scroll auto discovery

nix/discoverScrolls.nix

@@ -0,0 +1,29 @@
+{ self }:
+{ scrollsDir }:
+let
+  allSubDirs = builtins.attrNames (
+    builtins.readDir scrollsDir
+  );
+
+  directoriesOnly = builtins.filter (name:
+    let
+      type = (builtins.readDir scrollsDir).${name};
+    in type == "directory"
+  ) allSubDirs;
+
+  hasScrollNix = dir:
+    let
+      scrollPath = scrollsDir + "/${dir}/scroll.nix";
+    in builtins.pathExists scrollPath;
+
+  scrollDirs = builtins.filter hasScrollNix directoriesOnly;
+  missingScrollDirs = builtins.filter (dir: !(hasScrollNix dir)) directoriesOnly;
+
+  warnings =
+    if builtins.length missingScrollDirs > 0
+    then builtins.trace
+      "Warning: Found directories without scroll.nix: ${builtins.toString missingScrollDirs}"
+      null
+    else null;
+in
+scrollDirs