1 files changed, 46 insertions, 3 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index b5adee51055..6606e49e428 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -25451,14 +25451,49 @@ display_mode_line (struct window *w, enum face_id face_id, Lisp_Object format)
                          format_mode_line_unwind_data (NULL, NULL,
                                                        Qnil, false));
 
-  mode_line_target = MODE_LINE_DISPLAY;
-
   /* Temporarily make frame's keyboard the current kboard so that
      kboard-local variables in the mode_line_format will get the right
      values.  */
   push_kboard (FRAME_KBOARD (it.f));
   record_unwind_save_match_data ();
-  display_mode_element (&it, 0, 0, 0, format, Qnil, false);
+
+  if (NILP (Vmode_line_compact))
+    {
+      mode_line_target = MODE_LINE_DISPLAY;
+      display_mode_element (&it, 0, 0, 0, format, Qnil, false);
+    }
+  else
+    {
+      Lisp_Object mode_string = Fformat_mode_line (format, Qnil, Qnil, Qnil);
+      if (EQ (Vmode_line_compact, Qlong)
+          && window_body_width (XWINDOW (selected_window), FALSE) >=
+          SCHARS (mode_string))
+        {
+          display_string (SSDATA (mode_string), Qnil, Qnil, 0, 0, &it, 0, 0, 0,
+                          STRING_MULTIBYTE (mode_string));
+        }
+      else
+        {
+          char *string = xmalloc (SBYTES (mode_string) + 1),
+            *ostring = SSDATA (mode_string);
+          char *s = string, prev = 0;
+
+          /* Copy over the data from the mode line string, but ignore
+             repeating spaces.  This should be safe even for multibyte
+             strings, since this is UTF-8. */
+          for (int i = 0; i < SBYTES (mode_string); i++)
+            {
+              char c = ostring[i];
+              if (!(c == ' ' && prev == ' '))
+                prev = *s++ = c;
+            }
+          *s = 0;
+
+          display_string (string, Qnil, Qnil, 0, 0, &it, 0, 0, 0,
+                          STRING_MULTIBYTE (mode_string));
+          xfree (string);
+        }
+    }
   pop_kboard ();
 
   unbind_to (count, Qnil);
@@ -34805,6 +34840,14 @@ wide as that tab on the display.  */);
 The face used for trailing whitespace is `trailing-whitespace'.  */);
   Vshow_trailing_whitespace = Qnil;
 
+  DEFVAR_LISP ("mode-line-compact", Vmode_line_compact,
+    doc: /* Non-nil means that mode lines should be compact.
+This means that repeating spaces will be replaced with a single space.
+If this variable is `long', only mode lines that are wider than the
+currently selected window are compressed. */);
+  Vmode_line_compact = Qnil;
+  DEFSYM (Qlong, "long");
+
   DEFVAR_LISP ("nobreak-char-display", Vnobreak_char_display,
     doc: /* Control highlighting of non-ASCII space and hyphen chars.
 If the value is t, Emacs highlights non-ASCII chars which have the