Make the one band raster creation method return data provider

Author: wonder-sk

python/core/raster/qgsrasterfilewriter.sip

@@ -30,14 +30,16 @@ class QgsRasterFileWriter
     QgsRasterFileWriter( const QString& outputUrl );
 
     /** Create a raster file with one band without initializing the pixel data.
+     * Returned provider may be used to initialize the raster using writeBlock() calls.
+     * Ownership of the returned provider is passed to the caller.
      * @note Does not work with tiled mode enabled.
-     * @returns true when the raster has been created successfully
+     * @returns Instance of data provider in editing mode (on success) or null on error.
      * @note added in QGIS 3.0
      */
-    bool createOneBandRaster( Qgis::DataType dataType,
-                              int width, int height,
-                              const QgsRectangle& extent,
-                              const QgsCoordinateReferenceSystem& crs );
+    QgsRasterDataProvider* createOneBandRaster( Qgis::DataType dataType,
+                                                int width, int height,
+                                                const QgsRectangle& extent,
+                                                const QgsCoordinateReferenceSystem& crs ) /Factory/;
 
     /** Write raster file
         @param pipe raster pipe

src/core/raster/qgsrasterfilewriter.cpp

@@ -29,19 +29,16 @@
 #include <QTextStream>
 #include <QMessageBox>
 
-bool QgsRasterFileWriter::createOneBandRaster( Qgis::DataType dataType, int width, int height, const QgsRectangle &extent, const QgsCoordinateReferenceSystem &crs )
+QgsRasterDataProvider* QgsRasterFileWriter::createOneBandRaster( Qgis::DataType dataType, int width, int height, const QgsRectangle &extent, const QgsCoordinateReferenceSystem &crs )
 {
   if ( mTiledMode )
-    return false;  // does not make sense with tiled mode
+    return nullptr;  // does not make sense with tiled mode
 
   double pixelSize;
   double geoTransform[6];
   globalOutputParameters( extent, width, height, geoTransform, pixelSize );
 
-  QgsRasterDataProvider* destProvider = initOutput( width, height, crs, geoTransform, 1, dataType, QList<bool>(), QList<double>() );
-  bool res = destProvider != nullptr;
-  delete destProvider;
-  return res;
+  return initOutput( width, height, crs, geoTransform, 1, dataType, QList<bool>(), QList<double>() );
 }
 
 QgsRasterFileWriter::QgsRasterFileWriter( const QString& outputUrl )

src/core/raster/qgsrasterfilewriter.h

@@ -56,14 +56,16 @@ class CORE_EXPORT QgsRasterFileWriter
     QgsRasterFileWriter( const QString& outputUrl );
 
     /** Create a raster file with one band without initializing the pixel data.
+     * Returned provider may be used to initialize the raster using writeBlock() calls.
+     * Ownership of the returned provider is passed to the caller.
      * @note Does not work with tiled mode enabled.
-     * @returns true when the raster has been created successfully
+     * @returns Instance of data provider in editing mode (on success) or null on error.
      * @note added in QGIS 3.0
      */
-    bool createOneBandRaster( Qgis::DataType dataType,
-                              int width, int height,
-                              const QgsRectangle& extent,
-                              const QgsCoordinateReferenceSystem& crs );
+    QgsRasterDataProvider* createOneBandRaster( Qgis::DataType dataType,
+        int width, int height,
+        const QgsRectangle& extent,
+        const QgsCoordinateReferenceSystem& crs );
 
     /** Write raster file
         @param pipe raster pipe

tests/src/core/testqgsrasterfilewriter.cpp

@@ -191,8 +191,15 @@ void TestQgsRasterFileWriter::testCreateOneBandRaster()
   int width = 200, height = 100;
 
   QgsRasterFileWriter writer( filename );
-  bool res = writer.createOneBandRaster( Qgis::Byte, width, height, extent, QgsCoordinateReferenceSystem( "EPSG:4326" ) );
-  QVERIFY( res );
+  QgsRasterDataProvider* dp = writer.createOneBandRaster( Qgis::Byte, width, height, extent, QgsCoordinateReferenceSystem( "EPSG:4326" ) );
+  QVERIFY( dp );
+  QCOMPARE( dp->xSize(), width );
+  QCOMPARE( dp->ySize(), height );
+  QCOMPARE( dp->extent(), extent );
+  QCOMPARE( dp->bandCount(), 1 );
+  QCOMPARE( dp->dataType( 1 ), Qgis::Byte );
+  QVERIFY( dp->isEditable() );
+  delete dp;
 
   QgsRasterLayer* rlayer = new QgsRasterLayer( filename, "tmp", "gdal" );
   QVERIFY( rlayer->isValid() );
@@ -201,6 +208,7 @@ void TestQgsRasterFileWriter::testCreateOneBandRaster()
   QCOMPARE( rlayer->extent(), extent );
   QCOMPARE( rlayer->bandCount(), 1 );
   QCOMPARE( rlayer->dataProvider()->dataType( 1 ), Qgis::Byte );
+  delete rlayer;
 }