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// 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_GFX_SELECTION_MODEL_H_
#define UI_GFX_SELECTION_MODEL_H_
#pragma once
#include <stdlib.h>
#include "ui/base/ui_export.h"
namespace gfx {
// 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 and on which edge of the character
// the visual cursor is bound to. For example, the visual cursor is bound to
// the trailing side of the 2nd character 'c' when pointing to right half of
// 'c'. And it is bound to the leading edge of the 3rd character 'D' when
// pointing to right of 'D'.
class UI_EXPORT SelectionModel {
public:
enum CaretPlacement {
LEADING,
TRAILING,
};
SelectionModel();
explicit SelectionModel(size_t pos);
SelectionModel(size_t end, size_t pos, CaretPlacement status);
SelectionModel(size_t start, size_t end, size_t pos, CaretPlacement status);
virtual ~SelectionModel();
size_t selection_start() const { return selection_start_; }
size_t selection_end() const { return selection_end_; }
size_t caret_pos() const { return caret_pos_; }
CaretPlacement caret_placement() const { return caret_placement_; }
bool Equals(const SelectionModel& sel) const;
private:
friend class RenderText;
void Init(size_t start, size_t end, size_t pos, CaretPlacement status);
void set_selection_start(size_t pos) { selection_start_ = pos; }
void set_selection_end(size_t pos) { selection_end_ = pos; }
void set_caret_pos(size_t pos) { caret_pos_ = pos; }
void set_caret_placement(CaretPlacement placement) {
caret_placement_ = placement;
}
// Logical selection start. If there is non-empty selection, if
// selection_start_ is less than selection_end_, the selection starts visually
// at the leading edge of the selection_start_. If selection_start_ is greater
// than selection_end_, the selection starts visually at the trailing edge of
// selection_start_'s previous grapheme. So, we do not need extra information
// for visual bounding.
size_t selection_start_;
// The logical cursor position that next character will be inserted into.
// It is also the end of the selection.
size_t selection_end_;
// The following two fields are used to guide cursor visual position.
// The index of the character that cursor is visually attached to.
size_t caret_pos_;
// The visual placement of the cursor, relative to its associated character.
CaretPlacement caret_placement_;
};
} // namespace gfx
#endif // UI_GFX_SELECTION_MODEL_H_
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