redraw_window in ui.c already compute the curs_y by itself, so don't update it from here. Also, introduce forward_line: moves the cursor up/down n lines. It's amazing sometimes how a good interface can simplify a large chunk of code!

possible leak? not confirmed, but this way it reads better.

Try to preserve as much as possible the current_line and top_line during wrap_page. In redraw_window recompute the correct y position.

instead of using the line_off + vline_nth, cache the current top line.

free ui.c from (strictly) non-ui code

prefix "→ " " " ended up using both as prefix for the line and the continuations the first string given, ignoring the second argument. Found and reported by tgl, thanks!!

mention the color0-255 set