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GeezerVison is showing github.com — Use CoreText to find macOS fonts by iccir · Pull Request #31977 · matplotlib/matplotlib

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iccir commented Jul 1, 2026

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Closes #28249
Closes #31965

Why is this change necessary?

Prior to this change, findSystemFonts() in font_manager.py called system_profiler -xml SPFontsDataType. This subprocess would load 1000+ font files in order to parse localized names. As we only need font paths, we can instead query CoreText directly. This finishes in ~63ms on my machine instead of ~7 seconds.

Differences in found fonts

system_profiler uses the private kCTFontCollectionIncludeInvisibleFontsOption option to find "invisible" fonts. These are fonts with names starting with '.'. These fonts are typically unavailable using the standard macOS font APIs. On my machine (macOS 14.8), the following fonts are "invisible":

  /System/Library/Fonts/ADTNumeric.ttc
  /System/Library/Fonts/AquaKana.ttc
  /System/Library/Fonts/HelveLTMM
  /System/Library/Fonts/Keyboard.ttf
  /System/Library/Fonts/LastResort.otf
  /System/Library/Fonts/NewYork.ttf
  /System/Library/Fonts/NewYorkItalic.ttf
  /System/Library/Fonts/SFArabic.ttf
  /System/Library/Fonts/SFArabicRounded.ttf
  /System/Library/Fonts/SFArmenian.ttf
  /System/Library/Fonts/SFArmenianRounded.ttf
  /System/Library/Fonts/SFCamera.ttf
  /System/Library/Fonts/SFCompact.ttf
  /System/Library/Fonts/SFCompactItalic.ttf
  /System/Library/Fonts/SFCompactRounded.ttf
  /System/Library/Fonts/SFGeorgian.ttf
  /System/Library/Fonts/SFGeorgianRounded.ttf
  /System/Library/Fonts/SFHebrew.ttf
  /System/Library/Fonts/SFHebrewRounded.ttf
  /System/Library/Fonts/SFNS.ttf
  /System/Library/Fonts/SFNSItalic.ttf
  /System/Library/Fonts/SFNSMono.ttf
  /System/Library/Fonts/SFNSMonoItalic.ttf
  /System/Library/Fonts/SFNSRounded.ttf
  /System/Library/Fonts/ThonburiUI.ttc
  /System/Library/Fonts/TimesLTMM

My change uses the CTFontCollectionCreateFromAvailableFonts() without this private option; hence, these fonts will be missing from the list returned by _get_macos_fonts().

However, font_manager.py later re-scans the "/System/Library/Fonts" path, so it should discover these invisible fonts at that time.

I tested this change on macOS Mojave (10.14) and macOS Sonoma (14.8). I was unable to test on 10.12 or 10.13 as I updated my 10.12 test device to 10.14. The CoreText API used has been available since 10.5, so I do not foresee any compatibility issues.

AI Disclosure

The original C-based implementation in #31965 is my own without any usage of AI. I used AI to help me convert it to C++ and return a py::set (my original implementation printed the paths). I used AI to check the resulting files and verify that I was following the correct formatting guidelines.

PR checklist

"closes #0000" is in the body of the PR description to link the related issue
new and changed code is tested
[N/A] Plotting related features are demonstrated in an example
[N/A] New Features and API Changes are noted with a directive and release note
Documentation complies with general and docstring guidelines

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iccir added 2 commits

July 1, 2026 11:00


          Use CoreText to find macOS fonts

50cbd1e


          Fix mypy-stubtest failure

aa947c8

melissawm added GUI: MacOSX topic: text/fonts labels

Jul 9, 2026

QuLogic mentioned this pull request

Jul 16, 2026

[MNT]: findSystemFonts - Use system API instead to look into folder #24001

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QuLogic linked an issue

Jul 16, 2026

that may be closed by this pull request

[MNT]: findSystemFonts - Use system API instead to look into folder #24001

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greglucas reviewed

Jul 24, 2026

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lib/matplotlib/tests/test_font_manager.py Resolved

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lib/matplotlib/_c_internal_utils.pyi Outdated

		@@ -1,5 +1,6 @@
		def display_is_valid() -> bool: ...
		def xdisplay_is_valid() -> bool: ...
		def find_available_fonts() -> set[str] \| None: ...

greglucas Jul 24, 2026

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Suggested change

	def find_available_fonts() -> set[str] \| None: ...
	def get_available_fonts() -> set[str] \| None: ...

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src/_c_internal_utils.cpp

		}
		return fonts;
		#else
		return py::none();

greglucas Jul 24, 2026

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should this be a py::set() call so that you can iterate it on the returning item even on a non macos platform? It is private, so probably not a big deal either way, but you are calling it as for x in None in the _get_macos helper above which would raise instead of returning empty.

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iccir Jul 24, 2026

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I was trying to mimic the "on other platforms, returns None" in Win32_GetCurrentProcessExplicitAppUserModelID and Win32_GetForegroundWindow.

I think _get_macos_fonts() should be changed to check for None rather than returning an empty set. To me, an empty set would indicate that the platform-specific code ran but found no fonts.

I think raising NotImplementedError might be the proper solution if the other functions in that file would do the same? I'm not sure (still learning!) :)

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          Changes based on feedback

0122e2d

github-actions Bot removed GUI: MacOSX topic: text/fonts labels

Jul 24, 2026

greglucas approved these changes

Jul 24, 2026

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lib/matplotlib/tests/test_font_manager.py Resolved

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          Update lib/matplotlib/tests/test_font_manager.py

dbbcd59

Co-authored-by: Greg Lucas <[email protected]>

QuLogic reviewed

Jul 28, 2026

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src/_c_internal_utils.cpp Resolved

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iccir and others added 6 commits

July 27, 2026 19:42


          Update lib/matplotlib/tests/test_font_manager.py

058dfc0

Co-authored-by: Elliott Sales de Andrade <[email protected]>


          Update lib/matplotlib/tests/test_font_manager.py

a592719

Co-authored-by: Elliott Sales de Andrade <[email protected]>


          Update lib/matplotlib/tests/test_font_manager.py

a980e73

Co-authored-by: Elliott Sales de Andrade <[email protected]>


          Update src/_c_internal_utils.cpp

aca9614

Co-authored-by: Elliott Sales de Andrade <[email protected]>


          Use snake_case

22e92ce


          Use std::make_unique instead of new

f76a6ed

melissawm added the OS: Apple label

Jul 28, 2026

QuLogic commented Jul 29, 2026

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I happened across foliojs/font-manager#19 while looking at these functions. Is that also a problem in this implementation (and was it something that we supported before)?

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iccir commented Jul 29, 2026 •

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I happened across foliojs/font-manager#19 while looking at these functions. Is that also a problem in this implementation (and was it something that we supported before)?

I'm not sure what is going on in the linked bug. ~/Library/Fonts is being checked on my test devices:

>>> pprint.pp([x for x in _c_internal_utils.get_available_fonts() if "iccir" in x])
['/Users/iccir/Library/Fonts/SF-Mono-Light.otf',
 '/Users/iccir/Library/Fonts/SF-Mono-Bold.otf',
 '/Users/iccir/Library/Fonts/DINishCondensed-Heavy.ttf',
 '/Users/iccir/Library/Fonts/DINish-Italic.otf',
…

My suspicion is one of the following:

There was a bug circa-2017 with CoreText.
The node process didn't have access to ~/Library/Fonts. I wouldn't expect this back in 2017. It would be more common nowadays with all of the additional macOS restrictions.
The user was placing fonts in ~/Library/Fonts without actually registering them with macOS via Font Book. Although the user mentions that they are available in TextEdit so I wouldn't expect this to be the case.

I'm leaning towards 1.

In any case, our previous implemented ran system_profiler as a subprocess, which also uses CTFontCollectionCreateFromAvailableFonts() internally. It's possible that ~/Library/Fonts isn't being accessed on some versions of macOS, but I wouldn't expect that to be a regression from the previous implementation.

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QuLogic approved these changes

Jul 29, 2026

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iccir commented Jul 29, 2026

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I did some more digging last night.

system_profiler calls CTFontCollectionCreateFromAvailableFonts() with kCTFontCollectionIncludeDisabledFontsOption turned on. This means that fonts explicitly deactivated/disabled by the user were being included in _get_macos_fonts().

The new code calls CTFontCollectionCreateFromAvailableFonts() with NULL, so deactivated/disabled fonts will not be included.

This is a subtle change of behavior, but I'm not sure if the old behavior is correct. There are situations where a user may have multiple user-level fonts installed with the same name and wants to deactivate one of them.

Assuming we want to change this behavior, should the version number of the font cache be bumped in font_manager.py? It's currently:

    __version__ = '3.11.0'

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QuLogic commented Aug 6, 2026

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Hmm, yes, I think that is correct, as we did the same thing for Windows: #22859

You can bump the cache key to 3.12.0a1 or similar.

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          Bump font manager version due to macOS CoreText change

7a279ce

QuLogic merged commit 8aedfd2 into matplotlib:main

Aug 6, 2026

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QuLogic added this to the v3.12.0 milestone

Aug 6, 2026

iccir deleted the coretext-find-fonts branch

September 7, 2026 16:57

iccir mentioned this pull request

Sep 9, 2026

[Bug]: macOS font discovery raises KeyError('_items') for an incomplete system_profiler font record #32328

Open

happyarts mentioned this pull request

Sep 17, 2026

Keep matplotlib off the system fonts in the diarization worker, so a broken font record on macOS no longer kills speaker detection kaixxx/noScribe#346

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[MNT]: Possibly use CoreText to find fonts for faster performance font finding in OSX produces 200+ lines of warnings [MNT]: findSystemFonts - Use system API instead to look into folder

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iccir commented Jul 1, 2026

Why is this change necessary?

Differences in found fonts

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QuLogic commented Jul 29, 2026

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iccir commented Jul 29, 2026 •

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