master 1da6a6d327 1/2: Always wait for XdndStatus before sending XdndDrop

[Po Lu]

branch: master
commit 1da6a6d3271be003b545e41ae21c3071faf22f86
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    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.
---
 src/xterm.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 55 insertions(+), 9 deletions(-)

diff --git a/src/xterm.c b/src/xterm.c
index 6a357b473d..de8e973173 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)