~/.Xmodmap
Xmodmap's keyboard mapping configuration.
https://cgit.freedesktop.org/xorg/app/xwininfo/
http://www.xfree86.org/current/xwininfo.1.html
Shows window information. Comes with X.
There are several pages for it, but I have this one working:
https://github.com/dlitz/xtoolwait
Xtoolwait notably decreases the startup time of an X session by reducing the load on the X server and the OS.
It starts an X client in the background, waits for a window to be mapped on the root window, and then exits. It can improve performance for users who start a bunch of X clients automatically (for example, xterm, xlock, xconsole, whatever) when the X session starts.
This is a problem I had with PCLinuxOS 2007 while using my Dell 2407WFPb.
Platform (computer) > Linux (distribution) > X > Window manager > Operating Environment >
coming later
twm is the default window manager.