textpath.py

from collections import OrderedDict
import logging
import urllib.parse

import numpy as np

from matplotlib import _text_helpers, dviread
from matplotlib.font_manager import (
    FontProperties, get_font, fontManager as _fontManager
)
from matplotlib.ft2font import LOAD_NO_HINTING, LOAD_TARGET_LIGHT
from matplotlib.mathtext import MathTextParser
from matplotlib.path import Path
from matplotlib.texmanager import TexManager
from matplotlib.transforms import Affine2D

_log = logging.getLogger(__name__)


class TextToPath:
    """A class that converts strings to paths."""

    FONT_SCALE = 100.
    DPI = 72

    def __init__(self):
        self.mathtext_parser = MathTextParser('path')
        self._texmanager = None

    def _get_font(self, prop):
        """
        Find the `FT2Font` matching font properties *prop*, with its size set.
        """
        filenames = _fontManager._find_fonts_by_props(prop)
        font = get_font(filenames)
        font.set_size(self.FONT_SCALE, self.DPI)
        return font

    def _get_hinting_flag(self):
        return LOAD_NO_HINTING

    def _get_char_id(self, font, ccode):
        """
        Return a unique id for the given font and character-code set.
        """
        return urllib.parse.quote(f"{font.postscript_name}-{ccode:x}")

    def get_text_width_height_descent(self, s, prop, ismath):
        fontsize = prop.get_size_in_points()

        if ismath == "TeX":
            return TexManager().get_text_width_height_descent(s, fontsize)

        scale = fontsize / self.FONT_SCALE

        if ismath:
            prop = prop.copy()
            prop.set_size(self.FONT_SCALE)
            width, height, descent, *_ = \
                self.mathtext_parser.parse(s, 72, prop)
            return width * scale, height * scale, descent * scale

        font = self._get_font(prop)
        font.set_text(s, 0.0, flags=LOAD_NO_HINTING)
        w, h = font.get_width_height()
        w /= 64.0  # convert from subpixels
        h /= 64.0
        d = font.get_descent()
        d /= 64.0
        return w * scale, h * scale, d * scale

    def get_text_path(self, prop, s, ismath=False):
        """
        Convert text *s* to path (a tuple of vertices and codes for
        matplotlib.path.Path).

        Parameters
        ----------
        prop : `~matplotlib.font_manager.FontProperties`
            The font properties for the text.
        s : str
            The text to be converted.
        ismath : {False, True, "TeX"}
            If True, use mathtext parser.  If "TeX", use tex for rendering.

        Returns
        -------
        verts : list
            A list of arrays containing the (x, y) coordinates of the vertices.
        codes : list
            A list of path codes.

        Examples
        --------
        Create a list of vertices and codes from a text, and create a `.Path`
        from those::

            from matplotlib.path import Path
            from matplotlib.text import TextToPath
            from matplotlib.font_manager import FontProperties

            fp = FontProperties(family="Comic Neue", style="italic")
            verts, codes = TextToPath().get_text_path(fp, "ABC")
            path = Path(verts, codes, closed=False)

        Also see `TextPath` for a more direct way to create a path from a text.
        """
        if ismath == "TeX":
            glyph_info, glyph_map, rects = self.get_glyphs_tex(prop, s)
        elif not ismath:
            font = self._get_font(prop)
            glyph_info, glyph_map, rects = self.get_glyphs_with_font(font, s)
        else:
            glyph_info, glyph_map, rects = self.get_glyphs_mathtext(prop, s)

        verts, codes = [], []
        for glyph_id, xposition, yposition, scale in glyph_info:
            verts1, codes1 = glyph_map[glyph_id]
            verts.extend(verts1 * scale + [xposition, yposition])
            codes.extend(codes1)
        for verts1, codes1 in rects:
            verts.extend(verts1)
            codes.extend(codes1)

        # Make sure an empty string or one with nothing to print
        # (e.g. only spaces & newlines) will be valid/empty path
        if not verts:
            verts = np.empty((0, 2))

        return verts, codes

    def get_glyphs_with_font(self, font, s, glyph_map=None,
                             return_new_glyphs_only=False):
        """
        Convert string *s* to vertices and codes using the provided ttf font.
        """

        if glyph_map is None:
            glyph_map = OrderedDict()

        if return_new_glyphs_only:
            glyph_map_new = OrderedDict()
        else:
            glyph_map_new = glyph_map

        xpositions = []
        glyph_ids = []
        for item in _text_helpers.layout(s, font):
            char_id = self._get_char_id(item.ft_object, ord(item.char))
            glyph_ids.append(char_id)
            xpositions.append(item.x)
            if char_id not in glyph_map:
                glyph_map_new[char_id] = item.ft_object.get_path()

        ypositions = [0] * len(xpositions)
        sizes = [1.] * len(xpositions)

        rects = []

        return (list(zip(glyph_ids, xpositions, ypositions, sizes)),
                glyph_map_new, rects)

    def get_glyphs_mathtext(self, prop, s, glyph_map=None,
                            return_new_glyphs_only=False):
        """
        Parse mathtext string *s* and convert it to a (vertices, codes) pair.
        """

        prop = prop.copy()
        prop.set_size(self.FONT_SCALE)

        width, height, descent, glyphs, rects = self.mathtext_parser.parse(
            s, self.DPI, prop)

        if not glyph_map:
            glyph_map = OrderedDict()

        if return_new_glyphs_only:
            glyph_map_new = OrderedDict()
        else:
            glyph_map_new = glyph_map

        xpositions = []
        ypositions = []
        glyph_ids = []
        sizes = []

        for font, fontsize, ccode, ox, oy in glyphs:
            char_id = self._get_char_id(font, ccode)
            if char_id not in glyph_map:
                font.clear()
                font.set_size(self.FONT_SCALE, self.DPI)
                font.load_char(ccode, flags=LOAD_NO_HINTING)
                glyph_map_new[char_id] = font.get_path()

            xpositions.append(ox)
            ypositions.append(oy)
            glyph_ids.append(char_id)
            size = fontsize / self.FONT_SCALE
            sizes.append(size)

        myrects = []
        for ox, oy, w, h in rects:
            vert1 = [(ox, oy), (ox, oy + h), (ox + w, oy + h),
                     (ox + w, oy), (ox, oy), (0, 0)]
            code1 = [Path.MOVETO,
                     Path.LINETO, Path.LINETO, Path.LINETO, Path.LINETO,
                     Path.CLOSEPOLY]
            myrects.append((vert1, code1))

        return (list(zip(glyph_ids, xpositions, ypositions, sizes)),
                glyph_map_new, myrects)

    def get_glyphs_tex(self, prop, s, glyph_map=None,
                       return_new_glyphs_only=False):
        """Convert the string *s* to vertices and codes using usetex mode."""
        # Mostly borrowed from pdf backend.

        dvifile = TexManager().make_dvi(s, self.FONT_SCALE)
        with dviread.Dvi(dvifile, self.DPI) as dvi:
            page, = dvi

        if glyph_map is None:
            glyph_map = OrderedDict()

        if return_new_glyphs_only:
            glyph_map_new = OrderedDict()
        else:
            glyph_map_new = glyph_map

        glyph_ids, xpositions, ypositions, sizes = [], [], [], []

        # Gather font information and do some setup for combining
        # characters into strings.
        for text in page.text:
            font = get_font(text.font_path)
            char_id = self._get_char_id(font, text.glyph)
            if char_id not in glyph_map:
                font.clear()
                font.set_size(self.FONT_SCALE, self.DPI)
                glyph_name_or_index = text.glyph_name_or_index
                if isinstance(glyph_name_or_index, str):
                    index = font.get_name_index(glyph_name_or_index)
                    font.load_glyph(index, flags=LOAD_TARGET_LIGHT)
                elif isinstance(glyph_name_or_index, int):
                    self._select_native_charmap(font)
                    font.load_char(
                        glyph_name_or_index, flags=LOAD_TARGET_LIGHT)
                else:  # Should not occur.
                    raise TypeError(f"Glyph spec of unexpected type: "
                                    f"{glyph_name_or_index!r}")
                glyph_map_new[char_id] = font.get_path()

            glyph_ids.append(char_id)
            xpositions.append(text.x)
            ypositions.append(text.y)
            sizes.append(text.font_size / self.FONT_SCALE)

        myrects = []

        for ox, oy, h, w in page.boxes:
            vert1 = [(ox, oy), (ox + w, oy), (ox + w, oy + h),
                     (ox, oy + h), (ox, oy), (0, 0)]
            code1 = [Path.MOVETO,
                     Path.LINETO, Path.LINETO, Path.LINETO, Path.LINETO,
                     Path.CLOSEPOLY]
            myrects.append((vert1, code1))

        return (list(zip(glyph_ids, xpositions, ypositions, sizes)),
                glyph_map_new, myrects)

    @staticmethod
    def _select_native_charmap(font):
        # Select the native charmap. (we can't directly identify it but it's
        # typically an Adobe charmap).
        for charmap_code in [
                1094992451,  # ADOBE_CUSTOM.
                1094995778,  # ADOBE_STANDARD.
        ]:
            try:
                font.select_charmap(charmap_code)
            except (ValueError, RuntimeError):
                pass
            else:
                break
        else:
            _log.warning("No supported encoding in font (%s).", font.fname)


text_to_path = TextToPath()


class TextPath(Path):
    """
    Create a path from the text.
    """

    def __init__(self, xy, s, size=None, prop=None,
                 _interpolation_steps=1, usetex=False):
        r"""
        Create a path from the text. Note that it simply is a path,
        not an artist. You need to use the `.PathPatch` (or other artists)
        to draw this path onto the canvas.

        Parameters
        ----------
        xy : tuple or array of two float values
            Position of the text. For no offset, use ``xy=(0, 0)``.

        s : str
            The text to convert to a path.

        size : float, optional
            Font size in points. Defaults to the size specified via the font
            properties *prop*.

        prop : `~matplotlib.font_manager.FontProperties`, optional
            Font property. If not provided, will use a default
            `.FontProperties` with parameters from the
            :ref:`rcParams<customizing-with-dynamic-rc-settings>`.

        _interpolation_steps : int, optional
            (Currently ignored)

        usetex : bool, default: False
            Whether to use tex rendering.

        Examples
        --------
        The following creates a path from the string "ABC" with Helvetica
        font face; and another path from the latex fraction 1/2::

            from matplotlib.text import TextPath
            from matplotlib.font_manager import FontProperties

            fp = FontProperties(family="Helvetica", style="italic")
            path1 = TextPath((12, 12), "ABC", size=12, prop=fp)
            path2 = TextPath((0, 0), r"$\frac{1}{2}$", size=12, usetex=True)

        Also see :doc:`/gallery/text_labels_and_annotations/demo_text_path`.
        """
        # Circular import.
        from matplotlib.text import Text

        prop = FontProperties._from_any(prop)
        if size is None:
            size = prop.get_size_in_points()

        self._xy = xy
        self.set_size(size)

        self._cached_vertices = None
        s, ismath = Text(usetex=usetex)._preprocess_math(s)
        super().__init__(
            *text_to_path.get_text_path(prop, s, ismath=ismath),
            _interpolation_steps=_interpolation_steps,
            readonly=True)
        self._should_simplify = False

    def set_size(self, size):
        """Set the text size."""
        self._size = size
        self._invalid = True

    def get_size(self):
        """Get the text size."""
        return self._size

    @property
    def vertices(self):
        """
        Return the cached path after updating it if necessary.
        """
        self._revalidate_path()
        return self._cached_vertices

    @property
    def codes(self):
        """
        Return the codes
        """
        return self._codes

    def _revalidate_path(self):
        """
        Update the path if necessary.

        The path for the text is initially create with the font size of
        `.FONT_SCALE`, and this path is rescaled to other size when necessary.
        """
        if self._invalid or self._cached_vertices is None:
            tr = (Affine2D()
                  .scale(self._size / text_to_path.FONT_SCALE)
                  .translate(*self._xy))
            self._cached_vertices = tr.transform(self._vertices)
            self._cached_vertices.flags.writeable = False
            self._invalid = False