Improve documentation of 'no-special-glyphs' frame parameter

* doc/lispref/frames.texi (Layout Parameters): Document
limitations of support for 'no-special-glyphs' frame parameter.
(Bug#71163)
* doc/lispref/display.texi (Truncation): Update for when
'fringe-mode' is off.

2 files changed, 12 insertions, 5 deletions

diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 869bf15a40a..ef44c8d80f5 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -148,7 +148,8 @@ boundary.  @xref{Filling}.
 
    On a graphical display, tiny arrow images in the window fringes
 indicate truncated and continued lines (@pxref{Fringes}).  On a text
-terminal, a @samp{$} in the rightmost column of the window indicates
+terminal, and on a graphical display when @code{fringe-mode} was
+turned off, a @samp{$} in the rightmost column of the window indicates
 truncation; a @samp{\} on the rightmost column indicates a line that
 wraps.  (The display table can specify alternate characters to use
 for this; @pxref{Display Tables}).
diff --git a/doc/lispref/frames.texi b/doc/lispref/frames.texi
index edc080153d6..fe5745a85ab 100644
--- a/doc/lispref/frames.texi
+++ b/doc/lispref/frames.texi
@@ -1928,10 +1928,16 @@ integer).  @xref{Line Height}, for more information.
 @vindex no-special-glyphs@r{, a frame parameter}
 @item no-special-glyphs
 If this is non-@code{nil}, it suppresses the display of any truncation
-and continuation glyphs (@pxref{Truncation}) for all buffers displayed
-by this frame.  This is useful to eliminate such glyphs when fitting a
-frame to its buffer via @code{fit-frame-to-buffer} (@pxref{Resizing
-Windows}).
+(@pxref{Truncation}) and continuation glyphs for all the buffers
+displayed by this frame.  This is useful to eliminate such glyphs when
+fitting a frame to its buffer via @code{fit-frame-to-buffer}
+(@pxref{Resizing Windows}).  This frame parameter has effect only for
+GUI frames shown on graphical displays, and only if the fringes are
+disabled.  This parameter is intended as a purely-presentation
+feature, and in particular should not be used for frames where the
+user can interactively insert text, or more generally where the cursor
+is shown.  A notable example of frames where this is used is tooltip
+frames (@pxref{Tooltips}).
 @end table