Added the possibility to unselect an optional (required="no" into interface-description of the grass module) to fix #1134.

git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@11329 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: rugginoso

src/plugins/grass/qgsgrassmodule.cpp

@@ -2633,6 +2633,13 @@ QgsGrassModuleGdalInput::QgsGrassModuleGdalInput(
   }
   adjustTitle();
 
+  // Check if this parameter is required
+  if (gnode.toElement().attribute("required") == "yes") {
+      mRequired = true;
+  } else {
+      mRequired = false;
+  }
+
   QDomNode promptNode = gnode.namedItem( "gisprompt" );
   QDomElement promptElem = promptNode.toElement();
   QString element = promptElem.attribute( "element" );
@@ -2700,6 +2707,14 @@ void QgsGrassModuleGdalInput::updateQgisLayers()
   mUri.resize( 0 );
   mOgrLayers.resize( 0 );
 
+  // If not required, add an empty item to combobox and a padding item into
+  // layer containers.
+  if (!mRequired){
+      mUri.push_back(QString());
+      mOgrLayers.push_back(QString());
+      mLayerComboBox->addItem(tr("Select a layer"), QVariant());
+  }
+
   QgsMapCanvas *canvas = mModule->qgisIface()->mapCanvas();
 
   int nlayers = canvas->layerCount();

src/plugins/grass/qgsgrassmodule.h

@@ -695,6 +695,9 @@ class QgsGrassModuleGdalInput: public QgsGrassModuleGroupBoxItem
 
     //! Ogr where clauses
     std::vector<QString> mOgrWheres;
+
+    //! Required field
+    bool mRequired;
 };
 
 /*********************** QgsGrassModuleField **********************/