has-range-on-open

Arguments: outline-item

This outline-item property allows an outline-item to avoid displaying a leaf pixmap when a custom range-on-open method is expected to supply child items for it later when it is opened.

has-range-on-open returns nil by default, but may be set to true if needed by calling (setf has-range-on-open) or, more typically, by passing the :has-range-on-open initarg to make-instance when creating an outline-item.

An application should set this property to true if the item has no child items initially but a range-on-open method that the application has supplied for this outline is expected to return one or more child items for this item. If no custom range-on-open method is supplied for this outline, then there is no need to set the value of the has-range-on-open property.

An outline-item will display its outline-item-leaf-pixmap (rather than its outline-item-opened-pixmap or its outline-item-closed-pixmap) when it currently has no child items (that is, its range is nil) and when its has-range-on-open property is nil. Otherwise it will display its opened or closed pixmap, depending on its current state (assuming that draw-icons is enabled for the outline). The plus or minus pixmap is also displayed whenever the leaf pixmap is not displayed (assuming that draw-plus-minus is enabled for the outline).

Compatibility note: This property is new in release 6.1. In earlier releases, it was possible to achieve a similar effect by defining a leaf-pixmap method on an outline subclass that really returned a non-leaf pixmap for items that are expected to be given child items by range-on-open. That technique was not documented, and did not manage the plus/minus icons properly. That technique should continue to work as well as it did, but is now deprecated since has-range-on-open is a more intuitive and complete solution.

Copyright (c) 1998-2001, Franz Inc. Berkeley, CA., USA. All rights reserved.
Documentation for Allegro CL version 6.1 update # 1. This page was not revised.
Created 2001.12.15.