A gauge is a horizontal or vertical bar for displaying the output value of a bounded integer quantity. Each guage has an adjustable range, and the gauge's current value is always between 0 and its range, inclusive. Use set-value to set the value of the gauge.
If label is a string, it is used as the gauge label; otherwise the gauge does not display a label.
If an ampersand (``&'') occurs in label, it is specially parsed; under Windows and X, the character following an ampersand is underlined in the displayed control to indicate a keyboard mnemonic. (Under MacOS, mnemonic underlines are not shown.) The mnemonic is meaningless for a gauge (as far as on-traverse-char is concerned), but it is supported for consistentcy with other control types. A programmer may assign a meaning to the mneumonic, e.g., by overriding on-traverse-char.
The range argument is an integer specifying the maximum value of the gauge (inclusive). The minimum guage value is always 0.
The style list must include either 'horizontal, specifying a horizontal gauge, or 'vertical, specifying a vertical gauge.