1 files changed, 10 insertions, 3 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 714c18be466..23667388b56 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -4413,9 +4413,16 @@ single_display_spec_string_p (Lisp_Object prop, Lisp_Object string)
       prop = XCDR (prop);
       if (!CONSP (prop))
         return 0;
-      /* FIXME: We should eval the condition following `when', like
-         handle_single_display_spec does, and retrun zero if it
-         evaluates to nil.  */
+      /* Actually, the condition following `when' should be eval'ed,
+         like handle_single_display_spec does, and we should return
+         zero if it evaluates to nil.  However, this function is
+         called only when the buffer was already displayed and some
+         glyph in the glyph matrix was found to come from a display
+         string.  Therefore, the condition was already evaluated, and
+         the result was non-nil, otherwise the display string wouldn't
+         have been displayed and we would have never been called for
+         this property.  Thus, we can skip the evaluation and assume
+         its result is non-nil.  */
       prop = XCDR (prop);
     }