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, 48 insertions, 0 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index c0e821a934c..05880617385 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -23924,6 +23924,27 @@ decode_mode_spec (struct window *w, register int c, int field_width,
         return " Narrow";
       break;
 
+      /* Display the "degree of travel" of the window through the buffer.  */
+    case 'o':
+      {
+        ptrdiff_t toppos = marker_position (w->start);
+        ptrdiff_t botpos = BUF_Z (b) - w->window_end_pos;
+        ptrdiff_t begv = BUF_BEGV (b);
+        ptrdiff_t zv = BUF_ZV (b);
+
+        if (zv <= botpos)
+          return toppos <= begv ? "All" : "Bottom";
+        else if (toppos <= begv)
+          return "Top";
+        else
+          {
+          sprintf (decode_mode_spec_buf, "%2d%%",
+                   percent99 (toppos - begv, (toppos - begv) + (zv - botpos)));
+          return decode_mode_spec_buf;
+          }
+      }
+
+      /* Display percentage of buffer above the top of the screen.  */
     case 'p':
       {
         ptrdiff_t pos = marker_position (w->start);
@@ -23961,6 +23982,33 @@ decode_mode_spec (struct window *w, register int c, int field_width,
           }
       }
 
+      /* Display percentage offsets of top and bottom of the window,
+         using "All" (but not "Top" or "Bottom") where appropriate.  */
+    case 'q':
+      {
+        ptrdiff_t toppos = marker_position (w->start);
+        ptrdiff_t botpos = BUF_Z (b) - w->window_end_pos;
+        ptrdiff_t begv = BUF_BEGV (b);
+        ptrdiff_t zv = BUF_ZV (b);
+
+        if ((toppos <= begv) && (zv <= botpos))
+          return "All   ";
+
+        if (toppos <= begv)
+          strcpy (decode_mode_spec_buf, "0-");
+        else
+          sprintf (decode_mode_spec_buf, "%d-",
+                   percent99 (toppos - begv, zv - begv));
+
+        if (zv <= botpos)
+          strcat (decode_mode_spec_buf, "100%");
+        else
+          sprintf (&decode_mode_spec_buf [strlen (decode_mode_spec_buf)],
+                   "%d%%", percent99 (botpos - begv, zv - begv));
+
+        return decode_mode_spec_buf;
+      }
+
     case 's':
       /* status of process */
       obj = Fget_buffer_process (Fcurrent_buffer ());