1. CS 497C – Introduction to UNIX Lecture 37: - X Windows Chin-Chih Chang chang@cs.twsu.edu chang@cs.twsu.edu

2. X Window The X Window system was developed as part of Project Athena at MIT. In 1987, X Version 11 is released. X is now controlled and maintained by the Open Group. There are reasons to use X Window System: –Youll come across situations when its easier to do a thing in X. –When it comes to viewing graphics, the command line has no answer. –Applications are quickly moving to X Window platform.

3. The Graphic User Interface in X X Window uses a bit-mapped display where each pixel can be manipulated individually. The entire display is known as the root window, and individual applications are displayed as windows on this root window. Its possible to change the appearance of a window instantly by running a separate program after starting X. This program is called the window manager.

4. Starting and Stopping X X is started with the startx or xinit commands. X can also be invoked during system startup with the xdm comand. xdm can otherwise be invoked by the root user only. Use the menu like Exit Session or Log out on the desktop to quit X. X splits an application into two components – client and server.

5. The X Architecture The server program controls the monitor, keyboard and mouse, while the application itself is the client. X programs are portable since they dont bother about the window drawing. X also runs in a TCP/IP network, it is possible for a client to run on one machine and have its display on another. The xhost client controls access to the server.

6. Running X Programs Remotely xhost + bugs adds bugs to access control list. xhost + enables display for others. xhost - disables display for others. The environment variable DISPLAY determines where the client should display its output. DISPLAY=bugs:0.0; export DISPLAY

7. X Techniques and Components The –display option can be used with any X Client to direct program output. rsh bugs xcalc –display sisko:0 All windows have a title bar comprising a number of buttons. The left button brings up he Window menu. A window can be moved, resized, minimized, maximized and closed using these buttons.

8. X Techniques and Components A window is brought to focus generally by clicking on the window or its title bar. X windows comprise a number of widgets (components). They can be buttons, scrollbars, checkboxes, radio buttons, tabs and drop-down boxes. By default, X clients dont have any window management functions. A special client, the window manager, must be invoked at the start of an X session.

9. The Window Manager – A Special Client A window manager makes it possible to move and resize windows. The standard window manager for UNIX has been Motif (mwm) but is replaced by dtwm of CDE. fvwm and kwm are two of the many window managers available in Linux. Nowadays, KDE and GENOM are two widely used window managers in Linux.

10. CDE: The Command Desktop Environment The Command Desktop Environment (CDE) provides a standard look for both the desktop and the window manager. It features a Front Panel from which you can launch many applications. The File Manager handles the file and directory functions, and the Trash Can stores deleted files. The Front Panel also offers a Workspace Switch that lets you create virtual desktops.

11. xterm: The Main Client You can invoke all UNIX commands and X programs form the UNIX command lien available in an xterm window. xterm can also be used with a scrollbar ( -sb ), and the number of lines saved can be specified ( -sl ). X programs run with a number of common options.

12. Command Line Options You can position and specify the size and position of a window ( -geometry ) and its foreground and background color ( -fg and -bg ). You can start a program as an icon ( -icon ) and provide a name ( -name ) or title ( -title ). You can copy text from any window by merely selecting it with the mouse button.

13. Copy and Paste The copied text is pasted back by clicking the middle button. Multiple sections of copied text can be stored in the xclipboard client from which it can be pasted anywhere. There are several clients available in X. X offers a clock ( xclock ) and a calculator ( xcalc ). xclock –digital &

14. Standard X Clients xbiff is mailbox flag for X. xbiff -rv -title biff -file $MAIL xload displays the system load, and is often used with remote machines. xkill kills a window. It can kill all root-level window in one invocation ( -all ). X can be easily customized. You can start X clients from the file.xinitrc, the startup file used by xinit.

15. X Resources. X resources enable you to change practically any X feature. These features can be stored in.Xdefaults, and xrdb can used any time to read this file. These settings can also be overriden with the –xrm option available in every X client.