catching keys when lost focus

This is a discussion on catching keys when lost focus within the Windows Programming forums, part of the Platform Specific Boards category; Hi! Is it possible to catch users key presses from a MFC app, even when its window has lost the ...

  1. #1
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    catching keys when lost focus

    Hi!
    Is it possible to catch users key presses from a MFC app, even when its window has lost the focus?
    For example, a MFC app is running in the background, and the user types something in notepad- can the MFC program read what user types? If itís possible, please tell me how to do it.
    Thanks.

  2. #2
    Software Developer jverkoey's Avatar
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    I believe the best way would be to use asynchronous key checking using the function:
    GetAsyncKeyState

    macro:
    Code:
     #define KEY_DOWN(vk_code)	((GetAsyncKeyState((vk_code))&0x8000 ? 1:0))
    Probably not the best way to do it, as you'll need to have a loop sitting in the background checking the state every few milliseconds. I'd suggest putting Sleep function in there so the program doesn't hog the cpu.

    so you might do something like this:

    Code:
     while(isGoing)
     {
     	 Sleep(100);
     	 if(KEY_DOWN(VK_ESCAPE))
     	 {
     			// do stuff!
     	 }
     }
    or something like that

    -hope that helps

  3. #3
    mustang benny bennyandthejets's Avatar
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    I'm thinking you could handle the WM_KILLFOCUS message, and hook into the window that took the focus from you, and basically follow the focus around wherever it goes. It's not too elegant, but it sure is kinda cool.
    benforbes@optusnet.com.au
    Microsoft Visual Studio .NET 2003 Enterprise Architect
    Windows XP Pro

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