if you select lines of text at the top/bottom of the screen and then, while holding the mouse button down, move the cursor to the edge (and beyond), we don't automatically start scrolling the screen.  this is a common idiom in terminal emulators so people can easily select output from a program that has filled the screen and more.

currently, people are forced to manually scroll the screen while keeping the selection active by using the mouse wheel, or pressing page up/down on the keyboard.