How to autofit the textlayer aka textitem in accordance for showing of the fulltext?

every time the little plus showed at the bottom-right,
it means some text is hidden away from the text layer,
why they design the software this way and not the other way around always pains me in thinking and doing my job in reality

Now would you please anybody provide me the remedy to this problem.
My script needs to know the status of if the plus appears in the box to do its job correctly,
and out the several pages in your manual,
I can't find a boolean variable that feedbacks the existence of the '+,'
or is there any alternative, no matter how awkward it is to circumvent the problem
and expand the textbox enough to reveal the whole text?
Thank you

