1 files changed, 33 insertions, 9 deletions

diff --git a/src/minibuf.c b/src/minibuf.c
index b7f9fd4838c..74d55a8abfd 100644
--- a/src/minibuf.c
+++ b/src/minibuf.c
@@ -2342,7 +2342,7 @@ Return nil if there is no valid completion, else t.  */)
 }
 
 DEFUN ("display-completion-list", Fdisplay_completion_list, Sdisplay_completion_list,
-       1, 1, 0,
+       1, 2, 0,
        doc: /* Display the list of completions, COMPLETIONS, using `standard-output'.
 Each element may be just a symbol or string
 or may be a list of two strings to be printed as if concatenated.
@@ -2352,14 +2352,23 @@ alternative, the second serves as annotation.
 The actual completion alternatives, as inserted, are given `mouse-face'
 properties of `highlight'.
 At the end, this runs the normal hook `completion-setup-hook'.
-It can find the completion buffer in `standard-output'.  */)
-     (completions)
+It can find the completion buffer in `standard-output'.
+The optional second arg COMMON-SUBSTRING is a string.
+It is used to put faces, `completions-first-difference` and
+`completions-common-part' on the completion buffer. The
+`completions-common-part' face is put on the common substring
+specified by COMMON-SUBSTRING. If COMMON-SUBSTRING is nil,
+the faces are not put.
+Internally, COMMON-SUBSTRING is bound to `completion-common-substring'
+during running `completion-setup-hook'. */)
+     (completions, common_substring)
      Lisp_Object completions;
+     Lisp_Object common_substring;
 {
   Lisp_Object tail, elt;
   register int i;
   int column = 0;
-  struct gcpro gcpro1, gcpro2;
+  struct gcpro gcpro1, gcpro2, gcpro3;
   struct buffer *old = current_buffer;
   int first = 1;
 
@@ -2368,7 +2377,7 @@ It can find the completion buffer in `standard-output'.  */)
      except for ELT.  ELT can be pointing to a string
      when terpri or Findent_to calls a change hook.  */
   elt = Qnil;
-  GCPRO2 (completions, elt);
+  GCPRO3 (completions, elt, common_substring);
 
   if (BUFFERP (Vstandard_output))
     set_buffer_internal (XBUFFER (Vstandard_output));
@@ -2517,17 +2526,32 @@ It can find the completion buffer in `standard-output'.  */)
 	}
     }
 
-  UNGCPRO;
-
   if (BUFFERP (Vstandard_output))
     set_buffer_internal (old);
 
   if (!NILP (Vrun_hooks))
-    call1 (Vrun_hooks, intern ("completion-setup-hook"));
+    {
+      int count1 = SPECPDL_INDEX ();
+
+      specbind (intern ("completion-common-substring"), common_substring);
+      call1 (Vrun_hooks, intern ("completion-setup-hook"));
+
+      unbind_to (count1, Qnil);
+    }
+
+  UNGCPRO;
 
   return Qnil;
 }
 
+
+static Lisp_Object
+display_completion_list_1 (list)
+     Lisp_Object list;
+{
+  return Fdisplay_completion_list (list, Qnil);
+}
+
 DEFUN ("minibuffer-completion-help", Fminibuffer_completion_help, Sminibuffer_completion_help,
        0, 0, "",
        doc: /* Display a list of possible completions of the current minibuffer contents.  */)
@@ -2549,7 +2573,7 @@ DEFUN ("minibuffer-completion-help", Fminibuffer_completion_help, Sminibuffer_co
     }
   else
     internal_with_output_to_temp_buffer ("*Completions*",
-					 Fdisplay_completion_list,
+					 display_completion_list_1,
 					 Fsort (completions, Qstring_lessp));
   return Qnil;
 }