qgsvectortilelayerrenderer.cpp

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/***************************************************************************
  qgsvectortilelayerrenderer.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 "qgsvectortilelayerrenderer.h"
 
#include <QElapsedTimer>
 
#include "qgsexpressioncontextutils.h"
#include "qgsfeedback.h"
#include "qgslogger.h"
 
#include "qgsvectortilemvtdecoder.h"
#include "qgsvectortilelayer.h"
#include "qgsvectortileloader.h"
#include "qgsvectortileutils.h"
 
#include "qgslabelingengine.h"
#include "qgsvectortilelabeling.h"
 
 
QgsVectorTileLayerRenderer::QgsVectorTileLayerRenderer( QgsVectorTileLayer *layer, QgsRenderContext &context )
  : QgsMapLayerRenderer( layer->id(), &context )
  , mSourceType( layer->sourceType() )
  , mSourcePath( layer->sourcePath() )
  , mSourceMinZoom( layer->sourceMinZoom() )
  , mSourceMaxZoom( layer->sourceMaxZoom() )
  , mRenderer( layer->renderer()->clone() )
  , mDrawTileBoundaries( layer->isTileBorderRenderingEnabled() )
  , mFeedback( new QgsFeedback )
{
 
  if ( QgsLabelingEngine *engine = context.labelingEngine() )
  {
    if ( layer->labeling() )
    {
      mLabelProvider = layer->labeling()->provider( layer );
      if ( mLabelProvider )
      {
        engine->addProvider( mLabelProvider );
      }
    }
  }
 
}
 
bool QgsVectorTileLayerRenderer::render()
{
  QgsRenderContext &ctx = *renderContext();
 
  if ( ctx.renderingStopped() )
    return false;
 
  QElapsedTimer tTotal;
  tTotal.start();
 
  QgsDebugMsgLevel( QStringLiteral( "Vector tiles rendering extent: " ) + ctx.extent().toString( -1 ), 2 );
  QgsDebugMsgLevel( QStringLiteral( "Vector tiles map scale 1 : %1" ).arg( ctx.rendererScale() ), 2 );
 
  mTileZoom = QgsVectorTileUtils::scaleToZoomLevel( ctx.rendererScale(), mSourceMinZoom, mSourceMaxZoom );
  QgsDebugMsgLevel( QStringLiteral( "Vector tiles zoom level: %1" ).arg( mTileZoom ), 2 );
 
  mTileMatrix = QgsTileMatrix::fromWebMercator( mTileZoom );
 
  mTileRange = mTileMatrix.tileRangeFromExtent( ctx.extent() );
  QgsDebugMsgLevel( QStringLiteral( "Vector tiles range X: %1 - %2  Y: %3 - %4" )
                    .arg( mTileRange.startColumn() ).arg( mTileRange.endColumn() )
                    .arg( mTileRange.startRow() ).arg( mTileRange.endRow() ), 2 );
 
  // view center is used to sort the order of tiles for fetching and rendering
  QPointF viewCenter = mTileMatrix.mapToTileCoordinates( ctx.extent().center() );
 
  if ( !mTileRange.isValid() )
  {
    QgsDebugMsgLevel( QStringLiteral( "Vector tiles - outside of range" ), 2 );
    return true;   // nothing to do
  }
 
  bool isAsync = ( mSourceType == QStringLiteral( "xyz" ) );
 
  std::unique_ptr<QgsVectorTileLoader> asyncLoader;
  QList<QgsVectorTileRawData> rawTiles;
  if ( !isAsync )
  {
    QElapsedTimer tFetch;
    tFetch.start();
    rawTiles = QgsVectorTileLoader::blockingFetchTileRawData( mSourceType, mSourcePath, mTileMatrix, viewCenter, mTileRange );
    QgsDebugMsgLevel( QStringLiteral( "Tile fetching time: %1" ).arg( tFetch.elapsed() / 1000. ), 2 );
    QgsDebugMsgLevel( QStringLiteral( "Fetched tiles: %1" ).arg( rawTiles.count() ), 2 );
  }
  else
  {
    asyncLoader.reset( new QgsVectorTileLoader( mSourcePath, mTileMatrix, mTileRange, viewCenter, mFeedback.get() ) );
    QObject::connect( asyncLoader.get(), &QgsVectorTileLoader::tileRequestFinished, [this]( const QgsVectorTileRawData & rawTile )
    {
      QgsDebugMsgLevel( QStringLiteral( "Got tile asynchronously: " ) + rawTile.id.toString(), 2 );
      if ( !rawTile.data.isEmpty() )
        decodeAndDrawTile( rawTile );
    } );
  }
 
  if ( ctx.renderingStopped() )
    return false;
 
  // add @zoom_level variable which can be used in styling
  QgsExpressionContextScope *scope = new QgsExpressionContextScope( QObject::tr( "Tiles" ) ); // will be deleted by popper
  scope->setVariable( "zoom_level", mTileZoom, true );
  QgsExpressionContextScopePopper popper( ctx.expressionContext(), scope );
 
  mRenderer->startRender( *renderContext(), mTileZoom, mTileRange );
 
  QMap<QString, QSet<QString> > requiredFields = mRenderer->usedAttributes( ctx );
 
  if ( mLabelProvider )
  {
    QMap<QString, QSet<QString> > requiredFieldsLabeling = mLabelProvider->usedAttributes( ctx, mTileZoom );
    for ( QString layerName : requiredFieldsLabeling.keys() )
    {
      requiredFields[layerName].unite( requiredFieldsLabeling[layerName] );
    }
  }
 
  QMap<QString, QgsFields> perLayerFields;
  for ( QString layerName : requiredFields.keys() )
    mPerLayerFields[layerName] = QgsVectorTileUtils::makeQgisFields( requiredFields[layerName] );
 
  if ( mLabelProvider )
  {
    mLabelProvider->setFields( mPerLayerFields );
    QSet<QString> attributeNames;  // we don't need this - already got referenced columns in provider constructor
    if ( !mLabelProvider->prepare( ctx, attributeNames ) )
    {
      ctx.labelingEngine()->removeProvider( mLabelProvider );
      mLabelProvider = nullptr; // provider is deleted by the engine
    }
  }
 
  if ( !isAsync )
  {
    for ( QgsVectorTileRawData &rawTile : rawTiles )
    {
      if ( ctx.renderingStopped() )
        break;
 
      decodeAndDrawTile( rawTile );
    }
  }
  else
  {
    // Block until tiles are fetched and rendered. If the rendering gets canceled at some point,
    // the async loader will catch the signal, abort requests and return from downloadBlocking()
    asyncLoader->downloadBlocking();
  }
 
  mRenderer->stopRender( ctx );
 
  ctx.painter()->setClipping( false );
 
  QgsDebugMsgLevel( QStringLiteral( "Total time for decoding: %1" ).arg( mTotalDecodeTime / 1000. ), 2 );
  QgsDebugMsgLevel( QStringLiteral( "Drawing time: %1" ).arg( mTotalDrawTime / 1000. ), 2 );
  QgsDebugMsgLevel( QStringLiteral( "Total time: %1" ).arg( tTotal.elapsed() / 1000. ), 2 );
 
  return !ctx.renderingStopped();
}
 
void QgsVectorTileLayerRenderer::decodeAndDrawTile( const QgsVectorTileRawData &rawTile )
{
  QgsRenderContext &ctx = *renderContext();
 
  QgsDebugMsgLevel( QStringLiteral( "Drawing tile " ) + rawTile.id.toString(), 2 );
 
  QElapsedTimer tLoad;
  tLoad.start();
 
  // currently only MVT encoding supported
  QgsVectorTileMVTDecoder decoder;
  if ( !decoder.decode( rawTile.id, rawTile.data ) )
  {
    QgsDebugMsgLevel( QStringLiteral( "Failed to parse raw tile data! " ) + rawTile.id.toString(), 2 );
    return;
  }
 
  if ( ctx.renderingStopped() )
    return;
 
  QgsCoordinateTransform ct = ctx.coordinateTransform();
 
  QgsVectorTileRendererData tile( rawTile.id );
  tile.setFields( mPerLayerFields );
  tile.setFeatures( decoder.layerFeatures( mPerLayerFields, ct ) );
  tile.setTilePolygon( QgsVectorTileUtils::tilePolygon( rawTile.id, ct, mTileMatrix, ctx.mapToPixel() ) );
 
  mTotalDecodeTime += tLoad.elapsed();
 
  // calculate tile polygon in screen coordinates
 
  if ( ctx.renderingStopped() )
    return;
 
  // set up clipping so that rendering does not go behind tile's extent
 
  ctx.painter()->setClipRegion( QRegion( tile.tilePolygon() ) );
 
  QElapsedTimer tDraw;
  tDraw.start();
 
  mRenderer->renderTile( tile, ctx );
  mTotalDrawTime += tDraw.elapsed();
 
  if ( mLabelProvider )
    mLabelProvider->registerTileFeatures( tile, ctx );
 
  if ( mDrawTileBoundaries )
  {
    ctx.painter()->setClipping( false );
 
    QPen pen( Qt::red );
    pen.setWidth( 3 );
    ctx.painter()->setPen( pen );
    ctx.painter()->drawPolygon( tile.tilePolygon() );
  }
}