http://forum.team-mediaportal.com/threads/skin-setstring-slows-down-render-process.119672/

The skin action skin.setstring (skin.togglesetting, etc. also) hog the main process for some time stopping all rendering. This results in a jerky interface, esp. if setstring is used in an onfocus handler.

To recreate show some continuous animation and trigger skin.setstring on focus change. See forum thread for exact details.