RE: longlines mode

[Drew Adams]

> i turned on longlines-mode so my lines would be wrapped, and
> found out that are not wrapped in the end of a window, but relative to
> the variable fill-column.
> 
> So my question is: is there another mode i can use for wrapping lines
> (soft wrap) that is set according to the current window size?

You can use this trivial command (in any mode):

(defun foo ()
  "Set `fill-column' to width of selected window."
  (setq fill-column (window-width))
  (message "Fill column is now %d" fill-column))

You can of course combine that with entry to longlines mode or whatever.