QGIS print composer preview atlas combo box limited to 499 features

Question

Yes, really. I generate an atlas with a coverage layer with 883 features, and the combo box from which to select the current preview list only the first 499 features as shown in the screenshot below (tested this with a variety of other big coverage layers):

Nevertheless, the higher numbers are accessible as well. I can select the higher numbers by going to #499 and clicking Next Feature button or go to the Last Feature and clicking Previous Feature, but then I see only the feature number without the page name:

Furthermore when I want, let's say, no. 700 I have to click next or previous about 200 times. That's somehow inconvenient.

I observerved this in QGIS 2.14.15 LTR as well as the latest 2.18.14 LTR, so isn't there anybody before me having more than 499 coverage features?!

It's definitly not due to Qt, where combos with 1000's of items a no problem, the author must have set explicitly the_combo.setMaxCount(499) somewhere, but why (cp. http://doc.qt.io/qt-5/qcombobox.html#maxCount-prop)?

Question before raising an issue: Are there any technical or practical reasons for such limitation, or do I miss a setting somewhere?

Answer 1

If show the QGIS code you can found this limitation.

void QgsComposer::updateAtlasPageComboBox( int pageCount )
{
  if ( !mComposition )
    return;

  mAtlasPageComboBox->blockSignals( true );
  mAtlasPageComboBox->clear();
  for ( int i = 1; i <= pageCount && i < 500; ++i )
  {
    QString name = mComposition->atlasComposition().nameForPage( i - 1 );
    QString fullName = ( !name.isEmpty() ? QString( "%1: %2" ).arg( i ).arg( name ) : QString::number( i ) );

    mAtlasPageComboBox->addItem( fullName, i );
    mAtlasPageComboBox->setItemData( i - 1, name, Qt::UserRole + 1 );
    mAtlasPageComboBox->setItemData( i - 1, fullName, Qt::UserRole + 2 );
  }
  mAtlasPageComboBox->blockSignals( false );
}

the Important line is for ( int i = 1; i <= pageCount && i < 500; ++i )

https://github.com/qgis/QGIS/blob/release-2_18/src/app/composer/qgscomposer.cpp#L1056

and the answer to the next feature button working is because this call to nextFeature() method :

https://github.com/qgis/QGIS/blob/release-2_18/src/core/composer/qgsatlascomposition.cpp#L337

and emits a signal emit featureChanged( &mCurrentFeature ); , this signal is received by void QgsComposer::atlasFeatureChanged( QgsFeature *feature )

https://github.com/qgis/QGIS/blob/release-2_18/src/app/composer/qgscomposer.cpp#L1068

And put the new feature value :

 mAtlasPageComboBox->setCurrentIndex( mComposition->atlasComposition().currentFeatureNumber() );

without taking into account the initial limitation

it's a strange way of putting it I think

Answer 2

I have the same issue. I cannot see more than 499 feature in the atlas preview combo box. I have a polygon shapefile composed of 539 polygons, and yes, only 499 I can see:

As a workaround and in order to see the atlas page number along with the name you can insert a text box and write the following expression:

 @atlas_featurenumber || ': ' || Field_NAME    # Field_NAME is the field that contains the name of each polygon