In my case, it is still "On the spot" in qtconfig. To use uim, first you shoud run the program. If you run the qt program, for example kapi, on the terminal, you can see some informations on the terminal.
After that, you can see Chinese input method when you press sw button on the tray.
Or, by press fn-clik the text box, you can check whether uim works properly.
Unfortunately, I don't know how to tpye Chinese. Here is an example of Korean input.
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I don't know uim conflicts with scim, but you don't need both of them because you can write cjk character in qt and gtk2 using uim.
Enjoy!