fix fonts for flatpaks

plasma.nix

@@ -20,4 +20,48 @@
     enable = true;
     pulse.enable = true;
   };
+
+  system.fsPackages = [ pkgs.bindfs ];
+  fileSystems = let
+    mkRoSymBind = path: {
+      device = path;
+      fsType = "fuse.bindfs";
+      options = [ "ro" "resolve-symlinks" "x-gvfs-hide" ];
+    };
+    fontsPkgs = config.fonts.packages;
+    x11Fonts = pkgs.runCommand "X11-fonts"
+      {
+        preferLocalBuild = true;
+        nativeBuildInputs = with pkgs; [
+          gzip
+          xorg.mkfontscale
+          xorg.mkfontdir
+        ];
+      }
+      (''
+        mkdir -p "$out/share/fonts"
+        font_regexp='.*\.\(ttf\|ttc\|otb\|otf\|pcf\|pfa\|pfb\|bdf\)\(\.gz\)?'
+      ''
+      + (builtins.concatStringsSep "\n" (builtins.map (pkg: ''
+          find ${toString pkg} -regex "$font_regexp" \
+            -exec ln -sf -t "$out/share/fonts" '{}' \;
+        '') fontsPkgs
+        ))
+      + ''
+        cd "$out/share/fonts"
+        mkfontscale
+        mkfontdir
+        cat $(find ${pkgs.xorg.fontalias}/ -name fonts.alias) >fonts.alias
+      '');
+    aggregatedIcons = pkgs.buildEnv {
+      name = "system-icons";
+      paths = fontsPkgs;
+      pathsToLink = [
+        "/share/icons"
+      ];
+    };
+  in {
+    "/usr/share/icons" = mkRoSymBind (aggregatedIcons + "/share/icons");
+    "/usr/share/fonts" = mkRoSymBind (x11Fonts + "/share/fonts");
+  };
 }