Merge remote-tracking branch 'origin/master' into feature/android

1 files changed, 47 insertions, 2 deletions

diff --git a/src/window.c b/src/window.c
index 8c42d3cdd0c..6423060b985 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5475,6 +5475,48 @@ window_wants_mode_line (struct window *w)
 
 
 /**
+ * null_header_line_format:
+ *
+ * Return non-zero when header line format FMT indicates that the
+ * header line should not be displayed at all, for windows on frame F.
+ *
+ * This is when FMT is nil, or if FMT is a cons cell and either its
+ * car is a symbol whose value as a variable is nil or void, or its
+ * car is the symbol ':eval' and its cadr evaluates to nil.
+ */
+static bool
+null_header_line_format (Lisp_Object fmt, struct frame *f)
+{
+  Lisp_Object car;
+  Lisp_Object val;
+
+  if (NILP (fmt))
+    return true;
+
+  if (CONSP (fmt))
+    {
+      car = XCAR (fmt);
+      if (SYMBOLP (car))
+        {
+          if (EQ (car, QCeval))
+            {
+              val = safe_eval_inhibit_quit (XCAR (XCDR (fmt)));
+              if (!FRAME_LIVE_P (f))
+                signal_error (":eval deleted the frame being displayed", fmt);
+              return NILP (val);
+            }
+          val = find_symbol_value (car);
+          return (SYMBOLP (car)
+                  && (EQ (val, Qunbound)
+                      || NILP (val)));
+        }
+    }
+
+  return false;
+}
+
+
+/**
  * window_wants_header_line:
  *
  * Return 1 if window W wants a header line and is high enough to
@@ -5494,12 +5536,15 @@ window_wants_header_line (struct window *w)
   Lisp_Object window_header_line_format =
     window_parameter (w, Qheader_line_format);
 
+  struct frame *f = WINDOW_XFRAME(w);
+
   return (WINDOW_LEAF_P (w)
           && !MINI_WINDOW_P (w)
           && !WINDOW_PSEUDO_P (w)
           && !EQ (window_header_line_format, Qnone)
-          && (!NILP (window_header_line_format)
-              || !NILP (BVAR (XBUFFER (WINDOW_BUFFER (w)), header_line_format)))
+          && (!null_header_line_format (window_header_line_format, f)
+              || !null_header_line_format (BVAR (XBUFFER (WINDOW_BUFFER (w)),
+                                                 header_line_format), f))
           && (WINDOW_PIXEL_HEIGHT (w)
               > (window_wants_mode_line (w)
                  ? 2 * WINDOW_FRAME_LINE_HEIGHT (w)