Display name of layers in need of rasterization when saving as PDF (#4539)

python/core/qgsmapsettingsutils.sip

@@ -22,11 +22,11 @@ class QgsMapSettingsUtils
 %End
   public:
 
-    static bool containsAdvancedEffects( const QgsMapSettings &mapSettings );
+    static const QStringList containsAdvancedEffects( const QgsMapSettings &mapSettings );
 %Docstring
  Checks whether any of the layers attached to a map settings object contain advanced effects
  \param mapSettings map settings
- :rtype: bool
+ :rtype: list of str
 %End
 
     static QString worldFileContent( const QgsMapSettings &mapSettings );

src/app/qgsmapsavedialog.cpp

@@ -66,7 +66,23 @@ QgsMapSaveDialog::QgsMapSaveDialog( QWidget *parent, QgsMapCanvas *mapCanvas, co
   {
     mSaveWorldFile->setVisible( false );
 
-    mSaveAsRaster->setChecked( QgsMapSettingsUtils::containsAdvancedEffects( mapCanvas->mapSettings() ) );
+    QStringList layers = QgsMapSettingsUtils::containsAdvancedEffects( mapCanvas->mapSettings() );
+    if ( !layers.isEmpty() )
+    {
+      // Limit number of items to avoid extreme dialog height
+      if ( layers.count() >= 10 )
+      {
+        layers = layers.mid( 0, 9 );
+        layers << QChar( 0x2026 );
+      }
+      mInfo->setText( tr( "The following layer(s) use advanced effects:\n%1\nRasterizing map is recommended for proper rendering." ).arg(
+                        QChar( 0x2022 ) + QString( " " ) + layers.join( QString( "\n" ) + QChar( 0x2022 ) + QString( " " ) ) ) );
+      mSaveAsRaster->setChecked( true );
+    }
+    else
+    {
+      mSaveAsRaster->setChecked( false );
+    }
     mSaveAsRaster->setVisible( true );
 
     this->setWindowTitle( tr( "Save map as PDF" ) );

src/core/composer/qgscomposermap.cpp

@@ -1082,7 +1082,7 @@ bool QgsComposerMap::containsAdvancedEffects() const
 
   QgsMapSettings ms;
   ms.setLayers( layersToRender() );
-  return QgsMapSettingsUtils::containsAdvancedEffects( ms );
+  return ( !QgsMapSettingsUtils::containsAdvancedEffects( ms ).isEmpty() );
 }
 
 void QgsComposerMap::connectUpdateSlot()

src/core/qgsmapsettingsutils.cpp

@@ -23,8 +23,10 @@
 
 #include <QString>
 
-bool QgsMapSettingsUtils::containsAdvancedEffects( const QgsMapSettings &mapSettings )
+const QStringList QgsMapSettingsUtils::containsAdvancedEffects( const QgsMapSettings &mapSettings )
 {
+  QSet< QString > layers;
+
   QgsTextFormat layerFormat;
   Q_FOREACH ( QgsMapLayer *layer, mapSettings.layers() )
   {
@@ -32,7 +34,7 @@ bool QgsMapSettingsUtils::containsAdvancedEffects( const QgsMapSettings &mapSett
     {
       if ( layer->blendMode() != QPainter::CompositionMode_SourceOver )
       {
-        return true;
+        layers << layer->name();
       }
       // if vector layer, check labels and feature blend mode
       QgsVectorLayer *currentVectorLayer = qobject_cast<QgsVectorLayer *>( layer );
@@ -40,11 +42,11 @@ bool QgsMapSettingsUtils::containsAdvancedEffects( const QgsMapSettings &mapSett
       {
         if ( currentVectorLayer->layerTransparency() != 0 )
         {
-          return true;
+          layers << layer->name();
         }
         if ( currentVectorLayer->featureBlendMode() != QPainter::CompositionMode_SourceOver )
         {
-          return true;
+          layers << layer->name();
         }
         // check label blend modes
         if ( QgsPalLabeling::staticWillUseLayer( currentVectorLayer ) )
@@ -52,12 +54,15 @@ bool QgsMapSettingsUtils::containsAdvancedEffects( const QgsMapSettings &mapSett
           // Check all label blending properties
           layerFormat.readFromLayer( currentVectorLayer );
           if ( layerFormat.containsAdvancedEffects() )
-            return true;
+          {
+            layers << layer->name();
+          }
         }
       }
     }
   }
-  return false;
+
+  return layers.toList();
 }
 
 QString QgsMapSettingsUtils::worldFileContent( const QgsMapSettings &mapSettings )

src/core/qgsmapsettingsutils.h

@@ -35,7 +35,7 @@ class CORE_EXPORT QgsMapSettingsUtils
     /** Checks whether any of the layers attached to a map settings object contain advanced effects
      * \param mapSettings map settings
      */
-    static bool containsAdvancedEffects( const QgsMapSettings &mapSettings );
+    static const QStringList containsAdvancedEffects( const QgsMapSettings &mapSettings );
 
     /** Creates the content of a world file.
      * \param mapSettings map settings

src/ui/qgsmapsavedialog.ui

@@ -16,6 +16,13 @@
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <layout class="QGridLayout" name="gridLayout">
+     <item row="9" column="0" colspan="2">
+      <widget class="QLabel" name="mInfo">
+       <property name="enabled">
+        <bool>false</bool>
+       </property>
+      </widget>
+     </item>
      <item row="8" column="0" colspan="2">
       <widget class="QCheckBox" name="mSaveAsRaster">
        <property name="text">