[BUGFIX] Relative path for GDAL subdataset

For some raster layer, the datasource is not stored in the project as relative.
 It's the case for NETCDF, HDF4, HDF5, NITF and RADARSAT2 raster format.

This patch keeps the datasource structure but updates the path part.

It will be interesting to backport it to 2.8 branch.

Author: rldhont

src/core/qgsmaplayer.cpp

@@ -46,6 +46,7 @@
 #include "qgsrectangle.h"
 #include "qgsvectorlayer.h"
 
+
 QgsMapLayer::QgsMapLayer( QgsMapLayer::LayerType type,
                           QString lyrname,
                           QString source ) :
@@ -291,6 +292,34 @@ bool QgsMapLayer::readLayerXML( const QDomElement& layerElement )
     }
     // <<< BACKWARD COMPATIBILITY < 1.9
   }
+  else if ( provider == "gdal" )
+  {
+    QStringList theURIParts = mDataSource.split( ":" );
+    if ( theURIParts[0] == "NETCDF" )
+    {
+      QString src = theURIParts[1];
+      src.replace( "\"", "" );
+      src = QgsProject::instance()->readPath( src );
+      theURIParts[1] = "\"" + src + "\"";
+    }
+    else if ( theURIParts[0] == "HDF4_SDS" )
+    {
+      theURIParts[2] = QgsProject::instance()->readPath( theURIParts[2] );
+    }
+    else if ( theURIParts[0] == "HDF5" )
+    {
+      theURIParts[1] = QgsProject::instance()->readPath( theURIParts[1] );
+    }
+    else if ( theURIParts[0] == "NITF_IM" )
+    {
+      theURIParts[2] = QgsProject::instance()->readPath( theURIParts[2] );
+    }
+    else if ( theURIParts[0] == "RADARSAT_2_CALIB" )
+    {
+      theURIParts[2] = QgsProject::instance()->readPath( theURIParts[2] );
+    }
+    mDataSource = theURIParts.join( ":" );
+  }
   else
   {
     mDataSource = QgsProject::instance()->readPath( mDataSource );
@@ -488,6 +517,39 @@ bool QgsMapLayer::writeLayerXML( QDomElement& layerElement, QDomDocument& docume
     urlDest.setQueryItems( urlSource.queryItems() );
     src = QString::fromAscii( urlDest.toEncoded() );
   }
+  else if ( !vlayer )
+  {
+    QgsRasterLayer *rlayer = qobject_cast<QgsRasterLayer *>( this );
+    // Update path for subdataset
+    if ( rlayer && rlayer->providerType() == "gdal" )
+    {
+      QStringList theURIParts = src.split( ":" );
+      if ( theURIParts[0] == "NETCDF" )
+      {
+        src = theURIParts[1];
+        src.replace( "\"", "" );
+        src = QgsProject::instance()->writePath( src, relativeBasePath );
+        theURIParts[1] = "\"" + src + "\"";
+      }
+      else if ( theURIParts[0] == "HDF4_SDS" )
+      {
+        theURIParts[2] = QgsProject::instance()->writePath( theURIParts[2], relativeBasePath );
+      }
+      else if ( theURIParts[0] == "HDF5" )
+      {
+        theURIParts[1] = QgsProject::instance()->writePath( theURIParts[1], relativeBasePath );
+      }
+      else if ( theURIParts[0] == "NITF_IM" )
+      {
+        theURIParts[2] = QgsProject::instance()->writePath( theURIParts[2], relativeBasePath );
+      }
+      else if ( theURIParts[0] == "RADARSAT_2_CALIB" )
+      {
+        theURIParts[2] = QgsProject::instance()->writePath( theURIParts[2], relativeBasePath );
+      }
+      src = theURIParts.join( ":" );
+    }
+  }
   else
   {
     src = QgsProject::instance()->writePath( src, relativeBasePath );