Chromium in container Fontconfig error: Cannot load default config file: No such file: (null)

[yajo]

Describe the bug

It seems to be a resurrection of #101211, or at least I found proper STR.

When Chromium is executed inside a container, it cannot find fontconfig and it fails.

Steps To Reproduce

Steps to reproduce the behavior:

1. Add this flake.nix:

   {
     inputs.nixpkgs.url = "nixpkgs/f1c9c23aad972787f00f175651e4cb0d7c7fd5ea";
     outputs = {
       self,
       nixpkgs,
     }: let
       pkgs = nixpkgs.legacyPackages.x86_64-linux;
     in {
       packages.x86_64-linux.default = pkgs.dockerTools.streamLayeredImage {
         name = "chromium";
         tag = "latest";
         config = {
           Cmd = [
             "${pkgs.chromium}/bin/chromium"
             "--headless"
             "--no-default-browser-check"
             "--no-first-run"
             "--disable-extensions"
             "--disable-background-networking"
             "--disable-background-timer-throttling"
             "--disable-backgrounding-occluded-windows"
             "--disable-renderer-backgrounding"
             "--disable-breakpad"
             "--disable-client-side-phishing-detection"
             "--disable-crash-reporter"
             "--disable-default-apps"
             "--disable-dev-shm-usage"
             "--disable-device-discovery-notifications"
             "--disable-namespace-sandbox"
             "--user-data-dir=/tmp/chrome-data-dir"
             "--disable-translate"
             "--autoplay-policy=no-user-gesture-required"
             "--window-size=1366x768"
             "--remote-debugging-address=127.0.0.1"
             "--remote-debugging-port=0"
             "--no-sandbox"
             "--disable-gpu"
           ];
         };
       };
       devShells.x86_64-linux.default = pkgs.mkShell {
         buildInputs = [pkgs.podman];
       };
     };
   }

2. Run these commands:

   nix develop # to enter the shell with podman
   nix build
   ./result | podman load
   podman run --rm -it --mount type=tmpfs,tmpfs-size=512M,destination=/tmp localhost/chromium:latest

Expected behavior

Chromium shouldn't fail with the fontconfig error.

Screenshots

N/A

Additional context

I'm packaging Odoo in a container. It uses Chromium behind the scenes to run unit tests. I included all the flags it uses (resolved) to run Chromium in a container-friendly fashion.

Tests fail with Inspector.targetCrashed error.

A similar container-based approach based on debian doesn't crash like this. I inspected the same command in both containers and found that this issue's error is the main difference.

When I run the same command outside the container, Chromium works happily. My guess is that it's getting the font config from my host OS (Fedora Silverblue 36). I'm not using NixOS FWIW.

Notify maintainers

@primeos @thefloweringash

Metadata

I gave a nix flake to get it more reproducible, so I guess this is the required metadata:

[user@system:~]$ nix --version
nix (Nix) 2.8.0

[yajo]

The problem goes away with this patch:

           "--no-sandbox"
           "--disable-gpu"
         ];
+        Env = [
+          "FONTCONFIG_FILE=${pkgs.fontconfig.out}/etc/fonts/fonts.conf"
+          "FONTCONFIG_PATH=${pkgs.fontconfig.out}/etc/fonts/"
+        ];
       };
     };
     devShells.x86_64-linux.default = pkgs.mkShell {

I'm not sure if this is expected behaviour. It was surprising to me TBH.

[jtojnar]

I would say that is expected. Fontconfig requires /etc/fonts/fonts.conf to exist so if you want to run GUI apps in a container, you will need to create the file or use the environment variable workaround.

Though I guess it might make sense to patch fontconfig as follows to allow it working in environments where fontconfig is not installed globally:

--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -80,6 +80,7 @@ AM_CPPFLAGS = 						\
 	$(WARN_CFLAGS)					\
 	-DFC_CACHEDIR='"$(FC_CACHEDIR)"'                \
 	-DCONFIGDIR='"$(CONFIGDIR)"'			\
+	-DFALLBACK_FONTCONFIG_PATH='"$(prefix)/etc/fonts"'\
 	-DFONTCONFIG_PATH='"$(BASECONFIGDIR)"'		\
 	-DFC_TEMPLATEDIR='"$(TEMPLATEDIR)"'
 LDADD  = $(LIBINTL)
--- a/src/fccfg.c
+++ b/src/fccfg.c
@@ -2439,7 +2439,7 @@ FcConfigGetPath (void)
     int	    npath;
     int	    i;
 
-    npath = 2;	/* default dir + null */
+    npath = 3;	/* default dir + fallback dir + null */
     env = (FcChar8 *) getenv ("FONTCONFIG_PATH");
     if (env)
     {
@@ -2491,6 +2491,14 @@ FcConfigGetPath (void)
     if (!path[i])
 	goto bail1;
     strcpy ((char *) path[i], (const char *) dir);
+
+    // Fallback for Nixpkgs.
+    dir = (FcChar8 *) FALLBACK_FONTCONFIG_PATH;
+    path[i] = malloc (strlen ((char *) dir) + 1);
+    if (!path[i])
+        goto bail1;
+    strcpy ((char *) path[i], (const char *) dir);
+
     return path;
 
 bail1:

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/imagemagicks-convert-command-fails-due-to-fontconfig-error/20518/3

[kfiz]

I would say that is expected. Fontconfig requires /etc/fonts/fonts.conf to exist so if you want to run GUI apps in a container, you will need to create the file or use the environment variable workaround.

Though I guess it might make sense to patch fontconfig as follows to allow it working in environments where fontconfig is not installed globally:

--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -80,6 +80,7 @@ AM_CPPFLAGS = 						\
 	$(WARN_CFLAGS)					\
 	-DFC_CACHEDIR='"$(FC_CACHEDIR)"'                \
 	-DCONFIGDIR='"$(CONFIGDIR)"'			\
+	-DFALLBACK_FONTCONFIG_PATH='"$(prefix)/etc/fonts"'\
 	-DFONTCONFIG_PATH='"$(BASECONFIGDIR)"'		\
 	-DFC_TEMPLATEDIR='"$(TEMPLATEDIR)"'
 LDADD  = $(LIBINTL)
--- a/src/fccfg.c
+++ b/src/fccfg.c
@@ -2439,7 +2439,7 @@ FcConfigGetPath (void)
     int	    npath;
     int	    i;
 
-    npath = 2;	/* default dir + null */
+    npath = 3;	/* default dir + fallback dir + null */
     env = (FcChar8 *) getenv ("FONTCONFIG_PATH");
     if (env)
     {
@@ -2491,6 +2491,14 @@ FcConfigGetPath (void)
     if (!path[i])
 	goto bail1;
     strcpy ((char *) path[i], (const char *) dir);
+
+    // Fallback for Nixpkgs.
+    dir = (FcChar8 *) FALLBACK_FONTCONFIG_PATH;
+    path[i] = malloc (strlen ((char *) dir) + 1);
+    if (!path[i])
+        goto bail1;
+    strcpy ((char *) path[i], (const char *) dir);
+
     return path;
 
 bail1:

Can we please merge this? I just spent too many hours until I figured out why my application that depends on fontconfig via chromedriver did not work.

[truvatech]

I'm seeing this issue in my nested VM.
Nixos host, nixos guest workstation VM.
Whenever this pops up, chrome (well, in my case, Brave) freezes entirely for a good 15-20 seconds.
I've been able to reproduce this issue any time I visit reddit and attempt to scroll down, for example.
This is followed by errors related to accessing memory and the GPU process crashing (not currently on that VM. can share logs if useful later.

Not seeing this problem on an Arch guest, so unfortunately this is a big limiting factor in using nixos as a workstation guest

If something in the previous comments solves the issue, can someone indiciate where I have to make that change manually by any chance? I am not familiar enough with nixos/linux perhaps to understand where to add these snippets of code.
Thanks

[kfiz]

If your working with docker tools this should work:
#176081 (comment)

Or you could clone nixpkgs and apply this patch #176081 (comment) to fontconfig and then install whatever package you want to use from your clone.

If not, then you should make sure that those environment variables are set correctly in the context of the binary that you are trying to use.