Display(4)

NAME
Display request - 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:

    When the display operation can be deemed completed What user gesture signals the completion of the display 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 register 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. The notation is the same as in the .

To display a PostScript document contained in a file, the application can send a Display request with the file attribute 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:

    The file that was alleged to contain the document does not exist.
    The in-mode contents argument had no value and the file attribute of the message was not set.
    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.