When you CLICK into a textfield, if you want to select the existing text you might do something like this:
The above works fine when you CLICK into the field. I haven't dug into the source yet, but it looks like Ext probably just listens to the focus event and if that setting is true it deselects the text (for a brief moment I can see the contents get selected then deselect).
selectOnFocus: true,//select all of the existing text
The problem: if you tab or shift+tab to gain focus it doesn't honor the selectOnFocus setting.
Not sure if that's my mis-use, a bug, or the intended behavior.