increment

Arguments: scroll-bar-mixin

Returns the value of the increment property of its argument. This property is a numeric (fixnum) value relating to the range of the object. For instance, if the range is (0 100) and the increment is 1, then pressing an arrow key will advance the control's slider bar 1/100 of the way across the dialog in that arrow's direction.

increment is a property of the up-down-control, trackbar, horizontal-scroll-bar, and vertical-scroll-bar classes.

Alternate value for up-down-controls

For an up-down-control, alternate values are allowed to determine how the control continues to increment as the user holds down the mouse button after clicking on an arrow. In particular, if the value is an association list of non-negative integers of the form ((elapsed-seconds increment) (elapsed-seconds increment) ...), then the increment will change at various points in time. For example, a value of ((1 1)(1 3)(2 10)(4 100)) indicates that the up-down-control should increment (or decrement) by 1 for the first second, by 3 for the next second, by 10 for the next 2 seconds, and then by 100 thereafter until either the mouse button is released or the maximum or minimum value of the control's range is reached. If the value is instead a single integer, then the control will continue to increment by that single amount. The default value is nil, which means to use the default increment pattern.

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Created 2010.1.21.