Show raster band description

Fix #53831

python/core/auto_generated/raster/qgsrasterdataprovider.sip.in

@@ -786,6 +786,8 @@ Data providers that have NativeRasterAttributeTable provider capability will try
 .. versionadded:: 3.30
 %End
 
+    virtual QString bandDescription( int bandNumber );   // Note: not const because GDAL init on demand
+
 
   signals:
 

src/core/providers/gdal/qgsgdalprovider.cpp

@@ -626,6 +626,39 @@ QString QgsGdalProvider::htmlMetadata()
   return myMetadata;
 }
 
+QString QgsGdalProvider::bandDescription( int bandNumber )
+{
+  QMutexLocker locker( mpMutex );
+  if ( !initIfNeeded() )
+    return QString();
+
+  GDALDriverH hDriver = GDALGetDriverByName( mDriverName.toLocal8Bit().constData() );
+  if ( !hDriver )
+    return QString();
+
+  if ( GDALGetRasterCount( mGdalDataset ) > 0 )
+  {
+    GDALRasterBandH gdalBand = GDALGetRasterBand( mGdalDataset, bandNumber );
+    if ( gdalBand )
+    {
+      char **GDALmetadata = GDALGetMetadata( gdalBand, nullptr );
+      if ( GDALmetadata )
+      {
+        const QStringList metadata = QgsOgrUtils::cStringListToQStringList( GDALmetadata );
+        const auto description = std::find_if( metadata.constBegin(), metadata.constEnd(), []( const QString & md )
+        {
+          return md.startsWith( QStringLiteral( "DESCRIPTION=" ) );
+        } );
+        if ( description != metadata.constEnd() )
+        {
+          return description->mid( 12 );
+        }
+      }
+    }
+  }
+  return QString();
+}
+
 QgsRasterBlock *QgsGdalProvider::block( int bandNo, const QgsRectangle &extent, int width, int height, QgsRasterBlockFeedback *feedback )
 {
   std::unique_ptr< QgsRasterBlock > block = std::make_unique< QgsRasterBlock >( dataType( bandNo ), width, height );

src/core/providers/gdal/qgsgdalprovider.h

@@ -160,6 +160,7 @@ class QgsGdalProvider final: public QgsRasterDataProvider, QgsGdalProviderBase
     double bandOffset( int bandNo ) const override;
     QList<QgsColorRampShader::ColorRampItem> colorTable( int bandNo )const override;
     QString htmlMetadata() override;
+    QString bandDescription( int bandNumber ) override;
     QStringList subLayers() const override;
 
     static QList< QgsProviderSublayerDetails > sublayerDetails( GDALDatasetH dataset, const QString &baseUri );

src/core/raster/qgsrasterdataprovider.cpp

@@ -763,6 +763,12 @@ bool QgsRasterDataProvider::readNativeAttributeTable( QString *errorMessage )
   return false;
 }
 
+QString QgsRasterDataProvider::bandDescription( int bandNumber )
+{
+  Q_UNUSED( bandNumber )
+  return QString();
+}
+
 bool QgsRasterDataProvider::readFileBasedAttributeTable( int bandNumber, const QString &path, QString *errorMessage )
 {
   QGIS_PROTECT_QOBJECT_THREAD_ACCESS

src/core/raster/qgsrasterdataprovider.h

@@ -831,6 +831,13 @@ class CORE_EXPORT QgsRasterDataProvider : public QgsDataProvider, public QgsRast
      */
     virtual bool readNativeAttributeTable( QString *errorMessage SIP_OUT  = nullptr );
 
+    /**
+     * Returns the description for band \a bandNumber, or an empty string if the band is not valid or has not description.
+     * The default implementation returns an empty string.
+     * \since QGIS 3.34
+     */
+    virtual QString bandDescription( int bandNumber );   // Note: not const because GDAL init on demand
+
 
   signals:
 

src/gui/raster/qgsrasterbandcombobox.cpp

@@ -166,5 +166,7 @@ QString QgsRasterBandComboBox::displayBandName( QgsRasterDataProvider *provider,
   if ( !provider )
     return QString();
 
-  return provider->displayBandName( band );
+  QString name {  provider->displayBandName( band ) };
+  const QString description { provider->bandDescription( band ) };
+  return description.isEmpty() ? name : QStringLiteral( "%1 - %2" ).arg( name, description );
 }