Information may be communicated from IPF to an application in response to user interaction in a help window. This information may be in the form of application events or errors, and is communicated to the application in the form of a message passed to the application window specified in the WinCreateHelpInstance() function. Such messages originate from the main help window, as part of the window procedure supplied by Presentation Manager for that window.
HM_INFORM Message
This message is passed to the application when the user selects a hypertext or hypergraphic item in a help window, for which the reftype=inform attribute has been specified. The first parameter of the HM_INFORM message contains the identifier specified by the res= attribute in the hypertext or hypergraphic link definition.
An application window typically processes the HM_INFORM message by examining the identifier in the first message parameter, and dispatching a message of the appropriate class to itself or another application window, in order to initiate the action requested by the HM_INFORM message.
HM_ERROR
This message is passed to the application when an error occurs during a user interaction with a help window. This message allows the application to display its own error message in such cases, thereby providing a consistent appearance for error messages. The first parameter of the message indicates the reason for the error. These reasons are documented in the IBM OS/2 Version 2.0 Information Presentation Reference.
An application typically processes the HM_ERROR message by displaying an appropriate message box and returning zero to Presentation Manager. If the application does not process the message, Presentation Manager takes no action.
HM_EXT_HELP_UNDEFINED
This message indicates that the user selected the "Extended help" item on the "Help" pulldown menu, and that no such help panel was defined for the active application window.
An application may process this message in one of three ways:
If the application does not process this message, no panel is displayed and the user's request is simply ignored.
HM_SUBITEM_NOT_FOUND
This message indicates that the user issued a help request on an item for which no help panel is defined in the current help table. The application may process this message in one of three ways, as described in HM_EXT_HELP_UNDEFINED above. The application should then return TRUE to Presentation Manager.
If the application does not process this message, the extended help panel for the currently active window is displayed by IPF.