chart-items-max-index

Arguments: chart-widget

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

chart-items-max-index is the index of the last chart item of a chart-widget that should be displayed at the current time. The value should be a non-negative integer, or else nil for no maximum. The default value is nil.

If set-chart-value has been used to add items to the chart, then any item whose index is greater than this property value (if it is a number) will not appear in the chart. When the property value is nil, then no items are excluded. This property can be used to display only a subset of collected values that are of interest at the moment.

If instead a chart-value-returner function is used for looking up chart data, then this property should always be set to a non-negative integer to tell the chart the maximum item index that it should pass to the chart-value-returner function. Otherwise the chart-widget has no way of knowing how many items your function is prepared to return. (The property will arbitrarily default to 100 in this case, though that would usually not match the available data.)

This property is the maximum index that will be included, rather than the number of indeces to include. So for a chart-value-returner function to cover all values from a 100-element vector, for example, the value of this property should be 99 rather than 100.

See also chart-items-min-index.

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

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This page was not revised from the 10.0 page.
Created 2019.8.20.