CS 497C – Introduction to UNIXLecture 37: - X Windows

Chin-Chih Changchang@cs.twsu.edu

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:– You’ll come across situations when it’s 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.

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.

• It’s possible to change the appearance of a window instantly by running a separate program after starting X. This program is called the window manager.

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.

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 don’t 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.

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

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.

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 don’t have any window management functions. A special client, the window manager, must be invoked at the start of an X session.

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.

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.

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.

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.

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 &

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.

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.