[Mac] Implement the system dictionary popup by implementing NSTextInput methods.

chrome/browser/renderer_host/text_input_client_mac.h

+// Copyright (c) 2011 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 CHROME_BROWSER_RENDERER_HOST_TEXT_INPUT_CLIENT_MAC_H_
+#define CHROME_BROWSER_RENDERER_HOST_TEXT_INPUT_CLIENT_MAC_H_
+
+#import <Cocoa/Cocoa.h>
+
+#include "base/scoped_nsobject.h"
+#include "base/synchronization/condition_variable.h"
+#include "base/synchronization/lock.h"
+#include "ui/gfx/point.h"
+
+template <typename T> struct DefaultSingletonTraits;
+
+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).

[jeremy, 2011/02/21 09:19:47]

Could you explain why it's OK to do this in this instance?

[Robert Sesek, 2011/02/24 23:26:52]

I think the first sentence explains this.

+class 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);
+
+ private:
+  friend struct DefaultSingletonTraits<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_;
+  scoped_nsobject<NSAttributedString> substring_;
+
+  base::Lock lock_;
+  base::ConditionVariable condition_;
+
+  DISALLOW_COPY_AND_ASSIGN(TextInputClientMac);
+};
+
+#endif  // CHROME_BROWSER_RENDERER_HOST_TEXT_INPUT_CLIENT_MAC_H_