Handles.BeginGUI(); is work well but Handles.BeginGUI(rect);
GUI Error: You are pushing more GUIClips than you are popping. Make sure they are balanced (type:2)
UnityEngine.GUIUtility:EndGUI(Int32, Int32, IDList)
code
@CustomEditor(UIEditor)
class _GUI extends Editor
{
function OnSceneGUI()
{
Handles.BeginGUI(Rect(10.0,10.0,100.0,200.0));
GUILayout.Box("hello world");
Handles.EndGUI();
}
}