do not expose task and make it thread safe

python/core/core_auto.sip

@@ -336,6 +336,7 @@
 %Include qgsmessageoutput.sip
 %Include qgsnetworkaccessmanager.sip
 %Include qgsnetworkcontentfetcher.sip
+%Include qgsnetworkcontentfetcherregistry.sip
 %Include qgsnetworkcontentfetchertask.sip
 %Include qgsofflineediting.sip
 %Include qgspluginlayer.sip

python/core/qgsapplication.sip.in

@@ -645,8 +645,7 @@ within SVG files.
 
     static QgsNetworkContentFetcherRegistry *networkContentFetcherRegistry();
 %Docstring
-Returns the application's SVG cache, used for caching SVG images and handling parameter replacement
-within SVG files.
+Returns the application's network content registry used for fetching temporary files during QGIS session
 
 .. versionadded:: 3.2
 %End

python/core/qgsnetworkcontentfetcherregistry.sip.in

@@ -0,0 +1,131 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsnetworkcontentfetcherregistry.h                          *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+
+
+
+class QgsFetchedContent : QObject
+{
+%Docstring
+FetchedContent holds useful information about a network content being fetched
+
+.. seealso:: :py:class:`QgsNetworkContentFetcherRegistry`
+
+.. versionadded:: 3.2
+%End
+
+%TypeHeaderCode
+#include "qgsnetworkcontentfetcherregistry.h"
+%End
+  public:
+    enum ContentStatus
+    {
+      NotStarted,
+      Downloading,
+      Finished,
+      Failed
+    };
+
+    explicit QgsFetchedContent( QTemporaryFile *file = 0, ContentStatus status = NotStarted );
+%Docstring
+Constructs a FetchedContent with pointer to the downloaded file and status of the download
+%End
+
+
+    const QString filePath() const;
+%Docstring
+Return the path to the local file, an empty string if the file is not accessible yet.
+%End
+
+    ContentStatus status() const;
+%Docstring
+Return the status of the download
+%End
+
+    QNetworkReply::NetworkError error() const;
+%Docstring
+Return the potential error of the download
+%End
+
+  public slots:
+
+    void download( bool redownload = false );
+%Docstring
+ Start the download
+
+:param redownload: if set to true, it will restart any achieved or pending download.
+%End
+
+  signals:
+    void fetched();
+%Docstring
+Sent when the file is fetched and accessible
+%End
+
+    void downloadStarted( const bool redownload );
+%Docstring
+Sent went the download actually starts
+%End
+
+};
+
+class QgsNetworkContentFetcherRegistry : QObject
+{
+%Docstring
+ Registry for temporary fetched files
+
+This provides a simple way of downloading and accessing
+remote files during QGIS application running.
+
+.. seealso:: :py:class:`QgsFetchedContent`
+
+.. versionadded:: 3.2
+%End
+
+%TypeHeaderCode
+#include "qgsnetworkcontentfetcherregistry.h"
+%End
+  public:
+    enum FetchingMode
+    {
+      DownloadLater,
+      DownloadImmediately,
+    };
+
+    explicit QgsNetworkContentFetcherRegistry();
+%Docstring
+Create the registry for temporary downloaded files
+%End
+
+    ~QgsNetworkContentFetcherRegistry();
+
+    const QgsFetchedContent *fetch( const QUrl &url, const FetchingMode &fetchingMode = DownloadLater );
+%Docstring
+ Initialize a download for the given URL
+
+:param url: the URL to be fetched
+:param fetchingMode: defines if the download will start immediately or shall be manually triggered
+
+.. note::
+
+   If the download starts immediately, it will not redownload any already fetched or currently fetching file.
+%End
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsnetworkcontentfetcherregistry.h                          *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/

src/core/qgsapplication.cpp

@@ -1667,7 +1667,7 @@ QgsSvgCache *QgsApplication::svgCache()
 
 QgsNetworkContentFetcherRegistry *QgsApplication::networkContentFetcherRegistry()
 {
-  return members()->mNetworkContentFertcherRegistry;
+  return members()->mNetworkContentFetcherRegistry;
 }
 
 QgsSymbolLayerRegistry *QgsApplication::symbolLayerRegistry()
@@ -1749,7 +1749,7 @@ QgsApplication::ApplicationMembers::ApplicationMembers()
   mAnnotationRegistry = new QgsAnnotationRegistry();
   m3DRendererRegistry = new Qgs3DRendererRegistry();
   mProjectStorageRegistry = new QgsProjectStorageRegistry();
-  mNetworkContentFertcherRegistry = new QgsNetworkContentFetcherRegistry();
+  mNetworkContentFetcherRegistry = new QgsNetworkContentFetcherRegistry();
 }
 
 QgsApplication::ApplicationMembers::~ApplicationMembers()
@@ -1773,7 +1773,7 @@ QgsApplication::ApplicationMembers::~ApplicationMembers()
   delete mSvgCache;
   delete mSymbolLayerRegistry;
   delete mTaskManager;
-  delete mNetworkContentFertcherRegistry;
+  delete mNetworkContentFetcherRegistry;
 }
 
 QgsApplication::ApplicationMembers *QgsApplication::members()

src/core/qgsapplication.h

@@ -588,8 +588,7 @@ class CORE_EXPORT QgsApplication : public QApplication
     static QgsSvgCache *svgCache();
 
     /**
-     * Returns the application's SVG cache, used for caching SVG images and handling parameter replacement
-     * within SVG files.
+     * Returns the application's network content registry used for fetching temporary files during QGIS session
      * \since QGIS 3.2
      */
     static QgsNetworkContentFetcherRegistry *networkContentFetcherRegistry();
@@ -810,7 +809,7 @@ class CORE_EXPORT QgsApplication : public QApplication
       QgsColorSchemeRegistry *mColorSchemeRegistry = nullptr;
       QgsFieldFormatterRegistry *mFieldFormatterRegistry = nullptr;
       QgsGpsConnectionRegistry *mGpsConnectionRegistry = nullptr;
-      QgsNetworkContentFetcherRegistry *mNetworkContentFertcherRegistry = nullptr;
+      QgsNetworkContentFetcherRegistry *mNetworkContentFetcherRegistry = nullptr;
       QgsMessageLog *mMessageLog = nullptr;
       QgsPaintEffectRegistry *mPaintEffectRegistry = nullptr;
       QgsPluginLayerRegistry *mPluginLayerRegistry = nullptr;

src/core/qgsnetworkcontentfetcherregistry.cpp

@@ -3,7 +3,7 @@
                              -------------------
     begin                : April, 2018
     copyright            : (C) 2018 by Denis Rouzaud
-    email                : denis.rouzaud@gmail.com
+    email                : denis@opengis.ch
 
  ***************************************************************************/
 
@@ -28,66 +28,78 @@ QgsNetworkContentFetcherRegistry::QgsNetworkContentFetcherRegistry()
 
 QgsNetworkContentFetcherRegistry::~QgsNetworkContentFetcherRegistry()
 {
-  QMap<QUrl, FetchedContent>::const_iterator it = mFileRegistry.constBegin();
+  QMap<QUrl, QgsFetchedContent *>::const_iterator it = mFileRegistry.constBegin();
   for ( ; it != mFileRegistry.constEnd(); ++it )
   {
-    it.value().mFile->deleteLater();
+    it.value()->mFile->close();
+    delete it.value()->mFile;
   }
+  mFileRegistry.clear();
 }
 
-const QgsNetworkContentFetcherTask *QgsNetworkContentFetcherRegistry::fetch( const QUrl &url, const bool reload )
+const QgsFetchedContent *QgsNetworkContentFetcherRegistry::fetch( const QUrl &url, const FetchingMode &fetchingMode )
 {
   if ( mFileRegistry.contains( url ) )
   {
-    if ( !reload )
-    {
-      return mFileRegistry.value( url ).mFetchingTask;
-    }
-    else
+    return mFileRegistry.value( url );
+  }
+
+  QgsFetchedContent *content = new QgsFetchedContent( nullptr, QgsFetchedContent::NotStarted );
+  QgsNetworkContentFetcherTask *fetcher = new QgsNetworkContentFetcherTask( url );
+
+  QObject::connect( content, &QgsFetchedContent::downloadStarted, this, [ = ]( const bool redownload )
+  {
+    QMutexLocker locker( &mMutex );
+    if ( mFileRegistry.contains( url ) && redownload )
     {
-      FetchedContent content = mFileRegistry.take( url );
-      if ( content.mFetchingTask )
+      const QgsFetchedContent *content = mFileRegistry[url];
+      if ( mFileRegistry.value( url )->status() == QgsFetchedContent::Downloading && content->mFetchingTask )
       {
-        content.mFetchingTask->cancel();
+        content->mFetchingTask->cancel();
       }
-      if ( content.mFile )
+      if ( content->mFile )
       {
-        content.mFile->deleteLater();
+        content->mFile->deleteLater();
+        mFileRegistry[url]->setFilePath( QStringLiteral() );
       }
     }
-  }
-
-  QgsNetworkContentFetcherTask *fetcher = new QgsNetworkContentFetcherTask( url );
-  QgsApplication::instance()->taskManager()->addTask( fetcher );
-  mFileRegistry.insert( url,
-                        FetchedContent( nullptr,
-                                        QgsNetworkContentFetcherRegistry::Downloading ) );
+    if ( ( mFileRegistry.contains( url ) && mFileRegistry.value( url )->status() == QgsFetchedContent::NotStarted ) || redownload )
+    {
+      QgsApplication::instance()->taskManager()->addTask( fetcher );
+    }
+  } );
 
   QObject::connect( fetcher, &QgsNetworkContentFetcherTask::fetched, this, [ = ]()
   {
+    QMutexLocker locker( &mMutex );
     QNetworkReply *reply = fetcher->reply();
-    FetchedContent content = mFileRegistry.take( url );
+    QgsFetchedContent *content = mFileRegistry.value( url );
     if ( reply->error() == QNetworkReply::NoError )
     {
-      content.setFile( new QTemporaryFile( QStringLiteral( "XXXXXX" ) ) );
-      content.mFile->write( reply->readAll() );
-      content.setStatus( Finished );
+      QTemporaryFile *tf = new QTemporaryFile( QStringLiteral( "XXXXXX" ) );
+      content->setFile( tf );
+      tf->open();
+      content->mFile->write( reply->readAll() );
+      // Qt docs notes that on some system if fileName is not called before close, file might get deleted
+      content->setFilePath( tf->fileName() );
+      tf->close();
+      content->setStatus( QgsFetchedContent::Finished );
     }
     else
     {
-      content.setStatus( Failed );
-      content.setError( reply->error() );
+      content->setStatus( QgsFetchedContent::Failed );
+      content->setError( reply->error() );
+      content->setFilePath( QStringLiteral() );
     }
-    mFileRegistry.insert( url, content );
+    content->emitFetched();
   } );
 
+  if ( fetchingMode == DownloadImmediately )
+    content->download();
+  mFileRegistry.insert( url, content );
 
-  return fetcher;
+  return content;
 }
 
 
 
-QgsNetworkContentFetcherRegistry::FetchedContent QgsNetworkContentFetcherRegistry::file( const QUrl &url )
-{
-  return mFileRegistry.value( url );
-}