Presentation Modules

Generating a Graphic Object

Generally, a new platform has a new implementation of the hypertext object. A GUI client must overwrite the graphic object modules in the Library in order to take advantage of a more advanced user-interface. The graphic object as defined in the Library has two interfaces, depending on how much of the Library code the client wants to handle on its own:

SGML Level

If the client has its own HTML parser then the interface is between the client HTML parser and the Library SGML parser. The SGML parser is a general SGML parser which can be setup with a specific DTD and it feeds the HTML parser with structured data. In this case, you will be emulating the HTML module, and generating a hypertext object from the structured stream. The actual structured stream definition is in the SGML module.

HTML Level

If the client wants to use the HTML parser in the Library then this is the second interface to the Library. The hypertext object is parsed and the communication with the client is based on a set of call-back functions in the HTML parser. The call-back functions are all defined as prototypes in the HText module but the client must provide the actual code that defines the presentation method used for a specific HTML tag. If you wish to maintain the structure of the SGML file within your object, then the SGML interface will be a better place to connect your code.