Support canceling network content fetching tasks

(cherry-picked from 83f548)

Author: nyalldawson

python/core/qgsnetworkcontentfetcher.sip.in

@@ -63,6 +63,13 @@ Returns a reference to the network reply
 Returns the fetched content as a string
 
 :return: string containing network content
+%End
+
+    void cancel();
+%Docstring
+Cancels any ongoing request.
+
+.. versionadded:: 3.2
 %End
 
   signals:

python/core/qgsnetworkcontentfetchertask.sip.in

@@ -50,6 +50,8 @@ the specified network ``request``.
 
     virtual bool run();
 
+    virtual void cancel();
+
 
     QNetworkReply *reply();
 %Docstring

src/core/qgsnetworkcontentfetcher.cpp

@@ -44,6 +44,7 @@ void QgsNetworkContentFetcher::fetchContent( const QUrl &url )
 void QgsNetworkContentFetcher::fetchContent( const QNetworkRequest &request )
 {
   mContentLoaded = false;
+  mIsCanceled = false;
 
   if ( mReply )
   {
@@ -82,6 +83,19 @@ QString QgsNetworkContentFetcher::contentAsString() const
   return codec->toUnicode( array );
 }
 
+void QgsNetworkContentFetcher::cancel()
+{
+  mIsCanceled = true;
+
+  if ( mReply )
+  {
+    //cancel any in progress requests
+    mReply->abort();
+    mReply->deleteLater();
+    mReply = nullptr;
+  }
+}
+
 QTextCodec *QgsNetworkContentFetcher::codecForHtml( QByteArray &array ) const
 {
   //QTextCodec::codecForHtml fails to detect "<meta charset="utf-8"/>" type tags
@@ -125,6 +139,12 @@ void QgsNetworkContentFetcher::contentLoaded( bool ok )
 {
   Q_UNUSED( ok );
 
+  if ( mIsCanceled )
+  {
+    emit finished();
+    return;
+  }
+
   if ( mReply->error() != QNetworkReply::NoError )
   {
     QgsMessageLog::logMessage( tr( "HTTP fetch %1 failed with error %2" ).arg( mReply->url().toString(), mReply->errorString() ) );

src/core/qgsnetworkcontentfetcher.h

@@ -74,6 +74,12 @@ class CORE_EXPORT QgsNetworkContentFetcher : public QObject
      */
     QString contentAsString() const;
 
+    /**
+     * Cancels any ongoing request.
+     * \since QGIS 3.2
+     */
+    void cancel();
+
   signals:
 
     /**
@@ -93,6 +99,8 @@ class CORE_EXPORT QgsNetworkContentFetcher : public QObject
 
     bool mContentLoaded = false;
 
+    bool mIsCanceled = false;
+
     /**
      * Tries to create a text codec for decoding html content. Works around bugs in Qt's built in method.
      * \param array input html byte array

src/core/qgsnetworkcontentfetchertask.cpp

@@ -43,7 +43,7 @@ bool QgsNetworkContentFetcherTask::run()
   connect( mFetcher, &QgsNetworkContentFetcher::finished, &loop, &QEventLoop::quit );
   connect( mFetcher, &QgsNetworkContentFetcher::downloadProgress, this, [ = ]( qint64 bytesReceived, qint64 bytesTotal )
   {
-    if ( bytesTotal > 0 )
+    if ( !isCanceled() && bytesTotal > 0 )
     {
       int progress = ( bytesReceived * 100 ) / bytesTotal;
       // don't emit 100% progress reports until completely fetched - otherwise we get
@@ -54,11 +54,20 @@ bool QgsNetworkContentFetcherTask::run()
   } );
   mFetcher->fetchContent( mRequest );
   loop.exec();
-  setProgress( 100 );
+  if ( !isCanceled() )
+    setProgress( 100 );
   emit fetched();
   return true;
 }
 
+void QgsNetworkContentFetcherTask::cancel()
+{
+  if ( mFetcher )
+    mFetcher->cancel();
+
+  QgsTask::cancel();
+}
+
 QNetworkReply *QgsNetworkContentFetcherTask::reply()
 {
   return mFetcher ? mFetcher->reply() : nullptr;

src/core/qgsnetworkcontentfetchertask.h

@@ -65,6 +65,7 @@ class CORE_EXPORT QgsNetworkContentFetcherTask : public QgsTask
     ~QgsNetworkContentFetcherTask();
 
     bool run() override;
+    void cancel() override;
 
     /**
      * Returns the network reply. Ownership is not transferred.