Explain effects of setting a zero-width fringe

* lisp/fringe.el (fringe-mode): Not non-obvious effects of setting
a fringe to zero width.

diff --git a/lisp/fringe.el b/lisp/fringe.el
index 8c833f02429dec08eb2a558295fd85f742b5e573..1cfcce4542ab50ff504da45960675359461bd977 100644 (file)
--- a/lisp/fringe.el
+++ b/lisp/fringe.el
@@ -244,10 +244,18 @@ When used in a Lisp program, MODE should be one of these:
   nil (meaning the default width).
 - a single integer, which specifies the pixel widths of both
   fringes.
+
 This command may round up the left and right width specifications
 to ensure that their sum is a multiple of the character width of
 a frame.  It never rounds up a fringe width of 0.
 
+Note that removing a right or left fringe (by setting the width
+to zero) makes Emacs reserve one column of the window body to
+display a line continuation marker.  (This happens for both the
+left and right fringe, since Emacs can display both left-to-right
+and right-to-left text.)  You can use `window-max-characters-per-line'
+to check the effective width.
+
 Fringe widths set by `set-window-fringes' override the default
 fringe widths set by this command.  This command applies to all
 frames that exist and frames to be created in the future.  If you