[SeanLuke]

> If you are referring to window toolkits, they are all compatible in the sense that you can run different ones side-by-side.

So what? I can run X Windows on my Mac using Apple's X app. That doesn't mean they're compatible with one another. I can't drag-and-drop between them. I can't transfer font or color preferences between them. I can't even properly cut and paste between them.

As it turns out, this is, amazingly, also the case for widget toolkits on X -- on the same windowing system!. There are major toolkits which are missing interoperability. Drag and drop is particularly bad. But in some cases even cut and paste is an issue.

> If you are referring to a consistent look, the two major ones (GTK and Qt) each have themes which render their widgets in the other toolkit (GTK-Qt and QGtkStyle, respectively).

Ah, the plaintive cry of the X person who still thinks that graphical interfaces are skins. So 1985, thanks for the memories.