mac: Add support for asynchronous dictionary lookup

content/browser/renderer_host/text_input_client_mac.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_TEXT_INPUT_CLIENT_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_TEXT_INPUT_CLIENT_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
+#include "base/mac/scoped_block.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/lock.h"
 #include "content/common/content_export.h"
 #include "ui/gfx/point.h"
 
 template <typename T> struct DefaultSingletonTraits;
 
 namespace content {
 class RenderWidgetHost;
 
 // This class helps with the Mac OS X dictionary popup. For the design overview,
 // look at this document:
 //   http://dev.chromium.org/developers/design-documents/system-dictionary-pop-up-architecture
 //
 // This service is used to marshall information for these three methods that are
 // implemented in RenderWidgetHostViewMac:
 //   -[NSTextInput characterIndexForPoint:]
 //   -[NSTextInput attributedSubstringFromRange:]
 //   -[NSTextInput firstRectForCharacterRange:]
 //
 // Because these methods are part of a synchronous system API, implementing them
 // requires getting information from the renderer synchronously. Rather than
 // using an actual sync IPC message, a normal async ViewMsg is used with a lock
 // and condition (managed by this service).
+//
+// Mac OS 10.8 introduced -[NSResponder quickLookWithEvent:].
+// We can use it to implement asynchronous dictionary lookup when the user
+// taps a word using three fingers.
+// But currently the "Look Up in Dictionary" context menu item still goes
+// through the above synchronous IPC.
 class CONTENT_EXPORT TextInputClientMac {
  public:
   // Returns the singleton instance.
   static TextInputClientMac* GetInstance();
 
   // Each of the three methods mentioned above has an associated pair of methods
   // to get data from the renderer. The Get*() methods block the calling thread
   // (always the UI thread) with a short timeout after the async message has
   // been sent to the renderer to lookup the information needed to respond to
   // the system. The Set*AndSignal() methods store the looked up information in
   // this service and signal the condition to allow the Get*() methods to
   // unlock and return that stored value.
   //
   // Returns NSNotFound if the request times out or is not completed.
   NSUInteger GetCharacterIndexAtPoint(RenderWidgetHost* rwh, gfx::Point point);
   // Returns nil if the request times out or is completed.
   NSAttributedString* GetAttributedSubstringFromRange(
       RenderWidgetHost* rwh, NSRange range);
   // Returns NSZeroRect if the request times out or is not completed. The result
   // is in WebKit coordinates.
   NSRect GetFirstRectForRange(RenderWidgetHost* rwh, NSRange range);
 
   // When the renderer sends the ViewHostMsg reply, the RenderMessageFilter will
   // call the corresponding method on the IO thread to unlock the condition and
   // allow the Get*() methods to continue/return.
   void SetCharacterIndexAndSignal(NSUInteger index);
   void SetFirstRectAndSignal(NSRect first_rect);
   void SetSubstringAndSignal(NSAttributedString* string);
 
+  // This async method is invoked from RenderWidgetHostViewCocoa's
+  // -quickLookWithEvent:, when the user taps a word using 3 fingers.
+  // The reply callback will be invoked from the IO thread, the caller is
+  // responsible for bouncing to the main thread if necessary.
+  // The callback parameters provide the attributed word under the point and
+  // the lower left baseline point of the text.
+  void GetStringAtPoint(RenderWidgetHost* rwh,
+                        gfx::Point point,
+                        void (^replyHandler)(NSAttributedString*, NSPoint));
+  // This is called on the IO thread when we get the renderer's reply for
+  // GetStringAtPoint.
+  void GetStringAtPointReply(NSAttributedString*, NSPoint);
+
  private:
   friend struct DefaultSingletonTraits<TextInputClientMac>;
   TextInputClientMac();
   ~TextInputClientMac();
 
   // The critical sections that the Condition guards are in Get*() methods.
   // These methods lock the internal condition for use before the asynchronous
   // message is sent to the renderer to lookup the required information. These
   // are only used on the UI thread.
   void BeforeRequest();
   // Called at the end of a critical section. This will release the lock and
   // condition.
   void AfterRequest();
 
   NSUInteger character_index_;
   NSRect first_rect_;
   base::scoped_nsobject<NSAttributedString> substring_;
 
   base::Lock lock_;
   base::ConditionVariable condition_;
 
+  base::mac::ScopedBlock<void(^)(NSAttributedString*, NSPoint)> replyHandler_;
+
   DISALLOW_COPY_AND_ASSIGN(TextInputClientMac);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_TEXT_INPUT_CLIENT_MAC_H_