hod for a mask sprite based on a
<code>mouseDown</code> event being dispatched by the sprite, set the
sprite's <code>buttonMode</code> property to <code><a href="../../Bool.html">true</a></code>.</p>
<p>When display objects are cached by setting the
<code>cacheAsBitmap</code> property to <code><a href="../../Bool.html">true</a></code> an the
<code>cacheAsBitmapMatrix</code> property to a Matrix object, both the
mask and the display object being masked must be part of the same cached
bitmap. Thus, if the dis