im-chooser is a GUI frontend application featured with IMSettings to choose the input method you want to use. It can also disable input methods entirely on the desktop. This allows you to pick an input method and switch it on demand without restarting either your applications or your desktop.
libgxim is an X Input Method (a.k.a. XIM) protocol library that is implemented by GObject. This library helps you implement XIM servers or client applications to communicate through the XIM protocol without using the Xlib API directly, particularly if your application uses a GObject-based main loop.