[martin_ky]

This release of Qt for WebAssembly is the first officially released prototype of this technology. Qt comes from the native desktop world where it relies and builds on top of the whole rich world of native OS APIs. There's nowhere near that API support on the web platform at the moment. Also Qt might not be using the full capabilities of the web platform in this first release. Naturally, the first results are crude. But Qt has a great platform abstraction mechanism, so I'm sure it will only improve over time, either making better use of existing web APIs or support new ones as they become available.

Also it is worth to point out, that there are really 2 GUI toolkits in Qt:

Qt Widgets - the more classical, desktop UI paradigm. Yes, this renders everything into a bitmap and therefore translates better to the Canvas model on the web.

QML / Qt Quick - more DOM like, declarative UI with modern animation, scripting and data binding features. This maps better to the HTML DOM model. In theory at least, however, the similarity is only superficial. Under the hood, the QML visual elements are rendered with WebGL.