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// 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 UI_GFX_SELECTION_MODEL_H_
#define UI_GFX_SELECTION_MODEL_H_
#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 {
CURSOR_LEFT,
CURSOR_RIGHT
};
enum LogicalCursorDirection {
CURSOR_BACKWARD,
CURSOR_FORWARD
};
// 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 {
public:
// Create a default SelectionModel to be overwritten later.
SelectionModel();
// Create a SelectionModel representing a caret |position| without a
// selection. The |affinity| is meaningful only when the caret is positioned
// between bidi runs that are not visually contiguous: in that case, it
// indicates the run to which the caret is attached for display purposes.
SelectionModel(size_t position, LogicalCursorDirection affinity);
// Create a SelectionModel representing a selection (which may be empty).
// The caret position is the end of the range.
SelectionModel(const Range& selection, LogicalCursorDirection affinity);
const Range& selection() const { return selection_; }
size_t caret_pos() const { return selection_.end(); }
LogicalCursorDirection caret_affinity() const { return caret_affinity_; }
// WARNING: Generally the selection start should not be changed without
// considering the effect on the caret affinity.
void set_selection_start(size_t pos) { selection_.set_start(pos); }
bool operator==(const SelectionModel& sel) const;
bool operator!=(const SelectionModel& sel) const { return !(*this == sel); }
std::string ToString() const;
private:
// Logical selection. The logical caret position is the end of the selection.
Range selection_;
// The logical direction from the caret position (selection_.end()) to the
// character it is attached to for display purposes. This matters only when
// the surrounding characters are not visually contiguous, which happens only
// in bidi text (and only at bidi run boundaries). The text is treated as
// though it was surrounded on both sides by runs in the dominant text
// direction. For example, supposing the dominant direction is LTR and the
// logical text is "abcDEF", where DEF is right-to-left text, the visual
// cursor will display as follows:
// caret position CURSOR_BACKWARD affinity CURSOR_FORWARD affinity
// 0 |abcFED |abcFED
// 1 a|bcFED a|bcFED
// 2 ab|cFED ab|cFED
// 3 abc|FED abcFED|
// 4 abcFE|D abcFE|D
// 5 abcF|ED abcF|ED
// 6 abc|FED abcFED|
LogicalCursorDirection caret_affinity_;
};
} // namespace gfx
#endif // UI_GFX_SELECTION_MODEL_H_
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