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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#define LOG_TAG "Minikin"
#include <cutils/log.h>
#include <cmath>
#include <unicode/uchar.h>
#include <minikin/GraphemeBreak.h>
#include <minikin/Measurement.h>
namespace android {
// These could be considered helper methods of layout, but need only be loosely coupled, so
// are separate.
static float getRunAdvance(Layout& layout, const uint16_t* buf, size_t layoutStart, size_t start,
size_t count, size_t offset) {
float advance = 0.0f;
size_t lastCluster = start;
float clusterWidth = 0.0f;
for (size_t i = start; i < offset; i++) {
float charAdvance = layout.getCharAdvance(i - layoutStart);
if (charAdvance != 0.0f) {
advance += charAdvance;
lastCluster = i;
clusterWidth = charAdvance;
}
}
if (offset < start + count && layout.getCharAdvance(offset - layoutStart) == 0.0f &&
!GraphemeBreak::isGraphemeBreak(buf, start, count, offset)) {
// In the middle of a cluster, distribute width of cluster so that each grapheme cluster
// gets an equal share.
// TODO: get caret information out of font when that's available
size_t nextCluster;
for (nextCluster = offset + 1; nextCluster < start + count; nextCluster++) {
if (layout.getCharAdvance(nextCluster - layoutStart) != 0.0f) break;
}
int numGraphemeClusters = 0;
int numGraphemeClustersAfter = 0;
for (size_t i = lastCluster; i < nextCluster; i++) {
bool isAfter = i >= offset;
if (GraphemeBreak::isGraphemeBreak(buf, start, count, i)) {
numGraphemeClusters++;
if (isAfter) {
numGraphemeClustersAfter++;
}
}
}
if (numGraphemeClusters > 0) {
advance -= clusterWidth * numGraphemeClustersAfter / numGraphemeClusters;
}
}
return advance;
}
float getRunAdvance(Layout& layout, const uint16_t* buf, size_t start, size_t count,
size_t offset) {
return getRunAdvance(layout, buf, start, start, count, offset);
}
/**
* Essentially the inverse of getRunAdvance. Compute the value of offset for which the
* measured caret comes closest to the provided advance param, and which is on a grapheme
* cluster boundary.
*
* The actual implementation fast-forwards through clusters to get "close", then does a finer-grain
* search within the cluster and grapheme breaks.
*/
size_t getOffsetForAdvance(Layout& layout, const uint16_t* buf, size_t start, size_t count,
float advance) {
float x = 0.0f, xLastClusterStart = 0.0f, xSearchStart = 0.0f;
size_t lastClusterStart = start, searchStart = start;
for (size_t i = start; i < start + count; i++) {
if (GraphemeBreak::isGraphemeBreak(buf, start, count, i)) {
searchStart = lastClusterStart;
xSearchStart = xLastClusterStart;
}
float width = layout.getCharAdvance(i - start);
if (width != 0.0f) {
lastClusterStart = i;
xLastClusterStart = x;
x += width;
if (x > advance) {
break;
}
}
}
size_t best = searchStart;
float bestDist = FLT_MAX;
for (size_t i = searchStart; i <= start + count; i++) {
if (GraphemeBreak::isGraphemeBreak(buf, start, count, i)) {
// "getRunAdvance(layout, buf, start, count, i) - advance" but more efficient
float delta = getRunAdvance(layout, buf, start, searchStart, count - searchStart, i)
+ xSearchStart - advance;
if (std::abs(delta) < bestDist) {
bestDist = std::abs(delta);
best = i;
}
if (delta >= 0.0f) {
break;
}
}
}
return best;
}
}
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