Topic       : TOS - The Operating System
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Version     : tos.hyp (December 19, 2008)
Subject     : Programmieren/Atari
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Compiled on : Atari
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View Ref-File13.8.29.5  ID4-Server                                              TOS

Important: If ID4 is to function with memory protection the GLOBAL- 
flag should be set in the ID4-Server program header!

If a Client would like to embed an object, the Server will receive an 
OLGA_EMBED message from the Manager, to which it must reply with 
OLGA_EMBEDDED.

To draw, the Client calls CBDraw-Callback. During processing of the 
Callback the Server as a rule may not make any AES calls (it closes 
wind_update!). The Server must also not adjust the palette. If the 
Server makes changes to an object, it can immediately send an 
OLGA_INPLACEUPDATE message to the Client so that it can perform an 
immediate update.

To avoid passing an undefined pointer on terminating a Server or 
closing of documents, the Server must proceed as follows:

For each object, the Server tests whether OLGAObjectInfo.CBLock<=0. If 
this is the case, the Server first sets CBLock to -16000, then CBDraw 
to NULL.

Everything must be enclosed in an evnt_timer loop and repeated until 
no more objects are assigned. Only then may the Server terminate or 
close the document window.

Once the Server has set all corresponding CBDraw pointers to NULL, an 
OLGA_UNEMBED message must be sent to the Client. On receipt of this 
message the Client can mark the objects as 'invalid', for example by 
drawing a white rectangle crossed out by a red cross.

In order for a Server to determine if a Client is still using an 
embedded object, the Clients will call CBUNEMBED Callback to dissolve 
the connection. An ID4-Server should react the same way on receipt of 
OLGA_CLIENTTERMINATED.

In order to avoid any problems resulting from a Server crash, the 
Server should overwrite etv_critic, and by running this routine CBDraw 
will set all objects to NULL and CBLock to -16000.

This function was added to OLGA in Rev 1.2 (1996-11-20).

See also: OLGA protocol   OLGA_EMBEDDED   OLGA_UNEMBED 
OLGA_INPLACEUPDATE   CBDraw   CBUnembed