commit 0af1850485f3ad1519e52de2b1694efa922917f4
Author: Pip Cet <pipcet@gmail.com>
Date:   Sat Jun 22 07:53:28 2019 +0000

    snapshot

diff --git a/src/callint.c b/src/callint.c
index 88a3c348d0..6f2e5d5066 100644
--- a/src/callint.c
+++ b/src/callint.c
@@ -824,6 +824,7 @@ syms_of_callint (void)
   DEFSYM (Qlet, "let");
   DEFSYM (Qif, "if");
   DEFSYM (Qwhen, "when");
+  DEFSYM (Qgen, "gen");
   DEFSYM (Qletx, "let*");
   DEFSYM (Qsave_excursion, "save-excursion");
   DEFSYM (Qprogn, "progn");
diff --git a/src/xdisp.c b/src/xdisp.c
index 5699aac61b..717fb30ec3 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -2728,7 +2728,6 @@ safe_call2 (Lisp_Object fn, Lisp_Object arg1, Lisp_Object arg2)
   return safe_call (3, fn, arg1, arg2);
 }
 
-
 
 /***********************************************************************
 			      Debugging
@@ -4893,6 +4892,7 @@ handle_display_spec (struct it *it, Lisp_Object spec, Lisp_Object object,
 #endif
       && !EQ (XCAR (spec), Qspace)
       && !EQ (XCAR (spec), Qwhen)
+      && !EQ (XCAR (spec), Qgen)
       && !EQ (XCAR (spec), Qslice)
       && !EQ (XCAR (spec), Qspace_width)
       && !EQ (XCAR (spec), Qheight)
@@ -4991,6 +4991,8 @@ display_prop_end (struct it *it, Lisp_Object object, struct text_pos start_pos)
    Value is non-zero if something was found which replaces the display
    of buffer or string text.  */
 
+extern Lisp_Object *lface_id_to_name;
+
 static int
 handle_single_display_spec (struct it *it, Lisp_Object spec, Lisp_Object object,
 			    Lisp_Object overlay, struct text_pos *position,
@@ -5002,6 +5004,46 @@ handle_single_display_spec (struct it *it, Lisp_Object spec, Lisp_Object object,
   struct text_pos start_pos = *position;
   void *itdata = NULL;
 
+  if (it != NULL &&
+      CONSP (spec) &&
+      EQ (XCAR (spec), Qgen))
+    {
+      spec = XCDR (spec);
+      if (!CONSP (spec))
+	return 0;
+      Lisp_Object gen = XCAR (spec);
+      struct face *face = FACE_FROM_ID (it->f, it->face_id);
+      Lisp_Object lface = Qnil;
+      Lisp_Object props[] = {
+	QCtype,
+	QCfamily,
+	QCfoundry,
+	QCwidth,
+	QCheight,
+	QCweight,
+	QCslant,
+	QCunderline,
+	QCinverse_video,
+	QCforeground,
+	QCbackground,
+	QCstipple,
+	QCoverline,
+	QCstrike_through,
+	QCbox,
+	QCfont,
+	QCinherit,
+	QCfontset,
+	QCdistant_foreground,
+      };
+      for (int i = 0; i < LFACE_VECTOR_SIZE; i++)
+	lface = Fcons (Fcons (props[i], face->lface[i]),
+		       lface);
+      Lisp_Object font = Qnil;
+      XSETFONT (font, face->font);
+      lface = Fcons (Fcons (QCfont, font), lface);
+      spec = safe_call1 (gen, lface);
+    }
+
   /* If SPEC is a list of the form `(when FORM . VALUE)', evaluate FORM.
      If the result is non-nil, use VALUE instead of SPEC.  */
   form = Qt;
diff --git a/src/xfaces.c b/src/xfaces.c
index 012cc96470..47453c2b31 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -294,7 +294,7 @@ #define FACE_CACHE_BUCKETS_SIZE 1001
 
 /* A vector mapping Lisp face Id's to face names.  */
 
-static Lisp_Object *lface_id_to_name;
+Lisp_Object *lface_id_to_name;
 static ptrdiff_t lface_id_to_name_size;
 
 #ifdef HAVE_WINDOW_SYSTEM