Upgrade the save as image function into a background task (#4382)

python/core/core.sip

@@ -95,6 +95,7 @@
 %Include qgsmaprendererjob.sip
 %Include qgsmaprendererparalleljob.sip
 %Include qgsmaprenderersequentialjob.sip
+%Include qgsmaprenderertask.sip
 %Include qgsmapsettings.sip
 %Include qgsmaptopixel.sip
 %Include qgsmapunitscale.sip

python/core/qgsmaprenderertask.sip

@@ -0,0 +1,76 @@
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsmaprenderertask.h                                        *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+
+
+
+
+
+class QgsMapRendererTask : QgsTask
+{
+%Docstring
+ QgsTask task which draws a map to an image file or a painter as a background
+ task. This can be used to draw maps without blocking the QGIS interface.
+.. versionadded:: 3.0
+%End
+
+%TypeHeaderCode
+#include "qgsmaprenderertask.h"
+%End
+  public:
+
+    enum ErrorType
+    {
+      ImageAllocationFail,
+      ImageSaveFail
+    };
+
+    QgsMapRendererTask( const QgsMapSettings &ms,
+                        const QString &fileName,
+                        const QString &fileFormat = QString( "PNG" ) );
+%Docstring
+ Constructor for QgsMapRendererTask to render a map to an image file.
+%End
+
+    QgsMapRendererTask( const QgsMapSettings &ms,
+                        QPainter *p );
+%Docstring
+ Constructor for QgsMapRendererTask to render a map to a painter object.
+%End
+
+    void addAnnotations( QList< QgsAnnotation * > annotations );
+%Docstring
+ Adds ``annotations`` to be rendered on the map.
+%End
+
+  signals:
+
+    void renderingComplete();
+%Docstring
+ Emitted when the map rendering is successfully completed.
+%End
+
+    void errorOccurred( int error );
+%Docstring
+ Emitted when map rendering failed.
+%End
+
+  protected:
+
+    virtual bool run();
+    virtual void finished( bool result );
+
+};
+
+/************************************************************************
+ * This file has been generated automatically from                      *
+ *                                                                      *
+ * src/core/qgsmaprenderertask.h                                        *
+ *                                                                      *
+ * Do not edit manually ! Edit header and run scripts/sipify.pl again   *
+ ************************************************************************/
+

src/app/qgisapp.cpp

@@ -270,6 +270,7 @@
 #include "qgsvectorlayerutils.h"
 #include "qgshelp.h"
 #include "qgsvectorfilewritertask.h"
+#include "qgsmaprenderertask.h"
 #include "qgsnewnamedialog.h"
 
 #include "qgssublayersdialog.h"
@@ -5772,9 +5773,48 @@ void QgisApp::saveMapAsImage()
   QPair< QString, QString> myFileNameAndFilter = QgisGui::getSaveAsImageName( this, tr( "Choose a file name to save the map image as" ) );
   if ( myFileNameAndFilter.first != QLatin1String( "" ) )
   {
-    //save the mapview to the selected file
-    mMapCanvas->saveAsImage( myFileNameAndFilter.first, nullptr, myFileNameAndFilter.second );
-    statusBar()->showMessage( tr( "Saved map image to %1" ).arg( myFileNameAndFilter.first ) );
+    //TODO: GUI
+    int dpi = 90;
+    QSize size = mMapCanvas->size() * ( dpi / 90 );
+
+    QgsMapSettings ms = QgsMapSettings();
+    ms.setDestinationCrs( QgsProject::instance()->crs() );
+    ms.setExtent( mMapCanvas->extent() );
+    ms.setOutputSize( size );
+    ms.setOutputDpi( dpi );
+    ms.setBackgroundColor( mMapCanvas->canvasColor() );
+    ms.setRotation( mMapCanvas->rotation() );
+    ms.setLayers( mMapCanvas->layers() );
+
+    QgsMapRendererTask *mapRendererTask = new QgsMapRendererTask( ms, myFileNameAndFilter.first, myFileNameAndFilter.second );
+    mapRendererTask->addAnnotations( QgsProject::instance()->annotationManager()->annotations() );
+
+    connect( mapRendererTask, &QgsMapRendererTask::renderingComplete, this, [ = ]
+    {
+      QgsMessageBarItem *successMsg = new QgsMessageBarItem(
+        tr( "Successfully saved canvas to image" ),
+        QgsMessageBar::SUCCESS );
+      messageBar()->pushItem( successMsg );
+    } );
+    connect( mapRendererTask, &QgsMapRendererTask::errorOccurred, this, [ = ]( int error )
+    {
+      if ( error == QgsMapRendererTask::ImageAllocationFail )
+      {
+        QgsMessageBarItem *errorMsg = new QgsMessageBarItem(
+          tr( "Could not allocate required memory for image" ),
+          QgsMessageBar::WARNING );
+        messageBar()->pushItem( errorMsg );
+      }
+      else if ( error == QgsMapRendererTask::ImageAllocationFail )
+      {
+        QgsMessageBarItem *errorMsg = new QgsMessageBarItem(
+          tr( "Could not save the image to file" ),
+          QgsMessageBar::WARNING );
+        messageBar()->pushItem( errorMsg );
+      }
+    } );
+
+    QgsApplication::taskManager()->addTask( mapRendererTask );
   }
 
 } // saveMapAsImage

src/core/CMakeLists.txt

@@ -173,6 +173,7 @@ SET(QGIS_CORE_SRCS
   qgsmaprendererjob.cpp
   qgsmaprendererparalleljob.cpp
   qgsmaprenderersequentialjob.cpp
+  qgsmaprenderertask.cpp
   qgsmapsettings.cpp
   qgsmaptopixel.cpp
   qgsmaptopixelgeometrysimplifier.cpp
@@ -521,6 +522,7 @@ SET(QGIS_CORE_MOC_HDRS
   qgsmaprendererjob.h
   qgsmaprendererparalleljob.h
   qgsmaprenderersequentialjob.h
+  qgsmaprenderertask.h
   qgsmessagelog.h
   qgsmessageoutput.h
   qgsnetworkaccessmanager.h

src/core/qgsmaprenderertask.cpp

@@ -0,0 +1,133 @@
+/***************************************************************************
+                          qgsmaprenderertask.h
+                          -------------------------
+    begin                : Apr 2017
+    copyright            : (C) 2017 by Mathieu Pellerin
+    email                : nirvn dot asia 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 "qgsannotation.h"
+#include "qgsannotationmanager.h"
+#include "qgsmaprenderertask.h"
+#include "qgsmaprenderercustompainterjob.h"
+
+
+QgsMapRendererTask::QgsMapRendererTask( const QgsMapSettings &ms, const QString &fileName, const QString &fileFormat )
+  : QgsTask( tr( "Saving as image" ) )
+  , mMapSettings( ms )
+  , mFileName( fileName )
+  , mFileFormat( fileFormat )
+{
+}
+
+QgsMapRendererTask::QgsMapRendererTask( const QgsMapSettings &ms, QPainter *p )
+  : QgsTask( tr( "Saving as image" ) )
+  , mMapSettings( ms )
+  , mPainter( p )
+{
+}
+
+void QgsMapRendererTask::addAnnotations( QList< QgsAnnotation * > annotations )
+{
+  qDeleteAll( mAnnotations );
+  mAnnotations.clear();
+
+  Q_FOREACH ( const QgsAnnotation *a, annotations )
+  {
+    mAnnotations << a->clone();
+  }
+}
+
+bool QgsMapRendererTask::run()
+{
+  QImage img;
+  std::unique_ptr< QPainter > tempPainter;
+  QPainter *destPainter = mPainter;
+
+  if ( !mPainter )
+  {
+    // save rendered map to an image file
+    img = QImage( mMapSettings.outputSize(), QImage::Format_ARGB32 );
+    if ( img.isNull() )
+    {
+      mError = ImageAllocationFail;
+      return false;
+    }
+
+    tempPainter.reset( new QPainter( &img ) );
+    destPainter = tempPainter.get();
+  }
+
+  if ( !destPainter )
+    return false;
+
+  QgsMapRendererCustomPainterJob r( mMapSettings, destPainter );
+  r.renderSynchronously();
+
+  QgsRenderContext context = QgsRenderContext::fromMapSettings( mMapSettings );
+  context.setPainter( destPainter );
+
+  Q_FOREACH ( QgsAnnotation *annotation, mAnnotations )
+  {
+    if ( !annotation || !annotation->isVisible() )
+    {
+      continue;
+    }
+    if ( annotation->mapLayer() && !mMapSettings.layers().contains( annotation->mapLayer() ) )
+    {
+      continue;
+    }
+
+    context.painter()->save();
+    context.painter()->setRenderHint( QPainter::Antialiasing, context.flags() & QgsRenderContext::Antialiasing );
+
+    double itemX, itemY;
+    if ( annotation->hasFixedMapPosition() )
+    {
+      itemX = mMapSettings.outputSize().width() * ( annotation->mapPosition().x() - mMapSettings.extent().xMinimum() ) / mMapSettings.extent().width();
+      itemY = mMapSettings.outputSize().height() * ( 1 - ( annotation->mapPosition().y() - mMapSettings.extent().yMinimum() ) / mMapSettings.extent().height() );
+    }
+    else
+    {
+      itemX = annotation->relativePosition().x() * mMapSettings.outputSize().width();
+      itemY = annotation->relativePosition().y() * mMapSettings.outputSize().height();
+    }
+
+    context.painter()->translate( itemX, itemY );
+
+    annotation->render( context );
+    context.painter()->restore();
+  }
+  qDeleteAll( mAnnotations );
+  mAnnotations.clear();
+
+  if ( !mFileName.isEmpty() )
+  {
+    destPainter->end();
+    bool success = img.save( mFileName, mFileFormat.toLocal8Bit().data() );
+    if ( !success )
+    {
+      mError = ImageSaveFail;
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void QgsMapRendererTask::finished( bool result )
+{
+  if ( result )
+    emit renderingComplete();
+  else
+    emit errorOccurred( mError );
+}

src/core/qgsmaprenderertask.h

@@ -0,0 +1,99 @@
+/***************************************************************************
+                          qgsmaprenderertask.h
+                          -------------------------
+    begin                : Apr 2017
+    copyright            : (C) 2017 by Mathieu Pellerin
+    email                : nirvn dot asia 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.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSMAPRENDERERTASK_H
+#define QGSMAPRENDERERTASK_H
+
+#include "qgis.h"
+#include "qgis_core.h"
+#include "qgsannotation.h"
+#include "qgsannotationmanager.h"
+#include "qgsmapsettings.h"
+#include "qgstaskmanager.h"
+
+#include <QPainter>
+
+/**
+ * \class QgsMapRendererTask
+ * \ingroup core
+ * QgsTask task which draws a map to an image file or a painter as a background
+ * task. This can be used to draw maps without blocking the QGIS interface.
+ * \since QGIS 3.0
+ */
+class CORE_EXPORT QgsMapRendererTask : public QgsTask
+{
+    Q_OBJECT
+
+  public:
+
+    //! \brief Error type
+    enum ErrorType
+    {
+      ImageAllocationFail = 1,  // Image allocation failure
+      ImageSaveFail             // Image save failure
+    };
+
+    /**
+     * Constructor for QgsMapRendererTask to render a map to an image file.
+     */
+    QgsMapRendererTask( const QgsMapSettings &ms,
+                        const QString &fileName,
+                        const QString &fileFormat = QString( "PNG" ) );
+
+    /**
+     * Constructor for QgsMapRendererTask to render a map to a painter object.
+     */
+    QgsMapRendererTask( const QgsMapSettings &ms,
+                        QPainter *p );
+
+    /**
+     * Adds \a annotations to be rendered on the map.
+     */
+    void addAnnotations( QList< QgsAnnotation * > annotations );
+
+  signals:
+
+    /**
+     * Emitted when the map rendering is successfully completed.
+     */
+    void renderingComplete();
+
+    /**
+     * Emitted when map rendering failed.
+     */
+    void errorOccurred( int error );
+
+  protected:
+
+    virtual bool run() override;
+    virtual void finished( bool result ) override;
+
+  private:
+
+    QgsMapSettings mMapSettings;
+
+    QPainter *mPainter = nullptr;
+
+    QString mFileName;
+    QString mFileFormat;
+
+    QList< QgsAnnotation * > mAnnotations;
+
+    int mError = 0;
+};
+
+#endif