is a variable defined in `
Its value is
Display this many lines of leading context before the current message.
If nil and the left fringe is displayed, don't scroll the
compilation output window; an arrow in the left fringe points to
the current message. If nil and there is no left fringe, the message
displays at the top of the window; there is no arrow.
You can customize this variable.
This variable was introduced, or its default value was changed, in
version 22.1 of Emacs.