Returns the previous offset for the specified offset and movement
type. The movement is one of <code>SWT.MOVEMENT_CHAR</code>,
<code>SWT.MOVEMENT_CLUSTER</code> or <code>SWT.MOVEMENT_WORD</code>,
<code>SWT.MOVEMENT_WORD_END</code> or <code>SWT.MOVEMENT_WORD_START</code>.
@param offset the start offset
@param movement the movement type
@return the previous offset
@exception IllegalArgumentException <ul>
<li>ERROR_INVALID_ARGUMENT - if the offset is out of range</li>
</ul>
@exception SWTException <ul>
<li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li>
</ul>
Returns the previous offset for the specified offset and movement type. The movement is one of <code>SWT.MOVEMENT_CHAR</code>, <code>SWT.MOVEMENT_CLUSTER</code> or <code>SWT.MOVEMENT_WORD</code>, <code>SWT.MOVEMENT_WORD_END</code> or <code>SWT.MOVEMENT_WORD_START</code>.
@param offset the start offset @param movement the movement type @return the previous offset
@exception IllegalArgumentException <ul> <li>ERROR_INVALID_ARGUMENT - if the offset is out of range</li> </ul> @exception SWTException <ul> <li>ERROR_GRAPHIC_DISPOSED - if the receiver has been disposed</li> </ul>
@see #getNextOffset(int, int)