[PATCH] gnu: fontconfig: Add replacement with font-dejavu instead of gs-fonts.

[Marius Bakke <mbakke@fastmail.com>]

This fixes <https://bugs.gnu.org/41282> and <https://bugs.gnu.org/41241>.
Reported by Pierre Neidhardt, W Knight, and others.

* gnu/packages/fontutils.scm (fontconfig)[replacement]: New field.
(fontconfig/font-dejavu): New variable.
---
Guix,

This is a hack to make (some) fonts working when users don't have fonts
specified in their system configuration, and (crucially) places where
the fontconfig cache may be unavailable such as 'guix pack's.

I'm not sure whether font-dejavu is a good replacement here.  Another
approach could be to convert gs-fonts to TrueType or OpenType format.

Thoughts?  I don't know much about fonts and would appreciate feedback.

---
 gnu/packages/fontutils.scm | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/gnu/packages/fontutils.scm b/gnu/packages/fontutils.scm
index e552ece50b..27c84d5814 100644
--- a/gnu/packages/fontutils.scm
+++ b/gnu/packages/fontutils.scm
@@ -37,6 +37,7 @@
   #:use-module (gnu packages perl)
   #:use-module (gnu packages pkg-config)
   #:use-module (gnu packages autotools)
+  #:use-module (gnu packages fonts)
   #:use-module (gnu packages gettext)
   #:use-module (gnu packages python)
   #:use-module (gnu packages python-xyz)
@@ -292,6 +293,12 @@ fonts to/from the WOFF2 format.")
 (define-public fontconfig
   (package
    (name "fontconfig")
+
+   ;; This replacement is not security-related, but works around the fact
+   ;; that gs-fonts are not recognized by Pango, causing many applications
+   ;; to fail to find fonts otherwise.
+   (replacement fontconfig/font-dejavu)
+
    (version "2.13.1")
    (source (origin
             (method url-fetch)
@@ -348,6 +355,13 @@ high quality, anti-aliased and subpixel rendered text on a display.")
                        "See COPYING in the distribution."))
    (home-page "https://www.freedesktop.org/wiki/Software/fontconfig")))
 
+(define fontconfig/font-dejavu
+  (package
+    (inherit fontconfig)
+    (inputs
+     ;; XXX: Reuse the name to avoid having to override the configure flags.
+     `(("gs-fonts" ,font-dejavu)))))
+
 (define-public t1lib
   (package
    (name "t1lib")
-- 
2.26.2