1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <stdint.h>
18#include <unicode/uchar.h>
19#include <unicode/utf16.h>
20
21#include <minikin/GraphemeBreak.h>
22
23namespace android {
24
25bool GraphemeBreak::isGraphemeBreak(const uint16_t* buf, size_t start, size_t count,
26        size_t offset) {
27    // This implementation closely follows Unicode Standard Annex #29 on
28    // Unicode Text Segmentation (http://www.unicode.org/reports/tr29/),
29    // implementing a tailored version of extended grapheme clusters.
30    // The GB rules refer to section 3.1.1, Grapheme Cluster Boundary Rules.
31
32    // Rule GB1, sot /; Rule GB2, / eot
33    if (offset <= start || offset >= start + count) {
34        return true;
35    }
36    if (U16_IS_TRAIL(buf[offset])) {
37        // Don't break a surrogate pair
38        return false;
39    }
40    uint32_t c1 = 0;
41    uint32_t c2 = 0;
42    size_t offset_back = offset;
43    U16_PREV(buf, start, offset_back, c1);
44    U16_NEXT(buf, offset, count, c2);
45    int32_t p1 = u_getIntPropertyValue(c1, UCHAR_GRAPHEME_CLUSTER_BREAK);
46    int32_t p2 = u_getIntPropertyValue(c2, UCHAR_GRAPHEME_CLUSTER_BREAK);
47    // Rule GB3, CR x LF
48    if (p1 == U_GCB_CR && p2 == U_GCB_LF) {
49        return false;
50    }
51    // Rule GB4, (Control | CR | LF) /
52    if (p1 == U_GCB_CONTROL || p1 == U_GCB_CR || p1 == U_GCB_LF) {
53        return true;
54    }
55    // Rule GB5, / (Control | CR | LF)
56    if (p2 == U_GCB_CONTROL || p2 == U_GCB_CR || p2 == U_GCB_LF) {
57        // exclude zero-width control characters from breaking (tailoring of TR29)
58        if (c2 == 0x00ad
59                || (c2 >= 0x200b && c2 <= 0x200f)
60                || (c2 >= 0x2028 && c2 <= 0x202e)
61                || (c2 >= 0x2060 && c2 <= 0x206f)) {
62            return false;
63        }
64        return true;
65    }
66    // Rule GB6, L x ( L | V | LV | LVT )
67    if (p1 == U_GCB_L && (p2 == U_GCB_L || p2 == U_GCB_V || p2 == U_GCB_LV || p2 == U_GCB_LVT)) {
68        return false;
69    }
70    // Rule GB7, ( LV | V ) x ( V | T )
71    if ((p1 == U_GCB_LV || p1 == U_GCB_V) && (p2 == U_GCB_V || p2 == U_GCB_T)) {
72        return false;
73    }
74    // Rule GB8, ( LVT | T ) x T
75    if ((p1 == U_GCB_L || p1 == U_GCB_T) && p2 == U_GCB_T) {
76        return false;
77    }
78    // Rule GB8a, Regional_Indicator x Regional_Indicator
79    if (p1 == U_GCB_REGIONAL_INDICATOR && p2 == U_GCB_REGIONAL_INDICATOR) {
80        return false;
81    }
82    // Rule GB9, x Extend; Rule GB9a, x SpacingMark
83    if (p2 == U_GCB_EXTEND || p2 == U_GCB_SPACING_MARK) {
84        if (c2 == 0xe33) {
85            // most other implementations break THAI CHARACTER SARA AM
86            // (tailoring of TR29)
87            return true;
88        }
89        return false;
90    }
91    // Cluster indic syllables togeter (tailoring of TR29)
92    if (u_getIntPropertyValue(c1, UCHAR_CANONICAL_COMBINING_CLASS) == 9  // virama
93            && u_getIntPropertyValue(c2, UCHAR_GENERAL_CATEGORY) == U_OTHER_LETTER) {
94        return false;
95    }
96    // Rule GB10, Any / Any
97    return true;
98}
99
100size_t GraphemeBreak::getTextRunCursor(const uint16_t* buf, size_t start, size_t count,
101        size_t offset, MoveOpt opt) {
102    switch (opt) {
103    case AFTER:
104        if (offset < start + count) {
105            offset++;
106        }
107        // fall through
108    case AT_OR_AFTER:
109        while (!isGraphemeBreak(buf, start, count, offset)) {
110            offset++;
111        }
112        break;
113    case BEFORE:
114        if (offset > start) {
115            offset--;
116        }
117        // fall through
118    case AT_OR_BEFORE:
119        while (!isGraphemeBreak(buf, start, count, offset)) {
120            offset--;
121        }
122        break;
123    case AT:
124        if (!isGraphemeBreak(buf, start, count, offset)) {
125            offset = (size_t)-1;
126        }
127        break;
128    }
129    return offset;
130}
131
132}  // namespace android
133