Description of the new feature/enhancement

Currently, if you drag back the scrollbar and then resize the window, the viewport jumps back to the "regular" position (the end of the data buffer, and the bottom position of the scrollbar).

It would be better to (approximately) maintain the scrolled position, so that the user keeps seeing whichever data was previously shown.

In VTE we usually track the position at the bottom of the viewport and try to keep that at the bottom; except when fully scrolled back to the top. More details in doc/rewrap.txt.