Always wait for XdndStatus before sending XdndDrop

* src/xterm.c (x_dnd_do_drop): New function.
(x_dnd_begin_drag_and_drop): Clear new flag.
(handle_one_xevent): Use that function; send drops upon receipt
of pending XdndStatus, to avoid race conditions where we don't
yet know the selected action.

1 files changed, 55 insertions, 9 deletions

diff --git a/src/xterm.c b/src/xterm.c
index 6a357b473d6..de8e973173f 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -1268,6 +1268,13 @@ static Window x_dnd_waiting_for_status_window;
    upon receiving an XdndStatus event from said window.  */
 static XEvent x_dnd_pending_send_position;
 
+/* If true, send a drop from `x_dnd_finish_frame' to the pending
+   status window after receiving all pending XdndStatus events.  */
+static bool x_dnd_need_send_drop;
+
+/* The protocol version of any such drop.  */
+static int x_dnd_send_drop_proto;
+
 /* The action the drop target actually chose to perform.
 
    Under XDND, this is set upon receiving the XdndFinished or
@@ -4529,6 +4536,19 @@ x_dnd_send_drop (struct frame *f, Window target, Time timestamp,
   return true;
 }
 
+static bool
+x_dnd_do_drop (Window target, int supported)
+{
+  if (x_dnd_waiting_for_status_window != target)
+    return x_dnd_send_drop (x_dnd_frame, target,
+                            x_dnd_selection_timestamp, supported);
+
+  x_dnd_need_send_drop = true;
+  x_dnd_send_drop_proto = supported;
+
+  return true;
+}
+
 static void
 x_set_dnd_targets (Atom *targets, int ntargets)
 {
@@ -11398,6 +11418,9 @@ x_dnd_begin_drag_and_drop (struct frame *f, Time time, Atom xaction,
   ltimestamp = x_timestamp_for_selection (FRAME_DISPLAY_INFO (f),
                                           QXdndSelection);
 
+  if (NILP (ltimestamp))
+    error ("No local value for XdndSelection");
+
   if (BIGNUMP (ltimestamp))
     x_dnd_selection_timestamp = bignum_to_intmax (ltimestamp);
   else
@@ -11538,6 +11561,7 @@ x_dnd_begin_drag_and_drop (struct frame *f, Time time, Atom xaction,
   x_dnd_allow_current_frame = allow_current_frame;
   x_dnd_movement_frame = NULL;
   x_dnd_init_type_lists = false;
+  x_dnd_need_send_drop = false;
 #ifdef HAVE_XKB
   x_dnd_keyboard_state = 0;
 
@@ -16426,8 +16450,10 @@ handle_one_xevent (struct x_display_info *dpyinfo,
       {
         int rc;
 
-        if (x_dnd_in_progress
-            && FRAME_DISPLAY_INFO (x_dnd_frame) == dpyinfo
+        if (((x_dnd_in_progress
+              && FRAME_DISPLAY_INFO (x_dnd_frame) == dpyinfo)
+             || (x_dnd_waiting_for_finish
+                 && FRAME_DISPLAY_INFO (x_dnd_finish_frame) == dpyinfo))
             && event->xclient.message_type == dpyinfo->Xatom_XdndStatus)
           {
             Window target;
@@ -16436,6 +16462,7 @@ handle_one_xevent (struct x_display_info *dpyinfo,
             target = event->xclient.data.l[0];
 
             if (x_dnd_last_protocol_version != -1
+                && x_dnd_in_progress
                 && target == x_dnd_last_seen_window
                 && event->xclient.data.l[1] & 2)
               {
@@ -16452,7 +16479,8 @@ handle_one_xevent (struct x_display_info *dpyinfo,
               x_dnd_mouse_rect_target = None;
 
             if (x_dnd_last_protocol_version != -1
-                && target == x_dnd_last_seen_window)
+                && (x_dnd_in_progress
+                    && target == x_dnd_last_seen_window))
               {
                 if (event->xclient.data.l[1] & 1)
                   {
@@ -16484,6 +16512,26 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                   }
                 else
                   x_dnd_waiting_for_status_window = None;
+
+                /* Send any pending drop if warranted.  */
+                if (x_dnd_waiting_for_finish && x_dnd_need_send_drop
+                    && x_dnd_waiting_for_status_window == None)
+                  {
+                    if (event->xclient.data.l[1] & 1)
+                      {
+                        if (x_dnd_send_drop_proto >= 2)
+                          x_dnd_action = event->xclient.data.l[4];
+                        else
+                          x_dnd_action = dpyinfo->Xatom_XdndActionCopy;
+                      }
+                    else
+                      x_dnd_action = None;
+
+                    x_dnd_waiting_for_finish
+                      = x_dnd_send_drop (x_dnd_finish_frame,
+                                         target, x_dnd_selection_timestamp,
+                                         x_dnd_send_drop_proto);
+                  }
               }
 
             goto done;
@@ -18948,9 +18996,8 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                         x_dnd_waiting_for_finish_proto = x_dnd_last_protocol_version;
 
                         x_dnd_waiting_for_finish
-                          = x_dnd_send_drop (x_dnd_frame, x_dnd_last_seen_window,
-                                             x_dnd_selection_timestamp,
-                                             x_dnd_last_protocol_version);
+                          = x_dnd_do_drop (x_dnd_last_seen_window,
+                                           x_dnd_last_protocol_version);
                         x_dnd_finish_display = dpyinfo->display;
                       }
                     else if (x_dnd_last_seen_window != None)
@@ -20354,9 +20401,8 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                               x_dnd_waiting_for_finish_proto = x_dnd_last_protocol_version;
 
                               x_dnd_waiting_for_finish
-                                = x_dnd_send_drop (x_dnd_frame, x_dnd_last_seen_window,
-                                                   x_dnd_selection_timestamp,
-                                                   x_dnd_last_protocol_version);
+                                = x_dnd_do_drop (x_dnd_last_seen_window,
+                                                 x_dnd_last_protocol_version);
                               x_dnd_finish_display = dpyinfo->display;
                             }
                           else if (x_dnd_last_seen_window != None)