# CGGetEventTapList(_:_:_:) Gets a list of currently installed event taps. ``` func CGGetEventTapList(_ maxNumberOfTaps: UInt32, _ tapList: UnsafeMutablePointer?, _ eventTapCount: UnsafeMutablePointer?) -> 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](/documentation/CoreGraphics/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. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)