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F. Shein, Ph.D., P.Eng.
T. Nantais, B.A.Sc., P.Eng.
R. Nishiyama, B.Sc.
Bloorview MacMillan Children’s Centre
350 Rumsey Road
Toronto, ON M4G 1R8
Phone: (416) 425-6220
Single-switch automatic row-column scanning is the most common scanning approach used to access computers by individuals who are limited to switch access. However, other scanning methods exist that may be more efficient and less taxing, but these are often not well-understood. Efficient manipulation of Windows objects through scanning without mouse emulation is also under-realized. This paper discusses these methods within the context of WiViK on-screen keyboard.
WIVIK® ON-SCREEN KEYBOARD
WiViK is an on-screen keyboard, (Shein et al, 1991, 1992), that enables people with physical disabilities to access any application within Microsoft Windows. Recently, it has been significantly updated for Windows 2000/XP. The WiViK keyboard is displayed within a window that you can move and size. It supports both pointing access (e.g., with a mouse, trackball, touchpad, or headpointer) as well as switch-based scanning. All keys work just as they would if you were typing on a physical keyboard. With switch-based scanning, a highlight moves or scans across the keyboard.
WiViK’s uniqueness in scanning is twofold. First, rather than choose from a limited set of scanning methods, you define a unique strategy based on the number of switches (1 - 6); scanning method (automatic, directed, inverse/step etc.); the style of scanning or highlighting (item, row/column, column/row, quadrant) along with a variety of preferences that vary according to the other settings. Second, WiViK applies scanning to Windows objects, through specialized keyboards, such that you can open menus, edit text, move or resize windows, jump to other applications -- all without emulating the mouse cursor.
NUMBER OF SWITCHES
Generally speaking, as the number of switches increases, your degree of control also increases. Although a single-switch is common, additional switches can provide enhancements, such as the ability to cancel an action, adjust scanning rate, and reverse direction, that improve overall effectiveness. Specific switch actions that are possible vary with scanning method that is chosen. A maximum of six switches may be defined within WiViK.
(1) Automatic. With automatic scanning, groups or items are automatically highlighted or scanned in sequence. The highlight pauses at each group/item for a pre-set time. A Select switch is used to choose a group or item. You must be able to activate this switch within the pre-set time to make a selection. Additional switches may be set to allow cancelling of selections, advancing the scanning faster, and reversing the direction. Experience suggests that the addition of a Cancel switch is the most important second switch to add as it provides the user with significant independence.
(2) Inverse. With inverse scanning you advance the highlight by holding a Move switch down. While the switch is held down, the highlight pauses at each item for a pre-set time. Step scanning is a variation where you advance by repeatedly activating the Move switch. Sometimes, step and inverse scanning are combined. The advantage of inverse/step scanning is that timing is not as critical as with automatic scanning and you have greater overall control. Groups or items are selected with a Select switch or by dwelling if no Select switch is available. Typically two or three switches are used with Move, Select and Cancel actions assigned to switches.
(3) Directed. Directed scanning matches separate directional switches with moving the highlight across individual keys. These switches are used in a step or inverse fashion. The switches are often housed in a gated joystick, allowing you to direct the scanning cursor as you would drive an electric wheelchair. Items are selected by activating a Select switch or by dwelling for some period. Directed scanning requires the greatest degree of control, but with WiViK, it is possible to accomplish directed scanning with as little as two switches. One switch may be defined to move Right/Left, the second switch defined as Up/Down, and a third switch as a Select. Cancelling may be achieved by dwelling if a Select switch is defined, or vice versa.
A wide number of switch actions are available to take advantage of varying skills and degree of control. Some of the available switch actions are listed in the table below.
Scanning Method AUTOMATIC INVERSE DIRECTED Switch Actions Select
2 Speed toggle
Forward/Reverse toggle Select
Move/Reverse toggle Select
Right, Left, Up, Down
Note that the following highlighting styles only apply to automatic and inverse/step scanning.
(1) Row-column. Rows of items are highlighted from the top down one at a time. A selected row is then highlighted column-by-column (item-by-item) until the desired item is reached and selected. The highlighting returns to the first row after a selection. Column-Row highlighting is also available for some languages which are oriented in columns.
(2) Row-group-item. Groups of items in a selected row are highlighted until a group containing the desired item is selected. Then items within that group are highlighted until the desired item is reached and selected. The highlighting returns to the first row after a selection.
(3) Quadrant scanning. The keyboard is divided into quadrants. Each quadrant is highlighted in succession. Sub-quadrants within a selected quadrant are highlighted and the process continues until individual items are highlighted. The advantage of quadrant scanning is that all areas of the keyboard are more equally accessed.
(4) Item scanning. Each item is highlighted one at a time, usually from left-to-right and top-to-bottom until an item is selected. After a selection, highlighting begins again with the first item and repeats scanning. Item scanning is typically limited to less than 15 items.
Timing is the most important aspect of scanning access. WiViK incorporates several timing settings that accommodate wide ranging abilities. All are based on the setting of a basic scan interval time. This is the time interval that the highlight pauses at one location before advancing while switch activation is maintained; also, the time interval between repeating keystrokes. This should be set so that you can hit or release the switch before the highlight passes the desired row, group or item. When step scanning is used, this should be set high so that the highlight does not advance over more than one item with each hit.
A Speed Factor decreases the basic time interval by this factor when using a switch defined as Overdrive, 2 Speed, or Fast. It allows you to quickly move to the approximate location of the desired row, group or item. Typically Speed Factor is set to 2 or 3. You must stop before reaching the target.
A Dwell Factor increases the basic time interval by this factor to dwell or wait to make a selection or to cancel scanning. If no Select switch is defined, selection is automatically set to dwelling. Dwell Cancel is only available when a Select switch is defined. Typically Dwell Factor is set to 4 or 5 for dwell selection and 6-10 for dwell cancelling.
Accessing Windows by scanning can be difficult and awkward if you use scanning mouse emulation. WiViK includes an alternate solution of using appropriate keystroke sequences and repeating these under your control (Shein et al, 1994; Shein 1997, 1998). You can either directly select the keystroke commands or select WiViK keys that hold repeating sequences of keystrokes.
When keys that perform actions are repeated, window interface objects move on their own by scanning, e.g., menus scan in succession. Pressing the Select switch stops the scanning sequence (e.g., scanning across menus) and begins the next sequence (e.g., scanning down menus). Pressing the Select switch in the last sequence stops the scanning (e.g., selects a menu item).
You do not have to concern yourself with how to position and direct a pointer, nor remember keystroke sequences. WiViK includes scanning keyboards with all of the necessary keystrokes defined behind a graphical or text label representing the action. This approach is used when the task involves movement (e.g., choosing menus, sizing, positioning, scrolling) rather than single command selection. If you do not want to complete a scanning sequence, then you can stop scanning with a second Cancel switch.
Figure 1 below shows a WiViK scanning keyboard keys arrangement optimized for row/column scanning. Note the bottom row of icons which provide scanning control of text cursors, menus, switching applications, dialogs, window buttons, resizing/moving windows, and exiting.
Figure 2 below shows the same WiViK keyboard with the page of keys related to scanning text cursors. Here you can advance the cursor by letters, words, lines and paragraphs either forwards or backwards. You can also choose a key to begin and extend highlighting text to cut, copy or even speak.
Shein, F., Hamann, G., Brownlow, N., Treviranus, J., Milner, M., & Parnes, P. (1991). WiViK: A Visual Keyboard for Windows 3.0. Proceedings of the 14th Annual Conference of RESNA, Kansas, MO, 160–162.
Shein, F., Treviranus, J., Hamann, G., Galvin, R., Parnes, P., & Milner, M. (1992). New Directions in Visual Keyboards for Graphical User Interfaces. Proceedings of the 7th Annual Conference Technology and Persons with Disabilities, CSUN, CA, 465-469.
Shein, F., Galvin, R., Hamann, G., & Treviranus, J. (1994). Scanning the Windows Desktop without Mouse Emulation. Proceedings of the RESNA ’94 Annual Conference, 391-393.
Shein, F. (1997). Towards Task Transparency In Alternative Computer Access: Selection Of Text Through Switch-Based Scanning. PhD Thesis, Department of Mechanical and Industrial Engineering, University of Toronto.
Shein, F. (1998). Towards Task Transparency: Scanning Text Selection. Proceedings of RESNA ’98 Annual Conference, Minneapolis, MN, 246-248.
WiViK is a registered trademark of Bloorview MacMillan Children’s Centre.
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