Bug 179743 Parameter Validate Event is not Called
I have tested the validate event on parameters and it never appears to get called.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/EngineTask.java
*/
	public void cancel( )
	{
		cancelFlag = true;
		executionContext.cancel( );
	}
	public void cancel( Object signal )
	{
		if ( signal == null )
		{
			throw new IllegalArgumentException( "signal can't be null" );
		}
		cancelFlag = true;
		long waitingTime = 0;
		do
		{
			waitingTime += 100;
			try
			{
				Thread.sleep( 100 );
			}
			catch ( Exception ex )
			{
			}
			if ( runningStatus != STATUS_RUNNING )
			{
				return;
			}
		} while ( waitingTime < 5000 );
		return;