Topic       : TOS - The Operating System
Author      : 
Version     : tos.hyp (December 19, 2008)
Subject     : Programmieren/Atari
Nodes       : 3010
Index Size  : 93790
HCP-Version : 5
Compiled on : Atari
@charset    : atarist
@lang       : 
@default    : Title
@help       : 
@options    : +g -i -s +x +zz -t4
@width      : 70
View Ref-File12.1.11.5  callMacContext                                          TOS

This serves to produce the required Macintosh environment for calling 
any MacOS routines. The routine must be called in Mac-mode and in 
supervisor-mode and not from an interrupt.

For this one should pass on the stack the address of the routine that 
is to be called as a subroutine in the Mac context. The normal user 
stack of MagiC Mac is used for the called routine; in addition the 
register a5 is loaded with macA5 and if virtual memory is active, a 
switch is made to user-mode. As this function alters the stack, it is 
not possible to pass parameters via the stack. The registers d0-d2/ 
a0/a1/a5/a7 are altered both at the call and also at the return of the 
subroutine (although a5/a7 after return from 'callMacContext' have the 
same values as before the call). The other registers are not altered 
and can be used for parameter passing and returns.

The execution of this subroutine implicitly brings calls of intrLock 
and intrUnlock with it, meaning that during this no Mac-tasks will be 
processed, even if one switches into Atari-mode occasionally. To allow 
processing of Mac-tasks despite of this, one can call the function 
'giveTimeToMac'.

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