When acting as a drop target, the webview keeps a cache of

the drop data so we don't have to send it over the IPC for
each drag move.  However, if a page load happens during
the drop, the webview changes and we lose the cached
data.

To handle this, we keep track of which RVH we're dragging
over and if it changes, we re-send the drop data.
Review URL: http://codereview.chromium.org/8744

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@4249 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 33 insertions, 7 deletions

diff --git a/chrome/browser/web_drop_target.cc b/chrome/browser/web_drop_target.cc
index 0d451bd..fe5ee53 100644
--- a/chrome/browser/web_drop_target.cc
+++ b/chrome/browser/web_drop_target.cc
@@ -9,6 +9,7 @@
 
 #include "base/clipboard_util.h"
 #include "base/gfx/point.h"
+#include "chrome/browser/render_view_host.h"
 #include "chrome/browser/web_contents.h"
 #include "chrome/common/os_exchange_data.h"
 #include "googleurl/src/gurl.h"
@@ -77,6 +78,7 @@ class InterstitialDropTarget {
 WebDropTarget::WebDropTarget(HWND source_hwnd, WebContents* web_contents)
     : BaseDropTarget(source_hwnd),
       web_contents_(web_contents),
+      current_rvh_(NULL),
       is_drop_target_(false),
       interstitial_drop_target_(new InterstitialDropTarget(web_contents)) {
 }
@@ -88,14 +90,16 @@ DWORD WebDropTarget::OnDragEnter(IDataObject* data_object,
                                  DWORD key_state,
                                  POINT cursor_position,
                                  DWORD effect) {
+  current_rvh_ = web_contents_->render_view_host();
+
   // Don't pass messages to the renderer if an interstitial page is showing
   // because we don't want the interstitial page to navigate.  Instead,
   // pass the messages on to a separate interstitial DropTarget handler.
   if (web_contents_->showing_interstitial_page())
     return interstitial_drop_target_->OnDragEnter(data_object, effect);
 
-  // TODO(tc): PopulateWebDropData is kind of slow, maybe we can do this in a
-  // background thread.
+  // 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::PopulateWebDropData(data_object, &drop_data);
 
@@ -119,6 +123,10 @@ DWORD WebDropTarget::OnDragOver(IDataObject* data_object,
                                 DWORD key_state,
                                 POINT cursor_position,
                                 DWORD effect) {
+  DCHECK(current_rvh_);
+  if (current_rvh_ != web_contents_->render_view_host())
+    OnDragEnter(data_object, key_state, cursor_position, effect);
+
   if (web_contents_->showing_interstitial_page())
     return interstitial_drop_target_->OnDragOver(data_object, effect);
 
@@ -135,6 +143,10 @@ DWORD WebDropTarget::OnDragOver(IDataObject* data_object,
 }
 
 void WebDropTarget::OnDragLeave(IDataObject* data_object) {
+  DCHECK(current_rvh_);
+  if (current_rvh_ != web_contents_->render_view_host())
+    return;
+
   if (web_contents_->showing_interstitial_page()) {
     interstitial_drop_target_->OnDragLeave(data_object);
   } else {
@@ -142,11 +154,17 @@ void WebDropTarget::OnDragLeave(IDataObject* data_object) {
   }
 }
 
-
 DWORD WebDropTarget::OnDrop(IDataObject* data_object,
                             DWORD key_state,
                             POINT cursor_position,
                             DWORD effect) {
+  DCHECK(current_rvh_);
+  if (current_rvh_ != web_contents_->render_view_host())
+    OnDragEnter(data_object, key_state, cursor_position, effect);
+
+  if (web_contents_->showing_interstitial_page())
+    interstitial_drop_target_->OnDragOver(data_object, effect);
+
   if (web_contents_->showing_interstitial_page())
     return interstitial_drop_target_->OnDrop(data_object, effect);
 
@@ -156,8 +174,9 @@ DWORD WebDropTarget::OnDrop(IDataObject* data_object,
       gfx::Point(client_pt.x, client_pt.y),
       gfx::Point(cursor_position.x, cursor_position.y));
 
+  current_rvh_ = NULL;
+
   // We lie and always claim that the drop operation didn't happen because we
   // don't want to wait for the renderer to respond.
   return DROPEFFECT_NONE;
 }
-
diff --git a/chrome/browser/web_drop_target.h b/chrome/browser/web_drop_target.h
index 45b4c4e..28f4073 100644
--- a/chrome/browser/web_drop_target.h
+++ b/chrome/browser/web_drop_target.h
@@ -9,6 +9,7 @@
 #include "base/scoped_ptr.h"
 
 class InterstitialDropTarget;
+class RenderViewHost;
 class WebContents;
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -52,14 +53,20 @@ class WebDropTarget : public BaseDropTarget {
   // Our associated WebContents.
   WebContents* web_contents_;
 
-  // A special drop target handler for when we try to d&d while an interstitial
-  // page is showing.
-  scoped_ptr<InterstitialDropTarget> interstitial_drop_target_;
+  // We keep track of the render view host we're dragging over.  If it changes
+  // during a drag, we need to re-send the DragEnter message.  WARNING:
+  // this pointer should never be dereferenced.  We only use it for comparing
+  // pointers.
+  RenderViewHost* current_rvh_;
 
   // Used to determine what cursor we should display when dragging over web
   // content area.  This can be updated async during a drag operation.
   bool is_drop_target_;
 
+  // A special drop target handler for when we try to d&d while an interstitial
+  // page is showing.
+  scoped_ptr<InterstitialDropTarget> interstitial_drop_target_;
+
   DISALLOW_EVIL_CONSTRUCTORS(WebDropTarget);
 };