title: Extjs: Disable Tab Key Navigation in a Form
body: <p>I have an ExtJS Form with several form fields, few of them are ComboBoxes - with a special handler on Tab Key Press. 
  While I am able to handle the Tab key press to show a popup with options for further filtering, The Tab key press also sets focus on the next form field. I want to know a way to disable focus change on Tab Key press in the form.</p>