Lib/fontTools/svgLib/path/parser.py

# 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 __future__ import (
    print_function, division, absolute_import, unicode_literals)
from fontTools.misc.py23 import *
import re

COMMANDS = set('MmZzLlHhVvCcSsQqTtAa')
UPPERCASE = set('MZLHVCSQTA')

COMMAND_RE = re.compile("([MmZzLlHhVvCcSsQqTtAa])")
FLOAT_RE = re.compile("[-+]?[0-9]*\.?[0-9]+(?:[eE][-+]?[0-9]+)?")


def _tokenize_path(pathdef):
    for x in COMMAND_RE.split(pathdef):
        if x in COMMANDS:
            yield x
        for token in FLOAT_RE.findall(x):
            yield token


def parse_path(pathdef, pen, current_pos=(0, 0)):
    """ 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.

    Arc segments (commands "A" or "a") are not currently supported, and raise
    NotImplementedError.
    """
    # 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

    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':
            raise NotImplementedError('arcs are not supported')

    # no final Z command, it's an open path
    if start_pos is not None:
        pen.endPath()