xlsclients doesn't show all applications that are connected to a display; in particular I noticed that some Java applications are not listed. Examples are kSar (http://sourceforge.net/projects/ksar/) and Oxygen XML editor (http://www.oxygenxml.com/). In both cases the number of clients listed by xlsclients -a doesn't change when starting or terminating the application. With "xwininfo -root -children" the new window is listed however (as "net-atomique-ksar-Main").
This doesn't happen for all Java applications. Eg. jvisualvm, jconsole and Netbeans are not affected as far as I can tell, and they do show up in xlsclients (though with Name, Icon Name, Command and Instance/Class set to <unknown>).
This happens on Scientific Linux 6.4 x86_64, with xorg-x11-server-Xorg-1.13.0-11.sl6.x86_64 from RPM, xlsclients 1.1.2, and Java 1.7.0_45-b18.
I would expect that xlsclients would list all clients which are connected to the server, even if there are details missing for some clients. I.e. The number of clients listed by xlsclients should be correct, even if the details are incomplete.
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