New class QgsScopedProxyProgressTask, which makes it easy

to create proxy progress tasks and have their lifetime
managed automatically.

python/core/auto_generated/qgsproxyprogresstask.sip.in

@@ -52,6 +52,36 @@ This method is safe to call from the main thread.
 
 };
 
+class QgsScopedProxyProgressTask
+{
+%Docstring
+
+Scoped :py:class:`QgsScopedProxyProgressTask`, which automatically adds the proxy task
+to the application task manager on construction and finalizes the task
+when it goes out of scope.
+
+.. versionadded:: 3.4
+%End
+
+%TypeHeaderCode
+#include "qgsproxyprogresstask.h"
+%End
+  public:
+
+    QgsScopedProxyProgressTask( const QString &description );
+%Docstring
+Constructor for QgsScopedProxyProgressTask, with the specified ``description``.
+%End
+
+    ~QgsScopedProxyProgressTask();
+
+    void setProgress( double progress );
+%Docstring
+Sets the ``progress`` (from 0 to 100) for the proxied operation.
+%End
+
+};
+
 /************************************************************************
  * This file has been generated automatically from                      *
  *                                                                      *

src/app/qgisapp.cpp

@@ -1712,8 +1712,7 @@ void QgisApp::handleDropUriList( const QgsMimeDataUtils::UriList &lst )
   // added all layers, and only emit the signal once for the final layer added
   mBlockActiveLayerChanged = true;
 
-  QgsProxyProgressTask *proxyTask = new QgsProxyProgressTask( tr( "Loading layers" ) );
-  QgsApplication::taskManager()->addTask( proxyTask );
+  QgsScopedProxyProgressTask task( tr( "Loading layers" ) );
 
   // insert items in reverse order as each one is inserted on top of previous one
   int count = 0;
@@ -1756,11 +1755,9 @@ void QgisApp::handleDropUriList( const QgsMimeDataUtils::UriList &lst )
       openFile( u.uri, QStringLiteral( "project" ) );
     }
 
-    proxyTask->setProxyProgress( 100.0 * static_cast< double >( count ) / lst.size() );
+    task.setProgress( 100.0 * static_cast< double >( count ) / lst.size() );
   }
 
-  proxyTask->finalize( true );
-
   mBlockActiveLayerChanged = false;
   emit activeLayerChanged( activeLayer() );
 }

src/core/qgsproxyprogresstask.cpp

@@ -41,3 +41,23 @@ void QgsProxyProgressTask::setProxyProgress( double progress )
 {
   QMetaObject::invokeMethod( this, "setProgress", Qt::AutoConnection, Q_ARG( double, progress ) );
 }
+
+//
+// QgsScopedProxyProgressTask
+//
+
+QgsScopedProxyProgressTask::QgsScopedProxyProgressTask( const QString &description )
+  : mTask( new QgsProxyProgressTask( description ) )
+{
+  QgsApplication::taskManager()->addTask( mTask );
+}
+
+QgsScopedProxyProgressTask::~QgsScopedProxyProgressTask()
+{
+  mTask->finalize( true );
+}
+
+void QgsScopedProxyProgressTask::setProgress( double progress )
+{
+  mTask->setProxyProgress( progress );
+}

src/core/qgsproxyprogresstask.h

@@ -69,4 +69,35 @@ class CORE_EXPORT QgsProxyProgressTask : public QgsTask
 
 };
 
+/**
+ * \ingroup core
+ *
+ * Scoped QgsScopedProxyProgressTask, which automatically adds the proxy task
+ * to the application task manager on construction and finalizes the task
+ * when it goes out of scope.
+ *
+ * \since QGIS 3.4
+ */
+class CORE_EXPORT QgsScopedProxyProgressTask
+{
+  public:
+
+    /**
+     * Constructor for QgsScopedProxyProgressTask, with the specified \a description.
+     */
+    QgsScopedProxyProgressTask( const QString &description );
+
+    ~QgsScopedProxyProgressTask();
+
+    /**
+     * Sets the \a progress (from 0 to 100) for the proxied operation.
+     */
+    void setProgress( double progress );
+
+  private:
+
+    QgsProxyProgressTask *mTask = nullptr;
+
+};
+
 #endif // QGSPROXYPROGRESSTASK_H