Scanning is a technique that is mainly used for providing computer access to people with hand-motor impairments. The basic idea of scanning is that a special “marker” (e.g., a coloured frame) indicates the interaction item (e.g., a button, a menu) that has the input focus. The user can shift the focus marker to the next / previous interaction object using any kind of switches (e.g., keyboard keys, special switch hardware, or even his voice). When the focus is on an object the user wants to interact with (e.g., a chess piece to be selected, a button to be pressed), he uses another switch that indicates “selection”. Additionally, in cases where the user can use just a single switch, focus movement can be automatically generated by the system on constant time intervals. This variation of the technique is referred as “automatic scanning”, while any other case is generically called “manual scanning” (even if the hands are not used at all).
Scanning can be used:
- With the keyboard (or any switch emulating the keyboard events),
using the following keys:
- Next: “]”,“Page Down” or “Tab”
- Previous: “[“,“Page Up” or “Shift+Tab”
- Select: “Space”, “End”, ‘Insert’, ‘0(zero)’ or “Enter”
- With speech recognition, using the following commands:
- “Scan next”: moves focus to the next item.
- “Scan previous”: moves focus to the previous item.
- “Scan select”: the item that has the focus is selected.
- With the mouse wheel:
- Next: move the wheel upwards.
- Previous: move the wheel downwards.
In general, there are two types of objects the user can interact with:
- Container objects, used to group related objects and increase scanning efficiency. When such an object is selected, scanning is “locked” inside its contents until the user selects to exit. Examples of container objects are: the menus, the moves list, the chessboard, as well as the pieces, since each one of them is considered as a collection of possible moves.
- Simple objects, which cannot contain any other object. When such an object is selected, a corresponding action is performed. Examples of simple objects are: buttons, destination moves, menu and list items.
Depending on the object type, the focus frame can have two different states, indicated by corresponding colours and frame shapes:
Figure 1: Scanning: Different states of the input focus.
- Select/ enter state (green rectangle, Figure 1a). Upon
selection, if the object’s type is:
- “simple”, then a related action will be activated (e.g., a menu item will be selected, a button pressed, a piece will move to the selected square).
- “container”, then the scanning focus will shift to its contents (e.g., the board’s pieces, the moves list’s or a menu’s contents).
- Exit state (red rectangle with an X, Figure 1b). Only “container” objects can be in this state. Upon user selection, the state changes to “enter”, so that the user can either re-enter the object’s contents (using “select”), or move on (using “next” / “previous”). Note: the “X” symbol is used so that colour blind players can differentiate the two states.
Example of play using scanning:
- First the focus is on the chessboard (Figure 2a). Press “select”
- You can use “next” / “previous” to move to the moves list or the menu, respectively.
- The focus (i.e., green frame) shifts over the first piece that can move, which is highlighted (Figure 2b).
- Using “next” / “previous”, you can switch between all the pieces that can move.
- When the focus is over the piece you want to move, press “select”.
- The focus is transferred on the first possible move (Figure 2c).
- Using “next” / “previous”, you can scan
all possible moves.
- In case you decide that you do not want to move the selected piece, when the focus frame is over it (it will be in “exit” state, i.e. red colour, see (Figure 2d), press “select”.
- When the focus is over the square you want to move, press “select” (Figure 2e).
- The piece moves to the selected square and input control is handed
to the opponent player (Figure 2f).
Figure 2: Selecting and moving a piece using scanning