Fix drawing of map items (grids, overviews) when rendering map item as a raster item

Author: nyalldawson

python/core/layout/qgslayoutitemmap.sip

@@ -457,7 +457,7 @@ This is calculated using the width of the map item and the width of the
 current visible map extent.
 %End
 
-    QgsMapSettings mapSettings( const QgsRectangle &extent, QSizeF size, int dpi ) const;
+    QgsMapSettings mapSettings( const QgsRectangle &extent, QSizeF size, double dpi ) const;
 %Docstring
 Return map settings that will be used for drawing of the map.
 %End

src/app/layout/qgslayoutdesignerdialog.cpp

@@ -1529,7 +1529,7 @@ void QgsLayoutDesignerDialog::exportToRaster()
   switch ( exporter.exportToImage( fileNExt.first, settings ) )
   {
     case QgsLayoutExporter::Success:
-      mMessageBar->pushInfo( tr( "Export layout" ), tr( "Successfully exported layout to %1" ).arg( fileNExt.first ) );
+      mMessageBar->pushInfo( tr( "Export layout" ), tr( "Successfully exported layout to <a href=\"%1\">%2</a>" ).arg( QUrl::fromLocalFile( fileNExt.first ).toString(), fileNExt.first ) );
       break;
 
     case QgsLayoutExporter::PrintError:

src/core/layout/qgslayoutitemmap.cpp

@@ -756,11 +756,12 @@ void QgsLayoutItemMap::paint( QPainter *painter, const QStyleOptionGraphicsItem
   if ( thisPaintRect.width() == 0 || thisPaintRect.height() == 0 )
     return;
 
-  painter->save();
-  painter->setClipRect( thisPaintRect );
+  //TODO - try to reduce the amount of duplicate code here!
 
   if ( mLayout->context().isPreviewRender() )
   {
+    painter->save();
+    painter->setClipRect( thisPaintRect );
     if ( !mCacheFinalImage || mCacheFinalImage->isNull() )
     {
       // No initial render available - so draw some preview text alerting user
@@ -800,6 +801,23 @@ void QgsLayoutItemMap::paint( QPainter *painter, const QStyleOptionGraphicsItem
       //restore rotation
       painter->restore();
     }
+
+    painter->setClipRect( thisPaintRect, Qt::NoClip );
+
+    if ( shouldDrawPart( OverviewMapExtent ) )
+    {
+      mOverviewStack->drawItems( painter );
+    }
+    if ( shouldDrawPart( Grid ) )
+    {
+      mGridStack->drawItems( painter );
+    }
+    drawAnnotations( painter );
+    if ( shouldDrawPart( Frame ) )
+    {
+      drawMapFrame( painter );
+    }
+    painter->restore();
   }
   else
   {
@@ -811,42 +829,73 @@ void QgsLayoutItemMap::paint( QPainter *painter, const QStyleOptionGraphicsItem
     if ( !paintDevice )
       return;
 
-    // Fill with background color
-    if ( shouldDrawPart( Background ) )
-    {
-      drawMapBackground( painter );
-    }
-
     QgsRectangle cExtent = extent();
     QSizeF size( cExtent.width() * mapUnitsToLayoutUnits(), cExtent.height() * mapUnitsToLayoutUnits() );
 
     if ( containsAdvancedEffects() && ( !mLayout || !( mLayout->context().flags() & QgsLayoutContext::FlagForceVectorOutput ) ) )
     {
       // rasterise
-      double destinationDpi = mLayout ? mLayout->context().dpi() : style->matrix.m11() * 25.4;
-
-      double layoutUnitsToPixels = mLayout ? mLayout->convertFromLayoutUnits( 1, QgsUnitTypes::LayoutPixels ).length() : destinationDpi / 25.4;
-      double widthInPixels = boundingRect().width() * layoutUnitsToPixels;
-      double heightInPixels = boundingRect().height() * layoutUnitsToPixels;
+      double destinationDpi = style->matrix.m11() * 25.4;
+      double layoutUnitsInInches = mLayout ? mLayout->convertFromLayoutUnits( 1, QgsUnitTypes::LayoutInches ).length() : 1;
+      int widthInPixels = std::round( boundingRect().width() * layoutUnitsInInches * destinationDpi );
+      int heightInPixels = std::round( boundingRect().height() * layoutUnitsInInches * destinationDpi );
       QImage image = QImage( widthInPixels, heightInPixels, QImage::Format_ARGB32 );
 
       image.fill( Qt::transparent );
       image.setDotsPerMeterX( 1000 * destinationDpi / 25.4 );
       image.setDotsPerMeterY( 1000 * destinationDpi / 25.4 );
+      double dotsPerMM = destinationDpi / 25.4;
       QPainter p( &image );
-      double dotsPerMM = image.logicalDpiX() / 25.4;
-      drawMap( &p, cExtent, image.size(), destinationDpi );
-      p.end();
 
-      dotsPerMM = paintDevice->logicalDpiX() / 25.4;
+      QPointF tl = -boundingRect().topLeft();
+      QRect imagePaintRect( std::round( tl.x() * dotsPerMM ),
+                            std::round( tl.y() * dotsPerMM ),
+                            std::round( thisPaintRect.width() * dotsPerMM ),
+                            std::round( thisPaintRect.height() * dotsPerMM ) );
+      p.setClipRect( imagePaintRect );
+
+      p.translate( imagePaintRect.topLeft() );
+
+      // Fill with background color - must be drawn onto the flattened image
+      // so that layers with opacity or blend modes can correctly interact with it
+      if ( shouldDrawPart( Background ) )
+      {
+        p.scale( dotsPerMM, dotsPerMM );
+        drawMapBackground( &p );
+        p.scale( 1.0 / dotsPerMM, 1.0 / dotsPerMM );
+      }
+
+      drawMap( &p, cExtent, imagePaintRect.size(), image.logicalDpiX() );
+
+      // important - all other items, overviews, grids etc must be rendered to the
+      // flattened image, in case these have blend modes must need to interact
+      // with the map
+      p.scale( dotsPerMM, dotsPerMM );
+
+      if ( shouldDrawPart( OverviewMapExtent ) )
+      {
+        mOverviewStack->drawItems( &p );
+      }
+      if ( shouldDrawPart( Grid ) )
+      {
+        mGridStack->drawItems( &p );
+      }
+      drawAnnotations( &p );
+
       painter->save();
       painter->scale( 1 / dotsPerMM, 1 / dotsPerMM ); // scale painter from mm to dots
-      painter->drawImage( 0, 0, image );
-      painter->restore();
-
+      painter->drawImage( std::round( -tl.x()* dotsPerMM ), std::round( -tl.y() * dotsPerMM ), image );
+      painter->scale( dotsPerMM, dotsPerMM );
     }
     else
     {
+      // Fill with background color
+      if ( shouldDrawPart( Background ) )
+      {
+        drawMapBackground( painter );
+      }
+
+      painter->setClipRect( thisPaintRect );
       painter->save();
       painter->translate( mXOffset, mYOffset );
 
@@ -856,31 +905,28 @@ void QgsLayoutItemMap::paint( QPainter *painter, const QStyleOptionGraphicsItem
       drawMap( painter, cExtent, size, paintDevice->logicalDpiX() );
 
       painter->restore();
-    }
 
-    mDrawing = false;
-  }
-
-  painter->setClipRect( thisPaintRect, Qt::NoClip );
+      painter->setClipRect( thisPaintRect, Qt::NoClip );
 
-  if ( shouldDrawPart( OverviewMapExtent ) )
-  {
-    mOverviewStack->drawItems( painter );
-  }
-  if ( shouldDrawPart( Grid ) )
-  {
-    mGridStack->drawItems( painter );
-  }
+      if ( shouldDrawPart( OverviewMapExtent ) )
+      {
+        mOverviewStack->drawItems( painter );
+      }
+      if ( shouldDrawPart( Grid ) )
+      {
+        mGridStack->drawItems( painter );
+      }
+      drawAnnotations( painter );
 
-  //draw canvas items
-  drawAnnotations( painter );
+    }
 
-  if ( shouldDrawPart( Frame ) )
-  {
-    drawMapFrame( painter );
+    if ( shouldDrawPart( Frame ) )
+    {
+      drawMapFrame( painter );
+    }
+    painter->restore();
+    mDrawing = false;
   }
-
-  painter->restore();
 }
 
 int QgsLayoutItemMap::numberExportLayers() const
@@ -994,7 +1040,7 @@ void QgsLayoutItemMap::recreateCachedImageInBackground( double viewScaleFactor )
   mPainterJob->start();
 }
 
-QgsMapSettings QgsLayoutItemMap::mapSettings( const QgsRectangle &extent, QSizeF size, int dpi ) const
+QgsMapSettings QgsLayoutItemMap::mapSettings( const QgsRectangle &extent, QSizeF size, double dpi ) const
 {
   QgsExpressionContext expressionContext = createExpressionContext();
   QgsCoordinateReferenceSystem renderCrs = crs();

src/core/layout/qgslayoutitemmap.h

@@ -408,7 +408,7 @@ class CORE_EXPORT QgsLayoutItemMap : public QgsLayoutItem
     /**
      * Return map settings that will be used for drawing of the map.
      */
-    QgsMapSettings mapSettings( const QgsRectangle &extent, QSizeF size, int dpi ) const;
+    QgsMapSettings mapSettings( const QgsRectangle &extent, QSizeF size, double dpi ) const;
 
     void finalizeRestoreFromXml() override;
 

src/core/layout/qgslayoutitemmapgrid.cpp

@@ -1219,7 +1219,11 @@ void QgsLayoutItemMapGrid::drawCoordinateAnnotation( QPainter *p, QPointF pos, c
         ypos += ( mAnnotationFrameDistance + textHeight + gridFrameDistance );
         xpos -= textWidth / 2.0;
         if ( extension )
+        {
           extension->bottom = std::max( extension->bottom, mAnnotationFrameDistance + gridFrameDistance + textHeight );
+          extension->left = std::max( extension->left, textWidth / 2.0 ); // annotation at bottom left/right may extend outside the bounds
+          extension->right = std::max( extension->right, textWidth / 2.0 );
+        }
       }
       else if ( mBottomGridAnnotationDirection == QgsLayoutItemMapGrid::VerticalDescending )
       {

tests/src/core/testqgslayoutmap.cpp

@@ -28,6 +28,7 @@
 #include "qgsmapthemecollection.h"
 #include "qgsproperty.h"
 #include "qgslayoutpagecollection.h"
+#include "qgslayoutitempolyline.h"
 #include <QObject>
 #include "qgstest.h"
 
@@ -53,6 +54,7 @@ class TestQgsLayoutMap : public QObject
     void mapPolygonVertices(); // test mapPolygon function with no map rotation
     void dataDefinedLayers(); //test data defined layer string
     void dataDefinedStyles(); //test data defined styles
+    void rasterized();
 
   private:
     QgsRasterLayer *mRasterLayer = nullptr;
@@ -440,5 +442,66 @@ void TestQgsLayoutMap::dataDefinedStyles()
   QVERIFY( checker.testLayout( mReport, 0, 0 ) );
 }
 
+void TestQgsLayoutMap::rasterized()
+{
+  // test a map which must be rasterised
+  QgsLayout l( QgsProject::instance() );
+  l.initializeDefaults();
+
+  QgsLayoutItemMap *map = new QgsLayoutItemMap( &l );
+  map->attemptMove( QgsLayoutPoint( 20, 30 ) );
+  map->attemptResize( QgsLayoutSize( 200, 100 ) );
+  map->setFrameEnabled( true );
+  map->setExtent( QgsRectangle( -110.0, 25.0, -90, 40.0 ) );
+  QList<QgsMapLayer *> layers = QList<QgsMapLayer *>() << mLinesLayer;
+  map->setLayers( layers );
+  map->setBackgroundColor( Qt::yellow );
+  l.addLayoutItem( map );
+
+  // add some guide lines, just for reference
+  QPolygonF points;
+  points << QPointF( 0, 30 ) << QPointF( 10, 30 );
+  QgsLayoutItemPolyline *line1 = new QgsLayoutItemPolyline( points, &l );
+  l.addLayoutItem( line1 );
+  points.clear();
+  points << QPointF( 0, 30 + map->rect().height() ) << QPointF( 10, 30 + map->rect().height() );
+  QgsLayoutItemPolyline *line2 = new QgsLayoutItemPolyline( points, &l );
+  l.addLayoutItem( line2 );
+  points.clear();
+  points << QPointF( 20, 0 ) << QPointF( 20, 20 );
+  QgsLayoutItemPolyline *line3 = new QgsLayoutItemPolyline( points, &l );
+  l.addLayoutItem( line3 );
+  points.clear();
+  points << QPointF( 220, 0 ) << QPointF( 220, 20 );
+  QgsLayoutItemPolyline *line4 = new QgsLayoutItemPolyline( points, &l );
+  l.addLayoutItem( line4 );
+
+  // force rasterization
+  QgsLayoutItemMapGrid *grid = new QgsLayoutItemMapGrid( "test", map );
+  grid->setIntervalX( 10 );
+  grid->setIntervalY( 10 );
+  grid->setBlendMode( QPainter::CompositionMode_Darken );
+  grid->setAnnotationEnabled( true );
+  grid->setAnnotationDisplay( QgsLayoutItemMapGrid::ShowAll, QgsLayoutItemMapGrid::Left );
+  grid->setAnnotationDisplay( QgsLayoutItemMapGrid::ShowAll, QgsLayoutItemMapGrid::Top );
+  grid->setAnnotationDisplay( QgsLayoutItemMapGrid::ShowAll, QgsLayoutItemMapGrid::Right );
+  grid->setAnnotationDisplay( QgsLayoutItemMapGrid::ShowAll, QgsLayoutItemMapGrid::Bottom );
+  map->grids()->addGrid( grid );
+  map->updateBoundingRect();
+
+  QVERIFY( map->containsAdvancedEffects() );
+
+  QgsLayoutChecker checker( QStringLiteral( "layoutmap_rasterized" ), &l );
+  checker.setControlPathPrefix( QStringLiteral( "composer_map" ) );
+  QVERIFY( checker.testLayout( mReport, 0, 0 ) );
+
+  // try rendering again, without requiring rasterization, for comparison
+  // (we can use the same test image, because CompositionMode_Darken doesn't actually have any noticable
+  // rendering differences for the black grid!)
+  grid->setBlendMode( QPainter::CompositionMode_SourceOver );
+  QVERIFY( !map->containsAdvancedEffects() );
+  QVERIFY( checker.testLayout( mReport, 0, 0 ) );
+}
+
 QGSTEST_MAIN( TestQgsLayoutMap )
 #include "testqgslayoutmap.moc"