Dynamic data formatting (DDF) allows you to incorporate text, bit maps, or metafiles in an IPF window at execution time. You can use the dynamic data formatting facility in conjunction with the dynamic data format tag (:ddf.). The :ddf. tag functions as a request by IPF to the application for the DDF data, and a set of DDF application programming interface calls that provide primitives for formatting text. The DDF calls also allow you to incorporate bit maps and metafiles dynamically, and to specify a hypertext or inform link from DDF data to non-DDF data.

IPF has no knowledge of the DDF data it displays, other than that a block of data has been provided to it by the application program. Therefore, DDF data cannot be searched or printed. In effect, DDF is a specific extension of application-controlled windows. When the :ddf. tag is encountered at execution time, IPF sends the HM_QUERY_DDF_DATA message to the application window procedure with which the current instance of help is associated. IPF sends the message either by a WinAssociateHelpInstance request or a HM_SET_OBJCOM_WINDOW message.