Add filter for fm_calculated_context() to support additional contexts and overrides

fieldmanager.php

@@ -367,6 +367,23 @@ function fm_calculate_context() {
 
 	if ( empty( $calculated_context ) ) {
 		$calculated_context = array( null, null );
+
+		/**
+		 * Filter the calculated context to allow for custom contexts and overrides to be used.
+		 *
+		 * @since 1.0.0
+		 *
+		 * @param array $calculated_context {
+		 *     Array of context information.
+		 *
+		 *     @type  string|null A Fieldmanager context of "post", "quickedit", "term",
+		 *                        "submenu", or "user", or null if one isn't found.
+		 *     @type  string|null A "type" dependent on the context. For "post" and
+		 *                        "quickedit", the post type. For "term", the taxonomy.
+		 *                        For "submenu", the group name. For all others, null.
+		 * }
+		 */
+		$calculated_context = apply_filters( 'fm_calculated_context', $calculated_context );
 	}
 
 	return $calculated_context;