Okular, flpsed, and most likely all other PDF software on Gentoo, currently displays the missing glyph tofu for all check boxes due to this bug:
This affects IRS forms and a lot of bank documents.
Fix was upstreamed in fontconfig many years ago. Why the problem resurfacing? Because the fix (Aliasing Zapf Dingbats to Dingbats from URW has been moved out of fontconfig in 2017.)
From commit comments:
They have become a part of (URW)++ upstream release now:
+NOTE: The (URW)++ fonts mappings of generics to specifics were removed, because
+ upstream now includes them in their release of (URW)++ Core Font Set here:
The fix is now here:
It seems our urw-fonts package is based on Fedora Core 13. This is what Redhat has to say about this problem:
The 'urw-fonts' package is now obsolete and has been replaced with new 'urw-base35-fonts', which is being kept up-to-date.
'urw-fonts' will be dropped at the end-of-life of Fedora 27.
Please, update your specfile and make sure your package builds/works properly with new version of the (URW)++ fonts.
Note that current Fedora version is 31.
So the problem is we have latest fontconfig, which expects the fix to be in latest urw-base35-fonts. But we don't have the latest urw-base35-fonts. Only the ancient urw-fonts without this fix.
We seem to have a previous effort to package the new fonts. https://bugs.gentoo.org/589890 But no activity on it for some time.
Meanwhile more and more packages drop support for the old urw-fonts causing other problems. https://bugs.gentoo.org/621100
We need to package the new version before the old version decays to an unmaintainable mess.
I can confirm the checkbox problem is fixed in both Okular and flpsed with the urw-fonts-20170801.ebuild from https://bugs.gentoo.org/589890 and enabled 30-urw-d050000l.conf. Confirmed upstream 20170801 is still the latest release.
Created attachment 646636 [details, diff]
Restore fontconfig aliases for URW++ fonts
This patch was developed for fontconfig-2.12.6 by reverting the commit that removed the aliases. It fixed the checkbox issue for me in fontconfig-2.12.6, and appears to do so in the current stable fontconfig-2.13.0-r4. It is a bandage for the problem, not a fix. The bugs referenced in other comments describe better fixes which are not yet implemented in Gentoo, but for those who would like help getting checkboxes to work again, I hope this patch will help.