core/vectortile/qgsvectortilemvtdecoder.cpp

/***************************************************************************
  qgsvectortilemvtdecoder.cpp
  --------------------------------------
  Date                 : March 2020
  Copyright            : (C) 2020 by Martin Dobias
  Email                : wonder dot sk at gmail dot com
 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#include <string>

#include "qgsvectortilemvtdecoder.h"

#include "qgsvectortilelayerrenderer.h"
#include "qgsvectortilemvtutils.h"
#include "qgsvectortileutils.h"

#include "qgslogger.h"
#include "qgsmultipoint.h"
#include "qgslinestring.h"
#include "qgsmultilinestring.h"
#include "qgsmultipolygon.h"
#include "qgspolygon.h"

#include <QPointer>


QgsVectorTileMVTDecoder::QgsVectorTileMVTDecoder() = default;

QgsVectorTileMVTDecoder::~QgsVectorTileMVTDecoder() = default;

bool QgsVectorTileMVTDecoder::decode( QgsTileXYZ tileID, const QByteArray &rawTileData )
{
  if ( !tile.ParseFromArray( rawTileData.constData(), rawTileData.count() ) )
    return false;

  mTileID = tileID;

  mLayerNameToIndex.clear();
  for ( int layerNum = 0; layerNum < tile.layers_size(); layerNum++ )
  {
    const ::vector_tile::Tile_Layer &layer = tile.layers( layerNum );
    const QString layerName = layer.name().c_str();
    mLayerNameToIndex[layerName] = layerNum;
  }
  return true;
}

QStringList QgsVectorTileMVTDecoder::layers() const
{
  QStringList layerNames;
  for ( int layerNum = 0; layerNum < tile.layers_size(); layerNum++ )
  {
    const ::vector_tile::Tile_Layer &layer = tile.layers( layerNum );
    const QString layerName = layer.name().c_str();
    layerNames << layerName;
  }
  return layerNames;
}

QStringList QgsVectorTileMVTDecoder::layerFieldNames( const QString &layerName ) const
{
  if ( !mLayerNameToIndex.contains( layerName ) )
    return QStringList();

  const ::vector_tile::Tile_Layer &layer = tile.layers( mLayerNameToIndex[layerName] );
  QStringList fieldNames;
  for ( int i = 0; i < layer.keys_size(); ++i )
  {
    const QString fieldName = layer.keys( i ).c_str();
    fieldNames << fieldName;
  }
  return fieldNames;
}

QgsVectorTileFeatures QgsVectorTileMVTDecoder::layerFeatures( const QMap<QString, QgsFields> &perLayerFields, const QgsCoordinateTransform &ct, const QSet<QString> *layerSubset ) const
{
  QgsVectorTileFeatures features;

  const int numTiles = static_cast<int>( pow( 2, mTileID.zoomLevel() ) ); // assuming we won't ever go over 30 zoom levels
  double z0xMin = -20037508.3427892, z0yMin = -20037508.3427892;
  double z0xMax =  20037508.3427892, z0yMax =  20037508.3427892;
  const double tileDX = ( z0xMax - z0xMin ) / numTiles;
  const double tileDY = ( z0yMax - z0yMin ) / numTiles;
  const double tileXMin = z0xMin + mTileID.column() * tileDX;
  const double tileYMax = z0yMax - mTileID.row() * tileDY;

  for ( int layerNum = 0; layerNum < tile.layers_size(); layerNum++ )
  {
    const ::vector_tile::Tile_Layer &layer = tile.layers( layerNum );

    const QString layerName = layer.name().c_str();
    if ( layerSubset && !layerSubset->contains( QString() ) && !layerSubset->contains( layerName ) )
      continue;

    QVector<QgsFeature> layerFeatures;
    const QgsFields layerFields = perLayerFields[layerName];

    // figure out how field indexes in MVT encoding map to field indexes in QgsFields (we may not use all available fields)
    QHash<int, int> tagKeyIndexToFieldIndex;
    for ( int i = 0; i < layer.keys_size(); ++i )
    {
      const int fieldIndex = layerFields.indexOf( layer.keys( i ).c_str() );
      if ( fieldIndex != -1 )
        tagKeyIndexToFieldIndex.insert( i, fieldIndex );
    }

    // go through features of a layer
    for ( int featureNum = 0; featureNum < layer.features_size(); featureNum++ )
    {
      const ::vector_tile::Tile_Feature &feature = layer.features( featureNum );

      QgsFeatureId fid;
#if 0
      // even if a feature has an internal ID, it's not guaranteed to be unique across different
      // tiles. This may violate the specifications, but it's been seen on mbtiles files in the wild...
      if ( feature.has_id() )
        fid = static_cast<QgsFeatureId>( feature.id() );
      else
#endif
      {
        // There is no assigned ID, but some parts of QGIS do not work correctly if all IDs are zero
        // (e.g. labeling will not register two features with the same FID within a single layer),
        // so let's generate some pseudo-unique FIDs to keep those bits happy
        fid = featureNum;
        fid |= ( layerNum & 0xff ) << 24;
        fid |= ( static_cast<QgsFeatureId>( mTileID.row() ) & 0xff ) << 32;
        fid |= ( static_cast<QgsFeatureId>( mTileID.column() ) & 0xff ) << 40;
      }

      QgsFeature f( layerFields, fid );

      //
      // parse attributes
      //

      for ( int tagNum = 0; tagNum + 1 < feature.tags_size(); tagNum += 2 )
      {
        const int keyIndex = static_cast<int>( feature.tags( tagNum ) );
        const int fieldIndex = tagKeyIndexToFieldIndex.value( keyIndex, -1 );
        if ( fieldIndex == -1 )
          continue;

        const int valueIndex = static_cast<int>( feature.tags( tagNum + 1 ) );
        if ( valueIndex >= layer.values_size() )
        {
          QgsDebugMsg( QStringLiteral( "Invalid value index for attribute" ) );
          continue;
        }
        const ::vector_tile::Tile_Value &value = layer.values( valueIndex );

        if ( value.has_string_value() )
          f.setAttribute( fieldIndex, QString::fromStdString( value.string_value() ) );
        else if ( value.has_float_value() )
          f.setAttribute( fieldIndex, static_cast<double>( value.float_value() ) );
        else if ( value.has_double_value() )
          f.setAttribute( fieldIndex, value.double_value() );
        else if ( value.has_int_value() )
          f.setAttribute( fieldIndex, static_cast<int>( value.int_value() ) );
        else if ( value.has_uint_value() )
          f.setAttribute( fieldIndex, static_cast<int>( value.uint_value() ) );
        else if ( value.has_sint_value() )
          f.setAttribute( fieldIndex, static_cast<int>( value.sint_value() ) );
        else if ( value.has_bool_value() )
          f.setAttribute( fieldIndex, static_cast<bool>( value.bool_value() ) );
        else
        {
          QgsDebugMsg( QStringLiteral( "Unexpected attribute value" ) );
        }
      }

      //
      // parse geometry
      //

      const int extent = static_cast<int>( layer.extent() );
      int cursorx = 0, cursory = 0;

      QVector<QgsPoint *> outputPoints; // for point/multi-point
      QVector<QgsLineString *> outputLinestrings;  // for linestring/multi-linestring
      QVector<QgsPolygon *> outputPolygons;
      QVector<QgsPoint> tmpPoints;

      for ( int i = 0; i < feature.geometry_size(); i ++ )
      {
        const unsigned g = feature.geometry( i );
        const unsigned cmdId = g & 0x7;
        const unsigned cmdCount = g >> 3;
        if ( cmdId == 1 ) // MoveTo
        {
          if ( i + static_cast<int>( cmdCount ) * 2 >= feature.geometry_size() )
          {
            QgsDebugMsg( QStringLiteral( "Malformed geometry: invalid cmdCount" ) );
            break;
          }

          if ( feature.type() == vector_tile::Tile_GeomType_POINT )
            outputPoints.reserve( outputPoints.size() + cmdCount );
          else
            tmpPoints.reserve( tmpPoints.size() + cmdCount );

          for ( unsigned j = 0; j < cmdCount; j++ )
          {
            const unsigned v = feature.geometry( i + 1 );
            const unsigned w = feature.geometry( i + 2 );
            const int dx = ( ( v >> 1 ) ^ ( -( v & 1 ) ) );
            const int dy = ( ( w >> 1 ) ^ ( -( w & 1 ) ) );
            cursorx += dx;
            cursory += dy;
            const double px = tileXMin + tileDX * double( cursorx ) / double( extent );
            const double py = tileYMax - tileDY * double( cursory ) / double( extent );

            if ( feature.type() == vector_tile::Tile_GeomType_POINT )
            {
              outputPoints.append( new QgsPoint( px, py ) );
            }
            else if ( feature.type() == vector_tile::Tile_GeomType_LINESTRING )
            {
              if ( tmpPoints.size() > 0 )
              {
                outputLinestrings.append( new QgsLineString( tmpPoints ) );
                tmpPoints.clear();
              }
              tmpPoints.append( QgsPoint( px, py ) );
            }
            else if ( feature.type() == vector_tile::Tile_GeomType_POLYGON )
            {
              tmpPoints.append( QgsPoint( px, py ) );
            }
            i += 2;
          }
        }
        else if ( cmdId == 2 ) // LineTo
        {
          if ( i + static_cast<int>( cmdCount ) * 2 >= feature.geometry_size() )
          {
            QgsDebugMsg( QStringLiteral( "Malformed geometry: invalid cmdCount" ) );
            break;
          }
          tmpPoints.reserve( tmpPoints.size() + cmdCount );
          for ( unsigned j = 0; j < cmdCount; j++ )
          {
            const unsigned v = feature.geometry( i + 1 );
            const unsigned w = feature.geometry( i + 2 );
            const int dx = ( ( v >> 1 ) ^ ( -( v & 1 ) ) );
            const int dy = ( ( w >> 1 ) ^ ( -( w & 1 ) ) );
            cursorx += dx;
            cursory += dy;
            const double px = tileXMin + tileDX * double( cursorx ) / double( extent );
            const double py = tileYMax - tileDY * double( cursory ) / double( extent );

            tmpPoints.push_back( QgsPoint( px, py ) );
            i += 2;
          }
        }
        else if ( cmdId == 7 ) // ClosePath
        {
          if ( feature.type() == vector_tile::Tile_GeomType_POLYGON )
          {
            tmpPoints.append( tmpPoints.first() );  // close the ring

            std::unique_ptr<QgsLineString> ring( new QgsLineString( tmpPoints ) );
            tmpPoints.clear();

            if ( QgsVectorTileMVTUtils::isExteriorRing( ring.get() ) )
            {
              // start a new polygon
              QgsPolygon *p = new QgsPolygon;
              p->setExteriorRing( ring.release() );
              outputPolygons.append( p );
            }
            else
            {
              // interior ring (hole)
              if ( outputPolygons.count() != 0 )
              {
                outputPolygons[outputPolygons.count() - 1]->addInteriorRing( ring.release() );
              }
              else
              {
                QgsDebugMsg( QStringLiteral( "Malformed geometry: first ring of a polygon is interior ring" ) );
              }
            }
          }

        }
        else
        {
          QgsDebugMsg( QStringLiteral( "Unexpected command ID: %1" ).arg( cmdId ) );
        }
      }

      QString geomType;
      if ( feature.type() == vector_tile::Tile_GeomType_POINT )
      {
        geomType = QStringLiteral( "Point" );
        if ( outputPoints.count() == 1 )
          f.setGeometry( QgsGeometry( outputPoints.at( 0 ) ) );
        else
        {
          QgsMultiPoint *mp = new QgsMultiPoint;
          mp->reserve( outputPoints.count() );
          for ( int k = 0; k < outputPoints.count(); ++k )
            mp->addGeometry( outputPoints[k] );
          f.setGeometry( QgsGeometry( mp ) );
        }
      }
      else if ( feature.type() == vector_tile::Tile_GeomType_LINESTRING )
      {
        geomType = QStringLiteral( "LineString" );

        // finish the linestring we have started
        outputLinestrings.append( new QgsLineString( tmpPoints ) );

        if ( outputLinestrings.count() == 1 )
          f.setGeometry( QgsGeometry( outputLinestrings.at( 0 ) ) );
        else
        {
          QgsMultiLineString *mls = new QgsMultiLineString;
          mls->reserve( outputLinestrings.size() );
          for ( int k = 0; k < outputLinestrings.count(); ++k )
            mls->addGeometry( outputLinestrings[k] );
          f.setGeometry( QgsGeometry( mls ) );
        }
      }
      else if ( feature.type() == vector_tile::Tile_GeomType_POLYGON )
      {
        geomType = QStringLiteral( "Polygon" );

        if ( outputPolygons.count() == 1 )
          f.setGeometry( QgsGeometry( outputPolygons.at( 0 ) ) );
        else
        {
          QgsMultiPolygon *mpl = new QgsMultiPolygon;
          mpl->reserve( outputPolygons.size() );
          for ( int k = 0; k < outputPolygons.count(); ++k )
            mpl->addGeometry( outputPolygons[k] );
          f.setGeometry( QgsGeometry( mpl ) );
        }
      }

      f.setAttribute( QStringLiteral( "_geom_type" ), geomType );
      f.geometry().transform( ct );

      layerFeatures.append( f );
    }

    features[layerName] = layerFeatures;
  }
  return features;
}