Help windows may be nested through the use of links embedded within the help information. Both text and graphics may be defined as selectable; selection of these items can then be used to trigger events such as:
Selectable items are known as links; text items are hypertext links, and graphical items are hypergraphic links. Each of these link types is described in the following sections.
Hypertext Links
Text items are defined using the :link tag, which defines the type of event triggered by the link operation, and details of the target object activated by the link. An example of a :link tag is shown in Figure "Hypertext Link".
The :link tag shown in the example above uses the reftype= attribute to identify the type of event to be triggered (in this case, the display of another help window). The res= attribute identifies the help window to be displayed when the hypertext item is selected.
Different values for the reftype= attribute will trigger different types of events:
The use of hypertext links provides a powerful means to develop sophisticated help text and online documentation, and to implement tutorials and "self-teaching" applications. This subject is discussed further in Self-Teaching Applications.
Hypergraphic Links
Bitmapped graphic items are defined in a slightly different manner to text items, using the :artlink tag. The :artlink tag is specified on the line immediately following the :artwork tag in the source file.
Multiple :artlink tags may be defined for the same bitmap, in order that the user may select different portions of the bitmap to trigger different events. If multiple :artlink tags are specified however, they must be placed in a link file, which is referenced using the linkfile= attribute to the :artwork tag.
Both techniques are illustrated in Figure "Hypergraphic Link".
The use of a link file is mandatory where multiple hypergraphic links exist for the same bitmap. The format of a link file is shown in Figure "Link File With Multiple Hypergraphic Links".
Multiple :link tags are nested within a single :artlink tag, and define various selectable areas of the bitmap, each of which triggers a specific event when selected by the user. Any of the types of events normally triggered by a :link tag may be initiated from a hypergraphic link.