Prevent invisible frames from acting as drag sources

* src/xterm.c (x_dnd_begin_drag_and_drop): Error out if f is
invisible.  It makes no sense for an invisible frame to be a
drag source, so the function just hangs.

diff --git a/src/xterm.c b/src/xterm.c
index 1b0b3ef793fbf5ec25cdb1b1ad09ff14ddbbd0f0..6485374e2ae63931b7bdc81d7331ff85a6e7e41b 100644 (file)
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -1093,6 +1093,9 @@ x_dnd_begin_drag_and_drop (struct frame *f, Time time, Atom xaction,
   char *atom_name;
   Lisp_Object action, ltimestamp;
 
+  if (!FRAME_VISIBLE_P (f))
+    error ("Frame is invisible");
+
   if (x_dnd_in_progress)
     error ("A drag-and-drop session is already in progress");