Topic       : TOS - das Betriebssystem
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View Ref-File15.11.4  The VIEW_XXX messages                                     TOS

This is a description of the View protocol messages. In contrast to to 
the VA_START and XAcc messages, these messages provide more refined 
control of what happens to the viewed file.

Please remember that these messages may be used if, and only if, the 
strings '2View' or 'NView' are found in the viewer's Extended XAcc 
name as described above.

In general, there are four messages; VIEW_FILE, which may be sent to 
the viewer, and VIEW_FAILED, VIEW_OPEN and VIEW_CLOSED that are used 
to inform the application of what has happened to its file.

The viewer is expected to answer every VIEW_FILE message it receives. 
At the very least, it should send a VIEW_FAILED(VIEWERR_ERROR) message 
(see below). However, if the viewer does not send an answer and the 
application expects one, the application should recover by using a 
timeout value (ten seconds should be sufficient).

It is possible for the viewer to send other messages (for example 
AV_ACCWINDOPEN) before answering the VIEW_FILE message!

Note: All strings are NULL-terminated (as in the 'C' programming 
language).