Bug summary

Some font files have the .ttc extension ("TrueType collection") but actually contain CFF data ("compact font format") which is not supported by the PDF and PS backends (#2869). Currently ttc files cause a crash which is easily fixed with

diff --git a/lib/matplotlib/backends/_backend_pdf_ps.py b/lib/matplotlib/backends/_backend_pdf_ps.py
index 3224fb90e3..eaf8c8c094 100644
--- a/lib/matplotlib/backends/_backend_pdf_ps.py
+++ b/lib/matplotlib/backends/_backend_pdf_ps.py
@@ -39,6 +39,10 @@ def get_glyphs_subset(fontfile, characters):
     # prevent subsetting FontForge Timestamp and other tables
     options.drop_tables += ['FFTM', 'PfEd']

+    if fontfile.endswith('ttc'):
+        options.font_number = 0
     with subset.load_font(fontfile, options) as font:
         subsetter = subset.Subsetter(options=options)
         subsetter.populate(text=characters)

but with this fix, some ttc fonts result in broken output files if using font type 42 (type 3 seems to be fine).

The font manager lists fonts using fc-list -f '%{file}\n' and selects based on file extensions. A better way might be fc-list :fontformat=TrueType -f '%{file}\n' since fontconfig knows about the real font format. However, FreeType supports CFF fonts so we probably shouldn't exclude them from other backends or type 3 embedding.

(The correct way to embed CFF fonts in PostScript is described in https://adobe-type-tools.github.io/font-tech-notes/pdfs/5176.CFF.pdf, and in PDF the font type needs to be Type1C, CIDFontType0C, or OpenType.)

Code for reproduction

# this needs the patch above

import matplotlib
from pathlib import Path
matplotlib.use('ps')
from matplotlib import pyplot as plt

# the following font is in CFF format on my Mac
font = Path('/System/Library/Fonts/AppleSDGothicNeo.ttc')

fig = plt.figure()
plt.axis((0,10,0,10))
plt.text(3,3,'Glib jocks quiz nymph to vex dwarf.', font=font)

matplotlib.rc('ps', fonttype=42)
plt.savefig('fmt42.ps')

matplotlib.rc('ps', fonttype=3)
plt.savefig('fmt3.ps')

Actual outcome

ps2pdf fmt42.ps errors out with

Error: /invalidfont in definefont
Operand stack:
   AppleSDGothicNeo-Regular   --dict:11/15(L)--   Font
Execution stack:
   %interp_exit   .runexec2   --nostringval--   definefont   --nostringval--   2   %stopped_push   --nostringval--   definefont   definefont   false   1   %stopped_push   1990   1   3   %oparray_pop   1989   1   3   %oparray_pop   1977   1   3   %oparray_pop   1833   1   3   %oparray_pop   --nostringval--   %errorexec_pop   .runexec2   --nostringval--   definefont   --nostringval--   2   %stopped_push   --nostringval--   1923   2   4   %oparray_pop
Dictionary stack:
   --dict:729/1123(ro)(G)--   --dict:0/20(G)--   --dict:76/200(L)--   --dict:10/12(L)--
Current allocation mode is local
Current file position is 11851
GPL Ghostscript 9.54.0: Unrecoverable error, exit code 1

Expected outcome

Operating system

macOS 11.5.2

Matplotlib Version

master as of a4e81e7 + some of my local changes

Matplotlib Backend

No response

Python version

No response

Jupyter version

No response

Other libraries

fontTools 4.24.4

Installation

source

Conda channel

No response