Provide an override for Webview drop effect....

webkit/glue/webview_impl.cc

 /*
 * Copyright 2007 Google Inc. All Rights Reserved.
 *
 * Portions Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
 *
 * ***** BEGIN LICENSE BLOCK *****
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
@@ skipping 345 matching lines @@
       new_navigation_loader_(NULL),
 #endif
       zoom_level_(0),
       context_menu_allowed_(false),
       doing_drag_and_drop_(false),
       suppress_next_keypress_event_(false),
       window_open_disposition_(IGNORE_ACTION),
       ime_accept_events_(true),
       drag_target_dispatch_(false),
       drag_identity_(0),
+      drop_effect_(DROP_EFFECT_DEFAULT),
+      drop_accept_(false),
       autocomplete_popup_showing_(false) {
   // WebKit/win/WebView.cpp does the same thing, except they call the
   // KJS specific wrapper around this method. We need to have threading
   // initialized because CollatorICU requires it.
   WTF::initializeThreading();
 
   // set to impossible point so we always get the first mouse pos
   last_mouse_position_ = WebPoint(-1, -1);
 
   // the page will take ownership of the various clients
@@ skipping 1261 matching lines @@
 
   current_drag_data_ =
       webkit_glue::WebDragDataToChromiumDataObject(web_drag_data);
   drag_identity_ = identity;
 
   DragData drag_data(
       current_drag_data_.get(),
       webkit_glue::WebPointToIntPoint(client_point),
       webkit_glue::WebPointToIntPoint(screen_point),
       kDropTargetOperation);
+
+  drop_effect_ = DROP_EFFECT_DEFAULT;
   drag_target_dispatch_ = true;
   DragOperation effect = page_->dragController()->dragEntered(&drag_data);
   drag_target_dispatch_ = false;
 
-  return effect != DragOperationNone;
+  if (drop_effect_ != DROP_EFFECT_DEFAULT)
+    return drop_accept_ = (drop_effect_ != DROP_EFFECT_NONE);
+  return drop_accept_ = (effect != DragOperationNone);
 }
 
 bool WebViewImpl::DragTargetDragOver(
     const WebPoint& client_point,
     const WebPoint& screen_point) {
   DCHECK(current_drag_data_.get());
 
   DragData drag_data(
       current_drag_data_.get(),
       webkit_glue::WebPointToIntPoint(client_point),
       webkit_glue::WebPointToIntPoint(screen_point),
       kDropTargetOperation);
+
+  drop_effect_ = DROP_EFFECT_DEFAULT;
   drag_target_dispatch_ = true;
   DragOperation effect = page_->dragController()->dragUpdated(&drag_data);
   drag_target_dispatch_ = false;
 
-  return effect != DragOperationNone;
+  if (drop_effect_ != DROP_EFFECT_DEFAULT)
+    return drop_accept_ = (drop_effect_ != DROP_EFFECT_NONE);
+  return drop_accept_ = (effect != DragOperationNone);
 }
 
 void WebViewImpl::DragTargetDragLeave() {
   DCHECK(current_drag_data_.get());
 
   DragData drag_data(
       current_drag_data_.get(),
       IntPoint(),
       IntPoint(),
       kDropTargetOperation);
+
   drag_target_dispatch_ = true;
   page_->dragController()->dragExited(&drag_data);
   drag_target_dispatch_ = false;
 
   current_drag_data_ = NULL;
+  drop_effect_ = DROP_EFFECT_DEFAULT;
+  drop_accept_ = false;
   drag_identity_ = 0;
 }
 
 void WebViewImpl::DragTargetDrop(
     const WebPoint& client_point,
     const WebPoint& screen_point) {
   DCHECK(current_drag_data_.get());
 
+  // If this webview transitions from the "drop accepting" state to the "not
+  // accepting" state, then our IPC message reply indicating that may be in-
+  // flight, or else delayed by javascript processing in this webview.  If a
+  // drop happens before our IPC reply has reached the browser process, then
+  // the browser forwards the drop to this webview.  So only allow a drop to
+  // proceed if our webview drop_accept_ state is true.
+
+  if (!drop_accept_) {  // IPC RACE CONDITION: do not allow this drop.
+    DragTargetDragLeave();
+    return;
+  }
+
   DragData drag_data(
       current_drag_data_.get(),
       webkit_glue::WebPointToIntPoint(client_point),
       webkit_glue::WebPointToIntPoint(screen_point),
       kDropTargetOperation);
+
   drag_target_dispatch_ = true;
   page_->dragController()->performDrag(&drag_data);
   drag_target_dispatch_ = false;
 
   current_drag_data_ = NULL;
+  drop_effect_ = DROP_EFFECT_DEFAULT;
+  drop_accept_ = false;
   drag_identity_ = 0;
 }
 
 int32 WebViewImpl::GetDragIdentity() {
   if (drag_target_dispatch_)
     return drag_identity_;
   return 0;
 }
 
+bool WebViewImpl::SetDropEffect(bool accept) {
+  if (drag_target_dispatch_) {
+    drop_effect_ = accept ? DROP_EFFECT_COPY : DROP_EFFECT_NONE;
+    return true;
+  } else {
+    return false;
+  }
+}
+
 SearchableFormData* WebViewImpl::CreateSearchableFormDataForFocusedNode() {
   if (!page_.get())
     return NULL;
 
   if (RefPtr<Frame> focused = page_->focusController()->focusedFrame()) {
     RefPtr<Document> document = focused->document();
     if (document.get()) {
       RefPtr<Node> focused_node = document->focusedNode();
       if (focused_node.get() &&
           focused_node->nodeType() == Node::ELEMENT_NODE) {
@@ skipping 176 matching lines @@
 
   return document->focusedNode();
 }
 
 HitTestResult WebViewImpl::HitTestResultForWindowPos(const IntPoint& pos) {
   IntPoint doc_point(
       page_->mainFrame()->view()->windowToContents(pos));
   return page_->mainFrame()->eventHandler()->
       hitTestResultAtPoint(doc_point, false);
 }