Improve safety of various DND callbacks

* src/xterm.c (x_dnd_begin_drag_and_drop): Restore selection
events if DND is no longer in progress and don't call
x-dnd-movement-function.

1 files changed, 23 insertions, 8 deletions

diff --git a/src/xterm.c b/src/xterm.c
index 94c996a11dc..5c591134692 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -10646,7 +10646,12 @@ x_dnd_begin_drag_and_drop (struct frame *f, Time time, Atom xaction,
               /* FIXME: how come this can end up with movement frames
                  from other displays on GTK builds?  */
               && (FRAME_X_DISPLAY (x_dnd_movement_frame)
-                  == FRAME_X_DISPLAY (f)))
+                  == FRAME_X_DISPLAY (f))
+              /* If both those variables are false, then F is no
+                 longer protected from deletion by Lisp code.  This
+                 can only happen during the final iteration of the DND
+                 event loop.  */
+              && (x_dnd_in_progress || x_dnd_waiting_for_finish))
             {
               XSETFRAME (frame_object, x_dnd_movement_frame);
               XSETINT (x, x_dnd_movement_x);
@@ -10677,14 +10682,24 @@ x_dnd_begin_drag_and_drop (struct frame *f, Time time, Atom xaction,
             {
               if (hold_quit.kind == SELECTION_REQUEST_EVENT)
                 {
-                  x_dnd_old_window_attrs = root_window_attrs;
-                  x_dnd_unwind_flag = true;
+                  /* It's not safe to run Lisp inside this function if
+                     x_dnd_in_progress and x_dnd_waiting_for_finish
+                     are unset, so push it back into the event queue.  */
+
+                  if (!x_dnd_in_progress && !x_dnd_waiting_for_finish)
+                    kbd_buffer_store_event (&hold_quit);
+                  else
+                    {
+                      x_dnd_old_window_attrs = root_window_attrs;
+                      x_dnd_unwind_flag = true;
+
+                      ref = SPECPDL_INDEX ();
+                      record_unwind_protect_ptr (x_dnd_cleanup_drag_and_drop, f);
+                      x_handle_selection_event ((struct selection_input_event *) &hold_quit);
+                      x_dnd_unwind_flag = false;
+                      unbind_to (ref, Qnil);
+                    }
 
-                  ref = SPECPDL_INDEX ();
-                  record_unwind_protect_ptr (x_dnd_cleanup_drag_and_drop, f);
-                  x_handle_selection_event ((struct selection_input_event *) &hold_quit);
-                  x_dnd_unwind_flag = false;
-                  unbind_to (ref, Qnil);
                   continue;
                 }