SystemControlA

Method for selectively disabling OS features. (V40)

SystemControl

varargs stub for SystemControlA().

This function is used to alter the operation of the system. Some of the alterations involve controlling what are normally regarded as system resources. In order to minimize confusion only one task is allowed to control any part of the system resources. This prevents the possiblity of two tasks fighting, each controlling a part of the system. If a tag is identified as task exclusive, it means that only one task can hold (set to TRUE) that tag. If another task attempts to set the same tag to TRUE, the call to SystemControl() will fail.

It is important to remember that SystemControl() can fail.

This is a low level function and certain tags do not fit the normal Amiga multitasking model.

tagList

pointer to an array of tags listing the features of the system to be enabled/disabled.

SCON_TakeOverSys (BOOL)

If TRUE Takes over the CPU to ensure that a program gets every ounce of CPU time (with the exception of crucial interrupts). When in this mode, the CPU will belong completely to the program. Task switching will be disabled and the program will get all CPU cycles. This means any calls to the OS that involve multitasking in some way will not execute correctly. Other tasks will not run until this tag is used with FALSE. However, during a Wait() on a signal, multitasking will automatically be turned back on until the signal is received. Once received, multitasking will again be disabled and the CPU will be exclusive to the owning program.

If FALSE relinquishes the CPU and reenables multitasking. This tag is task exculsive. This tag nests. A task may take over the CPU several times before relinquishing it.

SCON_KillReq (BOOL)

If TRUE Disables system requesters. These are the reasons for NOT disabling system requesters:

1. No calls in the program will cause a system requester.
   
   
2. The only thing that could cause a requester to appear is the lack of a CD in the drive and SCON_CDReboot is set to CDReboot_On, therefore a requester can't appear.
   
   
3. The only disk I/O is via a CD with SCON_CDReboot set to CDReboot_On and/or nonvolatile.library.
   
   

When requesters should not be disabled.

GAME PROGRAMS:

No DOS calls are used after loading; or SCON_CDReboot is CDReboot_On; and nonvolatile.library is used for loading and saving user data.

This fits the above case since; After loading either DOS calls are not used fitting reason 1, or the game is accessing the CD and has SCON_CDReboot set to CDReboot_On fitting reason 2. The game accesses high scores, game position, etc through nonvolatile.library, fitting reason 3.

If FALSE enables requesters for the program.

This tag nests. Tasks may disable requesters several times before enabling them. However, there must be a matching number of calls.

SCON_CDReboot (ULONG)

Can take either of the following values:

CDReboot_On

Ejecting the CD will cause a reboot of the system. Use this only if the program cannot deal with error conditions.

CDReboot_Off

Ejecting the CD will not cause a reboot of the system. Use this if the program needs to insert CDs while running.

CDReboot_Default

Restore the default reboot behavior for this system. This should be used upon exit, if this tag had been used to change the reboot behaviour. For the CD32 this value is synonomous with CDReboot_On. For Amiga computers this value is synonomous with CDReboot_Off.

Note that the default reboot behavior differs depending on the platform. If a program requires a specific behavior it must use this function to set the behavior. For example, a CD audio mixer would use this tag with the data CDReboot_Off. This will allow the changing of audio CDs on the game machine as well as Amiga computers.

If, however, there is no error detection code at all this tag should be used with the data CDReboot_On.

It is hoped that no program will require CDReboot_On. If all programs check for error condition and recover gracefully such a call should never be necessary. With the default behavior the CD32 will always reset on disk ejects, and programs run from Amiga computers will not reset. Thus, leaving the default will increase the market for a program to include both types of platforms.

This tag does not nest.

SCON_StopInput (BOOL)

When TRUE, stops input.device from using any CPU cycles. Also prevents input.device from passing along any events from either the keyboard and/or port 0.

This tag is task exclusive. This tag is NOT reversible. Attempting to reverse will result in confused/garbled input events.

SCON_AddCreateKeys (ULONG)

Starts creating rawkey codes for the joystick/game controller on the given unit. The unit value is checked for validity and must be either 0 or 1. Each different unit used results in some code added to the VBlank interrupt chain. This tag nests. The tag SCON_RemCreateKeys is used to undo this tag. Tasks may create rawkey codes several times before stopping them.

Note that when operating in an Intuition window, the controller's blue button is the equivilent of the mouse menu button. Therefore, Intuition will be capturing most blue button events. If notificiation of these events is important, review the documentation for WFLG_RMBTRAP in the intuition.library/OpenWindow() autodoc.

SCON_RemCreateKeys (ULONG)

stops rawkey codes for the joystick/game controller on the given unit. The unit value is checked for validity and must be either 0 or 1.

failTag

zero if all tags succeeded. A non-zero return indicates a tag that has failed. It is possible that other tags may fail as well.

If any tag fails there will be no change in the system due to other tags.

<libraries/lowlevel.h>