The display() method in backup/restore UI returns the HTML rather then echoing it

This implementation uses a hacky trick with the output buffer unless
someone finds a time to add support for returning the HTML from
quickforms.

backup/util/ui/base_ui.class.php

@@ -140,16 +140,14 @@ abstract class base_ui {
     /**
      * Displays the UI for the backup!
      *
-     * Note: The UI makes use of mforms (ewww!) thus it will automatically print
-     * out the result rather than returning a string of HTML like other parts of Moodle
-     *
-     * @return bool
+     * @throws base_ui_exception
+     * @return string HTML code
      */
     public function display() {
         if ($this->progress < self::PROGRESS_SAVED) {
             throw new base_ui_exception('backupsavebeforedisplay');
         }
-        $this->stage->display();
+        return $this->stage->display();
     }
     /**
      * Gets all backup tasks from the controller

backup/util/ui/base_ui_stage.class.php

@@ -108,17 +108,29 @@ abstract class base_ui_stage {
     final public function get_uniqueid() {
         return $this->ui->get_uniqueid();
     }
+
     /**
      * Displays the stage.
      *
      * By default this involves instantiating the form for the stage and the calling
-     * it to display. Remember this is a moodleform instance so it will print
-     * rather than return.
+     * it to display.
+     *
+     * @return string HTML code to display
      */
     public function display() {
+
         $form = $this->initialise_stage_form();
+        // a nasty hack follows to work around the sad fact that moodle quickforms
+        // do not allow to actually return the HTML content, just to echo it
+        flush();
+        ob_start();
         $form->display();
+        $output = ob_get_contents();
+        ob_end_clean();
+
+        return $output;
     }
+
     /**
      * Processes the stage.
      *

backup/util/ui/restore_ui.class.php

@@ -252,13 +252,15 @@ class restore_ui extends base_ui {
     }
     /**
      * Displays this stage
+     *
      * @param core_backup_renderer $renderer
+     * @return string HTML code to echo
      */
     public function display($renderer) {
         if ($this->progress < self::PROGRESS_SAVED) {
             throw new base_ui_exception('backupsavebeforedisplay');
         }
-        $this->stage->display($renderer);
+        return $this->stage->display($renderer);
     }
 }