Function

CGGetEventTapList(_:_:_:)

Gets a list of currently installed event taps.

Declaration

func CGGetEventTapList(_ maxNumberOfTaps: UInt32, _ tapList: UnsafeMutablePointer<CGEventTapInformation>?, _ eventTapCount: UnsafeMutablePointer<UInt32>?) -> CGError

Parameters

maxNumberOfTaps

The length of the array you provide in the tapList parameter.

tapList

An array of event tap information structures. You are responsible for allocating storage for the array. On return, your array contains a list of currently installed event taps. If you pass NULL in this parameter, the maxNumberOfTaps parameter is ignored, and the eventTapCount variable is filled in with the number of event taps that are currently installed.

eventTapCount

A pointer to a CGTableCount variable. On return, the variable contains actual number of array elements filled in.

Return Value

A result code. See the result codes described in Quartz Display Services.

Discussion

Each call to this function has the side effect of resetting the minimum and maximum latency values in the tapList parameter to the corresponding average values. Values reported in these fields reflect the minimum and maximum values seen since the preceding call, or the instantiation of the tap. This allows a monitoring tool to evaluate the best and worst case latency over time and under various operating conditions.