Is there way to prevent a Mac from going to sleep programmatically using Objective-C? The I/O kit fundamentals section on Apple\'s dev site tells me that a driver gets notif
Apple's Q&A1340 replaces Q&A1160. The latest Q&A answers the question "Q: How can my application get notified when the computer is going to sleep or waking from sleep? How do I prevent sleep?"
Listing 2 of Q&A1340:
#import <IOKit/pwr_mgt/IOPMLib.h>
// kIOPMAssertionTypeNoDisplaySleep prevents display sleep,
// kIOPMAssertionTypeNoIdleSleep prevents idle sleep
//reasonForActivity is a descriptive string used by the system whenever it needs
// to tell the user why the system is not sleeping. For example,
// "Mail Compacting Mailboxes" would be a useful string.
// NOTE: IOPMAssertionCreateWithName limits the string to 128 characters.
CFStringRef* reasonForActivity= CFSTR("Describe Activity Type");
IOPMAssertionID assertionID;
IOReturn success = IOPMAssertionCreateWithName(kIOPMAssertionTypeNoDisplaySleep,
kIOPMAssertionLevelOn, reasonForActivity, &assertionID);
if (success == kIOReturnSuccess)
{
//Add the work you need to do without
// the system sleeping here.
success = IOPMAssertionRelease(assertionID);
//The system will be able to sleep again.
}
Note that you can only stop idle time sleep, not sleep triggered by the user.
For applications supporting Mac OS X 10.6 and later, use the new IOPMAssertion family of functions. These functions allow other applications and utilities to see your application's desire not to sleep; this is critical to working seamlessly with third party power management software.
Here is the official Apple documentation (including code snippet):
Technical Q&A QA1340 - How to I prevent sleep?
Quote: Preventing sleep using I/O Kit in Mac OS X 10.6 Snow Leopard:
#import <IOKit/pwr_mgt/IOPMLib.h>
// kIOPMAssertionTypeNoDisplaySleep prevents display sleep,
// kIOPMAssertionTypeNoIdleSleep prevents idle sleep
// reasonForActivity is a descriptive string used by the system whenever it needs
// to tell the user why the system is not sleeping. For example,
// "Mail Compacting Mailboxes" would be a useful string.
// NOTE: IOPMAssertionCreateWithName limits the string to 128 characters.
CFStringRef* reasonForActivity= CFSTR("Describe Activity Type");
IOPMAssertionID assertionID;
IOReturn success = IOPMAssertionCreateWithName(kIOPMAssertionTypeNoDisplaySleep,
kIOPMAssertionLevelOn, reasonForActivity, &assertionID);
if (success == kIOReturnSuccess)
{
// Add the work you need to do without
// the system sleeping here.
success = IOPMAssertionRelease(assertionID);
// The system will be able to sleep again.
}
For older OSX version, check the following:
Technical Q&A QA1160 - How can I prevent system sleep while my application is running?
Quote: Example usage of UpdateSystemActivity (the canonical way for < 10.6)
#include <CoreServices/CoreServices.h>
void
MyTimerCallback(CFRunLoopTimerRef timer, void *info)
{
UpdateSystemActivity(OverallAct);
}
int
main (int argc, const char * argv[])
{
CFRunLoopTimerRef timer;
CFRunLoopTimerContext context = { 0, NULL, NULL, NULL, NULL };
timer = CFRunLoopTimerCreate(NULL, CFAbsoluteTimeGetCurrent(), 30, 0, 0, MyTimerCallback, &context);
if (timer != NULL) {
CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, kCFRunLoopCommonModes);
}
/* Start the run loop to receive timer callbacks. You don't need to
call this if you already have a Carbon or Cocoa EventLoop running. */
CFRunLoopRun();
CFRunLoopTimerInvalidate(timer);
CFRelease(timer);
return (0);
}
Just create an NSTimer that fires a function with this
UpdateSystemActivity(OverallAct);
I'm pretty sure that that's exactly what Caffeine does.