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      1 /*
      2  * Copyright 2018 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #include "SkClusterator.h"
      9 
     10 #include "SkGlyphRun.h"
     11 #include "SkTo.h"
     12 #include "SkUTF.h"
     13 
     14 static bool is_reversed(const uint32_t* clusters, uint32_t count) {
     15     // "ReversedChars" is how PDF deals with RTL text.
     16     // return true if more than one cluster and monotonicly decreasing to zero.
     17     if (count < 2 || clusters[0] == 0 || clusters[count - 1] != 0) {
     18         return false;
     19     }
     20     for (uint32_t i = 0; i + 1 < count; ++i) {
     21         if (clusters[i + 1] > clusters[i]) {
     22             return false;
     23         }
     24     }
     25     return true;
     26 }
     27 
     28 SkClusterator::SkClusterator(const SkGlyphRun& run)
     29     : fClusters(run.clusters().data())
     30     , fUtf8Text(run.text().data())
     31     , fGlyphCount(SkToU32(run.glyphsIDs().size()))
     32     , fTextByteLength(SkToU32(run.text().size()))
     33     , fReversedChars(fClusters ? is_reversed(fClusters, fGlyphCount) : false)
     34 {
     35     if (fClusters) {
     36         SkASSERT(fUtf8Text && fTextByteLength > 0 && fGlyphCount > 0);
     37     } else {
     38         SkASSERT(!fUtf8Text && fTextByteLength == 0);
     39     }
     40 }
     41 
     42 SkClusterator::Cluster SkClusterator::next() {
     43     if (fCurrentGlyphIndex >= fGlyphCount) {
     44         return Cluster{nullptr, 0, 0, 0};
     45     }
     46     if (!fClusters || !fUtf8Text) {
     47         return Cluster{nullptr, 0, fCurrentGlyphIndex++, 1};
     48     }
     49     uint32_t clusterGlyphIndex = fCurrentGlyphIndex;
     50     uint32_t cluster = fClusters[clusterGlyphIndex];
     51     do {
     52         ++fCurrentGlyphIndex;
     53     } while (fCurrentGlyphIndex < fGlyphCount && cluster == fClusters[fCurrentGlyphIndex]);
     54     uint32_t clusterGlyphCount = fCurrentGlyphIndex - clusterGlyphIndex;
     55     uint32_t clusterEnd = fTextByteLength;
     56     for (unsigned i = 0; i < fGlyphCount; ++i) {
     57        uint32_t c = fClusters[i];
     58        if (c > cluster && c < clusterEnd) {
     59            clusterEnd = c;
     60        }
     61     }
     62     uint32_t clusterLen = clusterEnd - cluster;
     63     return Cluster{fUtf8Text + cluster, clusterLen, clusterGlyphIndex, clusterGlyphCount};
     64 }
     65