Add an identity (id) to system drag & drop.

Used for gears file drag & drop in chrome, assign a drag id (identity) to
each drag and drop session.

Send the identity to the renderer WebViewImpl in drag enter notifications,
provide a getter method.

BUG=7995

Original patch by noel.gordon@gmail.com in:
http://codereview.chromium.org/28108/show

Review URL: http://codereview.chromium.org/28158

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@10430 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 71 insertions, 2 deletions

diff --git a/base/base_drop_target.cc b/base/base_drop_target.cc
index 9809255..1dda396 100644
--- a/base/base_drop_target.cc
+++ b/base/base_drop_target.cc
@@ -11,6 +11,7 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 IDropTargetHelper* BaseDropTarget::cached_drop_target_helper_ = NULL;
+int32 BaseDropTarget::drag_identity_ = 0;
 
 BaseDropTarget::BaseDropTarget(HWND hwnd)
     : hwnd_(hwnd),
@@ -53,6 +54,11 @@ HRESULT BaseDropTarget::DragEnter(IDataObject* data_object,
     *effect = DROPEFFECT_NONE;
     return S_OK;
   }
+
+  // Update the drag identity, skipping 0.
+  if (++drag_identity_ == 0)
+    ++drag_identity_;
+
   current_data_object_ = data_object;
   POINT screen_pt = { cursor_position.x, cursor_position.y };
   *effect = OnDragEnter(current_data_object_, key_state, screen_pt, *effect);
diff --git a/base/base_drop_target.h b/base/base_drop_target.h
index 9f20752..cf63be28 100644
--- a/base/base_drop_target.h
+++ b/base/base_drop_target.h
@@ -85,6 +85,9 @@ class BaseDropTarget : public IDropTarget {
                        POINT cursor_position,
                        DWORD effect);
 
+  // Return the drag identity.
+  static int32 GetDragIdentity() { return drag_identity_; }
+
  private:
   // Returns the cached drop helper, creating one if necessary. The returned
   // object is not addrefed. May return NULL if the object couldn't be created.
@@ -103,6 +106,14 @@ class BaseDropTarget : public IDropTarget {
   // first time it is actually used.
   static IDropTargetHelper* cached_drop_target_helper_;
 
+  // The drag identity (id). An up-counter that increases when the cursor first
+  // moves over the HWND in a DnD session (OnDragEnter). 0 is reserved to mean
+  // the "no/unknown" identity, and is used for initialization. The identity is
+  // sent to the renderer in drag enter notifications. Note: the identity value
+  // is passed over the renderer NPAPI interface to gears, so use int32 instead
+  // of int here.
+  static int32 drag_identity_;
+
   // The HWND of the source. This HWND is used to determine coordinates for
   // mouse events that are sent to the renderer notifying various drag states.
   HWND hwnd_;
diff --git a/chrome/browser/tab_contents/web_drop_target.cc b/chrome/browser/tab_contents/web_drop_target.cc
index 90ac002..eb740ee 100644
--- a/chrome/browser/tab_contents/web_drop_target.cc
+++ b/chrome/browser/tab_contents/web_drop_target.cc
@@ -100,7 +100,7 @@ DWORD WebDropTarget::OnDragEnter(IDataObject* data_object,
 
   // TODO(tc): PopulateWebDropData can be slow depending on what is in the
   // IDataObject.  Maybe we can do this in a background thread.
-  WebDropData drop_data;
+  WebDropData drop_data(GetDragIdentity());
   WebDropData::PopulateWebDropData(data_object, &drop_data);
 
   if (drop_data.url.is_empty())
@@ -136,6 +136,12 @@ DWORD WebDropTarget::OnDragOver(IDataObject* data_object,
       gfx::Point(client_pt.x, client_pt.y),
       gfx::Point(cursor_position.x, cursor_position.y));
 
+  // Again we don't wait on the renderer to respond, but this can lead to
+  // a race condition.  If the renderer does not want the drop data, then
+  // we won't know until the response from the renderer arrives.  So if a
+  // drop happens before the response arrives, we drop on a renderer that
+  // doesn't want the data.  TODO(noel): fix this.
+
   if (!is_drop_target_)
     return DROPEFFECT_NONE;
 
diff --git a/chrome/common/render_messages.h b/chrome/common/render_messages.h
index e2a0aa0..7fa88de 100755
--- a/chrome/common/render_messages.h
+++ b/chrome/common/render_messages.h
@@ -1539,6 +1539,7 @@ template <>
 struct ParamTraits<WebDropData> {
   typedef WebDropData param_type;
   static void Write(Message* m, const param_type& p) {
+    WriteParam(m, p.identity);
     WriteParam(m, p.url);
     WriteParam(m, p.url_title);
     WriteParam(m, p.file_extension);
@@ -1551,6 +1552,7 @@ struct ParamTraits<WebDropData> {
   }
   static bool Read(const Message* m, void** iter, param_type* p) {
     return
+      ReadParam(m, iter, &p->identity) &&
       ReadParam(m, iter, &p->url) &&
       ReadParam(m, iter, &p->url_title) &&
       ReadParam(m, iter, &p->file_extension) &&
diff --git a/webkit/glue/webdropdata.h b/webkit/glue/webdropdata.h
index 9afcd04..7c9fe19 100644
--- a/webkit/glue/webdropdata.h
+++ b/webkit/glue/webdropdata.h
@@ -16,7 +16,15 @@
 struct IDataObject;
 
 struct WebDropData {
-  // User is dropping a link on the webview.
+  // Construct with a given drag identity.  Note: identity is an int32 because
+  // it is passed over the renderer NPAPI interface to gears.
+  explicit WebDropData(int32 drag_identity) : identity(drag_identity) {}
+  int32 identity;
+
+  // For default constructions, use drag |identity| 0.
+  WebDropData() : identity(0) {}
+
+  // User is dragging a link into the webview.
   GURL url;
   std::wstring url_title;  // The title associated with |url|.
 
diff --git a/webkit/glue/webview.h b/webkit/glue/webview.h
index fbd4f33f..d8ef94d 100644
--- a/webkit/glue/webview.h
+++ b/webkit/glue/webview.h
@@ -185,6 +185,7 @@ class WebView : public WebWidget {
   virtual void DragTargetDragLeave() = 0;
   virtual void DragTargetDrop(
       int client_x, int client_y, int screen_x, int screen_y) = 0;
+  virtual int32 GetDragIdentity() = 0;
 
   // Notifies the webview that autofill suggestions are available for a node.
   virtual void AutofillSuggestionsForNode(
diff --git a/webkit/glue/webview_impl.cc b/webkit/glue/webview_impl.cc
index 6b0444d..4db2ac0 100644
--- a/webkit/glue/webview_impl.cc
+++ b/webkit/glue/webview_impl.cc
@@ -334,6 +334,8 @@ WebViewImpl::WebViewImpl()
       suppress_next_keypress_event_(false),
       window_open_disposition_(IGNORE_ACTION),
       ime_accept_events_(true),
+      drag_target_dispatch_(false),
+      drag_identity_(0),
       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
@@ -1472,37 +1474,61 @@ bool WebViewImpl::DragTargetDragEnter(const WebDropData& drop_data,
   DCHECK(!current_drop_data_.get());
 
   current_drop_data_ = webkit_glue::WebDropDataToChromiumDataObject(drop_data);
+  drag_identity_ = drop_data.identity;
 
   DragData drag_data(current_drop_data_.get(), IntPoint(client_x, client_y),
       IntPoint(screen_x, screen_y), kDropTargetOperation);
+  drag_target_dispatch_ = true;
   DragOperation effect = page_->dragController()->dragEntered(&drag_data);
+  drag_target_dispatch_ = false;
+
   return effect != DragOperationNone;
 }
 
 bool WebViewImpl::DragTargetDragOver(
     int client_x, int client_y, int screen_x, int screen_y) {
   DCHECK(current_drop_data_.get());
+
   DragData drag_data(current_drop_data_.get(), IntPoint(client_x, client_y),
       IntPoint(screen_x, screen_y), kDropTargetOperation);
+  drag_target_dispatch_ = true;
   DragOperation effect = page_->dragController()->dragUpdated(&drag_data);
+  drag_target_dispatch_ = false;
+
   return effect != DragOperationNone;
 }
 
 void WebViewImpl::DragTargetDragLeave() {
   DCHECK(current_drop_data_.get());
+
   DragData drag_data(current_drop_data_.get(), IntPoint(), IntPoint(),
                      DragOperationNone);
+  drag_target_dispatch_ = true;
   page_->dragController()->dragExited(&drag_data);
+  drag_target_dispatch_ = false;
+
   current_drop_data_ = NULL;
+  drag_identity_ = 0;
 }
 
 void WebViewImpl::DragTargetDrop(
     int client_x, int client_y, int screen_x, int screen_y) {
   DCHECK(current_drop_data_.get());
+
   DragData drag_data(current_drop_data_.get(), IntPoint(client_x, client_y),
       IntPoint(screen_x, screen_y), kDropTargetOperation);
+  drag_target_dispatch_ = true;
   page_->dragController()->performDrag(&drag_data);
+  drag_target_dispatch_ = false;
+
   current_drop_data_ = NULL;
+  drag_identity_ = 0;
+}
+
+int32 WebViewImpl::GetDragIdentity() {
+  if (drag_target_dispatch_)
+    return drag_identity_;
+  return 0;
 }
 
 SearchableFormData* WebViewImpl::CreateSearchableFormDataForFocusedNode() {
diff --git a/webkit/glue/webview_impl.h b/webkit/glue/webview_impl.h
index 9023d96..2c0a118 100644
--- a/webkit/glue/webview_impl.h
+++ b/webkit/glue/webview_impl.h
@@ -100,6 +100,7 @@ class WebViewImpl : public WebView, public base::RefCounted<WebViewImpl> {
   virtual void DragTargetDragLeave();
   virtual void DragTargetDrop(
       int client_x, int client_y, int screen_x, int screen_y);
+  virtual int32 GetDragIdentity();
   virtual void AutofillSuggestionsForNode(
       int64 node_id,
       const std::vector<std::wstring>& suggestions,
@@ -294,6 +295,14 @@ class WebViewImpl : public WebView, public base::RefCounted<WebViewImpl> {
   // Represents whether or not this object should process incoming IME events.
   bool ime_accept_events_;
 
+  // True while dispatching system drag and drop events to drag/drop targets
+  // within this WebView.
+  bool drag_target_dispatch_;
+
+  // Valid when drag_target_dispatch_ is true; the identity of the drag data
+  // copied from the WebDropData object sent from the browser process.
+  int32 drag_identity_;
+
   // The autocomplete popup.  Kept around and reused every-time new suggestions
   // should be shown.
   RefPtr<WebCore::PopupContainer> autocomplete_popup_;