X input method may choose not to support all the input styles.

Basically this line will make client always create an input context with preedit callback, which is not supported by input method.

The correct way to do this is to do GetIMValues first, to list all the supported style
https://www.x.org/releases/X11R7.6/doc/libX11/specs/XIM/xim.html#Getting_IM_Values

Then send over a style in XCreateIC that is supported by input method.