Polling the keyboard in Cocoa

Question

My Cocoa application should react continuously to the state of the keys pressed by the user. To that end, I would like to poll the keyboard at fixed intervals, instead of relying on keyboard events. Is there any Cocoa API to achieve this? If not, what other options exist?

Answer 1

Don't poll the keyboard, just implement -keydown: in your App delegate class.

Answer 2

Polling is never such a great idea. You shouldn't have to do that in most cases.

There is 2 API you may be interested for:

• Quartz Event Taps https://developer.apple.com/library/mac/#documentation/Carbon/Reference/QuartzEventServicesRef/Reference/reference.html

• IOKit HID API https://developer.apple.com/library/mac/#documentation/DeviceDrivers/Conceptual/HID/intro/intro.html#//apple_ref/doc/uid/TP40000970

Please note keyboard accesses may pose some security issues so the system may not allow you to read the keyboard state. Check the Accessibility settings (access to assistive devices).