public Table pad( Value top, Value left, Value bottom, Value right )
{
if( top == null )
throw new Exception( "top cannot be null." );
if( left == null )
throw new Exception( "left cannot be null." );
if( bottom == null )
throw new Exception( "bottom cannot be null." );
if( right == null )
throw new Exception( "right cannot be null." );
_padTop = top;
_padLeft = left;
_padBottom = bottom;
_padRight = right;
_sizeInvalid = true;
return this;
}