SortColumnComparator.java

/*******************************************************************************
 * Copyright (c) 2008 Ralf Ebert
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * Ralf Ebert - initial API and implementation
 *******************************************************************************/
package de.ralfebert.rcputils.tables.sort;

import org.eclipse.jface.viewers.Viewer;
import org.eclipse.jface.viewers.ViewerComparator;
import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Table;
import org.eclipse.swt.widgets.TableColumn;

import de.ralfebert.rcputils.properties.IValue;
import de.ralfebert.rcputils.tables.TableViewerBuilder;

/**
 * ColumnComparator is a ViewerComparator that uses table.getSortColumn() as
 * column to compare values. The column is queries for an IValue by the
 * column.getData(SORT_BY) and used this value to sort values. It also pays
 * attention to table.getSortDirection(), if it's DESC (SWT.DOWN), the values
 * are exchanged.
 * 
 * Internal implementation class for {@link TableViewerBuilder}.
 * 
 * @author Ralf Ebert <info@ralfebert.de>
 */
public final class SortColumnComparator extends ViewerComparator {
  public static final String SORT_BY = SortColumnComparator.class.getName() + ".sortBy";

  @SuppressWarnings({ "unchecked", "rawtypes" })
  @Override
  public int compare(Viewer viewer, Object e1, Object e2) {

    Table table = (Table) viewer.getControl();

    // exchange values for descending sort direction
    if (table.getSortDirection() == SWT.DOWN) {
      Object tmp = e1;
      e1 = e2;
      e2 = tmp;
    }

    // resolve SORT_BY data value
    TableColumn column = table.getSortColumn();
    if (column == null) {
      return super.compare(viewer, e1, e2);
    }

    IValue sortBy = (IValue) column.getData(SORT_BY);

    if (sortBy == null) {
      return super.compare(viewer, e1, e2);
    }

    // compare using the SORT_BY value
    Object v1 = sortBy.getValue(e1);
    Object v2 = sortBy.getValue(e2);
    if (v1 instanceof Comparable && v2 instanceof Comparable) {
      return ((Comparable) v1).compareTo(v2);
    }

    // fallback on default ViewerComparator behaviour
    return super.compare(viewer, e1, e2);

  }
}