Replacement for deprecated NXOpenEventStatus? - objective-c

Question

I need to get the tracking speed of the mouse on OSX 10.13. I found this code on the internet but NXOpenEventStatus is deprecated (as is IOHIDGetAccelerationWithKey), is there an alternative way?
#include <stdio.h>
#include <IOKit/IOKitLib.h>
#include <IOKit/hidsystem/IOHIDLib.h>
#include <IOKit/hidsystem/IOHIDParameter.h>
#include <IOKit/hidsystem/event_status_driver.h>
int main()
{
kern_return_t kr;
double trackpadAcceleration, mouseAcceleration;
NXEventHandle h = 0;
h = NXOpenEventStatus();
if (h == nil)
return -1;
kr = IOHIDGetAccelerationWithKey( h, CFSTR(kIOHIDMouseAccelerationType), &mouseAcceleration);
return 0;
}

Answer 1

Since NXOpenEventStatus and IOHIDGetAccelerationWithKey are both part of the open-source IOKit distribution, you can look at how they're implemented. It turns out we can do what those functions do, using only non-deprecated functions.
To boil it down to the bare minimum, you can get a dictionary of the HID system's properties like this:
#import <Foundation/Foundation.h>
#import <IOKit/hidsystem/IOHIDLib.h>
int main(int argc, const char * argv[]) {
#autoreleasepool {
io_service_t service = IORegistryEntryFromPath(kIOMasterPortDefault, kIOServicePlane ":/IOResources/IOHIDSystem");
CFDictionaryRef parameters = IORegistryEntryCreateCFProperty(service, CFSTR(kIOHIDParametersKey), kCFAllocatorDefault, kNilOptions);
NSLog(#"%#", parameters);
IOObjectRelease(service);
}
return 0;
}
Output (for me on macOS 10.13.4):
2018-04-05 17:06:55.560590-0500 accel[11924:131983] {
ActuateDetents = 1;
Clicking = 0;
DragLock = 0;
Dragging = 0;
EjectDelay = 0;
FirstClickThreshold = 1;
ForceSuppressed = 0;
HIDClickSpace = (
5,
5
);
HIDClickTime = 500000000;
HIDDefaultParameters = 1;
HIDF12EjectDelay = 250;
HIDFKeyMode = 1;
HIDInitialKeyRepeat = 250000000;
HIDKeyRepeat = 33333333;
HIDKeyboardModifierMappingPairs = (
);
HIDMouseAcceleration = 98304;
HIDMouseKeysOptionToggles = 0;
HIDPointerAcceleration = 45056;
HIDPointerButtonMode = 2;
HIDScrollAcceleration = 20480;
HIDScrollZoomModifierMask = 262144;
HIDSlowKeysDelay = 0;
HIDStickyKeysDisabled = 0;
HIDStickyKeysOn = 0;
HIDStickyKeysShiftToggles = 0;
HIDTrackpadAcceleration = 57344;
HIDWaitCursorFrameInterval = 16666667;
JitterNoClick = 1;
JitterNoMove = 1;
MouseButtonDivision = 55;
MouseButtonMode = TwoButton;
MouseHorizontalScroll = 1;
MouseMomentumScroll = 1;
MouseOneFingerDoubleTapGesture = 0;
MouseTwoFingerDoubleTapGesture = 0;
MouseTwoFingerHorizSwipeGesture = 0;
MouseVerticalScroll = 1;
"OutsidezoneNoAction When Typing" = 1;
"PalmNoAction Permanent" = 1;
"PalmNoAction When Typing" = 1;
SecondClickThreshold = 1;
"Trackpad Jitter Milliseconds" = 192;
TrackpadCornerSecondaryClick = 0;
TrackpadFiveFingerPinchGesture = 0;
TrackpadFourFingerHorizSwipeGesture = 2;
TrackpadFourFingerPinchGesture = 0;
TrackpadFourFingerVertSwipeGesture = 0;
TrackpadHandResting = 1;
TrackpadHorizScroll = 1;
TrackpadMomentumScroll = 1;
TrackpadPinch = 1;
TrackpadRightClick = 1;
TrackpadRotate = 1;
TrackpadScroll = 1;
TrackpadThreeFingerDrag = 0;
TrackpadThreeFingerHorizSwipeGesture = 2;
TrackpadThreeFingerTapGesture = 0;
TrackpadThreeFingerVertSwipeGesture = 0;
TrackpadThreeFingersRightClick = 0;
TrackpadTwoFingerDoubleTapGesture = 1;
TrackpadTwoFingerFromRightEdgeSwipeGesture = 0;
TwofingerNoAction = 1;
USBMouseStopsTrackpad = 0;
"Use Panther Settings for W" = 0;
UserPreferences = 1;
version = 1;
}
Program ended with exit code: 0
The kIOHIDMouseAccelerationType constant has value HIDMouseAcceleration. I also see HIDPointerAcceleration and HIDTrackpadAcceleration in there. There are kIOHID... constants for those too.
Note also that IOHIDGetAccelerationWithKey divides the registry value by 65536 before returning it. IOHIDSetAccelerationWithKey performs the opposite transformation.