chromium/ui/gfx/selection_model.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_GFX_SELECTION_MODEL_H_
#define UI_GFX_SELECTION_MODEL_H_

#include <stddef.h>
#include <vector>

#include <iosfwd>
#include <string>

#include "ui/gfx/gfx_export.h"
#include "ui/gfx/range/range.h"

namespace gfx {

// VisualCursorDirection and LogicalCursorDirection represent directions of
// motion of the cursor in BiDi text. The combinations that make sense are:
//
//  base::i18n::TextDirection  VisualCursorDirection  LogicalCursorDirection
//       LEFT_TO_RIGHT             CURSOR_LEFT           CURSOR_BACKWARD
//       LEFT_TO_RIGHT             CURSOR_RIGHT          CURSOR_FORWARD
//       RIGHT_TO_LEFT             CURSOR_RIGHT          CURSOR_BACKWARD
//       RIGHT_TO_LEFT             CURSOR_LEFT           CURSOR_FORWARD
enum VisualCursorDirection { … };
enum LogicalCursorDirection { … };

// TODO(xji): publish bidi-editing guide line and replace the place holder.
// SelectionModel is used to represent the logical selection and visual
// position of cursor.
//
// For bi-directional text, the mapping between visual position and logical
// position is not one-to-one. For example, logical text "abcDEF" where capital
// letters stand for Hebrew, the visual display is "abcFED". According to the
// bidi editing guide (http://bidi-editing-guideline):
// 1. If pointing to the right half of the cell of a LTR character, the current
// position must be set after this character and the caret must be displayed
// after this character.
// 2. If pointing to the right half of the cell of a RTL character, the current
// position must be set before this character and the caret must be displayed
// before this character.
//
// Pointing to the right half of 'c' and pointing to the right half of 'D' both
// set the logical cursor position to 3. But the cursor displayed visually at
// different places:
// Pointing to the right half of 'c' displays the cursor right of 'c' as
// "abc|FED".
// Pointing to the right half of 'D' displays the cursor right of 'D' as
// "abcFED|".
// So, besides the logical selection start point and end point, we need extra
// information to specify to which character the visual cursor is bound. This
// is given by a "caret affinity" which is either CURSOR_BACKWARD (indicating
// the trailing half of the 'c' in this case) or CURSOR_FORWARD (indicating
// the leading half of the 'D').
class GFX_EXPORT SelectionModel { … };

GFX_EXPORT std::ostream& operator<<(std::ostream& out,
                                    const SelectionModel& model);

}  // namespace gfx

#endif  // UI_GFX_SELECTION_MODEL_H_