.imag))
pen.closePath()
current_pos = start_pos
start_pos = None
command = None # You can't have implicit commands after closing.
elif command == "L":
x = elements.pop()
y = elements.pop()
pos = float(x) + float(y) * 1j
if not absolute:
pos += current_pos
pen.lineTo((pos.real, pos.imag))
current_pos = pos
elif command == "H":
x = elements.pop()
pos = float(x) + current_pos.imag * 1j
if not absolute:
pos += current_pos.real
pen.lineTo((pos.real, pos.imag))
current_pos = pos
elif command == "V":
y = elements.pop()
pos = current_pos.real + float(y) * 1j
if not absolute:
pos += current_pos.imag * 1j
pen.lineTo((pos.real, pos.imag))
current_pos = pos
elif command == "C":
control1 = float(elements.pop()) + float(elements.pop()) * 1j
control2 = float(elements.pop()) + float(elements.pop()) * 1j
end = float(elements.pop()) + float(elements.pop()) * 1j
if not absolute:
control1 += current_pos
control2 += current_pos
end += current_pos
pen.curveTo(
(control1.real, control1.imag),
(control2.real, control2.imag),
(end.real, end.imag),
)
current_pos = end
last_control = control2
elif command == "S":
# Smooth curve. First control point is the "reflection" of
# the second control point in the previous path.
if last_command not in "CS":
# If there is no previous command or if the previous command
# was not an C, c, S or s, assume the first control point is
# coincident with the current point.
control1 = current_pos
else:
# The first control point is assumed to be the reflection of
# the second control point on the previous command relative
# to the current point.
control1 = current_pos + current_pos - last_control
control2 = float(elements.pop()) + float(elements.pop()) * 1j
end = float(elements.pop()) + float(elements.pop()) * 1j
if not absolute:
control2 += current_pos
end += current_pos
pen.curveTo(
(control1.real, control1.imag),
(control2.real, control2.imag),
(end.real, end.imag),
)
current_pos = end
last_control = control2
elif command == "Q":
control = float(elements.pop()) + float(elements.pop()) * 1j
end = float(elements.pop()) + float(elements.pop()) * 1j
if not absolute:
control += current_pos
end += current_pos
pen.qCurveTo((control.real, control.imag), (end.real, end.imag))
current_pos = end
last_control = control
elif command == "T":
# Smooth curve. Control point is the "reflection" of
# the second control point in the previous path.
if last_command not in "QT":
# If there is no previous command or if the previous command
# was not an Q, q, T or t, assume the first control point is
# coincident with the current point.
control = current_pos
else:
# The control point is assumed to be the reflection of
# the control point on the previous command relative
# to the current point.
control = current_pos + current_pos - last_control
end = float(elements.pop()) + float(elements.pop()) * 1j
if not absolute:
end += current_pos
pen.qCurveTo((control.real, control.imag), (end.real, end.imag))
current_pos = end
last_control = control
elif command == "A":
rx = abs(float(elements.pop()))
ry = abs(float(elements.pop()))
rotation = float(elements.pop())
arc_large = bool(int(elements.pop()))
arc_sweep = bool(int(elements.pop()))
end = float(elements.pop()) + float(elements.pop()) * 1j
if not absolute:
end += current_pos
# if the pen supports arcs, pass the values unchanged, otherwise
# approximate the arc with a series of cubic bezier curves
if have_arcTo:
pen.arcTo(
rx,
ry,
rotation,
arc_large,
arc_sweep,
(end.real, end.imag),
)
else:
arc = arc_class(
current_pos, rx, ry, rotation, arc_large, arc_sweep, end
)
arc.draw(pen)
current_pos = end
# no final Z command, it's an open path
if start_pos is not None:
pen.endPath()
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