I don't know the dart Web UI package - but from the example code:
<span on-click="query('.q-example-overlay').xtag.show()">Launch Overlay</span> <x-overlay width="600px" class="q-example-overlay">
I don't know the dart Web UI package - but from the example code:
Does that then get transpiled into valid HTML (and inline javascript?) or is that what's actually served to the browser?