/*
|
* 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.
|
*/
|
|
#include "minikin/Measurement.h"
|
|
#include <cfloat>
|
#include <cmath>
|
|
#include "minikin/GraphemeBreak.h"
|
|
namespace minikin {
|
|
// These could be considered helper methods of layout, but need only be loosely coupled, so
|
// are separate.
|
|
static float getRunAdvance(const float* advances, 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 = advances[i - layoutStart];
|
if (charAdvance != 0.0f) {
|
advance += charAdvance;
|
lastCluster = i;
|
clusterWidth = charAdvance;
|
}
|
}
|
if (offset < start + count && advances[offset - layoutStart] == 0.0f) {
|
// 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 (advances[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(advances + (start - layoutStart), buf, start, count,
|
i)) {
|
numGraphemeClusters++;
|
if (isAfter) {
|
numGraphemeClustersAfter++;
|
}
|
}
|
}
|
if (numGraphemeClusters > 0) {
|
advance -= clusterWidth * numGraphemeClustersAfter / numGraphemeClusters;
|
}
|
}
|
return advance;
|
}
|
|
float getRunAdvance(const float* advances, const uint16_t* buf, size_t start, size_t count,
|
size_t offset) {
|
return getRunAdvance(advances, 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(const float* advances, 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(advances, buf, start, count, i)) {
|
searchStart = lastClusterStart;
|
xSearchStart = xLastClusterStart;
|
}
|
float width = advances[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(advances, buf, start, count, i)) {
|
// "getRunAdvance(layout, buf, start, count, i) - advance" but more efficient
|
float delta = getRunAdvance(advances, 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;
|
}
|
|
} // namespace minikin
|
