Move some X11 drag and drop processing to Lisp

* lisp/term/x-win.el: Set unsupported drop function.
* lisp/x-dnd.el (x-dnd-handle-unsupported-drop): New function.
* src/keyboard.c (kbd_buffer_get_event): Handle
UNSUPPORTED_DROP_EVENT.
* src/termhooks.h (enum event_kind): New event
`UNSUPPORTED_DROP_EVENT'.
* src/xterm.c (x_dnd_send_unsupported_drop): Send those events
instead.
(x_dnd_do_unsupported_drop): Move actual unsupported drop
handling here.
(syms_of_xterm): New variable `x-dnd-unsupported-drop-function'.
* src/xterm.h: Update prototypes.

1 files changed, 19 insertions, 0 deletions

diff --git a/src/termhooks.h b/src/termhooks.h
index 93ac9ba0d2e..0f02b56e9ee 100644
--- a/src/termhooks.h
+++ b/src/termhooks.h
@@ -208,6 +208,25 @@ enum event_kind
 				   representation of the dropped items.
 				   .timestamp gives a timestamp (in
 				   milliseconds) for the click.  */
+#ifdef HAVE_X_WINDOWS
+  UNSUPPORTED_DROP_EVENT,      /* Event sent when the regular C
+				  drag-and-drop machinery could not
+				  handle a drop to a window.
+
+			          .code is the XID of the window that
+			          could not be dropped to.
+
+			          .arg is a list of the local value of
+			          XdndSelection, a list of selection
+			          targets, and the intended action to
+			          be taken upon drop, and .timestamp
+			          gives the timestamp where the drop
+			          happened.
+
+			          .x and .y give the coordinates of
+			          the drop originating from the root
+			          window.  */
+#endif
   USER_SIGNAL_EVENT,		/* A user signal.
                                    code is a number identifying it,
                                    index into lispy_user_signals.  */