8000 Invalidate FT2Font cache when fork()ing. by anntzer · Pull Request #14535 · matplotlib/matplotlib · GitHub
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Invalidate FT2Font cache when fork()ing. #14535

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Merged
merged 1 commit into from
Jun 13, 2019
Merged

Invalidate FT2Font cache when fork()ing. #14535

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10 changes: 9 additions & 1 deletion lib/matplotlib/font_manager.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1264,12 +1264,20 @@ def is_opentype_cff_font(filename):
return False


_get_font = lru_cache(64)(ft2font.FT2Font)
_fmcache = os.path.join(
mpl.get_cachedir(), 'fontlist-v{}.json'.format(FontManager.__version__))
fontManager = None


_get_font = lru_cache(64)(ft2font.FT2Font)
# FT2Font objects cannot be used across fork()s because they reference the same
# FT_Library object. While invalidating *all* existing FT2Fonts after a fork
# would be too complicated to be worth it, the main way FT2Fonts get reused is
# via the cache of _get_font, which we can empty upon forking (in Py3.7+).
if hasattr(os, "register_at_fork"):
os.register_at_fork(after_in_child=_get_font.cache_clear)


def get_font(filename, hinting_factor=None):
if hinting_factor is None:
hinting_factor = rcParams['text.hinting_factor']
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9EB0 15 changes: 15 additions & 0 deletions lib/matplotlib/tests/test_font_manager.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
from io import BytesIO
import multiprocessing
import os
from pathlib import Path
import shutil
Expand Down Expand Up @@ -184,3 +185,17 @@ def test_user_fonts_win32():
# Now, the font should be available
fonts = findSystemFonts()
assert any(font_test_file in font for font in fonts)


def _model_handler(_):
fig, ax = plt.subplots()
fig.savefig(BytesIO(), format="pdf")
plt.close()


@pytest.mark.skipif(not hasattr(os, "register_at_fork"),
reason="Cannot register at_fork handlers")
def test_fork():
_model_handler(0) # Make sure the font cache is filled.
ctx = multiprocessing.get_context("fork")
ctx.Pool(processes=2).map(_model_handler, range(2))
0