Enhance mode-line percentage offset facility, with "%o" and "%q"

"%o" will display the percentage "travel" of the window through the buffer.
"%q" will display a combination of the percentage offsets of the top and
bottom of the window.  The new user option mode-line-percent-position will
facilitate selecting a setting for this part of the mode line.

* lisp/bindings.el (mode-line-percent-position): New customizable user option.
(mode-line-position): Use mode-line-percent-position in place of "%p", etc.

* src/xdisp.c (decode_mode_spec): Add handlers for "%o" and "%q".

* doc/lispref/modes.texi (Mode Line Variables): Document
mode-line-percent-position.
(%-Constructs): Document %o and %q.

* etc/NEWS: Add an entry for these new facilities.

1 files changed, 18 insertions, 0 deletions

diff --git a/doc/lispref/modes.texi b/doc/lispref/modes.texi
index eb72fcfd369..0e476b47a31 100644
--- a/doc/lispref/modes.texi
+++ b/doc/lispref/modes.texi
@@ -1972,6 +1972,14 @@ displays the buffer percentage and, optionally, the buffer size, the
 line number and the column number.
 @end defvar
 
+@defopt mode-line-percent-position
+This option is used in @code{mode-line-position}.  Its value specifies
+both the buffer percentage to display (one of @code{nil}, @code{"%o"},
+@code{"%p"}, @code{"%P"} or @code{"%q"}, @pxref{%-Constructs}) and a
+width to space-fill or truncate to.  You are recommended to set this
+option with the @code{customize-variable} facility.
+@end defopt
+
 @defvar vc-mode
 The variable @code{vc-mode}, buffer-local in each buffer, records
 whether the buffer's visited file is maintained with version control,
@@ -2147,6 +2155,12 @@ of the buffer.
 @samp{Narrow} when narrowing is in effect; nothing otherwise (see
 @code{narrow-to-region} in @ref{Narrowing}).
 
+@item %o
+The degree of @dfn{travel} of the window through (the visible portion
+of) the buffer, i.e. the size of the text above the top of the window
+expressed as a percentage of all the text outside the window, or
+@samp{Top}, @samp{Bottom} or @samp{All}.
+
 @item %p
 The percentage of the buffer text above the @strong{top} of window, or
 @samp{Top}, @samp{Bottom} or @samp{All}.  Note that the default mode
@@ -2158,6 +2172,10 @@ the window (which includes the text visible in the window, as well as
 the text above the top), plus @samp{Top} if the top of the buffer is
 visible on screen; or @samp{Bottom} or @samp{All}.
 
+@item %q
+The percentages of text above both the @strong{top} and the
+@strong{bottom} of the window, separated by @samp{-}, or @samp{All}.
+
 @item %s
 The status of the subprocess belonging to the current buffer, obtained with
 @code{process-status}.  @xref{Process Information}.