Add fictioneer_filter_body_attributes filter

FILTERS.md

@@ -115,6 +115,33 @@ Filters the intermediate output array in the `_article-cards.php` partial before
 
 ---
 
+### `apply_filters( 'fictioneer_filter_body_attributes', $attributes, $args )`
+Filters the intermediate output array of additional body attributes (except `class` which is handled by `body_class()`) before it is mapped, escaped, imploded, and rendered in the `header.php` template.
+
+**$attributes:**
+* `data-post-id` (int) – Current post ID (or -1 if null).
+* `data-story-id` (int|null) – Current story ID (if any). Unsafe.
+
+**$args:**
+* `post_id` (int|null) – Current post ID. Unsafe.
+* `post_type` (string|null) – Current post type. Unsafe.
+* `story_id` (int|null) – Current story ID (if chapter). Unsafe.
+* `header_image_url` (string|boolean) – URL of the filtered header image or false.
+* `header_image_source` (string) – Source of the header image. Either `'default'`, `'post'`, or `'story'`.
+* `header_args` (array) – Arguments passed to the header.php partial.
+
+**Example:**
+```php
+function child_add_body_attributes( $attributes ) {
+  $attributes['data-permalink'] = get_permalink();
+
+  return $attributes;
+}
+add_filter( 'fictioneer_filter_body_attributes', 'child_add_body_attributes' );
+```
+
+---
+
 ### `apply_filters( 'fictioneer_filter_breadcrumbs_array', $breadcrumbs, $args )`
 Filters the array of breadcrumb tuples inside the `fictioneer_get_breadcrumbs( $args )` function before the HTML is build.
 

header.php

@@ -98,6 +98,9 @@ if ( $story_id ) {
   $body_attributes['data-story-id'] = $story_id;
 }
 
+$body_attributes = apply_filters( 'fictioneer_filter_body_attributes', $body_attributes, $action_args );
+unset( $body_attributes['class'] ); // Prevent mistakes
+
 $body_attributes = array_map(
   function ( $key, $value ) { return $key . '="' . esc_attr( $value ) . '"'; },
   array_keys( $body_attributes ),