>>  Not sure how the concept of a line delimited by newlines relates to
>>moving the cursor up one physical line on the screen.
>
> Working out where to move the cursor to

Still I dare claim that moving a cursor up one visible line has
nothing to do with the concept of a line delimited by newlines. For
the movement, such delimited lines are completely irrelevant. For the
movement there is no difference whether there is a newline on the
previous visible line or the line was broken due to the width of the
window.

What I speak about is 'as if' clicking the mouse up one visible line.

R