Add a new WebContentsDelegate::CanDragEnter method. Allows applications using the Content API to selectively cancel (disallow) drag&drop operations on a per-WebContents basis. For example, applications may want to disable drag&drop completely or may want to disallow a drop based on the drag contents (only certain data types, URL formats, etc).

BUG=224440
TEST=none

Review URL: https://chromiumcodereview.appspot.com/16026010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@205550 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 100 insertions, 15 deletions

diff --git a/content/browser/web_contents/web_drag_dest_gtk.cc b/content/browser/web_contents/web_drag_dest_gtk.cc
index 8d6c668..d34526e 100644
--- a/content/browser/web_contents/web_drag_dest_gtk.cc
+++ b/content/browser/web_contents/web_drag_dest_gtk.cc
@@ -13,6 +13,7 @@
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/web_contents/drag_utils_gtk.h"
 #include "content/browser/web_contents/web_contents_impl.h"
+#include "content/public/browser/web_contents_delegate.h"
 #include "content/public/browser/web_drag_dest_delegate.h"
 #include "content/public/common/url_constants.h"
 #include "net/base/net_util.h"
@@ -53,6 +54,7 @@ WebDragDestGtk::WebDragDestGtk(WebContents* web_contents, GtkWidget* widget)
       context_(NULL),
       data_requests_(0),
       delegate_(NULL),
+      canceled_(false),
       method_factory_(this) {
   gtk_drag_dest_set(widget, static_cast<GtkDestDefaults>(0),
                     NULL, 0,
@@ -143,6 +145,9 @@ gboolean WebDragDestGtk::OnDragMotion(GtkWidget* sender,
                         time);
     }
   } else if (data_requests_ == 0) {
+    if (canceled_)
+      return FALSE;
+
     GetRenderViewHost()->DragTargetDragOver(
         ui::ClientPoint(widget_),
         ui::ScreenPoint(widget_),
@@ -236,6 +241,20 @@ void WebDragDestGtk::OnDragDataReceived(
     }
   }
 
+  if (data_requests_ == 0) {
+    // Give the delegate an opportunity to cancel the drag.
+    canceled_ = !web_contents_->GetDelegate()->CanDragEnter(
+        web_contents_,
+        *drop_data_,
+        GdkDragActionToWebDragOp(context->actions));
+    if (canceled_) {
+      drag_over_time_ = time;
+      UpdateDragStatus(WebDragOperationNone);
+      drop_data_.reset();
+      return;
+    }
+  }
+
   // For CHROME_BOOKMARK_ITEM, we have to handle the case where the drag source
   // doesn't have any data available for us. In this case we try to synthesize a
   // URL bookmark.
@@ -274,6 +293,9 @@ void WebDragDestGtk::OnDragLeave(GtkWidget* sender, GdkDragContext* context,
   // as an enter.
   context_ = NULL;
 
+  if (canceled_)
+    return;
+
   // Sometimes we get a drag-leave event before getting a drag-data-received
   // event. In that case, we don't want to bother the renderer with a
   // DragLeave event.
diff --git a/content/browser/web_contents/web_drag_dest_gtk.h b/content/browser/web_contents/web_drag_dest_gtk.h
index 7975fb6..1e0c8ad 100644
--- a/content/browser/web_contents/web_drag_dest_gtk.h
+++ b/content/browser/web_contents/web_drag_dest_gtk.h
@@ -101,6 +101,9 @@ class CONTENT_EXPORT WebDragDestGtk {
   // A delegate that can receive drag information about drag events.
   WebDragDestDelegate* delegate_;
 
+  // True if the drag has been canceled.
+  bool canceled_;
+
   base::WeakPtrFactory<WebDragDestGtk> method_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WebDragDestGtk);
diff --git a/content/browser/web_contents/web_drag_dest_mac.h b/content/browser/web_contents/web_drag_dest_mac.h
index 1fef383..3d4cbe5 100644
--- a/content/browser/web_contents/web_drag_dest_mac.h
+++ b/content/browser/web_contents/web_drag_dest_mac.h
@@ -41,6 +41,9 @@ CONTENT_EXPORT
 
   // The data for the current drag, or NULL if none is in progress.
   scoped_ptr<WebDropData> dropData_;
+
+  // True if the drag has been canceled.
+  bool canceled_;
 }
 
 // |contents| is the WebContentsImpl representing this tab, used to communicate
diff --git a/content/browser/web_contents/web_drag_dest_mac.mm b/content/browser/web_contents/web_drag_dest_mac.mm
index ba4cc26..b1dde18 100644
--- a/content/browser/web_contents/web_drag_dest_mac.mm
+++ b/content/browser/web_contents/web_drag_dest_mac.mm
@@ -9,6 +9,7 @@
 #include "base/strings/sys_string_conversions.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/web_contents/web_contents_impl.h"
+#include "content/public/browser/web_contents_delegate.h"
 #include "content/public/browser/web_drag_dest_delegate.h"
 #import "third_party/mozilla/NSPasteboard+Utils.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
@@ -44,6 +45,7 @@ int GetModifierFlags() {
 - (id)initWithWebContentsImpl:(WebContentsImpl*)contents {
   if ((self = [super init])) {
     webContents_ = contents;
+    canceled_ = false;
   }
   return self;
 }
@@ -103,6 +105,22 @@ int GetModifierFlags() {
   // we need to send a new enter message in draggingUpdated:.
   currentRVH_ = webContents_->GetRenderViewHost();
 
+  // Fill out a WebDropData from pasteboard.
+  scoped_ptr<WebDropData> dropData;
+  dropData.reset(new WebDropData());
+  [self populateWebDropData:dropData.get()
+             fromPasteboard:[info draggingPasteboard]];
+
+  NSDragOperation mask = [info draggingSourceOperationMask];
+
+  // Give the delegate an opportunity to cancel the drag.
+  canceled_ = !webContents_->GetDelegate()->CanDragEnter(
+      webContents_,
+      *dropData,
+      static_cast<WebDragOperationsMask>(mask));
+  if (canceled_)
+    return NSDragOperationNone;
+
   if ([self onlyAllowsNavigation]) {
     if ([[info draggingPasteboard] containsURLData])
       return NSDragOperationCopy;
@@ -114,17 +132,13 @@ int GetModifierFlags() {
     delegate_->OnDragEnter();
   }
 
-  // Fill out a WebDropData from pasteboard.
-  dropData_.reset(new WebDropData());
-  [self populateWebDropData:dropData_.get()
-             fromPasteboard:[info draggingPasteboard]];
+  dropData_.swap(dropData);
 
   // Create the appropriate mouse locations for WebCore. The draggingLocation
   // is in window coordinates. Both need to be flipped.
   NSPoint windowPoint = [info draggingLocation];
   NSPoint viewPoint = [self flipWindowPointToView:windowPoint view:view];
   NSPoint screenPoint = [self flipWindowPointToScreen:windowPoint view:view];
-  NSDragOperation mask = [info draggingSourceOperationMask];
   webContents_->GetRenderViewHost()->DragTargetDragEnter(
       *dropData_,
       gfx::Point(viewPoint.x, viewPoint.y),
@@ -143,6 +157,9 @@ int GetModifierFlags() {
   if (currentRVH_ != webContents_->GetRenderViewHost())
     return;
 
+  if (canceled_)
+    return;
+
   if ([self onlyAllowsNavigation])
     return;
 
@@ -159,6 +176,9 @@ int GetModifierFlags() {
   if (currentRVH_ != webContents_->GetRenderViewHost())
     [self draggingEntered:info view:view];
 
+  if (canceled_)
+    return NSDragOperationNone;
+
   if ([self onlyAllowsNavigation]) {
     if ([[info draggingPasteboard] containsURLData])
       return NSDragOperationCopy;
diff --git a/content/browser/web_contents/web_drag_dest_win.cc b/content/browser/web_contents/web_drag_dest_win.cc
index fb86f08..2e10183 100644
--- a/content/browser/web_contents/web_drag_dest_win.cc
+++ b/content/browser/web_contents/web_drag_dest_win.cc
@@ -11,6 +11,7 @@
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/web_contents/web_drag_utils_win.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_delegate.h"
 #include "content/public/browser/web_drag_dest_delegate.h"
 #include "googleurl/src/gurl.h"
 #include "net/base/net_util.h"
@@ -140,7 +141,8 @@ WebDragDest::WebDragDest(HWND source_hwnd, WebContents* web_contents)
       current_rvh_(NULL),
       drag_cursor_(WebDragOperationNone),
       interstitial_drop_target_(new InterstitialDropTarget(web_contents)),
-      delegate_(NULL) {
+      delegate_(NULL),
+      canceled_(false) {
 }
 
 WebDragDest::~WebDragDest() {
@@ -152,6 +154,24 @@ DWORD WebDragDest::OnDragEnter(IDataObject* data_object,
                                DWORD effects) {
   current_rvh_ = web_contents_->GetRenderViewHost();
 
+  // TODO(tc): PopulateWebDropData can be slow depending on what is in the
+  // IDataObject.  Maybe we can do this in a background thread.
+  scoped_ptr<WebDropData> drop_data;
+  drop_data.reset(new WebDropData());
+  PopulateWebDropData(data_object, drop_data.get());
+
+  if (drop_data->url.is_empty())
+    ui::OSExchangeDataProviderWin::GetPlainTextURL(data_object,
+                                                   &drop_data->url);
+
+  // Give the delegate an opportunity to cancel the drag.
+  canceled_ = !web_contents_->GetDelegate()->CanDragEnter(
+      web_contents_,
+      *drop_data,
+      WinDragOpMaskToWebDragOpMask(effects));
+  if (canceled_)
+    return DROPEFFECT_NONE;
+
   if (delegate_)
     delegate_->DragInitialize(web_contents_);
 
@@ -161,15 +181,7 @@ DWORD WebDragDest::OnDragEnter(IDataObject* data_object,
   if (web_contents_->ShowingInterstitialPage())
     return interstitial_drop_target_->OnDragEnter(data_object, effects);
 
-  // TODO(tc): PopulateWebDropData can be slow depending on what is in the
-  // IDataObject.  Maybe we can do this in a background thread.
-  drop_data_.reset(new WebDropData());
-  PopulateWebDropData(data_object, drop_data_.get());
-
-  if (drop_data_->url.is_empty())
-    ui::OSExchangeDataProviderWin::GetPlainTextURL(data_object,
-                                                   &drop_data_->url);
-
+  drop_data_.swap(drop_data);
   drag_cursor_ = WebDragOperationNone;
 
   POINT client_pt = cursor_position;
@@ -196,6 +208,9 @@ DWORD WebDragDest::OnDragOver(IDataObject* data_object,
   if (current_rvh_ != web_contents_->GetRenderViewHost())
     OnDragEnter(data_object, key_state, cursor_position, effects);
 
+  if (canceled_)
+    return DROPEFFECT_NONE;
+
   if (web_contents_->ShowingInterstitialPage())
     return interstitial_drop_target_->OnDragOver(data_object, effects);
 
@@ -218,6 +233,9 @@ void WebDragDest::OnDragLeave(IDataObject* data_object) {
   if (current_rvh_ != web_contents_->GetRenderViewHost())
     return;
 
+  if (canceled_)
+    return;
+
   if (web_contents_->ShowingInterstitialPage()) {
     interstitial_drop_target_->OnDragLeave(data_object);
   } else {
diff --git a/content/browser/web_contents/web_drag_dest_win.h b/content/browser/web_contents/web_drag_dest_win.h
index fb2ea17..5e8f024 100644
--- a/content/browser/web_contents/web_drag_dest_win.h
+++ b/content/browser/web_contents/web_drag_dest_win.h
@@ -78,6 +78,9 @@ class CONTENT_EXPORT WebDragDest : public ui::DropTargetWin {
   // The data for the current drag, or NULL if |context_| is NULL.
   scoped_ptr<WebDropData> drop_data_;
 
+  // True if the drag has been canceled.
+  bool canceled_;
+
   DISALLOW_COPY_AND_ASSIGN(WebDragDest);
 };
 
diff --git a/content/public/browser/web_contents_delegate.cc b/content/public/browser/web_contents_delegate.cc
index 6026328..a9299c8 100644
--- a/content/public/browser/web_contents_delegate.cc
+++ b/content/public/browser/web_contents_delegate.cc
@@ -110,6 +110,13 @@ bool WebContentsDelegate::PreHandleKeyboardEvent(
   return false;
 }
 
+bool WebContentsDelegate::CanDragEnter(
+    WebContents* source,
+    const WebDropData& data,
+    WebKit::WebDragOperationsMask operations_allowed) {
+  return true;
+}
+
 bool WebContentsDelegate::OnGoToEntryOffset(int offset) {
   return true;
 }
diff --git a/content/public/browser/web_contents_delegate.h b/content/public/browser/web_contents_delegate.h
index 8e4f794..492cae7 100644
--- a/content/public/browser/web_contents_delegate.h
+++ b/content/public/browser/web_contents_delegate.h
@@ -16,6 +16,7 @@
 #include "content/public/common/media_stream_request.h"
 #include "content/public/common/page_transition_types.h"
 #include "content/public/common/window_container_type.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebDragOperation.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/base/window_open_disposition.h"
 #include "ui/gfx/native_widget_types.h"
@@ -23,6 +24,7 @@
 #include "ui/gfx/vector2d.h"
 
 class GURL;
+struct WebDropData;
 
 namespace base {
 class FilePath;
@@ -266,6 +268,13 @@ class CONTENT_EXPORT WebContentsDelegate {
   virtual void HandleGestureBegin() {}
   virtual void HandleGestureEnd() {}
 
+  // Called when an external drag event enters the web contents window. Return
+  // true to allow dragging and dropping on the web contents window or false to
+  // cancel the operation. This method is used by Chromium Embedded Framework.
+  virtual bool CanDragEnter(WebContents* source,
+                            const WebDropData& data,
+                            WebKit::WebDragOperationsMask operations_allowed);
+
   // Render view drag n drop ended.
   virtual void DragEnded() {}