[kitsunesoba]

The problem with existing libraries is that they try to do away with the notion of different platforms in favor of a metaplatform. In reality, the divergent nature of platforms must be embraced in some ways. I imagine the aforementioned hypothetical thin wrapper as providing really easy ways of getting per-platform right; for instance, it could know the standard control heights and whitespace on each platform and automatically adjust your program's UI accordingly. It also wouldn't be hard to set up a system that allows for per platform verbiage, icon assets, etc.

[ori_b]

It's also widget selection; On Android, for example, you may want a hamburger menu. On KDE, your menus get reshuffled compared to your OSX or Windows UI.

I've seen plenty of systems that allow you to do mediocre UIs on all platforms. I haven't seen one that allows you to do an excellent UI without doing once per platform.

[kitsunesoba]

I think the answer here is to have a "base menu" that all applications start with instead of starting from zero and having developers fill in the blanks. The base menu knows where to put common special items (Preferences/Options and About for example) on each system, and developers build on top of this by adding their own custom items.

I'm not saying that it's possible for a cross-platform UI toolkit to be perfect, but it's certainly possible to get a lot closer to right than current toolkits do.