1 /*
2 * Copyright (C) 2015 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 "LayoutUtils.h"
18
19 namespace minikin {
20
21 /*
22 * Determine whether the code unit is a word space for the purposes of justification.
23 * TODO: Support NBSP and other stretchable whitespace (b/34013491 and b/68204709).
24 */
isWordSpace(uint16_t code_unit)25 bool isWordSpace(uint16_t code_unit) {
26 return code_unit == ' ';
27 }
28
29 /**
30 * For the purpose of layout, a word break is a boundary with no
31 * kerning or complex script processing. This is necessarily a
32 * heuristic, but should be accurate most of the time.
33 */
isWordBreakAfter(uint16_t c)34 static bool isWordBreakAfter(uint16_t c) {
35 if (c == ' ' || (0x2000 <= c && c <= 0x200A) || c == 0x3000) {
36 // spaces
37 return true;
38 }
39 // Note: kana is not included, as sophisticated fonts may kern kana
40 return false;
41 }
42
isWordBreakBefore(uint16_t c)43 static bool isWordBreakBefore(uint16_t c) {
44 // CJK ideographs (and yijing hexagram symbols)
45 return isWordBreakAfter(c) || (0x3400 <= c && c <= 0x9FFF);
46 }
47
48 /**
49 * Return offset of previous word break. It is either < offset or == 0.
50 */
getPrevWordBreakForCache(const U16StringPiece & textBuf,uint32_t offset)51 uint32_t getPrevWordBreakForCache(const U16StringPiece& textBuf, uint32_t offset) {
52 if (offset == 0) return 0;
53 if (offset > textBuf.size()) offset = textBuf.size();
54 if (isWordBreakBefore(textBuf[offset - 1])) {
55 return offset - 1;
56 }
57 for (uint32_t i = offset - 1; i > 0; i--) {
58 if (isWordBreakBefore(textBuf[i]) || isWordBreakAfter(textBuf[i - 1])) {
59 return i;
60 }
61 }
62 return 0;
63 }
64
65 /**
66 * Return offset of next word break. It is either > offset or == len.
67 */
getNextWordBreakForCache(const U16StringPiece & textBuf,uint32_t offset)68 uint32_t getNextWordBreakForCache(const U16StringPiece& textBuf, uint32_t offset) {
69 if (offset >= textBuf.size()) return textBuf.size();
70 if (isWordBreakAfter(textBuf[offset])) {
71 return offset + 1;
72 }
73 for (uint32_t i = offset + 1; i < textBuf.size(); i++) {
74 // No need to check isWordBreakAfter(chars[i - 1]) since it is checked
75 // in previous iteration. Note that isWordBreakBefore returns true
76 // whenever isWordBreakAfter returns true.
77 if (isWordBreakBefore(textBuf[i])) {
78 return i;
79 }
80 }
81 return textBuf.size();
82 }
83
84 } // namespace minikin
85