I am making a tree-widget, where I want to get all the items present in the visible region only (not all items present in tree-widget) while scrolling - like below image shown:
In the 1st image as you see, I want to get all the items present in the visible region. And in the second image, I changed the scrollbar and items present in the visible region are also changed. So I want to get all items as per visible region while scrolling.

