Add fontconfig to properly define fallback fonts

All fonts can fallback on default emoji font and NerdFontsSymbolsOnly

Enable embedded bitmaps for fonts

system/default.nix

@@ -106,6 +106,23 @@
         homeDirectory = "/home/${username}";
       };
       programs.home-manager.enable = true;
+      fonts.fontconfig = {
+        enable = true;
+        defaultFonts =
+          with config.stylix.fonts;
+          let
+            symbols = [
+              emoji.name
+              "Symbols Nerd Font"
+            ];
+          in
+          {
+            emoji = symbols;
+            monospace = [ monospace.name ] ++ symbols;
+            sansSerif = [ sansSerif.name ] ++ symbols;
+            serif = [ serif.name ] ++ symbols;
+          };
+      };
     };
     extraSpecialArgs = {
       inherit inputs;
@@ -217,10 +234,16 @@
         };
       };
   };
-  fonts.packages = with pkgs; [
-    dejavu_fonts # Compatibility
-    liberation_ttf # Documents
-    lmodern # LaTeX
-    (nerdfonts.override { fonts = [ "NerdFontsSymbolsOnly" ]; })
-  ];
+  fonts = {
+    packages = with pkgs; [
+      dejavu_fonts # Compatibility
+      liberation_ttf # Documents
+      lmodern # LaTeX
+      (nerdfonts.override { fonts = [ "NerdFontsSymbolsOnly" ]; })
+    ];
+    fontconfig = {
+      enable = true;
+      useEmbeddedBitmaps = true;
+    };
+  };
 }