Monday, January 18, 2010

The X Windows System

Before we dive into the details of working with the video display in Ubuntu, it helps to get a little background on how Linux generally handles video. If you run the Ubuntu server, or if you run your Ubuntu workstation in text mode, there’s not much involved for Ubuntu to interact with the video card and monitor. By default Ubuntu can use just about any video card and monitor in text mode to display 25 lines of 80-column text. This feature is built into the Ubuntu Linux software so that it can directly send text to the monitor at all times.

However, when you use the graphical mode on your workstation, things are a bit different. Instead of directly sending text to the monitor, Ubuntu must be able to draw lines, shade colors, and manipulate images. To do that, Ubuntu makes use of a special type of software called X Windows to interface with the video card and monitor.

What Is X Windows?
Two basic elements control the video environment on your workstation:
• The PC video card
• The monitor

The Ubuntu operating system must interact with the video card in your PC to produce the graphical images for your desktop to appear and to run graphical applications. The video card controls how to draw the images on the monitor display, what colors are available to use, what size of display area you can use, and at what speed the system can draw the images.

The video card must be able to interact with the monitor to display the images sent by Ubuntu. There’s wide choice of monitors available these days, with a wide variety of features, from standard old-style, picture-tube monitors to modern flat-screen plasma monitors. The combination of the video card features and monitor features determines the graphics capabilities of your workstation. Ubuntu needs to know how to use and exploit these features to produce the best possible graphics for the desktop and applications. Given the wide variety of video cards and monitors available, it would be difficult for the GNOME desktop developers to have to code the features found in GNOME for every possible video card and monitor environment available. Instead, the X Windows software helps do that.

The X Windows software operates as an intermediary between the Ubuntu system and the input and output devices connected to the workstation. It’s responsible for controlling the graphical environment so that GNOME doesn’t have to support different types of video cards and monitors. Instead, the X Windows software handles all of that, and the GNOME software has to interact with just the X Windows software to display images on any type of video card and monitor combination.

Besides dealing with the video card and monitor, X Windows also handles any input devices attached to the workstation, such as the keyboard and mouse. It’s the main clearinghouse for all interaction for the desktop environment.

Because the X Windows software handles all of the input and output functions for the Ubuntu workstation, it’s important to ensure that the X Windows software is working properly. It must know the type of input and output devices it’s communicating with so that you can interact with your desktop.

The X Windows software is actually a specification of how to interact in a client/server methodology, serving the input and output devices to Ubuntu applications. Two popular X Windows implementations are currently available in the Linux world.

Source of Information : Wiley Ubuntu Linux Secrets

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