<svg xmlns="http://www.w3.org/2000/svg" xmlns:h="http://www.w3.org/1999/xhtml">
<title>mask with only an empty container with a filter</title>
<h:link rel="help" href="https://drafts.fxtf.org/css-masking-1/#svg-masks"/>
<h:link rel="match" href="reference/mask-green-square-001-ref.svg"/>
<filter id="double" x="0" y="0" width="200" height="200" filterUnits="userSpaceOnUse">
<feOffset dy="100"/>
<feMerge>
<feMergeNode/>
<feMergeNode in="SourceGraphic"/>
</feMerge>
</filter>
<filter id="f" x="0" y="0" width="200" height="200" filterUnits="userSpaceOnUse">
<feFlood flood-color="#fff"/>
</filter>
<mask id="m" x="50" y="50" width="100" height="100" maskUnits="userSpaceOnUse">
<g filter="url(#f)"/>
</mask>
<rect width="100" height="200" fill="green" mask="url(#m)"/>
<rect width="100" height="100" x="100" fill="green" mask="url(#m)"
filter="url(#double)"/>
</svg>