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NAME
     Display - display a document

SYNOPSIS
     [file] Display(in mediaType contents
                    [in title docName]);

DESCRIPTION
     The Display request causes the handler to  display  (present
     or  manifest) a document to the user.  For example, an audio
     manipulation utility would  be  said  to  ``display''  audio
     documents when it plays them.

     The handler must decide issues such as:

        o  When the display operation can be deemed completed

        o  What  user  gesture  signals  the  completion  of  the
           display

        o  What the handling tool should  do  with  itself  after
           replying

     The contents argument is the contents of the  document.   If
     this  argument  is  unset  (in  other  words, has a value of
     (char *)0), then the contents of the  document  are  in  the
     file  named  in the message's file attribute.  The data type
     (mediaType) of  the  contents  argument  should  be  string,
     unless  nulls  are  valid  in the given media type, in which
     case the data type must be bytes.

     The docName argument contains the name of the document.   If
     the  docName  argument  is  absent and the file attribute is
     set, the file name is considered to  be  the  title  of  the
     document.   This  string  would be suitable for display in a
     window title bar, for example.

APPLICATION USAGE
     The ttmedia_ptype_declare(3) function can be used to  regis-
     ter for, and help process, this message.

     This message can be sent with the ttmedia_load(3) function.

     When the document to be displayed is read-only  or  unlikely
     to  be  modified  the  Display  message  is  frequently used
     instead of the Edit message.

EXAMPLES
     To display a PostScript document, the application can send a
     Display  request  with  a  first  argument  whose  vtype  is
     PostScript, and whose value is a vector of bytes such as:

          %!\n/inch {72 mul} def...

     The \n in the example represents the newline character.

     To display a PostScript document contained in  a  file,  the
     application  can send a Display request with the file attri-
     bute set to that file and with an unset first argument whose
     vtype is PostScript.

ERRORS
     The ToolTalk service may return one of the following  errors
     in processing the Display request:

        TT_DESKTOP_ENOENT
              The file that was alleged to contain  the  document
              does not exist.

        TT_DESKTOP_ENODATA
              The in-mode contents argument had no value and  the
              file attribute of the message was not set.

        TT_MEDIA_ERR_FORMAT
              The document is not a valid instance of  the  media
              type.

SEE ALSO
     ttmedia_ptype_declare(3), ttmedia_load(3); Intro, Deposit,
     Edit, Status requests.

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