]>
Commit | Line | Data |
---|---|---|
15c0b25d AP |
1 | // Copyright 2015 The Go Authors. All rights reserved. |
2 | // Use of this source code is governed by a BSD-style | |
3 | // license that can be found in the LICENSE file. | |
4 | ||
5 | //go:generate go run gen.go gen_trieval.go gen_ranges.go | |
6 | ||
7 | // Package bidi contains functionality for bidirectional text support. | |
8 | // | |
107c1cdb | 9 | // See https://www.unicode.org/reports/tr9. |
15c0b25d AP |
10 | // |
11 | // NOTE: UNDER CONSTRUCTION. This API may change in backwards incompatible ways | |
12 | // and without notice. | |
13 | package bidi // import "golang.org/x/text/unicode/bidi" | |
14 | ||
15 | // TODO: | |
16 | // The following functionality would not be hard to implement, but hinges on | |
17 | // the definition of a Segmenter interface. For now this is up to the user. | |
18 | // - Iterate over paragraphs | |
19 | // - Segmenter to iterate over runs directly from a given text. | |
20 | // Also: | |
21 | // - Transformer for reordering? | |
22 | // - Transformer (validator, really) for Bidi Rule. | |
23 | ||
24 | // This API tries to avoid dealing with embedding levels for now. Under the hood | |
25 | // these will be computed, but the question is to which extent the user should | |
26 | // know they exist. We should at some point allow the user to specify an | |
27 | // embedding hierarchy, though. | |
28 | ||
29 | // A Direction indicates the overall flow of text. | |
30 | type Direction int | |
31 | ||
32 | const ( | |
33 | // LeftToRight indicates the text contains no right-to-left characters and | |
34 | // that either there are some left-to-right characters or the option | |
35 | // DefaultDirection(LeftToRight) was passed. | |
36 | LeftToRight Direction = iota | |
37 | ||
38 | // RightToLeft indicates the text contains no left-to-right characters and | |
39 | // that either there are some right-to-left characters or the option | |
40 | // DefaultDirection(RightToLeft) was passed. | |
41 | RightToLeft | |
42 | ||
43 | // Mixed indicates text contains both left-to-right and right-to-left | |
44 | // characters. | |
45 | Mixed | |
46 | ||
47 | // Neutral means that text contains no left-to-right and right-to-left | |
48 | // characters and that no default direction has been set. | |
49 | Neutral | |
50 | ) | |
51 | ||
52 | type options struct{} | |
53 | ||
54 | // An Option is an option for Bidi processing. | |
55 | type Option func(*options) | |
56 | ||
57 | // ICU allows the user to define embedding levels. This may be used, for example, | |
58 | // to use hierarchical structure of markup languages to define embeddings. | |
59 | // The following option may be a way to expose this functionality in this API. | |
60 | // // LevelFunc sets a function that associates nesting levels with the given text. | |
61 | // // The levels function will be called with monotonically increasing values for p. | |
62 | // func LevelFunc(levels func(p int) int) Option { | |
63 | // panic("unimplemented") | |
64 | // } | |
65 | ||
66 | // DefaultDirection sets the default direction for a Paragraph. The direction is | |
67 | // overridden if the text contains directional characters. | |
68 | func DefaultDirection(d Direction) Option { | |
69 | panic("unimplemented") | |
70 | } | |
71 | ||
72 | // A Paragraph holds a single Paragraph for Bidi processing. | |
73 | type Paragraph struct { | |
74 | // buffers | |
75 | } | |
76 | ||
77 | // SetBytes configures p for the given paragraph text. It replaces text | |
78 | // previously set by SetBytes or SetString. If b contains a paragraph separator | |
79 | // it will only process the first paragraph and report the number of bytes | |
80 | // consumed from b including this separator. Error may be non-nil if options are | |
81 | // given. | |
82 | func (p *Paragraph) SetBytes(b []byte, opts ...Option) (n int, err error) { | |
83 | panic("unimplemented") | |
84 | } | |
85 | ||
86 | // SetString configures p for the given paragraph text. It replaces text | |
87 | // previously set by SetBytes or SetString. If b contains a paragraph separator | |
88 | // it will only process the first paragraph and report the number of bytes | |
89 | // consumed from b including this separator. Error may be non-nil if options are | |
90 | // given. | |
91 | func (p *Paragraph) SetString(s string, opts ...Option) (n int, err error) { | |
92 | panic("unimplemented") | |
93 | } | |
94 | ||
95 | // IsLeftToRight reports whether the principle direction of rendering for this | |
96 | // paragraphs is left-to-right. If this returns false, the principle direction | |
97 | // of rendering is right-to-left. | |
98 | func (p *Paragraph) IsLeftToRight() bool { | |
99 | panic("unimplemented") | |
100 | } | |
101 | ||
102 | // Direction returns the direction of the text of this paragraph. | |
103 | // | |
104 | // The direction may be LeftToRight, RightToLeft, Mixed, or Neutral. | |
105 | func (p *Paragraph) Direction() Direction { | |
106 | panic("unimplemented") | |
107 | } | |
108 | ||
109 | // RunAt reports the Run at the given position of the input text. | |
110 | // | |
111 | // This method can be used for computing line breaks on paragraphs. | |
112 | func (p *Paragraph) RunAt(pos int) Run { | |
113 | panic("unimplemented") | |
114 | } | |
115 | ||
116 | // Order computes the visual ordering of all the runs in a Paragraph. | |
117 | func (p *Paragraph) Order() (Ordering, error) { | |
118 | panic("unimplemented") | |
119 | } | |
120 | ||
121 | // Line computes the visual ordering of runs for a single line starting and | |
122 | // ending at the given positions in the original text. | |
123 | func (p *Paragraph) Line(start, end int) (Ordering, error) { | |
124 | panic("unimplemented") | |
125 | } | |
126 | ||
127 | // An Ordering holds the computed visual order of runs of a Paragraph. Calling | |
128 | // SetBytes or SetString on the originating Paragraph invalidates an Ordering. | |
129 | // The methods of an Ordering should only be called by one goroutine at a time. | |
130 | type Ordering struct{} | |
131 | ||
132 | // Direction reports the directionality of the runs. | |
133 | // | |
134 | // The direction may be LeftToRight, RightToLeft, Mixed, or Neutral. | |
135 | func (o *Ordering) Direction() Direction { | |
136 | panic("unimplemented") | |
137 | } | |
138 | ||
139 | // NumRuns returns the number of runs. | |
140 | func (o *Ordering) NumRuns() int { | |
141 | panic("unimplemented") | |
142 | } | |
143 | ||
144 | // Run returns the ith run within the ordering. | |
145 | func (o *Ordering) Run(i int) Run { | |
146 | panic("unimplemented") | |
147 | } | |
148 | ||
149 | // TODO: perhaps with options. | |
150 | // // Reorder creates a reader that reads the runes in visual order per character. | |
151 | // // Modifiers remain after the runes they modify. | |
152 | // func (l *Runs) Reorder() io.Reader { | |
153 | // panic("unimplemented") | |
154 | // } | |
155 | ||
156 | // A Run is a continuous sequence of characters of a single direction. | |
157 | type Run struct { | |
158 | } | |
159 | ||
160 | // String returns the text of the run in its original order. | |
161 | func (r *Run) String() string { | |
162 | panic("unimplemented") | |
163 | } | |
164 | ||
165 | // Bytes returns the text of the run in its original order. | |
166 | func (r *Run) Bytes() []byte { | |
167 | panic("unimplemented") | |
168 | } | |
169 | ||
170 | // TODO: methods for | |
171 | // - Display order | |
172 | // - headers and footers | |
173 | // - bracket replacement. | |
174 | ||
175 | // Direction reports the direction of the run. | |
176 | func (r *Run) Direction() Direction { | |
177 | panic("unimplemented") | |
178 | } | |
179 | ||
180 | // Position of the Run within the text passed to SetBytes or SetString of the | |
181 | // originating Paragraph value. | |
182 | func (r *Run) Pos() (start, end int) { | |
183 | panic("unimplemented") | |
184 | } | |
185 | ||
186 | // AppendReverse reverses the order of characters of in, appends them to out, | |
187 | // and returns the result. Modifiers will still follow the runes they modify. | |
188 | // Brackets are replaced with their counterparts. | |
189 | func AppendReverse(out, in []byte) []byte { | |
190 | panic("unimplemented") | |
191 | } | |
192 | ||
193 | // ReverseString reverses the order of characters in s and returns a new string. | |
194 | // Modifiers will still follow the runes they modify. Brackets are replaced with | |
195 | // their counterparts. | |
196 | func ReverseString(s string) string { | |
197 | panic("unimplemented") | |
198 | } |