Legacy Document

Inside Macintosh: Processes

Chapter 4 - Vertical Retrace Manager / Vertical Retrace Manager Reference

Vertical Retrace Manager Routines / System-Based Installation and Removal Routines

VInstall

You can use the VInstall function to install a task record into the system-based vertical retrace queue.

FUNCTION VInstall (vblTaskPtr: QElemPtr): OSErr;

vblTaskPtr

A pointer to the task record to add to the queue.

DESCRIPTION

The VInstall function installs the VBL task record specified by the vblTaskPtr parameter in the system-based vertical retrace queue. The Vertical Retrace Manager executes the task at intervals determined by the task record's vblCount and vblPhase fields. The task must reset the value of the task record's vblCount field if you want the task to be executed again.

In current versions of system software, the Vertical Retrace Manager does not continue to execute tasks installed using the VInstall function when the application that installed them is switched out, unless the address in the vblAddr field of the task record points in the system partition.

ASSEMBLY-LANGUAGE INFORMATION

The registers on entry and exit for VInstall are

Registers on entry
A0	Pointer to the task record

Registers on exit
D0	Result code

RESULT CODES

noErr	0	No error
vTypErr	-2	Invalid qType value (must be ORD(vType))