Scroll with mouse in 'less' without clearing the screen
This question is nearly identical to a question asked on SuperUser. Here's a portion of the answer:

So there you are: Either you switch to alternate screen and the terminal's hack converts scroll events into keypresses for less, and the normal screen is restored when you quit; or you don't, and then there can't be any magic converting scroll events to keypresses and less doesn't understand the scroll events.
So what could be done? Well, either implement mouse support in less and let it handle scroll events itself (and live with a nondefault click or copy-paste behavior), or implement another weird hack: upon quitting, after reverting to the normal screen, less could for the last time print a screenful of content, repeating whatever was displayed before you quit.