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 #define LOG_TAG "Minikin"
18
19 #include "LayoutUtils.h"
20
21 /**
22 * For the purpose of layout, a word break is a boundary with no
23 * kerning or complex script processing. This is necessarily a
24 * heuristic, but should be accurate most of the time.
25 */
isWordBreakAfter(int c)26 static bool isWordBreakAfter(int c) {
27 if (c == ' ' || (c >= 0x2000 && c <= 0x200a) || c == 0x3000) {
28 // spaces
29 return true;
30 }
31 // Note: kana is not included, as sophisticated fonts may kern kana
32 return false;
33 }
34
isWordBreakBefore(int c)35 static bool isWordBreakBefore(int c) {
36 // CJK ideographs (and yijing hexagram symbols)
37 return isWordBreakAfter(c) || (c >= 0x3400 && c <= 0x9fff);
38 }
39
40 /**
41 * Return offset of previous word break. It is either < offset or == 0.
42 */
getPrevWordBreakForCache(const uint16_t * chars,size_t offset,size_t len)43 size_t getPrevWordBreakForCache(
44 const uint16_t* chars, size_t offset, size_t len) {
45 if (offset == 0) return 0;
46 if (offset > len) offset = len;
47 if (isWordBreakBefore(chars[offset - 1])) {
48 return offset - 1;
49 }
50 for (size_t i = offset - 1; i > 0; i--) {
51 if (isWordBreakBefore(chars[i]) || isWordBreakAfter(chars[i - 1])) {
52 return i;
53 }
54 }
55 return 0;
56 }
57
58 /**
59 * Return offset of next word break. It is either > offset or == len.
60 */
getNextWordBreakForCache(const uint16_t * chars,size_t offset,size_t len)61 size_t getNextWordBreakForCache(
62 const uint16_t* chars, size_t offset, size_t len) {
63 if (offset >= len) return len;
64 if (isWordBreakAfter(chars[offset])) {
65 return offset + 1;
66 }
67 for (size_t i = offset + 1; i < len; i++) {
68 // No need to check isWordBreakAfter(chars[i - 1]) since it is checked
69 // in previous iteration. Note that isWordBreakBefore returns true
70 // whenever isWordBreakAfter returns true.
71 if (isWordBreakBefore(chars[i])) {
72 return i;
73 }
74 }
75 return len;
76 }
77