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PONo, really. What is the proper way to handle keyboard input in a game using Cocoa?
 

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  1. PONo, really. What is the proper way to handle keyboard input in a game using Cocoa?
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    <p>Let's say you're creating a game for Mac OS X. In fact, let's say you're creating Quake, only it's 2011 and you'd prefer to only use modern, non-deprecated frameworks.</p> <p>You want your game to be notified when the user presses (or releases) a key, <em>any key</em>, on the keyboard. This includes modifer keys, like shift and control. <strong>Edited to add:</strong> Also, you want to know if the left or right version of a modifier key was pressed.</p> <p>You also want your game to have a config screen, where the user can inspect and modify the keyboard config. It should contain things like:</p> <ul> <li>Move forward: W</li> <li>Jump: SPACE</li> <li>Fire: LCTRL</li> </ul> <p>What do you do? I've been trying to find a <em>good</em> answer to this for a day or so now, but haven't succeeded.</p> <p>This is what I've came up with:</p> <ul> <li>Subclass NSResponder, implement keyUp: and keyDown:, like in <a href="https://stackoverflow.com/questions/275088/how-do-i-collect-key-input-in-a-video-game-style-cocoa-app/275113">this answer</a>. A problem with this approach, is that keyUp: and keyDown: won't get called when the user presses only a modifier key. To work around that, you can implement flagsChanged:, but that feels like a hack.</li> <li>Use a <a href="http://developer.apple.com/library/mac/documentation/Carbon/Reference/QuartzEventServicesRef/Reference/reference.html#//apple_ref/c/func/CGEventTapCreate" rel="nofollow noreferrer">Quartz Event Tap</a>. This only works if the app runs as root, or the user has enabled access for assistive devices. Also, modifier key events still do not count as regular key events.</li> <li>Use the HIToolbox. There is virtually no mention at all of it in the 10.6 developer docs. It appears to be very, very deprecated.</li> </ul> <p>So, what's the proper way to do this? This really feels like a problem that should have a well-known, well-documented solution. It's not like games are incredibly niche.</p>
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    1. COFWIW, I don’t think `-flagsChanged:` or `NSFlagsChangedMask` is a hack. It is the documented way of being notified of changes in modifier keys like Control.
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    2. COI didn't mean to say that flagsChanged: is a hack, but rather that using it *for this purpose* feels like a hack. If you're writing, say, a text editor, treating modifier key events differently is a great idea! However, if you want to know which key was just pressed, no matter what kind of key that may be, flagsChanged: does not seem like a good fit to me. Sure, you could store the value of [event modifierFlags] and diff against that -- it could be done -- but it's enough of a kludge that I feel there should a better, more straightforward way. Is there?
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    3. COI don’t think there is another way. As far as I can tell, Cocoa follows the reasoning you’ve described: in most cases, modifier keys aren’t relevant by themselves alone. That said, you could abstract `-keyDown:`, `-keyUp:`, `-flagsChanged:` into one or two methods that effectively do the actions in your application — those three methods would simply filter events and call your custom method(s).
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