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-File12.1.10  Cooperation between MagiC and the MacOS                   TOS

MagiC Mac hooks itself directly into all interrupt vectors that the 
Macintosh uses. If MagiC is running and a hardware interrupt occurs, 
MagiC Mac switches the MMU back into the normal Macintosh-mode. At the 
end of the IntrRoutine one will be switched back into the Atari-mode 
and the programs running under MagiC will continue. As long as the 
Mac-mode is active, MagiC Mac does not meddle further with the Intr- 
processing, but does so only when the Atari-mode is active.

Whenever a switch is made from the Mac-mode back to the Atari-mode, a 
check is made whether a given amount of time has passed (measured in 
ticks; a tick is around 1/60s), in order to then perform periodic 
tasks. These tasks are called Mac-tasks here.

Mac-tasks perform the following, amongst others:

   . Poll the Mac events (functions GetOSEvent or WaitNextEvent)

   . Evaluate [Command]-[Q] and [Command]-[W]

   . Evaluate external Apple events, e.g. Suspend/Resume (switch MagiC 
     Mac into the background) and terminated externals

   . Cede CPU time to other Mac applications (with WaitNextEvent)

The decision whether to use GetOSEvent or WaitNextEvent (WNE) for 
polling the events can be set via 'Preferences' and also by a cookie 
function. Only if WNE is used will CPU time be allocated to other Mac 
applications as well.

Mac-tasks can be executed only if it is certain that no other MacOS 
function is being processed at the time, since the MacOS is not 
reentrant. Mac-tasks are therefore performed only if all of the 
following conditions apply:

   . After the interruption (an interrupt or a modeAtari call) the 
     Atari-mode will be active and the interrupt-level mask is zero, 
     i.e. there is no other interrupt being handled (to ensure this, 
     Intr-handlers that switch from Mac-mode into the Atari-mode have 
     to use intrLock correctly, see below)

   . No routine in the Mac-context is being executed at the time 
     (callMacContext)

   . MagiC Mac is not in the process of terminating itself