[feature] Layer transparency for vectors (fix #7692)

src/app/composer/qgscomposer.cpp

@@ -632,9 +632,9 @@ void QgsComposer::on_mActionExportAsPDF_triggered()
     showWMSPrintingWarning();
   }
 
-  if ( containsBlendModes() )
+  if ( containsAdvancedEffects() )
   {
-    showBlendModePrintingWarning();
+    showAdvancedEffectsWarning();
   }
 
   // If we are not printing as raster, temporarily disable advanced effects
@@ -828,9 +828,9 @@ void QgsComposer::on_mActionPrint_triggered()
     showWMSPrintingWarning();
   }
 
-  if ( containsBlendModes() )
+  if ( containsAdvancedEffects() )
   {
-    showBlendModePrintingWarning();
+    showAdvancedEffectsWarning();
   }
 
   // If we are not printing as raster, temporarily disable advanced effects
@@ -2056,9 +2056,9 @@ bool QgsComposer::containsWMSLayer() const
   return false;
 }
 
-bool QgsComposer::containsBlendModes() const
+bool QgsComposer::containsAdvancedEffects() const
 {
-  // Check if composer contains any blend modes
+  // Check if composer contains any blend modes or flattened layers for transparency
   QMap<QgsComposerItem*, QWidget*>::const_iterator item_it = mItemWidgetMap.constBegin();
   QgsComposerItem* currentItem = 0;
   QgsComposerMap* currentMap = 0;
@@ -2071,11 +2071,11 @@ bool QgsComposer::containsBlendModes() const
     {
       return true;
     }
-    // If item is a composer map, check if it contains any blended layers
+    // If item is a composer map, check if it contains any advanced effects
     currentMap = dynamic_cast<QgsComposerMap *>( currentItem );
     if ( currentMap )
     {
-      if ( currentMap->containsBlendModes() )
+      if ( currentMap->containsAdvancedEffects() )
       {
         return true;
       }
@@ -2111,13 +2111,13 @@ void QgsComposer::showWMSPrintingWarning()
   }
 }
 
-void QgsComposer::showBlendModePrintingWarning()
+void QgsComposer::showAdvancedEffectsWarning()
 {
   if ( ! mComposition->printAsRaster() )
   {
     QgsMessageViewer* m = new QgsMessageViewer( this, QgisGui::ModalDialogFlags, false );
-    m->setWindowTitle( tr( "Project contains blend modes" ) );
-    m->setMessage( tr( "Blend modes are enabled in this project, which cannot be printed as vectors. Printing as a raster is recommended." ), QgsMessageOutput::MessageText );
+    m->setWindowTitle( tr( "Project contains composition effects" ) );
+    m->setMessage( tr( "Advanced composition effects such as blend modes or vector layer transparency are enabled in this project, which cannot be printed as vectors. Printing as a raster is recommended." ), QgsMessageOutput::MessageText );
     m->setCheckBoxText( tr( "Print as raster" ) );
     m->setCheckBoxState( Qt::Checked );
     m->setCheckBoxVisible( true );

src/app/composer/qgscomposer.h

@@ -309,14 +309,14 @@ class QgsComposer: public QMainWindow, private Ui::QgsComposerBase
     //! True if a composer map contains a WMS layer
     bool containsWMSLayer() const;
 
-    //! True if a composer contains blend modes
-    bool containsBlendModes() const;
+    //! True if a composer contains advanced effects, such as blend modes
+    bool containsAdvancedEffects() const;
 
     //! Displays a warning because of possible min/max size in WMS
     void showWMSPrintingWarning();
 
     //! Displays a warning because of incompatibility between blend modes and QPrinter
-    void showBlendModePrintingWarning();
+    void showAdvancedEffectsWarning();
 
     //! Changes elements that are not suitable for this project
     void cleanupAfterTemplateRead();

src/core/composer/qgscomposermap.cpp

@@ -631,8 +631,9 @@ bool QgsComposerMap::containsWMSLayer() const
   return false;
 }
 
-bool QgsComposerMap::containsBlendModes() const
+bool QgsComposerMap::containsAdvancedEffects() const
 {
+  // check if map contains advanced effects like blend modes, or flattened layers for transparency
   if ( !mMapRenderer )
   {
     return false;
@@ -659,6 +660,10 @@ bool QgsComposerMap::containsBlendModes() const
       QgsVectorLayer* currentVectorLayer = qobject_cast<QgsVectorLayer *>( currentLayer );
       if ( currentVectorLayer )
       {
+        if ( currentVectorLayer->layerTransparency() != 0 )
+        {
+          return true;
+        }
         if ( currentVectorLayer->featureBlendMode() != QPainter::CompositionMode_SourceOver )
         {
           return true;

src/core/composer/qgscomposermap.h

@@ -183,8 +183,8 @@ class CORE_EXPORT QgsComposerMap : public QgsComposerItem
     /**True if composer map renders a WMS layer*/
     bool containsWMSLayer() const;
 
-    /**True if composer map contains layers with blend modes*/
-    bool containsBlendModes() const;
+    /**True if composer map contains layers with blend modes or flattened layers for vectors */
+    bool containsAdvancedEffects() const;
 
     /** stores state in Dom node
      * @param elem is Dom element corresponding to 'Composer' tag

src/core/qgsmaprenderer.cpp

@@ -523,7 +523,8 @@ void QgsMapRenderer::render( QPainter* painter, double* forceWidthScale )
       {
         QgsVectorLayer* vl = qobject_cast<QgsVectorLayer *>( ml );
         if (( vl->blendMode() != QPainter::CompositionMode_SourceOver && ( split || !mySettings.value( "/qgis/enable_render_caching", false ).toBool() ) )
-            || ( vl->featureBlendMode() != QPainter::CompositionMode_SourceOver ) )
+            || ( vl->featureBlendMode() != QPainter::CompositionMode_SourceOver )
+            || ( vl->layerTransparency() != 0 ) )
 
         {
           flattenedLayer = true;
@@ -595,6 +596,17 @@ void QgsMapRenderer::render( QPainter* painter, double* forceWidthScale )
       // If we flattened this layer for alternate blend modes, composite it now
       if ( flattenedLayer )
       {
+        QgsVectorLayer* vl = qobject_cast<QgsVectorLayer *>( ml );
+        if ( vl->layerTransparency() != 0 )
+        {
+          // a layer transparency has been set, so update the alpha for the flattened layer
+          // by combining it with the layer transparency
+          QColor transparentFillColor = QColor( 0, 0, 0, 255 - ( 255 * vl->layerTransparency() / 100 ) );
+          // use destination in composition mode to merge source's alpha with destination
+          mRenderContext.painter()->setCompositionMode( QPainter::CompositionMode_DestinationIn );
+          mRenderContext.painter()->fillRect( mypFlattenedImage->rect(), transparentFillColor );
+        }
+
         delete mRenderContext.painter();
         mRenderContext.setPainter( mypContextPainter );
         mypContextPainter->save();

src/core/qgsvectorlayer.cpp

@@ -123,6 +123,7 @@ QgsVectorLayer::QgsVectorLayer( QString vectorLayerPath,
     , mLabel( 0 )
     , mLabelOn( false )
     , mFeatureBlendMode( QPainter::CompositionMode_SourceOver ) // Default to normal feature blending
+    , mLayerTransparency( 0 )
     , mVertexMarkerOnlyForSelection( false )
     , mCache( new QgsGeometryCache( this ) )
     , mEditBuffer( 0 )
@@ -1767,6 +1768,14 @@ bool QgsVectorLayer::readSymbology( const QDomNode& node, QString& errorMessage
       QDomElement e = featureBlendModeNode.toElement();
       setFeatureBlendMode( QgsMapRenderer::getCompositionMode(( QgsMapRenderer::BlendMode ) e.text().toInt() ) );
     }
+
+    // get and set the layer transparency if it exists
+    QDomNode layerTransparencyNode = node.namedItem( "layerTransparency" );
+    if ( !layerTransparencyNode.isNull() )
+    {
+      QDomElement e = layerTransparencyNode.toElement();
+      setLayerTransparency( e.text().toInt() );
+    }    
 
     // use scale dependent visibility flag
     QDomElement e = node.toElement();
@@ -2099,6 +2108,12 @@ bool QgsVectorLayer::writeSymbology( QDomNode& node, QDomDocument& doc, QString&
     featureBlendModeElem.appendChild( featureBlendModeText );
     node.appendChild( featureBlendModeElem );
 
+    // add the layer transparency
+    QDomElement layerTransparencyElem  = doc.createElement( "layerTransparency" );
+    QDomText layerTransparencyText = doc.createTextNode( QString::number( layerTransparency() ) );
+    layerTransparencyElem.appendChild( layerTransparencyText );
+    node.appendChild( layerTransparencyElem );
+
     // add the display field
     QDomElement dField  = doc.createElement( "displayfield" );
     QDomText dFieldText = doc.createTextNode( displayField() );
@@ -3367,6 +3382,18 @@ QPainter::CompositionMode QgsVectorLayer::featureBlendMode() const
   return mFeatureBlendMode;
 }
 
+/** Write transparency for layer */
+void QgsVectorLayer::setLayerTransparency( int layerTransparency )
+{
+  mLayerTransparency = layerTransparency;
+}
+
+/** Read transparency for layer */
+int QgsVectorLayer::layerTransparency() const
+{
+  return mLayerTransparency;
+}
+
 void QgsVectorLayer::stopRendererV2( QgsRenderContext& rendererContext, QgsSingleSymbolRendererV2* selRenderer )
 {
   mRendererV2->stopRender( rendererContext );

src/core/qgsvectorlayer.h

@@ -1234,6 +1234,15 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
      * @note added in 2.0
      */
     QPainter::CompositionMode featureBlendMode() const;
+
+    /* Set the transparency for the vector layer
+     * @note added in 2.0
+     */
+    void setLayerTransparency( int layerTransparency );
+    /* Returns the current transparency for the vector layer
+     * @note added in 2.0
+     */
+    int layerTransparency() const;    
 
   public slots:
     /**
@@ -1491,6 +1500,9 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer
 
     /** Blend mode for features */
     QPainter::CompositionMode mFeatureBlendMode;
+
+    /** Layer transparency */
+    int mLayerTransparency;
 
     /**The current type of editing marker*/
     QgsVectorLayer::VertexMarkerType mCurrentVertexMarkerType;

src/gui/symbology-ng/qgsrendererv2propertiesdialog.cpp

@@ -91,6 +91,14 @@ QgsRendererV2PropertiesDialog::QgsRendererV2PropertiesDialog( QgsVectorLayer* la
 
   // Feature blend mode
   mFeatureBlendComboBox->setBlendMode( mLayer->featureBlendMode() );
+
+  // Layer transparency
+  mLayerTransparencySlider->setValue( mLayer->layerTransparency() );
+  mLayerTransparencySpnBx->setValue( mLayer->layerTransparency() );
+
+  // connect layer transparency slider and spin box
+  connect( mLayerTransparencySlider, SIGNAL( valueChanged( int ) ), mLayerTransparencySpnBx, SLOT( setValue( int ) ) );
+  connect( mLayerTransparencySpnBx, SIGNAL( valueChanged( int ) ), mLayerTransparencySlider, SLOT( setValue( int ) ) );    
 
   QPixmap pix;
   QgsRendererV2Registry* reg = QgsRendererV2Registry::instance();
@@ -179,6 +187,9 @@ void QgsRendererV2PropertiesDialog::apply()
   // set the blend modes for the layer
   mLayer->setBlendMode( mBlendModeComboBox->blendMode() );
   mLayer->setFeatureBlendMode( mFeatureBlendComboBox->blendMode() );
+
+  // set transparency for the layer
+  mLayer->setLayerTransparency( mLayerTransparencySlider->value() );
 }
 
 void QgsRendererV2PropertiesDialog::onOK()

src/ui/qgsrendererv2propsdialogbase.ui

@@ -24,19 +24,57 @@
      </property>
      <property name="saveCollapsedState" stdset="0">
       <bool>true</bool>
-     </property>     
-     <layout class="QHBoxLayout" name="horizontalLayout">
-      <item>
-       <widget class="QLabel" name="lblLayerBlend">
-        <property name="text">
-         <string>Layer blending mode</string>
-        </property>
-       </widget>
-      </item>
-      <item>
-       <widget class="QgsBlendModeComboBox" name="mBlendModeComboBox"/>
-      </item>
-     </layout>
+     </property>
+       <layout class="QGridLayout" name="gridLayout">
+        <item row="0" column="1" colspan="3">
+         <layout class="QHBoxLayout" name="horizontalLayout_2">
+          <item>
+           <widget class="QSlider" name="mLayerTransparencySlider">
+            <property name="maximum">
+             <number>100</number>
+            </property>
+            <property name="orientation">
+             <enum>Qt::Horizontal</enum>
+            </property>
+           </widget>
+          </item>
+          <item>
+           <widget class="QSpinBox" name="mLayerTransparencySpnBx">
+            <property name="maximum">
+             <number>100</number>
+            </property>
+           </widget>
+          </item>
+         </layout>
+        </item>
+        <item row="0" column="0">
+         <widget class="QLabel" name="lblTransparency">
+          <property name="text">
+           <string>Layer transparency</string>
+          </property>
+         </widget>
+        </item>
+        <item row="1" column="3">
+         <widget class="QgsBlendModeComboBox" name="mFeatureBlendComboBox"/>
+        </item>
+        <item row="1" column="2">
+         <widget class="QLabel" name="lblFeatureBlend">
+          <property name="text">
+           <string>Feature blending mode</string>
+          </property>
+         </widget>
+        </item>
+        <item row="1" column="0">
+         <widget class="QLabel" name="lblLayerBlend">
+          <property name="text">
+           <string>Layer blending mode</string>
+          </property>
+         </widget>
+        </item>
+        <item row="1" column="1">
+         <widget class="QgsBlendModeComboBox" name="mBlendModeComboBox"/>
+        </item>
+       </layout>
     </widget>
    </item>
    <item>
@@ -57,16 +95,6 @@
        </property>
       </spacer>
      </item>
-     <item>
-      <widget class="QLabel" name="lblFeatureBlend">
-       <property name="text">
-        <string>Feature blending mode</string>
-       </property>
-      </widget>
-     </item>
-     <item>
-      <widget class="QgsBlendModeComboBox" name="mFeatureBlendComboBox"/>
-     </item>
     </layout>
    </item>
    <item>
@@ -119,7 +147,7 @@
    <extends>QGroupBox</extends>
    <header>qgscollapsiblegroupbox.h</header>
    <container>1</container>
-  </customwidget>  
+  </customwidget>
  </customwidgets>
  <tabstops>
   <tabstop>cboRenderers</tabstop>