Bug 372106

Comment 1 Ivan Furnadjiev 2012-02-21 07:17:56 EST

Moritz, could you provide a snippet to reproduce the issue?

Comment 2 Moritz Post 2012-02-21 07:26:56 EST

My favorite answer :)

Tree:

  private void createVirtualTree( Display display, Composite parent ) {

    Composite composite = new Composite( parent, SWT.NONE );
    composite.setLayoutData( GridDataFactory.fillDefaults().grab( true, true ) );
    GridLayout layout = new GridLayout( 1, false );
    layout.marginHeight = 0;
    layout.marginWidth = 0;
    composite.setLayout( layout );
    tab2.setControl( composite );

    final TreeViewer treeViewer = new TreeViewer( composite, SWT.VIRTUAL
                                                             | SWT.H_SCROLL
                                                             | SWT.V_SCROLL );
    treeViewer.setUseHashlookup( true );
    treeViewer.setContentProvider( new LazyContentProvider( treeViewer ) );
    treeViewer.setLabelProvider( new LazyLabelProvider() );
    treeViewer.setInput( new TodoMockModel() );
    treeViewer.getTree().setToolTipText( "Large virtual tree" );
    treeViewer.getTree().setLayoutData( GridDataFactory.fillDefaults().grab( true, true ).create() );
  }

Provider:

public class LazyContentProvider implements ILazyTreeContentProvider {

  private static final long serialVersionUID = 1L;
  private final TreeViewer viewer;

  public LazyContentProvider( TreeViewer viewer ) {
    this.viewer = viewer;
  }

  public Object getParent( Object element ) {
    Object result = null;
    if( element instanceof Todo ) {
      result = ( ( Todo )element ).getParent();
    }
    return result;
  }

  public void updateElement( Object parent, int index ) {
    if( parent instanceof Category ) {
      Category parentItem = ( Category )parent;
      Todo child = parentItem.getTodos().get( index );
      if( child != null ) {
        viewer.replace( parent, index, child );
        viewer.setChildCount( child, 0 );
      }
    } else if( parent instanceof TodoMockModel ) {
      TodoMockModel parentItem = ( TodoMockModel )parent;
      List<Category> manyCategories = parentItem.getManyCategories();
      Category child = manyCategories.get( index );
      if( child != null ) {
        viewer.replace( parent, index, child );
        viewer.setChildCount( child, manyCategories.size() );
      }
    }
  }

  public void updateChildCount( Object element, int currentChildCount ) {
    if( element instanceof Category ) {
      Category category = ( Category )element;
      int childCount = category.getTodos().size();
      if( childCount != currentChildCount ) {
        viewer.setChildCount( element, childCount );
      }
    } else if( element instanceof TodoMockModel ) {
      TodoMockModel model = ( TodoMockModel )element;
      int childCount = model.getManyCategories().size();
      if( childCount != currentChildCount ) {
        viewer.setChildCount( element, childCount );
      }
    }
  }

  public void inputChanged( Viewer viewer, Object oldInput, Object newInput ) {
  }

  public void dispose() {
    // nothing
  }
}

public final class LazyLabelProvider extends CellLabelProvider {

  private static final long serialVersionUID = 1L;

  @Override
  public void update( final ViewerCell cell ) {
    Object element = cell.getElement();
    if( element instanceof Category ) {
      Category category = ( Category )element;
      cell.setText( category.getName() );
    } else if( element instanceof Todo ) {
      Todo todo = ( Todo )element;
      cell.setText( todo.getTitle() );
    }
  }

  @Override
  public String getToolTipText( final Object element ) {
    return "";
  }

}

Model:

public class TodoMockModel {

  public List<Category> getManyCategories() {
    List<Category> categories = new ArrayList<Category>();
    for( int i = 0; i < 500; i++ ) {
      Category cat = new Category();
      cat.setName( "Category " + i );
      categories.add( cat );
      for( int j = 0; j < 100; j++ ) {
        Todo todo = new Todo( cat, "(Cat " + i + ") -> Todo " + j );
        cat.getTodos().add( todo );
      }
    }
    return categories;
  }
}


public class Todo {

  private String title = "";
  private String description = "";
  private final Category parent;

  public Todo( Category parent, String summary ) {
    this.parent = parent;
    this.title = summary;
  }

  public Todo( Category parent, String summary, String description ) {
    this.parent = parent;
    this.title = summary;
    this.description = description;

  }

  public Category getParent() {
    return parent;
  }

  public String getTitle() {
    return title;
  }

  public void setTitle( String title ) {
    this.title = title;
  }

  public String getDescription() {
    return description;
  }

  public void setDescription( String description ) {
    this.description = description;
  }

  @Override
  public String toString() {
    return "Todo [title=" + title + ", description=" + description + "]";
  }

}

public class Category {

  private String name;
  private int sort;
  private final List<Todo> todos = new ArrayList<Todo>();

  public String getName() {
    return name;
  }

  public void setName( String name ) {
    this.name = name;
  }

  public int getSort() {
    return sort;
  }

  public void setSort( int sort ) {
    this.sort = sort;
  }

  public List<Todo> getTodos() {
    return todos;
  }

  @Override
  public String toString() {
    return "Category [name=" + name + ", sort=" + sort + ", todos=" + todos + "]";
  }

}

Comment 3 Moritz Post 2012-02-21 07:28:29 EST

Remove the line 

tab2.setControl( composite );

in the createTree method.

Comment 4 Ivan Furnadjiev 2012-02-21 08:59:27 EST

I think that this is a programming error. Replacing this line in LazyContentProvider#updateElement:
--------------------
viewer.setChildCount( child, manyCategories.size() );
--------------------
with:
--------------------
viewer.setChildCount( child, child.getTodos().size() );
--------------------
solves the problem. Before, for every child (TreeItem) the itemCount was set to 500 ( manyCategories.size() ), but the element list has only 100 elements.

Comment 5 Moritz Post 2012-02-21 09:46:08 EST

Your assumption was correct ivan.

Closed as invalid.