[feature] blend modes for composer map grids (fix #7777)

src/app/composer/qgscomposer.cpp

@@ -2087,6 +2087,14 @@ bool QgsComposer::containsAdvancedEffects() const
           return true;
         }
       }
+      if ( currentMap->gridEnabled() )
+      {
+        // map contains an grid, check its blend mode
+        if ( currentMap->gridBlendMode() != QPainter::CompositionMode_SourceOver )
+        {
+          return true;
+        }
+      }
     }
   }
   return false;

src/app/composer/qgscomposermapwidget.cpp

@@ -343,6 +343,9 @@ void QgsComposerMapWidget::updateGuiElements()
       mFrameStyleComboBox->setCurrentIndex( mFrameStyleComboBox->findText( tr( "No frame" ) ) );
     }
 
+    //grid blend mode
+    mGridBlendComboBox->setBlendMode( mComposerMap->gridBlendMode() );
+
     //grid annotation format
     QgsComposerMap::GridAnnotationFormat gf = mComposerMap->gridAnnotationFormat();
     mAnnotationFormatComboBox->setCurrentIndex(( int )gf );
@@ -423,6 +426,7 @@ void QgsComposerMapWidget::blockAllSignals( bool b )
   mSetToMapCanvasExtentButton->blockSignals( b );
   mUpdatePreviewButton->blockSignals( b );
   mGridLineStyleButton->blockSignals( b );
+  mGridBlendComboBox->blockSignals( b );
   mDrawAnnotationCheckableGroupBox->blockSignals( b );
   mAnnotationFontButton->blockSignals( b );
   mAnnotationFormatComboBox->blockSignals( b );
@@ -705,6 +709,16 @@ void QgsComposerMapWidget::on_mCrossWidthSpinBox_valueChanged( double d )
   mComposerMap->endCommand();
 }
 
+void QgsComposerMapWidget::on_mGridBlendComboBox_currentIndexChanged( int index )
+{
+  Q_UNUSED( index );
+  if ( mComposerMap )
+  {
+    mComposerMap->setGridBlendMode( mGridBlendComboBox->blendMode() );
+  }
+
+}
+
 void QgsComposerMapWidget::on_mAnnotationFontButton_clicked()
 {
   if ( !mComposerMap )

src/app/composer/qgscomposermapwidget.h

@@ -60,6 +60,7 @@ class QgsComposerMapWidget: public QWidget, private Ui::QgsComposerMapWidgetBase
     void on_mGridLineStyleButton_clicked();
     void on_mGridTypeComboBox_currentIndexChanged( const QString& text );
     void on_mCrossWidthSpinBox_valueChanged( double d );
+    void on_mGridBlendComboBox_currentIndexChanged( int index );
     void on_mAnnotationFontButton_clicked();
     void on_mDistanceToMapFrameSpinBox_valueChanged( double d );
 

src/core/composer/qgscomposermap.cpp

@@ -43,9 +43,10 @@ QgsComposerMap::QgsComposerMap( QgsComposition *composition, int x, int y, int w
     : QgsComposerItem( x, y, width, height, composition ), mKeepLayerSet( false ),
     mOverviewFrameMapId( -1 ), mOverviewBlendMode( QPainter::CompositionMode_SourceOver ), mOverviewInverted( false ), mGridEnabled( false ), mGridStyle( Solid ),
     mGridIntervalX( 0.0 ), mGridIntervalY( 0.0 ), mGridOffsetX( 0.0 ), mGridOffsetY( 0.0 ), mGridAnnotationPrecision( 3 ), mShowGridAnnotation( false ),
-    mLeftGridAnnotationPosition( OutsideMapFrame ), mRightGridAnnotationPosition( OutsideMapFrame ), mTopGridAnnotationPosition( OutsideMapFrame ),
-    mBottomGridAnnotationPosition( OutsideMapFrame ), mAnnotationFrameDistance( 1.0 ), mLeftGridAnnotationDirection( Horizontal ), mRightGridAnnotationDirection( Horizontal ),
-    mTopGridAnnotationDirection( Horizontal ), mBottomGridAnnotationDirection( Horizontal ), mGridFrameStyle( NoGridFrame ), mGridFrameWidth( 2.0 ),
+    mGridBlendMode( QPainter::CompositionMode_SourceOver ), mLeftGridAnnotationPosition( OutsideMapFrame ), mRightGridAnnotationPosition( OutsideMapFrame ),
+    mTopGridAnnotationPosition( OutsideMapFrame ), mBottomGridAnnotationPosition( OutsideMapFrame ), mAnnotationFrameDistance( 1.0 ),
+    mLeftGridAnnotationDirection( Horizontal ), mRightGridAnnotationDirection( Horizontal ), mTopGridAnnotationDirection( Horizontal ),
+    mBottomGridAnnotationDirection( Horizontal ), mGridFrameStyle( NoGridFrame ),  mGridFrameWidth( 2.0 ),
     mCrossLength( 3 ), mMapCanvas( 0 ), mDrawCanvasItems( true )
 {
   mComposition = composition;
@@ -86,9 +87,10 @@ QgsComposerMap::QgsComposerMap( QgsComposition *composition )
     : QgsComposerItem( 0, 0, 10, 10, composition ), mKeepLayerSet( false ), mOverviewFrameMapId( -1 ),
     mOverviewBlendMode( QPainter::CompositionMode_SourceOver ), mOverviewInverted( false ), mGridEnabled( false ), mGridStyle( Solid ),
     mGridIntervalX( 0.0 ), mGridIntervalY( 0.0 ), mGridOffsetX( 0.0 ), mGridOffsetY( 0.0 ), mGridAnnotationPrecision( 3 ), mShowGridAnnotation( false ),
-    mLeftGridAnnotationPosition( OutsideMapFrame ), mRightGridAnnotationPosition( OutsideMapFrame ), mTopGridAnnotationPosition( OutsideMapFrame ),
-    mBottomGridAnnotationPosition( OutsideMapFrame ), mAnnotationFrameDistance( 1.0 ), mLeftGridAnnotationDirection( Horizontal ), mRightGridAnnotationDirection( Horizontal ),
-    mTopGridAnnotationDirection( Horizontal ), mBottomGridAnnotationDirection( Horizontal ), mGridFrameStyle( NoGridFrame ), mGridFrameWidth( 2.0 ), mCrossLength( 3 ),
+    mGridBlendMode( QPainter::CompositionMode_SourceOver ), mLeftGridAnnotationPosition( OutsideMapFrame ), mRightGridAnnotationPosition( OutsideMapFrame ),
+    mTopGridAnnotationPosition( OutsideMapFrame ), mBottomGridAnnotationPosition( OutsideMapFrame ), mAnnotationFrameDistance( 1.0 ),
+    mLeftGridAnnotationDirection( Horizontal ), mRightGridAnnotationDirection( Horizontal ), mTopGridAnnotationDirection( Horizontal ),
+    mBottomGridAnnotationDirection( Horizontal ), mGridFrameStyle( NoGridFrame ), mGridFrameWidth( 2.0 ), mCrossLength( 3 ),
     mMapCanvas( 0 ), mDrawCanvasItems( true )
 {
   mOverviewFrameMapSymbol = 0;
@@ -792,6 +794,7 @@ bool QgsComposerMap::writeXML( QDomElement& elem, QDomDocument & doc ) const
   gridElem.setAttribute( "crossLength",  QString::number( mCrossLength ) );
   gridElem.setAttribute( "gridFrameStyle", mGridFrameStyle );
   gridElem.setAttribute( "gridFrameWidth", QString::number( mGridFrameWidth ) );
+  gridElem.setAttribute( "gridBlendMode", QgsMapRenderer::getBlendModeEnum( mGridBlendMode ) );
   QDomElement gridLineStyleElem = QgsSymbolLayerV2Utils::saveSymbol( QString(), mGridLineSymbol, doc );
   gridElem.appendChild( gridLineStyleElem );
 
@@ -938,6 +941,7 @@ bool QgsComposerMap::readXML( const QDomElement& itemElem, const QDomDocument& d
     mCrossLength = gridElem.attribute( "crossLength", "3" ).toDouble();
     mGridFrameStyle = ( QgsComposerMap::GridFrameStyle )gridElem.attribute( "gridFrameStyle", "0" ).toInt();
     mGridFrameWidth = gridElem.attribute( "gridFrameWidth", "2.0" ).toDouble();
+    setGridBlendMode( QgsMapRenderer::getCompositionMode(( QgsMapRenderer::BlendMode ) gridElem.attribute( "gridBlendMode", "0" ).toUInt() ) );
 
     QDomElement gridSymbolElem = gridElem.firstChildElement( "symbol" );
     delete mGridLineSymbol;
@@ -1035,6 +1039,10 @@ void QgsComposerMap::drawGrid( QPainter* p )
   QRectF thisPaintRect = QRectF( 0, 0, QGraphicsRectItem::rect().width(), QGraphicsRectItem::rect().height() );
   p->setClipRect( thisPaintRect );
 
+  // set the blend mode for drawing grid lines
+  p->save();
+  p->setCompositionMode( mGridBlendMode );
+
   //simpler approach: draw vertical lines first, then horizontal ones
   if ( mGridStyle == QgsComposerMap::Solid )
   {
@@ -1095,6 +1103,8 @@ void QgsComposerMap::drawGrid( QPainter* p )
       drawGridLine( QLineF( hIt->second.p2(), crossEnd1 ), p );
     }
   }
+  // reset composition mode
+  p->restore();
 
   p->setClipRect( thisPaintRect , Qt::NoClip );
 
@@ -1107,6 +1117,7 @@ void QgsComposerMap::drawGrid( QPainter* p )
   {
     drawCoordinateAnnotations( p, horizontalLines, verticalLines );
   }
+
 }
 
 void QgsComposerMap::drawGridFrame( QPainter* p, const QList< QPair< double, QLineF > >& hLines, const QList< QPair< double, QLineF > >& vLines )
@@ -1597,6 +1608,12 @@ QPen QgsComposerMap::gridPen() const
   return p;
 }
 
+void QgsComposerMap::setGridBlendMode( QPainter::CompositionMode blendMode )
+{
+  mGridBlendMode = blendMode;
+  update();
+}
+
 QRectF QgsComposerMap::boundingRect() const
 {
   return mCurrentRectangle;

src/core/composer/qgscomposermap.h

@@ -328,6 +328,11 @@ class CORE_EXPORT QgsComposerMap : public QgsComposerItem
     void setGridLineSymbol( QgsLineSymbolV2* symbol );
     QgsLineSymbolV2* gridLineSymbol() { return mGridLineSymbol; }
 
+    /** Returns the grid's blending mode */
+    QPainter::CompositionMode gridBlendMode() const {return mGridBlendMode;}
+    /** Sets the grid's blending mode*/
+    void setGridBlendMode( QPainter::CompositionMode blendMode );
+
     /**Sets mId to a number not yet used in the composition. mId is kept if it is not in use.
         Usually, this function is called before adding the composer map to the composition*/
     void assignFreeId();
@@ -421,6 +426,8 @@ class CORE_EXPORT QgsComposerMap : public QgsComposerItem
     int mGridAnnotationPrecision;
     /**True if coordinate values should be drawn*/
     bool mShowGridAnnotation;
+    /**Blend mode for grid*/
+    QPainter::CompositionMode mGridBlendMode;
 
     /**Annotation position for left map side (inside / outside / not shown)*/
     GridAnnotationPosition mLeftGridAnnotationPosition;

src/ui/qgscomposermapwidgetbase.ui

@@ -56,7 +56,7 @@
         <x>0</x>
         <y>-202</y>
         <width>440</width>
-        <height>1310</height>
+        <height>1347</height>
        </rect>
       </property>
       <property name="sizePolicy">
@@ -448,6 +448,16 @@
               </property>
              </widget>
             </item>
+            <item row="7" column="1">
+             <widget class="QgsBlendModeComboBox" name="mGridBlendComboBox"/>
+            </item>
+            <item row="7" column="0">
+             <widget class="QLabel" name="mGridBlendLabel">
+              <property name="text">
+               <string>Blend mode</string>
+              </property>
+             </widget>
+            </item>
            </layout>
           </item>
           <item>