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 21namespace minikin { 22 23const uint16_t CHAR_NBSP = 0x00A0; 24 25/* 26 * Determine whether the code unit is a word space for the purposes of justification. 27 */ 28bool isWordSpace(uint16_t code_unit) { 29 return code_unit == ' ' || code_unit == CHAR_NBSP; 30} 31 32/** 33 * For the purpose of layout, a word break is a boundary with no 34 * kerning or complex script processing. This is necessarily a 35 * heuristic, but should be accurate most of the time. 36 */ 37static bool isWordBreakAfter(uint16_t c) { 38 if (isWordSpace(c) || (c >= 0x2000 && c <= 0x200a) || c == 0x3000) { 39 // spaces 40 return true; 41 } 42 // Note: kana is not included, as sophisticated fonts may kern kana 43 return false; 44} 45 46static bool isWordBreakBefore(uint16_t c) { 47 // CJK ideographs (and yijing hexagram symbols) 48 return isWordBreakAfter(c) || (c >= 0x3400 && c <= 0x9fff); 49} 50 51/** 52 * Return offset of previous word break. It is either < offset or == 0. 53 */ 54size_t getPrevWordBreakForCache( 55 const uint16_t* chars, size_t offset, size_t len) { 56 if (offset == 0) return 0; 57 if (offset > len) offset = len; 58 if (isWordBreakBefore(chars[offset - 1])) { 59 return offset - 1; 60 } 61 for (size_t i = offset - 1; i > 0; i--) { 62 if (isWordBreakBefore(chars[i]) || isWordBreakAfter(chars[i - 1])) { 63 return i; 64 } 65 } 66 return 0; 67} 68 69/** 70 * Return offset of next word break. It is either > offset or == len. 71 */ 72size_t getNextWordBreakForCache( 73 const uint16_t* chars, size_t offset, size_t len) { 74 if (offset >= len) return len; 75 if (isWordBreakAfter(chars[offset])) { 76 return offset + 1; 77 } 78 for (size_t i = offset + 1; i < len; i++) { 79 // No need to check isWordBreakAfter(chars[i - 1]) since it is checked 80 // in previous iteration. Note that isWordBreakBefore returns true 81 // whenever isWordBreakAfter returns true. 82 if (isWordBreakBefore(chars[i])) { 83 return i; 84 } 85 } 86 return len; 87} 88 89} // namespace minikin 90