Adds a hy-phen-ator.

chrome/renderer/hyphenator/hyphenator.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 CHROME_RENDERER_HYPHENATOR_HYPHENATOR_H_
+#define CHROME_RENDERER_HYPHENATOR_HYPHENATOR_H_
+#pragma once
+
+#include <vector>
+
+#include "base/memory/scoped_ptr.h"
+#include "base/platform_file.h"
+#include "base/string16.h"
+
+namespace file_util {
+class MemoryMappedFile;
+}
+
+typedef struct _HyphenDict HyphenDict;
+
+// A class that hyphenates a word. This class encapsulates the hyphen library
+// and manages resources used by the library. When this class uses a huge
+// dictionary, it takes lots of memory. A renderer should create this object
+// only when it renders a page that needs hyphenation and deletes it when it
+// moves to a page that does not need hyphenation as listed in the following
+// snippet.
+//
+//   base::PlatformFile file("hyphen.us");
+//   scoped_ptr<Hyphenator> hyphenator(new Hyphenator(file));

[tony, 2012/03/05 18:59:00]

How slow is it to instantiate a new Hyphenator?  E.g., how slow will it be to
navigate to a few pages that use hyphenation in sequence?  Roughly how much
memory does Hyphenator use?

I wonder if we can just lazy init Hyphenator and keep it around as long as the
renderer is alive.  That is, changing domains will normally cause it to be
deleted.

The current patch is OK for now, just some things to think about.

[Hironori Bono, 2012/06/28 09:32:49]

Thanks for your comment. When I created a page-cycler test, hyphenation takes 4%
more time and 41MB more memory for now. (I have sent detailed data via a direct
e-mail.)

+//   size_t pos = hyphenator->ComputeLastHyphenLocation("organize", 8);
+//   ...
+//   hyphenator.reset();
+//
+class Hyphenator {
+ public:
+  explicit Hyphenator(base::PlatformFile file);
+  ~Hyphenator();
+
+  // Initializes the hyphen library and allocates resources needed for
+  // hyphenation.
+  bool Initialize();
+
+  // Returns the last hyphenation point, the position where we can insert a
+  // hyphen, before the given position. If there are not any hyphenation points,
+  // this function returns 0.
+  size_t ComputeLastHyphenLocation(const string16& word, size_t before_index);
+
+ private:
+  // The dictionary used by the hyphen library.
+  HyphenDict* dictionary_;
+
+  // The dictionary file and its memory-mapping object. (Our copy of the hyphen
+  // library uses a memory-mapped file opened by a browser so renderers can use
+  // it without opening the file.)
+  base::PlatformFile rule_file_;
+  scoped_ptr<file_util::MemoryMappedFile> rule_map_;
+
+  // A cached result. WebKit often calls ComputeLastHyphenLocation with the same
+  // word multiple times to find the best hyphenation point when it finds a line
+  // break. On the other hand, the hyphen library returns all hyphenation points
+  // for a word. This class caches the hyphenation points returned by the hyphen
+  // library to avoid calling the library multiple times.
+  string16 word_;
+  bool result_;
+  std::vector<int> hyphens_;
+};
+
+#endif  // CHROME_RENDERER_HYPHENATOR_HYPHENATOR_H_