[blub]

I think the difficulty is that none of the technologies that you are using were designed for building software applications, but for showing text and images on a screen.

In other words, there is a perfectly fine solution for offline G-mail, it's called "e-mail client".

[_urga]

Actually the problem may be that OS user interfaces, for all their native functionality, have not kept pace with browsers at showing text and images on a screen. Hypertext is an innovation that is hard to ignore.

[blub]

Native UI is vastly more powerful compared to HTML and CSS, which were designed to display web pages, not widgets and controls.

In fact I don't understand what kind of experience you have to say something like that. If you were a web designer you would know that the web UI is a painful to use hack. If you were a mobile/desktop developmer you would know that both types of UIs are better at showing pretty much anything on a screen - including a browser engine.