Code for cancellation of raster reading with GDAL 2 - disabled for now

There are still some questions around it and I need to find some data for thorough testing (many GDAL drivers do not support cancellation)
qgis · Jul 24, 2016 · 940883b · 940883b
1 parent 7b8c1c5
commit 940883b
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Showing 3 changed files with 31 additions and 4 deletions.
diff --git a/src/providers/gdal/qgsgdalprovider.cpp b/src/providers/gdal/qgsgdalprovider.cpp
@@ -437,7 +437,6 @@ void QgsGdalProvider::readBlock( int theBandNo, int xBlock, int yBlock, void *bl
 
 void QgsGdalProvider::readBlock( int theBandNo, QgsRectangle  const & theExtent, int thePixelWidth, int thePixelHeight, void *theBlock, QgsRasterBlockFeedback* feedback )
 {
-  Q_UNUSED( feedback );  // TODO: use with GDAL 2
   QgsDebugMsg( "thePixelWidth = "  + QString::number( thePixelWidth ) );
   QgsDebugMsg( "thePixelHeight = "  + QString::number( thePixelHeight ) );
   QgsDebugMsg( "theExtent: " + theExtent.toString() );
@@ -608,11 +607,12 @@ void QgsGdalProvider::readBlock( int theBandNo, QgsRectangle  const & theExtent,
   GDALRasterBandH gdalBand = GDALGetRasterBand( mGdalDataset, theBandNo );
   GDALDataType type = ( GDALDataType )mGdalDataType.at( theBandNo - 1 );
   CPLErrorReset();
+
   CPLErr err = gdalRasterIO( gdalBand, GF_Read,
                              srcLeft, srcTop, srcWidth, srcHeight,
                              ( void * )tmpBlock,
                              tmpWidth, tmpHeight, type,
-                             0, 0 );
+                             0, 0, feedback );
 
   if ( err != CPLE_None )
   {

diff --git a/src/providers/gdal/qgsgdalproviderbase.cpp b/src/providers/gdal/qgsgdalproviderbase.cpp
@@ -280,7 +280,17 @@ GDALDatasetH QgsGdalProviderBase::gdalOpen( const char *pszFilename, GDALAccess
   return hDS;
 }
 
-CPLErr QgsGdalProviderBase::gdalRasterIO( GDALRasterBandH hBand, GDALRWFlag eRWFlag, int nXOff, int nYOff, int nXSize, int nYSize, void * pData, int nBufXSize, int nBufYSize, GDALDataType eBufType, int nPixelSpace, int nLineSpace )
+static int CPL_STDCALL _gdalProgressFnWithFeedback( double dfComplete, const char *pszMessage, void *pProgressArg )
+{
+  Q_UNUSED( dfComplete );
+  Q_UNUSED( pszMessage );
+
+  QgsRasterBlockFeedback* feedback = static_cast<QgsRasterBlockFeedback*>( pProgressArg );
+  return !feedback->isCancelled();
+}
+
+
+CPLErr QgsGdalProviderBase::gdalRasterIO( GDALRasterBandH hBand, GDALRWFlag eRWFlag, int nXOff, int nYOff, int nXSize, int nYSize, void * pData, int nBufXSize, int nBufYSize, GDALDataType eBufType, int nPixelSpace, int nLineSpace, QgsRasterBlockFeedback* feedback )
 {
   // See http://hub.qgis.org/issues/8356 and http://trac.osgeo.org/gdal/ticket/5170
 #if GDAL_VERSION_MAJOR == 1 && ( (GDAL_VERSION_MINOR == 9 && GDAL_VERSION_REV <= 2) || (GDAL_VERSION_MINOR == 10 && GDAL_VERSION_REV <= 0) )
@@ -289,7 +299,24 @@ CPLErr QgsGdalProviderBase::gdalRasterIO( GDALRasterBandH hBand, GDALRWFlag eRWF
   QgsDebugMsg( "Disabled VSI_CACHE" );
 #endif
 
+#if GDAL_VERSION_MAJOR >= 2
+  GDALRasterIOExtraArg extra;
+  INIT_RASTERIO_EXTRA_ARG( extra );
+  if ( 0 && feedback )  // disabled!
+  {
+    // Currently the cancellation is disabled... When RasterIO call is cancelled,
+    // GDAL returns CE_Failure with error code = 0 (CPLE_None), however one would
+    // expect to get CPLE_UserInterrupt to clearly identify that the failure was
+    // caused by the cancellation and not that something dodgy is going on.
+    // Are both error codes acceptable?
+    extra.pfnProgress = _gdalProgressFnWithFeedback;
+    extra.pProgressData = ( void* ) feedback;
+  }
+  CPLErr err = GDALRasterIOEx( hBand, eRWFlag, nXOff, nYOff, nXSize, nYSize, pData, nBufXSize, nBufYSize, eBufType, nPixelSpace, nLineSpace, &extra );
+#else
+  Q_UNUSED( feedback );
   CPLErr err = GDALRasterIO( hBand, eRWFlag, nXOff, nYOff, nXSize, nYSize, pData, nBufXSize, nBufYSize, eBufType, nPixelSpace, nLineSpace );
+#endif
 
 #if GDAL_VERSION_MAJOR == 1 && ( (GDAL_VERSION_MINOR == 9 && GDAL_VERSION_REV <= 2) || (GDAL_VERSION_MINOR == 10 && GDAL_VERSION_REV <= 0) )
   CPLSetThreadLocalConfigOption( "VSI_CACHE", pszOldVal );

diff --git a/src/providers/gdal/qgsgdalproviderbase.h b/src/providers/gdal/qgsgdalproviderbase.h
@@ -49,7 +49,7 @@ class QgsGdalProviderBase
     static GDALDatasetH  gdalOpen( const char *pszFilename, GDALAccess eAccess );
 
     /** Wrapper function for GDALRasterIO to get around possible bugs in GDAL */
-    static CPLErr gdalRasterIO( GDALRasterBandH hBand, GDALRWFlag eRWFlag, int nXOff, int nYOff, int nXSize, int nYSize, void * pData, int nBufXSize, int nBufYSize, GDALDataType eBufType, int nPixelSpace, int nLineSpace );
+    static CPLErr gdalRasterIO( GDALRasterBandH hBand, GDALRWFlag eRWFlag, int nXOff, int nYOff, int nXSize, int nYSize, void * pData, int nBufXSize, int nBufYSize, GDALDataType eBufType, int nPixelSpace, int nLineSpace, QgsRasterBlockFeedback* feedback = nullptr );
 
     /** Wrapper function for GDALRasterIO to get around possible bugs in GDAL */
     static int gdalGetOverviewCount( GDALRasterBandH hBand );