fontconfig: leverage lib.genAttrs and use mkOrder (#1718)

Link: https://github.com/nix-community/stylix/pull/1718

Reviewed-by: NAHO <90870942+trueNAHO@users.noreply.github.com>
Reviewed-by: awwpotato <awwpotato@voidq.com>
Reviewed-by: Flameopathic <64027365+Flameopathic@users.noreply.github.com>

modules/fontconfig/fontconfig.nix

@@ -1,16 +1,17 @@
 { mkTarget }:
+{ lib, ... }:
 mkTarget {
   name = "fontconfig";
   humanName = "Fontconfig";
 
   configElements =
-    { fonts }:
+    { listTargetIndex, fonts }:
     {
-      fonts.fontconfig.defaultFonts = {
-        monospace = [ fonts.monospace.name ];
-        serif = [ fonts.serif.name ];
-        sansSerif = [ fonts.sansSerif.name ];
-        emoji = [ fonts.emoji.name ];
-      };
+      fonts.fontconfig.defaultFonts = lib.genAttrs [
+        "monospace"
+        "serif"
+        "sansSerif"
+        "emoji"
+      ] (family: lib.mkOrder listTargetIndex [ fonts.${family}.name ]);
     };
 }

stylix/darwin/default.nix

@@ -17,6 +17,7 @@ in
     ../target.nix
     ../release.nix
     ../overlays.nix
+    ../ordering.nix
   ] ++ autoload;
   config.warnings =
     lib.mkIf

stylix/droid/default.nix

@@ -13,6 +13,7 @@ in
     ../pixel.nix
     ../target.nix
     ../overlays.nix
+    ../ordering.nix
   ] ++ autoload;
 
   # See https://github.com/nix-community/nix-on-droid/issues/436

stylix/hm/default.nix

@@ -20,6 +20,7 @@ in
     ../target.nix
     ../release.nix
     ../overlays.nix
+    ../ordering.nix
   ] ++ autoload;
   config.warnings =
     lib.mkIf

stylix/nixos/default.nix

@@ -20,6 +20,7 @@ in
     ../target.nix
     ../release.nix
     ../overlays.nix
+    ../ordering.nix
   ] ++ autoload;
   config.warnings =
     lib.mkIf

stylix/ordering.nix

@@ -0,0 +1,13 @@
+{ lib, ... }:
+{
+  options.stylix.listTargetIndex = lib.mkOption {
+    description = ''
+      The target index at which stylix inserts into lists.
+      Intended for use as argument to `lib.mkOrder`.
+    '';
+    type = lib.types.int;
+    default = 600;
+    internal = true;
+    readOnly = true;
+  };
+}