[Server] Reactivate the capability to print selection with Server 2.18

The capability to print selection has been removed by the commit aaa7003 to
prevent accidental selections showing in exports from composer.

It is reactivated only for QGIS Server.

fixes #13459 QGIS Server WMS GetPrint request don't respect SELECTION parameter

src/core/composer/qgscomposermap.cpp

@@ -59,6 +59,7 @@ QgsComposerMap::QgsComposerMap( QgsComposition *composition, int x, int y, int w
     , mUpdatesEnabled( true )
     , mMapCanvas( nullptr )
     , mDrawCanvasItems( true )
+    , mDrawSelection( false )
     , mAtlasDriven( false )
     , mAtlasScalingMode( Auto )
     , mAtlasMargin( 0.10 )
@@ -229,7 +230,7 @@ QgsMapSettings QgsComposerMap::mapSettings( const QgsRectangle& extent, QSizeF s
   jobMapSettings.setDestinationCrs( ms.destinationCrs() );
   jobMapSettings.setCrsTransformEnabled( ms.hasCrsTransformEnabled() );
   jobMapSettings.setFlags( ms.flags() );
-  jobMapSettings.setFlag( QgsMapSettings::DrawSelection, false );
+  jobMapSettings.setFlag( QgsMapSettings::DrawSelection, mDrawSelection );
   jobMapSettings.setFlag( QgsMapSettings::RenderPartialOutput, false );
 
   if ( mComposition->plotStyle() == QgsComposition::Print ||

src/core/composer/qgscomposermap.h

@@ -639,6 +639,17 @@ class CORE_EXPORT QgsComposerMap : public QgsComposerItem
     void setDrawCanvasItems( bool b ) { mDrawCanvasItems = b; }
     bool drawCanvasItems() const { return mDrawCanvasItems; }
 
+    /** Set the flag to draw selection in map
+     * @note this function was added in version 2.18.21
+     * @note not available in Python bindings
+     */
+    void setDrawSelection( bool b ) { mDrawSelection = b; }
+    /** Get the flag to draw selection in map
+     * @note this function was added in version 2.18.21
+     * @note not available in Python bindings
+     */
+    bool drawSelection() const { return mDrawSelection; }
+
     /** Returns the conversion factor map units -> mm*/
     double mapUnitsToMM() const;
 
@@ -939,6 +950,9 @@ class CORE_EXPORT QgsComposerMap : public QgsComposerItem
     /** True if annotation items, rubber band, etc. from the main canvas should be displayed*/
     bool mDrawCanvasItems;
 
+    /** True if selection has to be drawn. For server only! */
+    bool mDrawSelection;
+
     /** Adjusts an extent rectangle to match the provided item width and height, so that extent
      * center of extent remains the same */
     void adjustExtentToItemShape( double itemWidth, double itemHeight, QgsRectangle& extent ) const;

src/server/qgswmsconfigparser.cpp

@@ -279,6 +279,9 @@ QgsComposition* QgsWMSConfigParser::createPrintComposition( const QString& compo
       }
     }
 
+    // Draw Selection
+    currentMap->setDrawSelection( true );
+
     //grid space x / y
     currentMap->grid()->setIntervalX( parameterMap.value( mapId + ":GRID_INTERVAL_X" ).toDouble() );
     currentMap->grid()->setIntervalY( parameterMap.value( mapId + ":GRID_INTERVAL_Y" ).toDouble() );