48 Chapter 2: iTool System Architecture
System Resources iTool Developer’s Guide
The value of the <Link> element specifies the specific content to be displayed from
the help system specified by the
book attribute. The value depends on the value of
the
type attribute:
If more than one
<Link> element is present, IDL will first attempt to use the element
with the
type attribute set to IDLHELP. If no <Link> element with the type
attribute set to
IDLHELP is present, IDL will choose which to display based on the
platform; on Windows platforms, the
<Link> element with the type attribute set to
MSHTMLHELP will be used, on Unix platforms, the <Link> entity with the type
attribute set to
PDF will be used. If the appropriate platform-specific <Link> is not
present, the first
<Link> entity of a type that can be displayed on the current platform
will be used.
Example: Help Topic for MyVisType
Suppose you have created a new iTool visualization type named MyVisType and
registered it with the iTool, and you have created a single-topic HTML file named
Link type Value of the Link Element
IDLHELP The base name of an HTML file (do not include the file
extension) to be displayed in the main window of the
IDL Assistant help viewer. The file must be located in the
same directory as the help system’s
.adp file. If no value is
provided, IDL displays home page specified in the help
system’s
.adp file.
MSHTMLHELP The context number. A context number is an integer used by
the Microsoft Windows HTMLHelp viewer to select a topic
from the help system’s .chm file. If no value is provided, IDL
displays the help system’s home page.
PDF Ignored. IDL will always display the first page of the file
specified by the
book attribute.
HTML An HTML anchor tag within the specified HTML file. If no
value is provided, IDL displays the top of the HTML page
specified by the
book attribute.
TEXT The full path to the text file to be displayed. If the value is
present, it takes precedence over the value of the
book
attribute (if any).
Table 2-4: Help Topic Link Values
