<!DOCTYPE html>
<html lang="en">
<meta charset="utf-8">
<title>Testcase for filters on canvas</title>
<style>
#checkbox {
filter: url(#filter);
}
</style>
<svg style="display: block; height: 0;">
<defs>
<filter id="filter" color-interpolation-filters="sRGB" x="-100%" y="-100%" width="300%" height="300%">
<feMorphology operator="dilate" radius="5" in="SourceAlpha" result="mask"/>
<feFlood flood-color="blue"/>
<feComposite operator="in" in2="mask"/>
<feMerge>
<feMergeNode/>
<feMergeNode in="SourceGraphic"/>
</feMerge>
</filter>
</defs>
</svg>
<input type="checkbox" id="checkbox">
<script>
document.getElementById("checkbox").focus();
</script>