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I have an issue with WindowsHookEx in vb.net. If my pc is overloaded especially from 3D rendering, windows automatically disconnects my keyboard hook and my hotkeys stop working. I searched around and it seems that there is no way to detect whether a hook is active or disconnected. So I tried this method presented by "moodforaday" Is it possible to detect when a low-level keyboard hook has been automatically disconnected by Windows? hook-has-been-automatically-d

He states that using GetLastInputInfo periodically and store GetLastInputInfo to another variable when a key is used and compare the results. If the tick is much newer than your older variable then its likely that its disconnected. Its a great method but the ticks can go up from other things like the mouse. In my Hook class there is no Mouse hook therefore I cannot store a variable of the tick count when the mouse is moved. So now I ended up having it create a new instance of the hook class and hook again. It checks every second if the stored tick is older than new tick by 10000 ticks.

Is it alright to keep creating new instances of Hooks? It will keep Hooking/Unhooking constantly and I'm wondering if that is going to be a problem for Windows.

Also if anyone has another method to detect if a hook is disconnected please let me know would fix this whole hassle.

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Zakukashi
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  • Hmm, don't do that. Just bump up the timeout value if this is a structural problem on the machine. HKEY_CURRENT_USER\Control Panel\Desktop\LowLevelHooksTimeout value. – Hans Passant Jun 25 '12 at 12:35
  • I cannot, this will be installed on other client machines. – Zakukashi Jun 25 '12 at 12:52
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    Then it sounds like it is a problem in your program. Never let the UI thread go dead for more than a second. It should be easy to recognize, Windows replaces your main window with a ghost window that says "Not responding" after 3 seconds. Solve that problem and the losing the hook is automatically solved as well. – Hans Passant Jun 25 '12 at 12:55
  • What do you mean dead? when it goes into Not Responding mode? – Zakukashi Jun 25 '12 at 14:32

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Do your 3D rendering in a background thread. Use Control.Invoke only for code where you directly access UI controls.

Alternately, you could split the rendering into very small pieces and post them to yourself as messages, to be handled on the main thread. This way you will be able to handle both internal and external messages.

In both cases, your application will be responding in a timely fashion, Windows will have no reason to consider it non-responding, and your keyboard shortcuts will stay in place.

Jirka Hanika
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