set correctly raster block nodata if layer extent or resolution is smaller than requested, fixes #7209

Author: blazek

src/core/raster/qgsrasterblock.cpp

@@ -846,9 +846,13 @@ bool QgsRasterBlock::createNoDataBitmap()
 
 QRect QgsRasterBlock::subRect( const QgsRectangle & theExtent, int theWidth, int theHeight, const QgsRectangle &  theSubExtent )
 {
+  QgsDebugMsg( "theExtent = " + theExtent.toString() );
+  QgsDebugMsg( "theSubExtent = " + theSubExtent.toString() );
   double xRes = theExtent.width() / theWidth;
   double yRes = theExtent.height() / theHeight;
 
+  QgsDebugMsg( QString( "theWidth = %1 theHeight = %2 xRes = %3 yRes = %4" ).arg( theWidth ).arg( theHeight ).arg( xRes ).arg( yRes ) );
+
   int top = 0;
   int bottom = theHeight - 1;
   int left = 0;
@@ -871,5 +875,7 @@ QRect QgsRasterBlock::subRect( const QgsRectangle & theExtent, int theWidth, int
   {
     right = qRound(( theSubExtent.xMaximum() - theExtent.xMinimum() ) / xRes ) - 1;
   }
-  return QRect( left, top, right - left + 1, bottom - top + 1 );
+  QRect subRect = QRect( left, top, right - left + 1, bottom - top + 1 );
+  QgsDebugMsg( QString( "subRect: %1 %2 %3 %4" ).arg( subRect.x() ).arg( subRect.y() ).arg( subRect.width() ).arg( subRect.height() ) );
+  return subRect;
 }

src/core/raster/qgsrasterdataprovider.cpp

@@ -99,6 +99,12 @@ QgsRasterBlock * QgsRasterDataProvider::block( int theBandNo, QgsRectangle  cons
   {
     // Read smaller extent or lower resolution
 
+    if ( !extent().contains( theExtent ) )
+    {
+      QRect subRect = QgsRasterBlock::subRect( theExtent, theWidth, theHeight, extent() );
+      block->setIsNoDataExcept( subRect );
+    }
+
     // Calculate row/col limits (before tmpExtent is aligned)
     int fromRow = qRound(( theExtent.yMaximum() - tmpExtent.yMaximum() ) / yRes );
     int toRow = qRound(( theExtent.yMaximum() - tmpExtent.yMinimum() ) / yRes ) - 1;
@@ -139,8 +145,6 @@ QgsRasterBlock * QgsRasterDataProvider::block( int theBandNo, QgsRectangle  cons
     QgsDebugMsg( QString( "Reading smaller block tmpWidth = %1 theHeight = %2" ).arg( tmpWidth ).arg( tmpHeight ) );
     QgsDebugMsg( QString( "tmpExtent = %1" ).arg( tmpExtent.toString() ) );
 
-    block->setIsNoData();
-
     QgsRasterBlock *tmpBlock;
     if ( srcHasNoDataValue( theBandNo ) && useSrcNoDataValue( theBandNo ) )
     {