Add common data types for input method support.

ui/base/ime/composition.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 UI_BASE_IME_COMPOSITION_H_
+#define UI_BASE_IME_COMPOSITION_H_
+#pragma once
+
+#include "base/string16.h"
+#include "ui/base/ime/composition_underline.h"
+#include "ui/base/range/range.h"
+
+namespace ui {
+
+// A struct represents the status of an ongoing composition.
+struct Composition {
+  Composition();
+  void Clear();
+
+  // Content of the composition text.
+  string16 text;
+
+  // Underline information of the composition text.
+  // They must be sorted in ascending order by their start_offset and cannot be
+  // overlapped with each other.
+  CompositionUnderlines underlines;
+
+  // Selection range in the composition text. It represents the caret position
+  // if the range length is zero.

[Peng, 2011/03/18 18:01:11]

What's the selection range in the composition text. If the length is not zero,
what's right behavior of the textfield and etc? Please add more detail in here.

[James Su, 2011/03/18 18:11:24]

It's the text range selected in the composition text, just like normal
selection. It usually indicates the target clause. Gtk doesn't have such
concept, background color is usually used instead. Both Windows and Mac has such
concept and WebKit is supposed to support it, though there is a bug. See:
https://bugs.webkit.org/show_bug.cgi?id=37788

[Peng, 2011/03/18 18:50:11]

Please add detail about the behavior in comment. If it is used only for display
(as Pango background), please write them down. It may confuse Client developers.

On 2011/03/18 18:11:24, James Su wrote:

[James Su, 2011/03/18 19:18:35]

Added some comments.

On 2011/03/18 18:50:11, Peng wrote:

+  Range selection;
+};
+
+}  // namespace ui
+
+#endif  // UI_BASE_IME_COMPOSITION_H_