Enable dragging of images to desktop (Finder), Preview, etc. (on Mac)....

chrome/browser/cocoa/web_drag_source.h

+// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import <Cocoa/Cocoa.h>
+
+#include "base/scoped_nsobject.h"
+#include "base/scoped_ptr.h"
+
+struct WebDropData;
+@class TabContentsViewCocoa;
+
+// A class that handles tracking and event processing for a drag and drop
+// originating from the content area.
+@interface WebDragSource : NSObject {
+ @private
+  // Our tab. Weak reference (owns or co-owns us).
+  TabContentsViewCocoa* contentsView_;
+
+  // Our drop data. Should only be initialized once.
+  scoped_ptr<WebDropData> dropData_;
+
+  // Our pasteboard.
+  scoped_nsobject<NSPasteboard> pasteboard_;
+}
+
+// Initialize a WebDragSource object for a drag (originating on the given
+// contentsView and with the given dropData and pboard). Fill the pasteboard
+// with data types appropriate for dropData.
+- (id)initWithContentsView:(TabContentsViewCocoa*)contentsView
+                  dropData:(const WebDropData*)dropData
+                pasteboard:(NSPasteboard*)pboard;
+
+// Call when asked to do a lazy write to the pasteboard; hook up to
+// -pasteboard:provideDataForType: (on the contentsView).
+- (void)lazyWriteToPasteboard:(NSPasteboard*)pboard
+                      forType:(NSString*)type;
+
+// Start the drag (on the originally provided contentsView); can do this right
+// after -initWithContentsView:....
+- (void)startDrag;
+
+// End the drag and clear the pasteboard; hook up to
+// -draggedImage:endedAt:operation:.
+- (void)endDragAt:(NSPoint)screenPoint
+      isCancelled:(BOOL)cancelled;
+
+// Drag moved; hook up to -draggedImage:movedTo:.
+- (void)moveDragTo:(NSPoint)screenPoint;
+
+// Call to drag a promised file to the given path (should be called before
+// -endDragAt:...); hook up to -namesOfPromisedFilesDroppedAtDestination:.
+// Returns the file name (not including path) of the file deposited (or which
+// will be deposited).
+- (NSString*)dragPromisedFileTo:(NSString*)path;
+
+@end