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