feat: add helper to differentiate user-defined layout from default

on-behalf-of: @Mermaid-Chart <hello@mermaidchart.com>

docs/config/setup/config/README.md

@@ -18,6 +18,7 @@
 
 - [addDirective](functions/addDirective.md)
 - [getConfig](functions/getConfig.md)
+- [getLayoutInfo](functions/getLayoutInfo.md)
 - [getSiteConfig](functions/getSiteConfig.md)
 - [reset](functions/reset.md)
 - [sanitize](functions/sanitize.md)

docs/config/setup/config/functions/getLayoutInfo.md

@@ -0,0 +1,27 @@
+> **Warning**
+>
+> ## THIS IS AN AUTOGENERATED FILE. DO NOT EDIT.
+>
+> ## Please edit the corresponding file in [/packages/mermaid/src/docs/config/setup/config/functions/getLayoutInfo.md](../../../../../packages/mermaid/src/docs/config/setup/config/functions/getLayoutInfo.md).
+
+[**mermaid**](../../README.md)
+
+---
+
+# Function: getLayoutInfo()
+
+> **getLayoutInfo**(): `object`
+
+Defined in: [packages/mermaid/src/config.ts:260](https://github.com/mermaid-js/mermaid/blob/master/packages/mermaid/src/config.ts#L260)
+
+## Returns
+
+`object`
+
+### isUserDefined
+
+> **isUserDefined**: `boolean`
+
+### layout
+
+> **layout**: `string`

packages/mermaid/src/config.ts

@@ -248,3 +248,19 @@ const checkConfig = (config: MermaidConfig) => {
     issueWarning('LAZY_LOAD_DEPRECATED');
   }
 };
+
+const isUserDefinedLayout = (): boolean => {
+  if (configFromInitialize?.layout) {
+    return true;
+  }
+
+  return directives.some((d) => !!d.layout);
+};
+
+export const getLayoutInfo = () => {
+  const cfg = getConfig();
+  return {
+    layout: cfg.layout ?? 'dagre',
+    isUserDefined: isUserDefinedLayout(),
+  };
+};