[tcdent]

If you implemented a web-like runtime from the ground up, you're saying you would write it from scratch?

The runtime has JavaScript support, it does not have a brand new interpreter.

The runtime has CSS support, it does not have a brand new interpreter.

The runtime has HTML/XML syntax. Why would they write a brand new interpreter?

[wvenable]

Because the XML syntax maps directly onto UI components; introducing an HTML canvas is vastly more complicated than that.

Mappping XML to a small subset of UI objects is so simple you don't really need to pull in an entire browser runtime for it.