19.8 Window Fringes
On a graphical display, each Emacs window normally has narrow
fringes on the left and right edges. The fringes display
indications about the text in the window.
The most common use of the fringes is to indicate a continuation
line, when one line of text is split into multiple lines on the
screen. The left fringe shows a curving arrow for each screen line
except the first, indicating that “this is not the real beginning.”
The right fringe shows a curving arrow for each screen line except the
last, indicating that “this is not the real end.”
The fringes indicate line truncation with short horizontal arrows
meaning “there's more text on this line which is scrolled
horizontally out of view;” clicking the mouse on one of the arrows
scrolls the display horizontally in the direction of the arrow. The
fringes can also indicate other things, such as empty lines, or where a
program you are debugging is executing (see Debuggers).
You can enable and disable the fringes for all frames using
M-x fringe-mode. To enable and disable the fringes
for the selected frame, use M-x set-fringe-style.