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Now I've been trying to create a similar functionality as there is in Push-To-Talk voice chat applications, but so far I couldn't find any fitting solutions to this. I am not using MFC or CLR.

The problem is quite simple. My window should be usually out of focus (ie minimized etc), but I need to react to keypresses (basically, I don't even want to know if the button is being held down or not). Unfortunately, WM_KEYDOWN only works if the window has keyboard focus. I do know that for example Teamspeak uses DirectInput for this, but I'm also aware that it can definitely be done without it as well, which I'd highly prefer.

The only other solution that I could make work is polling with GetAsyncKeyState, but it looks like this is far from being a good solution either. If at all possible, I'd still prefer using Windows messages.

dialer
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2 Answers2

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The problem can be solved either with RegisterHotKey or with a global low-level keyboard hook.

RegisterHotKey (which Cody Gray suggested in the commends) is probably the more suitable choice here.

Jon
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  • A low-level keyboard hook is one possible option, but certainly overkill for catching a few global hotkeys. A better solution is the [`RegisterHotKey` function](http://msdn.microsoft.com/en-us/library/ms646309.aspx). – Cody Gray - on strike Mar 10 '11 at 12:33
  • Okay now I feel a bit dumb for not guessing the name of the RegisterHotKey function; the API is too intuitive for me. Thanks to both of you. – dialer Mar 10 '11 at 13:20
  • @dialer: No reason to feel bad. I answered a question a few days ago suggesting a global hook when `RegisterHotKey` would have worked just fine. Thankfully, someone else corrected me (part of what makes this site wonderful). It's not that the Windows API is unintuitive (at least, it isn't to me), it's just that it's so large you forget about things if you don't use them all the time! Glad we could help. – Cody Gray - on strike Mar 10 '11 at 13:32
  • @Cody: Thanks for reminding me about `RegisterHotKey`. That's exactly what happened to me here: forgotten about it, and happened to use a keyboard hook more recently... – Jon Mar 10 '11 at 14:06
  • if another application uses the same hot key which i am going to use then RegisterHotKey would fail. won't it? in this case the alternate is to use global keyboard hook. is it not? – Jayapal Chandran Dec 11 '14 at 11:15
  • @JayapalChandran: Yes and yes -- I'm not 100% sure, but pretty much. – Jon Dec 11 '14 at 11:33
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I agree with Jon. Use user32.dll and the RegisterHotKey function. Very useful example code is located at: https://www.codeproject.com/kb/cs/kiosk_cs.aspx?display=print

If, like I initially was, the code looks like complete gibberish and you have no idea what to do, watch the tutorials: https://www.youtube.com/watch?v=qQWqGOaZiFI They're very useful!

If you try to register a system hotkey: However note that the code from the first link would return an error, depending on what system hotkey you try to register. My question on this which highlights the issue: How do you disable system hotkeys in user32.dll? (currently unsolved). There is also a code edit there that will fix one of the errors you will get, if you try to override system hotkeys: 

[DllImport("user32.dll", SetLastError = true)]

I did manage to block the Windows + E hotkey, but others like Alt + F4 and Home + Right did not get disabled and would return an error.

This should not be an issue for you if you do not try to override a system hotkey. I would however suggest you use the code below to diagnose your code, if one of your hotkeys fails to register.

Marshal.GetLastWin32Error()

^ Full context on that line of code is in the first link!

Community
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Rehaan
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