Ensure redisplay after evaluation

* lisp/progmodes/elisp-mode.el (elisp--eval-last-sexp): Revert
last change.
* lisp/frame.el (redisplay--variables): Populate the
redisplay--variables list.
* src/xdisp.c (maybe_set_redisplay): New function.
(syms_of_xdisp) <redisplay--variables>: New variable.
* src/window.h (maybe_set_redisplay): Declare prototype.
* src/data.c (set_internal): Call maybe_set_redisplay.  (Bug#21835)

3 files changed, 16 insertions, 0 deletions

diff --git a/src/data.c b/src/data.c
index 5382b01066e..4db93f5625f 100644
--- a/src/data.c
+++ b/src/data.c
@@ -1240,6 +1240,7 @@ set_internal (Lisp_Object symbol, Lisp_Object newval, Lisp_Object where,
         return;
     }
 
+  maybe_set_redisplay (symbol);
   sym = XSYMBOL (symbol);
 
  start:
diff --git a/src/window.h b/src/window.h
index eaff57eaedf..135f5de7d8a 100644
--- a/src/window.h
+++ b/src/window.h
@@ -1056,6 +1056,7 @@ extern void wset_redisplay (struct window *w);
 extern void fset_redisplay (struct frame *f);
 extern void bset_redisplay (struct buffer *b);
 extern void bset_update_mode_line (struct buffer *b);
+extern void maybe_set_redisplay (Lisp_Object);
 /* Call this to tell redisplay to look for other windows than selected-window
    that need to be redisplayed.  Calling one of the *set_redisplay functions
    above already does it, so it's only needed in unusual cases.  */
diff --git a/src/xdisp.c b/src/xdisp.c
index bdf2d09179e..f6d63ea702f 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -620,6 +620,16 @@ bset_update_mode_line (struct buffer *b)
   b->text->redisplay = true;
 }
 
+void
+maybe_set_redisplay (Lisp_Object symbol)
+{
+  if (!NILP (Fassoc_string (symbol, Vredisplay__variables, Qnil)))
+    {
+      bset_update_mode_line (current_buffer);
+      current_buffer->prevent_redisplay_optimizations_p = true;
+    }
+}
+
 #ifdef GLYPH_DEBUG
 
 /* True means print traces of redisplay if compiled with
@@ -31465,6 +31475,10 @@ display table takes effect; in this case, Emacs does not consult
   DEFVAR_LISP ("redisplay--mode-lines-cause", Vredisplay__mode_lines_cause,
                doc: /*  */);
   Vredisplay__mode_lines_cause = Fmake_hash_table (0, NULL);
+
+  DEFVAR_LISP ("redisplay--variables", Vredisplay__variables,
+     doc: /* A list of variables changes to which trigger a thorough redisplay.  */);
+  Vredisplay__variables = Qnil;
 }