Fix dw2pdf multipage struct output

When the dw2pdf plugin is used to export multiple pages in a
single document, all the pages are rendered in the same context
of a single page. In order to include struct data in the PDF,
let's skip the id related checks and allow multiple pages rendered
in a single instance of syntax_plugin_struct_output.

Signed-off-by: Frieder Schrempf <dev@fris.de>

syntax/output.php

@@ -98,9 +98,20 @@ public function render($format, Doku_Renderer $renderer, $data)
                 return true;
             }
         }
-        if ($ID != $INFO['id']) return true;
-        if (!$INFO['exists']) return true;
-        if ($this->hasBeenRendered) return true;
+
+        /*
+         * When the dw2pdf plugin is used to export multiple pages in a
+         * single document, all the pages are rendered in the same context
+         * of a single page. In order to include struct data in the PDF,
+         * let's skip the id related checks and allow multiple pages rendered
+         * in a single instance of syntax_plugin_struct_output.
+         */
+        if (!is_a($renderer, 'renderer_plugin_dw2pdf')) {
+            if ($ID != $INFO['id']) return true;
+            if (!$INFO['exists']) return true;
+            if ($this->hasBeenRendered) return true;
+        }
+
         if (!preg_match(self::WHITELIST_ACTIONS, act_clean($ACT))) return true;
 
         // do not render the output twice on the same page, e.g. when another page has been included