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Building and maintaining Linux graphic desktops
This course - the seventh of eleven courses covering LPIC-1 Linux certification - will explore Linux Display Managers and graphic Desktop Environments. You will learn how to:
- configure hardware peripherals for use in a GUI environment
- control graphic login sessions
- manage Display Managers like LightDM
- enable and manage Linux accessibility utilities to ensure that users with disabilities can access system resources, and
- build a graphic user interface on top of a virtual server in Amazon's AWS.
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Managing Linux system accessibility (for people with disabilities)
Linux developers have done terrific work opening up the operating system to users with disabilities. There are now utilities to assist individuals with limited vision, hearing, or movement. In this video, we'll explore how to work with the accessibility features available for Linux.
I will note that each Linux desktop, whether it's Unity, KDE, or some flavor of Gnome will place menu links to their accessibility control interfaces in different places. In fact, individual desktops will often undergo significant changes to their menu structure between one release and the next, which can sometimes be rather annoying. But for our purposes, it's not really so important exactly which menu sequence you use to get to them, as long as you are aware of these features and know how to apply them.
Linux visual and audio access tools
As it happens, I'm working with Ubuntu 14.04's Gnome fallback desktop. Accessibility tools are meant to help users access their screen, audio, keyboard, and mouse. We'll start with screen utilities. When you toggle the Orca Screenreader on, a voice will automatically audibly read whichever screen element currently has focus. It will therefore, read out each of the menu items that I click on or hover over as I work through options within a new menu I've opened. Using the keys on the number pad of your keyboard, you can also make Orca read previous or subsequent lines of text in relation to your cursor or window title and menu bars.
Turning on high contrast will temporarily reset your desktop theme to be more readable. It may look a bit ugly to us, but it can make a computer usable for someone with impaired vision. Large text will increase the text scale factor by about 25%. There is currently a known bug in the large text module that's affecting some Linux installations, including mine. Braille display will use the BRLTTY daemon to output text to USB connected, refreshable Braille display devices. Just in case you aren't aware, Braille is a universally used writing system that allows blind people to read using their sense of touch.
Oddly enough, the Linux screen magnifier has not always been installed by default over the past few years. As you can see from my universal access interface, there's currently no link. While I can't explain why that should be, you can easily fix it by installing a screen magnification software package, like KMag. Clicking on the mouse button on the type right will cause the KMag display to follow your mouse around your screen, displaying enlarged images.
For users with hearing impairments or perhaps individuals whose PCs lack speakers, missing audio alerts can be a concern. To add a visual cue to every audio alert, you can toggle visual alerts, and select between having just the window title flash or the whole screen.
Linux keyboard and mouse access tools
Using a keyboard and mouse can be particularly challenging for people with reduced motor control. Just imagine how hard it can be to execute certain multiple keystroke combinations if you can barely lift your arm, or even if your arm is temporarily in a cast. Sticky keys will interpret the pressing of a modifier key, like control or shift, followed by any other keystroke, as though they were pressed together. This can be helpful for people who find simultaneous keystroke combinations a problem. Slow keys, bounce keys, and repeat keys can add greater accuracy for individuals unable to completely control their finger movement.
Slow keys lengthens the time between the initial key stroke and the point where the key stroke will register. Bounce keys inserts a longer delay between key strokes, ignoring accidental key strokes caused by unwanted movements between one key and another. Repeat keys, accessed through the keyboard menu will allow more time for user to release a key at the end of a key stroke before considering it as a repeated command. You can lengthen or shorten the delay or disable repeat keys altogether.
The way the system reacts to your mouse can be controlled by a number of utilities. Enabling mouse keys will allow your keyboard arrow keys to take over the mouse cursor movements, providing easier control and movement accuracy. If double-clicking your mouse is difficult, you can set your mouse to accept a longer, single click in place of a double click through simulated secondary click. The acceptance delay setting lets you define how long you'll need to hold the mouse button down before a second click is simulated. Hover click, which is also sometimes referred to as dwell click, tells the system to interpret a mouse cursor that hovers for a set time as a click. This can help people who find it difficult to accurately click the left mouse button. It can also help children with smaller hands.
Finally, for people who are unable to use a keyboard at all, an onscreen keyboard displays a virtual keyboard that can be used with mouse clicks. Clicking on the large X at the top right of the keyboard will disable the tool. It took me a few anxious moments to figure that one out for myself.
Let's briefly review. People with reduced vision can use the audible screen reader, high contrast, a screen magnifying tool, and the USB Braille interface. Visual alerts provide visual cues in place of audio alerts. Users with movement issues can get help with their keyboards through sticky keys, slow keys, bounce keys, and repeat keys. Help with mouse control is available through mouse keys, simulated secondary click, hover click, and through an onscreen keyboard.
About the Author
David taught high school for twenty years, worked as a Linux system administrator for five years, and has been writing since he could hold a crayon between his fingers. His childhood bedroom wall has since been repainted.
Having worked directly with all kinds of technology, David derives great pleasure from completing projects that draw on as many tools from his toolkit as possible.
Besides being a Linux system administrator with a strong focus on virtualization and security tools, David writes technical documentation and user guides, and creates technology training videos.
His favorite technology tool is the one that should be just about ready for release tomorrow. Or Thursday.