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tacaswell merged 1 commit into from
Sep 17, 2025
+123 −50
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pdf/ps: Track full character map in CharacterTracker #30566

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108 changes: 94 additions & 14 deletions lib/matplotlib/backends/_backend_pdf_ps.py
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@


if typing.TYPE_CHECKING:
from .ft2font import FT2Font, GlyphIndexType
from .ft2font import CharacterCodeType, FT2Font, GlyphIndexType
from fontTools.ttLib import TTFont


Expand Down Expand Up @@ -107,23 +107,103 @@ class CharacterTracker:
"""
Helper for font subsetting by the PDF and PS backends.

Maintains a mapping of font paths to the set of glyphs that are being used from that
font.
"""
Maintains a mapping of font paths to the set of characters and glyphs that are being
used from that font.

Attributes
----------
subset_size : int
The size at which characters are grouped into subsets.
used : dict[tuple[str, int], dict[CharacterCodeType, GlyphIndexType]]
A dictionary of font files to character maps.

The key is a font filename and subset within that font.

def __init__(self) -> None:
self.used: dict[str, set[GlyphIndexType]] = {}
The value is a dictionary mapping a character code to a glyph index. Note this
mapping is the inverse of FreeType, which maps glyph indices to character codes.

def track(self, font: FT2Font, s: str) -> None:
"""Record that string *s* is being typeset using font *font*."""
If *subset_size* is not set, then there will only be one subset per font
filename.
"""

def __init__(self, subset_size: int = 0):
"""
Parameters
----------
subset_size : int, optional
The maximum size that is supported for an embedded font. If provided, then
characters will be grouped into these sized subsets.
"""
self.used: dict[tuple[str, int], dict[CharacterCodeType, GlyphIndexType]] = {}
self.subset_size = subset_size

def track(self, font: FT2Font, s: str) -> list[tuple[int, CharacterCodeType]]:
"""
Record that string *s* is being typeset using font *font*.

Parameters
----------
font : FT2Font
A font that is being used for the provided string.
s : str
The string that should be marked as tracked by the provided font.

Returns
-------
list[tuple[int, CharacterCodeType]]
A list of subset and character code pairs corresponding to the input string.
If a *subset_size* is specified on this instance, then the character code
will correspond with the given subset (and not necessarily the string as a
whole). If *subset_size* is not specified, then the subset will always be 0
and the character codes will be returned from the string unchanged.
"""
font_glyphs = []
char_to_font = font._get_fontmap(s)
for _c, _f in char_to_font.items():
glyph_index = _f.get_char_index(ord(_c))
self.used.setdefault(_f.fname, set()).add(glyph_index)

def track_glyph(self, font: FT2Font, glyph_index: GlyphIndexType) -> None:
"""Record that glyph index *glyph_index* is being typeset using font *font*."""
self.used.setdefault(font.fname, set()).add(glyph_index)
charcode = ord(_c)
glyph_index = _f.get_char_index(charcode)
if self.subset_size != 0:
subset = charcode // self.subset_size
subset_charcode = charcode % self.subset_size
else:
subset = 0
subset_charcode = charcode
self.used.setdefault((_f.fname, subset), {})[subset_charcode] = glyph_index
font_glyphs.append((subset, subset_charcode))
return font_glyphs

def track_glyph(
self, font: FT2Font, charcode: CharacterCodeType,
glyph: GlyphIndexType) -> tuple[int, CharacterCodeType]:
"""
Record character code *charcode* at glyph index *glyph* as using font *font*.

Parameters
----------
font : FT2Font
A font that is being used for the provided string.
charcode : CharacterCodeType
The character code to record.
glyph : GlyphIndexType
The corresponding glyph index to record.

Returns
-------
subset : int
The subset in which the returned character code resides. If *subset_size*
was not specified on this instance, then this is always 0.
subset_charcode : CharacterCodeType
The character code within the above subset. If *subset_size* was not
specified on this instance, then this is just *charcode* unmodified.
"""
if self.subset_size != 0:
subset = charcode // self.subset_size
subset_charcode = charcode % self.subset_size
else:
subset = 0
subset_charcode = charcode
self.used.setdefault((font.fname, subset), {})[subset_charcode] = glyph
return (subset, subset_charcode)


class RendererPDFPSBase(RendererBase):
Expand Down
52 changes: 22 additions & 30 deletions lib/matplotlib/backends/backend_pdf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,6 @@
import sys
import time
import types
import typing
import warnings
import zlib

Expand All @@ -36,8 +35,7 @@
from matplotlib.figure import Figure
from matplotlib.font_manager import get_font, fontManager as _fontManager
from matplotlib._afm import AFM
from matplotlib.ft2font import (
FT2Font, FaceFlags, GlyphIndexType, Kerning, LoadFlags, StyleFlags)
from matplotlib.ft2font import FT2Font, FaceFlags, Kerning, LoadFlags, StyleFlags
from matplotlib.transforms import Affine2D, BboxBase
from matplotlib.path import Path
from matplotlib.dates import UTC
Expand Down Expand Up @@ -962,9 +960,9 @@ def writeFonts(self):
else:
# a normal TrueType font
_log.debug('Writing TrueType font.')
glyphs = self._character_tracker.used.get(filename)
if glyphs:
fonts[Fx] = self.embedTTF(filename, glyphs)
charmap = self._character_tracker.used.get((filename, 0))
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@tacaswell tacaswell Sep 16, 2025

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do we need to loop and add all the partitions?

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@tacaswell tacaswell Sep 16, 2025

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Ah, this looks like more prep work as I see we never set subset size.

if charmap:
fonts[Fx] = self.embedTTF(filename, charmap)
self.writeObject(self.fontObject, fonts)

def _write_afm_font(self, filename):
Expand Down Expand Up @@ -1006,8 +1004,9 @@ def _embedTeXFont(self, dvifont):

# Reduce the font to only the glyphs used in the document, get the encoding
# for that subset, and compute various properties based on the encoding.
chars = frozenset(self._character_tracker.used[dvifont.fname])
t1font = t1font.subset(chars, self._get_subset_prefix(chars))
charmap = self._character_tracker.used[(dvifont.fname, 0)]
chars = frozenset(charmap.keys())
t1font = t1font.subset(chars, self._get_subset_prefix(charmap.values()))
fontdict['BaseFont'] = Name(t1font.prop['FontName'])
# createType1Descriptor writes the font data as a side effect
fontdict['FontDescriptor'] = self.createType1Descriptor(t1font)
Expand Down Expand Up @@ -1138,7 +1137,7 @@ def _get_xobject_glyph_name(self, filename, glyph_name):
end
end"""

def embedTTF(self, filename, glyphs):
def embedTTF(self, filename, charmap):
"""Embed the TTF font from the named file into the document."""
font = get_font(filename)
fonttype = mpl.rcParams['pdf.fonttype']
Expand All @@ -1154,7 +1153,7 @@ def cvt(length, upe=font.units_per_EM, nearest=True):
else:
return math.ceil(value)

def embedTTFType3(font, glyphs, descriptor):
def embedTTFType3(font, charmap, descriptor):
"""The Type 3-specific part of embedding a Truetype font"""
widthsObject = self.reserveObject('font widths')
fontdescObject = self.reserveObject('font descriptor')
Expand Down Expand Up @@ -1201,10 +1200,8 @@ def get_char_width(charcode):
# that we need from this font.
differences = []
multi_byte_chars = set()
charmap = {gind: ccode for ccode, gind in font.get_charmap().items()}
for gind in glyphs:
for ccode, gind in charmap.items():
glyph_name = font.get_glyph_name(gind)
ccode = charmap.get(gind)
if ccode is not None and ccode <= 255:
differences.append((ccode, glyph_name))
else:
Expand All @@ -1219,7 +1216,7 @@ def get_char_width(charcode):
last_c = c

# Make the charprocs array.
rawcharprocs = _get_pdf_charprocs(filename, glyphs)
rawcharprocs = _get_pdf_charprocs(filename, charmap.values())
charprocs = {}
for charname in sorted(rawcharprocs):
stream = rawcharprocs[charname]
Expand Down Expand Up @@ -1256,7 +1253,7 @@ def get_char_width(charcode):

return fontdictObject

def embedTTFType42(font, glyphs, descriptor):
def embedTTFType42(font, charmap, descriptor):
"""The Type 42-specific part of embedding a Truetype font"""
fontdescObject = self.reserveObject('font descriptor')
cidFontDictObject = self.reserveObject('CID font dictionary')
Expand All @@ -1266,8 +1263,9 @@ def embedTTFType42(font, glyphs, descriptor):
wObject = self.reserveObject('Type 0 widths')
toUnicodeMapObject = self.reserveObject('ToUnicode map')

_log.debug("SUBSET %s characters: %s", filename, glyphs)
with _backend_pdf_ps.get_glyphs_subset(filename, glyphs) as subset:
_log.debug("SUBSET %s characters: %s", filename, charmap)
with _backend_pdf_ps.get_glyphs_subset(filename,
charmap.values()) as subset:
fontdata = _backend_pdf_ps.font_as_file(subset)
_log.debug(
"SUBSET %s %d -> %d", filename,
Expand Down Expand Up @@ -1315,11 +1313,9 @@ def embedTTFType42(font, glyphs, descriptor):
cid_to_gid_map = ['\0'] * 65536
widths = []
max_ccode = 0
charmap = {gind: ccode for ccode, gind in font.get_charmap().items()}
for gind in glyphs:
for ccode, gind in charmap.items():
glyph = font.load_glyph(gind,
flags=LoadFlags.NO_SCALE | LoadFlags.NO_HINTING)
ccode = charmap[gind]
widths.append((ccode, cvt(glyph.horiAdvance)))
if ccode < 65536:
cid_to_gid_map[ccode] = chr(gind)
Expand Down Expand Up @@ -1358,8 +1354,8 @@ def embedTTFType42(font, glyphs, descriptor):

# Add XObjects for unsupported chars
glyph_indices = [
glyph_index for glyph_index in glyphs
if not _font_supports_glyph(fonttype, charmap[glyph_index])
glyph_index for ccode, glyph_index in charmap.items()
if not _font_supports_glyph(fonttype, ccode)
]

bbox = [cvt(x, nearest=False) for x in full_font.bbox]
Expand Down Expand Up @@ -1445,9 +1441,9 @@ def embedTTFType42(font, glyphs, descriptor):
}

if fonttype == 3:
return embedTTFType3(font, glyphs, descriptor)
return embedTTFType3(font, charmap, descriptor)
elif fonttype == 42:
return embedTTFType42(font, glyphs, descriptor)
return embedTTFType42(font, charmap, descriptor)

def alphaState(self, alpha):
"""Return name of an ExtGState that sets alpha to the given value."""
Expand Down Expand Up @@ -2212,7 +2208,7 @@ def draw_mathtext(self, gc, x, y, s, prop, angle):

self.file.output(Op.begin_text)
for font, fontsize, ccode, glyph_index, ox, oy in glyphs:
self.file._character_tracker.track_glyph(font, glyph_index)
self.file._character_tracker.track_glyph(font, ccode, glyph_index)
fontname = font.fname
if not _font_supports_glyph(fonttype, ccode):
# Unsupported chars (i.e. multibyte in Type 3 or beyond BMP in
Expand Down Expand Up @@ -2268,11 +2264,7 @@ def draw_tex(self, gc, x, y, s, prop, angle, *, mtext=None):
seq += [['font', pdfname, text.font.size]]
oldfont = text.font
seq += [['text', text.x, text.y, [bytes([text.glyph])], text.x+text.width]]
# TODO: This should use glyph indices, not character codes, but will be
# fixed soon.
self.file._character_tracker.track_glyph(text.font,
typing.cast('GlyphIndexType',
text.glyph))
self.file._character_tracker.track_glyph(text.font, text.glyph, text.index)

# Find consecutive text strings with constant y coordinate and
# combine into a sequence of strings and kerns, or just one
Expand Down
13 changes: 7 additions & 6 deletions lib/matplotlib/backends/backend_ps.py
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Original file line number Diff line number Diff line change
Expand Up @@ -826,7 +826,7 @@ def draw_mathtext(self, gc, x, y, s, prop, angle):
f"{angle:g} rotate\n")
lastfont = None
for font, fontsize, ccode, glyph_index, ox, oy in glyphs:
self._character_tracker.track_glyph(font, glyph_index)
self._character_tracker.track_glyph(font, ccode, glyph_index)
if (font.postscript_name, fontsize) != lastfont:
lastfont = font.postscript_name, fontsize
self._pswriter.write(
Expand Down Expand Up @@ -1069,18 +1069,19 @@ def print_figure_impl(fh):
print("mpldict begin", file=fh)
print("\n".join(_psDefs), file=fh)
if not mpl.rcParams['ps.useafm']:
for font_path, glyphs in ps_renderer._character_tracker.used.items():
if not glyphs:
for (font, subset_index), charmap in \
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@tacaswell tacaswell Sep 16, 2025

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but we do loop here?

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@QuLogic QuLogic Sep 17, 2025

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PS is a little different from PDF in that it just dumps all the fonts in the CharacterTracker instance, while PDF has its own tracking of fonts, so it needs a bit more in-depth change (that continues on #30512.)

This change here doesn't modify any logic, but just changes the loop to work over the new structure of the .used attribute.

ps_renderer._character_tracker.used.items():
if not charmap:
continue
fonttype = mpl.rcParams['ps.fonttype']
# Can't use more than 255 chars from a single Type 3 font.
if len(glyphs) > 255:
if len(charmap) > 255:
fonttype = 42
fh.flush()
if fonttype == 3:
fh.write(_font_to_ps_type3(font_path, glyphs))
fh.write(_font_to_ps_type3(font, charmap.values()))
else: # Type 42 only.
_font_to_ps_type42(font_path, glyphs, fh)
_font_to_ps_type42(font, charmap.values(), fh)
print("end", file=fh)
print("%%EndProlog", file=fh)

Expand Down
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