(display_mode_element): Don't let mode_line_proptrans_alist

grow without limit.  Move recently used elements to the front.

1 files changed, 14 insertions, 1 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 107218b928b..53770a4b138 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -13695,15 +13695,28 @@ display_mode_element (it, depth, field_width, precision, elt, props, risky)
 
                 aelt = Fassoc (elt, mode_line_proptrans_alist);
                 if (! NILP (aelt) && !NILP (Fequal (props, XCDR (aelt))))
-                  elt = XCAR (aelt);
+                  {
+                    mode_line_proptrans_alist
+                      = Fcons (aelt, Fdelq (aelt, mode_line_proptrans_alist));
+                    elt = XCAR (aelt);
+                  }
                 else
                   {
+                    Lisp_Object tem;
+
                     elt = Fcopy_sequence (elt);
                     Fset_text_properties (make_number (0), Flength (elt),
                                           props, elt);
+                    /* Add this item to mode_line_proptrans_alist.  */
                     mode_line_proptrans_alist
                       = Fcons (Fcons (elt, props),
                                mode_line_proptrans_alist);
+                    /* Truncate mode_line_proptrans_alist
+                       to at most 50 elements.  */
+                    tem = Fnthcdr (make_number (50),
+                                   mode_line_proptrans_alist);
+                    if (! NILP (tem))
+                      XSETCDR (tem, Qnil);
                   }
               }
           }