pango: pango crashes on macOS when an emoji is entered into a text field

[aSapien]

Nixpkgs version

• Unstable (26.05)

Describe the bug

Many packages use pango and it is generally stable. However, I've recently hit a branch in pango that resulted in a crash in MacOS.

While my specific use-case involved an Emacs flow and relies on existing database state to reproduce, I found that the bug has been reported and fixed upstream in this issue.

Unfortunately though, there hasn't been a pango release with the fix yet.
Other package managers (i.e Brew) fix the issue by applying the patch in the formula.

Can we take a similar approach and apply the patch in Nixpkgs#pango please?

I'm willing to introduce a the PR.

Steps to reproduce

As per original report:

• start gtk4-widget-factory
• select the "Page 3" tab
• right-click into a text box and select "Insert Emoji"
• observe that the application crashes with this message:

(gtk4-widget-factory:96563): Pango-WARNING **: 14:14:04.864: couldn't load font "emoji Not-Rotated With-Color 17.279px", modified variant/weight/stretch as fallback, expect ugly output.
(gtk4-widget-factory:96563): Pango-ERROR **: 14:14:04.864: Could not load fallback font, bailing out.
Trace/BPT trap

Expected behaviour

Should not crash

Screenshots

No response

Relevant log output

(gtk4-widget-factory:96563): Pango-WARNING **: 14:14:04.864: couldn't load font "emoji Not-Rotated With-Color 17.279px", modified variant/weight/stretch as fallback, expect ugly output.
(gtk4-widget-factory:96563): Pango-ERROR **: 14:14:04.864: Could not load fallback font, bailing out.
Trace/BPT trap

Additional context

It seems that the underlying issue may somehow correspond to a 2023 report here: #236671

However, the upstream bug report is addressing range of versions released in 2025, therefore I'm not sure whether it will anyhow contribute to it as well.

System metadata

• system: "aarch64-darwin"
• host os: Darwin 25.2.0, macOS 26.2
• multi-user?: yes
• sandbox: no
• version: nix-env (Nix) 2.33.1
• nixpkgs: /nix/store/kkx2hzq20ggrwhy385jglnxjncg4lqck-source

Notify maintainers

@7c6f434c @bobby285271 @dasj19 @hedning @jtojnar

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[7c6f434c]

Hm, in principle it might be that the crash is caused by a recent partial fix to the old issue?

[aSapien]

@7c6f434c I'm not sure which fix you're referring to, but I was able to confirm that applying the patch no longer crashes my Emacs.

Here's the overlay I used locally:

(final: prev: {
  pango = prev.pango.overrideAttrs (old: {
    # https://gitlab.gnome.org/GNOME/pango/-/issues/871
    patches =
      old.patches or []
      ++ [
        (prev.fetchpatch {
          url = "https://gitlab.gnome.org/GNOME/pango/-/commit/4403954455f2b4a815b32e11c44f79b2e665e94c.diff";
          hash = "sha256-9HtPsBwqBR56YewDEbik1U1jakC7wTaCkKR+YXb9s4E=";
        })
      ];
  });
})

[7c6f434c]

I meant that you cite the 2023 issue and ask whether it is too old.

[aSapien]

@7c6f434c That's hard to tell because the 2023 issue has no corresponding report in upstream Pango.

[aSapien]

@7c6f434c can I submit a PR to introduce this patch?
Should the patch be fetched from gitlab or introduced locally?

[7c6f434c]

Submitting a PR fixing a bug is always good (but not always easy to get merged); I did not suggest it as I haven't done much GTK-ecosystem mainteance lately, so it would be other maintainers saying what this needs for merging, e.g. in terms of the comment .possibly giving a brief summary of the issue).

Looks reasonable to me, from a glance.

If the commit is already inside a normally-not-rebased branch, fetching the upstream commit is probably preferred.

[aSapien]

Pango 1.57.1 was just released with the fix. I will introduce a PR

[aSapien]

@7c6f434c any chance you can look at #505692 ?

Is there anything else expected from me to get this PR merged?