Avoid multiple redundant requests for mapserver legends

qgis · Jun 10, 2019 · 5c84bbc · 5c84bbc
1 parent 3cad7ed
commit 5c84bbc
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Showing 2 changed files with 46 additions and 18 deletions.
diff --git a/src/providers/arcgisrest/qgsamsprovider.cpp b/src/providers/arcgisrest/qgsamsprovider.cpp
@@ -60,8 +60,10 @@ struct LessThanTileRequest
   }
 };
 
-QgsAmsLegendFetcher::QgsAmsLegendFetcher( QgsAmsProvider *provider )
-  : QgsImageFetcher( provider ), mProvider( provider )
+QgsAmsLegendFetcher::QgsAmsLegendFetcher( QgsAmsProvider *provider, const QImage &fetchedImage )
+  : QgsImageFetcher( provider )
+  , mProvider( provider )
+  , mLegendImage( fetchedImage )
 {
   mQuery = new QgsArcGisAsyncQuery( this );
   connect( mQuery, &QgsArcGisAsyncQuery::finished, this, &QgsAmsLegendFetcher::handleFinished );
@@ -70,18 +72,25 @@ QgsAmsLegendFetcher::QgsAmsLegendFetcher( QgsAmsProvider *provider )
 
 void QgsAmsLegendFetcher::start()
 {
-  // http://resources.arcgis.com/en/help/rest/apiref/mslegend.html
-  // http://sampleserver5.arcgisonline.com/arcgis/rest/services/CommunityAddressing/MapServer/legend?f=pjson
-  QgsDataSourceUri dataSource( mProvider->dataSourceUri() );
-  const QString authCfg = dataSource.authConfigId();
-  const QString referer = dataSource.param( QStringLiteral( "referer" ) );
-  QgsStringMap headers;
-  if ( !referer.isEmpty() )
-    headers[ QStringLiteral( "Referer" )] = referer;
-
-  QUrl queryUrl( dataSource.param( QStringLiteral( "url" ) ) + "/legend" );
-  queryUrl.addQueryItem( QStringLiteral( "f" ), QStringLiteral( "json" ) );
-  mQuery->start( queryUrl, authCfg, &mQueryReply, false, headers );
+  if ( mLegendImage.isNull() )
+  {
+    // http://resources.arcgis.com/en/help/rest/apiref/mslegend.html
+    // http://sampleserver5.arcgisonline.com/arcgis/rest/services/CommunityAddressing/MapServer/legend?f=pjson
+    QgsDataSourceUri dataSource( mProvider->dataSourceUri() );
+    const QString authCfg = dataSource.authConfigId();
+    const QString referer = dataSource.param( QStringLiteral( "referer" ) );
+    QgsStringMap headers;
+    if ( !referer.isEmpty() )
+      headers[ QStringLiteral( "Referer" )] = referer;
+
+    QUrl queryUrl( dataSource.param( QStringLiteral( "url" ) ) + "/legend" );
+    queryUrl.addQueryItem( QStringLiteral( "f" ), QStringLiteral( "json" ) );
+    mQuery->start( queryUrl, authCfg, &mQueryReply, false, headers );
+  }
+  else
+  {
+    QTimer::singleShot( 1, this, &QgsAmsLegendFetcher::sendCachedImage );
+  }
 }
 
 void QgsAmsLegendFetcher::handleError( const QString &errorTitle, const QString &errorMsg )
@@ -91,6 +100,11 @@ void QgsAmsLegendFetcher::handleError( const QString &errorTitle, const QString
   emit error( errorTitle + ": " + errorMsg );
 }
 
+void QgsAmsLegendFetcher::sendCachedImage()
+{
+  emit finish( mLegendImage );
+}
+
 void QgsAmsLegendFetcher::handleFinished()
 {
   // Parse result
@@ -154,6 +168,7 @@ void QgsAmsLegendFetcher::handleFinished()
       ++i;
     }
   }
+  emit fetchedNew( mLegendImage );
   emit finish( mLegendImage );
 }
 
@@ -167,7 +182,7 @@ QgsAmsProvider::QgsAmsProvider( const QString &uri, const ProviderOptions &optio
   if ( !referer.isEmpty() )
     mRequestHeaders[ QStringLiteral( "Referer" )] = referer;
 
-  mLegendFetcher = new QgsAmsLegendFetcher( this );
+  mLegendFetcher = new QgsAmsLegendFetcher( this, QImage() );
 
 
   const QString authcfg = dataSource.authConfigId();
@@ -291,7 +306,7 @@ QgsAmsProvider::QgsAmsProvider( const QgsAmsProvider &other, const QgsDataProvid
 // - mCachedImage
 // - mCachedImageExtent
 {
-  mLegendFetcher = new QgsAmsLegendFetcher( this );
+  mLegendFetcher = new QgsAmsLegendFetcher( this, other.mLegendFetcher->getImage() );
 
   // is this needed?
   mTimestamp = QDateTime::currentDateTime();
@@ -747,6 +762,7 @@ QImage QgsAmsProvider::getLegendGraphic( double /*scale*/, bool forceRefresh, co
   {
     return mLegendFetcher->getImage();
   }
+  mLegendFetcher->clear();
   QEventLoop evLoop;
   connect( mLegendFetcher, &QgsImageFetcher::finish, &evLoop, &QEventLoop::quit );
   connect( mLegendFetcher, &QgsImageFetcher::error, &evLoop, &QEventLoop::quit );
@@ -766,7 +782,12 @@ QImage QgsAmsProvider::getLegendGraphic( double /*scale*/, bool forceRefresh, co
 
 QgsImageFetcher *QgsAmsProvider::getLegendGraphicFetcher( const QgsMapSettings * /*mapSettings*/ )
 {
-  return new QgsAmsLegendFetcher( this );
+  QgsAmsLegendFetcher *fetcher = new QgsAmsLegendFetcher( this, mLegendFetcher->getImage() );
+  connect( fetcher, &QgsAmsLegendFetcher::fetchedNew, this, [ = ]( const QImage & fetched )
+  {
+    mLegendFetcher->setImage( fetched );
+  } );
+  return fetcher;
 }
 
 QgsRasterIdentifyResult QgsAmsProvider::identify( const QgsPointXY &point, QgsRaster::IdentifyFormat format, const QgsRectangle &extent, int width, int height, int dpi )

diff --git a/src/providers/arcgisrest/qgsamsprovider.h b/src/providers/arcgisrest/qgsamsprovider.h
@@ -32,16 +32,23 @@ class QgsAmsLegendFetcher : public QgsImageFetcher
 {
     Q_OBJECT
   public:
-    QgsAmsLegendFetcher( QgsAmsProvider *provider );
+    QgsAmsLegendFetcher( QgsAmsProvider *provider, const QImage &fetchedImage );
     void start() override;
     bool haveImage() const { return mLegendImage.isNull(); }
     QImage getImage() const { return mLegendImage; }
+    void setImage( const QImage &image ) { mLegendImage = image; }
+    void clear() { mLegendImage = QImage(); }
     const QString &errorTitle() const { return mErrorTitle; }
     const QString &errorMessage() const { return mError; }
 
+  signals:
+
+    void fetchedNew( const QImage &image );
+
   private slots:
     void handleFinished();
     void handleError( const QString &errorTitle, const QString &errorMsg );
+    void sendCachedImage();
 
   private:
     QgsAmsProvider *mProvider = nullptr;