improve error propagation for raster open errors (#1040)

git-svn-id: http://svn.osgeo.org/qgis/trunk@8694 c8812cc2-4d05-0410-92ff-de0c093fc19c

src/app/qgisapp.cpp

@@ -3126,6 +3126,7 @@ void QgisApp::openProject(const QString & fileName)
 bool QgisApp::openLayer(const QString & fileName)
 {
   QFileInfo fileInfo(fileName);
+
   // try to load it as raster
   QgsMapLayer* ok = NULL;
   CPLPushErrorHandler(CPLQuietErrorHandler); 
@@ -5323,7 +5324,9 @@ bool QgisApp::addRasterLayers(QStringList const &theFileNameQStringList, bool gu
       myIterator != theFileNameQStringList.end();
       ++myIterator)
   {
-    if (QgsRasterLayer::isValidRasterFileName(*myIterator))
+    QString errMsg;
+
+    if (QgsRasterLayer::isValidRasterFileName(*myIterator,errMsg))
     {
       QFileInfo myFileInfo(*myIterator);
       // get the directory the .adf file was in
@@ -5356,6 +5359,10 @@ bool QgisApp::addRasterLayers(QStringList const &theFileNameQStringList, bool gu
       if(guiWarning)
       {
         QString msg(*myIterator + tr(" is not a supported raster data source"));
+
+        if( errMsg.size() > 0 )
+            msg += "\n" + errMsg;
+
         QMessageBox::critical(this, tr("Unsupported Data Source"), msg);
       }
       returnValue = false;

src/core/raster/qgsrasterlayer.cpp

@@ -255,22 +255,28 @@ void QgsRasterLayer::registerGdalDrivers()
 
 
 /** This helper checks to see whether the filename appears to be a valid raster file name */
-bool QgsRasterLayer::isValidRasterFileName(QString const & theFileNameQString)
+bool QgsRasterLayer::isValidRasterFileName(QString const & theFileNameQString,
+                                           QString & retErrMsg )
 {
 
   GDALDatasetH myDataset;
   registerGdalDrivers();
 
+  CPLErrorReset();
+
   //open the file using gdal making sure we have handled locale properly
   myDataset = GDALOpen( QFile::encodeName(theFileNameQString).constData(), GA_ReadOnly );
   if( myDataset == NULL )
   {
+    if( CPLGetLastErrorNo() != CPLE_OpenFailed )
+      retErrMsg = CPLGetLastErrorMsg();
     return false;
   }
   else if( GDALGetRasterCount( myDataset ) == 0 )
   {
     GDALClose( myDataset );
     myDataset = NULL;
+    retErrMsg = "This raster file has no bands and is invalid as a raster layer.";
     return false;
   }
   else
@@ -280,6 +286,14 @@ bool QgsRasterLayer::isValidRasterFileName(QString const & theFileNameQString)
   }
 }
 
+bool QgsRasterLayer::isValidRasterFileName(QString const & theFileNameQString)
+
+{
+    QString retErrMsg;
+
+    return isValidRasterFileName( theFileNameQString, retErrMsg);
+}
+
 
 //////////////////////////////////////////////////////////
 //

src/core/raster/qgsrasterlayer.h

@@ -189,7 +189,12 @@ class CORE_EXPORT QgsRasterLayer : public QgsMapLayer
     static void registerGdalDrivers();
 
     /** This helper checks to see whether the filename appears to be a valid
-       raster file name */
+       raster file name.  If the filename looks like it could be valid,
+       but some sort of error occurs in processing the file, the error is
+       returned in retError. */
+    static bool isValidRasterFileName(const QString & theFileNameQString,
+                                      QString &retError );
+
     static bool isValidRasterFileName(const QString & theFileNameQString);
 
     //