X11 release 4 included routines to implement The Inter-Client Communications Conventions which allow clients to cooperate in the areas of selections, cut buffers, window management, session management, and resources. See the online XR5demo.c program for details. This chapter covers enough for most needs.
You can suggest to the window manager how it should display and handle your application. The window manager is at liberty to ignore the suggestions. These properties can be set individually or en masse.