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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef UI_GFX_SELECTION_MODEL_H_ | |
6 #define UI_GFX_SELECTION_MODEL_H_ | |
7 | |
8 #include <string> | |
9 | |
10 #include "ui/gfx/gfx_export.h" | |
11 #include "ui/gfx/range/range.h" | |
12 | |
13 namespace gfx { | |
14 | |
15 // VisualCursorDirection and LogicalCursorDirection represent directions of | |
16 // motion of the cursor in BiDi text. The combinations that make sense are: | |
17 // | |
18 // base::i18n::TextDirection VisualCursorDirection LogicalCursorDirection | |
19 // LEFT_TO_RIGHT CURSOR_LEFT CURSOR_BACKWARD | |
20 // LEFT_TO_RIGHT CURSOR_RIGHT CURSOR_FORWARD | |
21 // RIGHT_TO_LEFT CURSOR_RIGHT CURSOR_BACKWARD | |
22 // RIGHT_TO_LEFT CURSOR_LEFT CURSOR_FORWARD | |
23 enum VisualCursorDirection { | |
24 CURSOR_LEFT, | |
25 CURSOR_RIGHT | |
26 }; | |
27 enum LogicalCursorDirection { | |
28 CURSOR_BACKWARD, | |
29 CURSOR_FORWARD | |
30 }; | |
31 | |
32 // TODO(xji): publish bidi-editing guide line and replace the place holder. | |
33 // SelectionModel is used to represent the logical selection and visual | |
34 // position of cursor. | |
35 // | |
36 // For bi-directional text, the mapping between visual position and logical | |
37 // position is not one-to-one. For example, logical text "abcDEF" where capital | |
38 // letters stand for Hebrew, the visual display is "abcFED". According to the | |
39 // bidi editing guide (http://bidi-editing-guideline): | |
40 // 1. If pointing to the right half of the cell of a LTR character, the current | |
41 // position must be set after this character and the caret must be displayed | |
42 // after this character. | |
43 // 2. If pointing to the right half of the cell of a RTL character, the current | |
44 // position must be set before this character and the caret must be displayed | |
45 // before this character. | |
46 // | |
47 // Pointing to the right half of 'c' and pointing to the right half of 'D' both | |
48 // set the logical cursor position to 3. But the cursor displayed visually at | |
49 // different places: | |
50 // Pointing to the right half of 'c' displays the cursor right of 'c' as | |
51 // "abc|FED". | |
52 // Pointing to the right half of 'D' displays the cursor right of 'D' as | |
53 // "abcFED|". | |
54 // So, besides the logical selection start point and end point, we need extra | |
55 // information to specify to which character the visual cursor is bound. This | |
56 // is given by a "caret affinity" which is either CURSOR_BACKWARD (indicating | |
57 // the trailing half of the 'c' in this case) or CURSOR_FORWARD (indicating | |
58 // the leading half of the 'D'). | |
59 class GFX_EXPORT SelectionModel { | |
60 public: | |
61 // Create a default SelectionModel to be overwritten later. | |
62 SelectionModel(); | |
63 // Create a SelectionModel representing a caret |position| without a | |
64 // selection. The |affinity| is meaningful only when the caret is positioned | |
65 // between bidi runs that are not visually contiguous: in that case, it | |
66 // indicates the run to which the caret is attached for display purposes. | |
67 SelectionModel(size_t position, LogicalCursorDirection affinity); | |
68 // Create a SelectionModel representing a selection (which may be empty). | |
69 // The caret position is the end of the range. | |
70 SelectionModel(const Range& selection, LogicalCursorDirection affinity); | |
71 | |
72 const Range& selection() const { return selection_; } | |
73 size_t caret_pos() const { return selection_.end(); } | |
74 LogicalCursorDirection caret_affinity() const { return caret_affinity_; } | |
75 | |
76 // WARNING: Generally the selection start should not be changed without | |
77 // considering the effect on the caret affinity. | |
78 void set_selection_start(size_t pos) { selection_.set_start(pos); } | |
79 | |
80 bool operator==(const SelectionModel& sel) const; | |
81 bool operator!=(const SelectionModel& sel) const { return !(*this == sel); } | |
82 | |
83 std::string ToString() const; | |
84 | |
85 private: | |
86 // Logical selection. The logical caret position is the end of the selection. | |
87 Range selection_; | |
88 | |
89 // The logical direction from the caret position (selection_.end()) to the | |
90 // character it is attached to for display purposes. This matters only when | |
91 // the surrounding characters are not visually contiguous, which happens only | |
92 // in bidi text (and only at bidi run boundaries). The text is treated as | |
93 // though it was surrounded on both sides by runs in the dominant text | |
94 // direction. For example, supposing the dominant direction is LTR and the | |
95 // logical text is "abcDEF", where DEF is right-to-left text, the visual | |
96 // cursor will display as follows: | |
97 // caret position CURSOR_BACKWARD affinity CURSOR_FORWARD affinity | |
98 // 0 |abcFED |abcFED | |
99 // 1 a|bcFED a|bcFED | |
100 // 2 ab|cFED ab|cFED | |
101 // 3 abc|FED abcFED| | |
102 // 4 abcFE|D abcFE|D | |
103 // 5 abcF|ED abcF|ED | |
104 // 6 abc|FED abcFED| | |
105 LogicalCursorDirection caret_affinity_; | |
106 }; | |
107 | |
108 } // namespace gfx | |
109 | |
110 #endif // UI_GFX_SELECTION_MODEL_H_ | |
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