The following buffer-local variables control the position and width of fringes in windows showing that buffer.
The fringes normally appear between the display margins and the window
text. If the value is non-nil, they appear outside the display
margins. See Displaying in the Margins.
This variable, if non-nil, specifies the width of the left
fringe in pixels. A value of nil means to use the left fringe
width from the window’s frame.
This variable, if non-nil, specifies the width of the right
fringe in pixels. A value of nil means to use the right fringe
width from the window’s frame.
Any buffer which does not specify values for these variables uses
the values specified by the left-fringe and right-fringe
frame parameters (see Layout Parameters).
The above variables actually take effect via the function
set-window-buffer (see Buffers and Windows), which calls
set-window-fringes as a subroutine. If you change one of these
variables, the fringe display is not updated in existing windows
showing the buffer, unless you call set-window-buffer again in
each affected window. You can also use set-window-fringes to
control the fringe display in individual windows.
This function sets the fringe widths of window window.
If window is nil, the selected window is used.
The argument left specifies the width in pixels of the left
fringe, and likewise right for the right fringe. A value of
nil for either one stands for the default width. If
outside-margins is non-nil, that specifies that fringes
should appear outside of the display margins.
If window is not large enough to accommodate fringes of the desired width, this leaves the fringes of window unchanged.
The values specified here may be later overridden by invoking
set-window-buffer (see Buffers and Windows) on window
with its keep-margins argument nil or omitted. However,
if the optional fifth argument persistent is non-nil and
the other arguments are processed successfully, the values specified
here unconditionally survive subsequent invocations of
set-window-buffer. This can be used to permanently turn off
fringes in the minibuffer window, consult the description of
set-window-scroll-bars for an example (see Scroll Bars).
This function returns information about the fringes of a window
window. If window is omitted or nil, the selected
window is used. The value has the form (left-width
right-width outside-margins persistent).