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https://github.com/flutter/flutter.git
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95af01c57b
We were not taking context start into account when deciding whether to split a ligature, which was causing inconsistent behavior. This patch consistently references the widths array relative to the start of the context. Bug: 21549197 Change-Id: I7c71e10c1af84354fefe782fc0b87120016e6555
117 lines
4.1 KiB
C++
117 lines
4.1 KiB
C++
/*
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* Copyright (C) 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#define LOG_TAG "Minikin"
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#include <cutils/log.h>
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#include <cmath>
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#include <unicode/uchar.h>
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#include <minikin/GraphemeBreak.h>
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#include <minikin/Measurement.h>
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namespace android {
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// These could be considered helper methods of layout, but need only be loosely coupled, so
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// are separate.
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float getRunAdvance(Layout& layout, const uint16_t* buf, size_t start, size_t count,
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size_t offset) {
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float advance = 0.0f;
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size_t lastCluster = start;
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float clusterWidth = 0.0f;
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for (size_t i = start; i < offset; i++) {
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float charAdvance = layout.getCharAdvance(i - start);
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if (charAdvance != 0.0f) {
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advance += charAdvance;
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lastCluster = i;
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clusterWidth = charAdvance;
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}
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}
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if (offset < start + count && layout.getCharAdvance(offset - start) == 0.0f) {
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// In the middle of a cluster, distribute width of cluster so that each grapheme cluster
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// gets an equal share.
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// TODO: get caret information out of font when that's available
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size_t nextCluster;
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for (nextCluster = offset + 1; nextCluster < start + count; nextCluster++) {
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if (layout.getCharAdvance(nextCluster - start) != 0.0f) break;
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}
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int numGraphemeClusters = 0;
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int numGraphemeClustersAfter = 0;
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for (size_t i = lastCluster; i < nextCluster; i++) {
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bool isAfter = i >= offset;
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if (GraphemeBreak::isGraphemeBreak(buf, start, count, i)) {
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numGraphemeClusters++;
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if (isAfter) {
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numGraphemeClustersAfter++;
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}
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}
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}
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if (numGraphemeClusters > 0) {
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advance -= clusterWidth * numGraphemeClustersAfter / numGraphemeClusters;
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}
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}
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return advance;
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}
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/**
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* Essentially the inverse of getRunAdvance. Compute the value of offset for which the
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* measured caret comes closest to the provided advance param, and which is on a grapheme
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* cluster boundary.
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*
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* The actual implementation fast-forwards through clusters to get "close", then does a finer-grain
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* search within the cluster and grapheme breaks.
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*/
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size_t getOffsetForAdvance(Layout& layout, const uint16_t* buf, size_t start, size_t count,
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float advance) {
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float x = 0.0f, xLastClusterStart = 0.0f, xSearchStart = 0.0f;
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size_t lastClusterStart = start, searchStart = start;
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for (size_t i = start; i < start + count; i++) {
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if (GraphemeBreak::isGraphemeBreak(buf, start, count, i)) {
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searchStart = lastClusterStart;
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xSearchStart = xLastClusterStart;
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}
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float width = layout.getCharAdvance(i - start);
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if (width != 0.0f) {
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lastClusterStart = i;
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xLastClusterStart = x;
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x += width;
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if (x > advance) {
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break;
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}
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}
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}
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size_t best = searchStart;
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float bestDist = FLT_MAX;
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for (size_t i = searchStart; i <= start + count; i++) {
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if (GraphemeBreak::isGraphemeBreak(buf, start, count, i)) {
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// "getRunAdvance(layout, buf, start, count, bufSize, i) - advance" but more efficient
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float delta = getRunAdvance(layout, buf, searchStart, count, i) + xSearchStart
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- advance;
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if (std::abs(delta) < bestDist) {
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bestDist = std::abs(delta);
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best = i;
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}
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if (delta >= 0.0f) {
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break;
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}
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}
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}
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return best;
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}
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}
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