scroll-page-portion

Arguments: chart-widget

Returns the value of the scroll-page-portion property of a chart-widget. The value may be set at creation time by passing the :scroll-page-portion initarg, or any time later by calling (setf scroll-page-portion).

scroll-page-portion is the portion of a whole "page" by which a chart-widget will scroll along its item-axis when the user presses the PageUp or PageDown key. A "page" means the length of the item-axis, so a value of 1 would cause a keystroke to scroll all of the current contents off to reveal contents that lie just out of view.

The value should be a positive real number, and generally should be no greater than 1 to be useful. The default value is 0.7 so that a portion of the pre-scrolled contents remains in view after a page scroll for context.

See also scroll-line-items and scroll-on-drag.

See chart-widget and also cg-chart-widget.htm.

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Created 2010.1.21.