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;
@@ skipping 10 matching lines @@
 //
 // 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).
 class CONTENT_EXPORT TextInputClientMac {
  public:
   // Returns the singleton instance.
   static TextInputClientMac* GetInstance();
 
+  void GetStringAtPoint(RenderWidgetHost* rwh,
+                        gfx::Point point,
+                        void (^replyHandler)(NSAttributedString*, NSPoint));

[Avi (use Gerrit), 2014/03/12 04:55:40]

Two questions:

1. Is this async, given the callback? If so, then fix the class comment above
about how all these methods are synchronous.

2. What are the thread guarantees here about the reply handler? This function
needs to be called on the UI thread, of course, but you should document what
thread guarantees are given for the callback.

[Andre, 2014/03/12 16:59:26]

1. Yes, this is async. Updated comments accordingly.
2. Reply callback happens on the IO thread. Added documentation.

+  void GetStringAtPointReply(NSAttributedString*, NSPoint);
+
   // 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);
@@ skipping 25 matching lines @@
   // 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_