WM_KEYDOWN and GetAsyncKeyState() for parent window

I have an application which displays files in a listview, and has several buttons to press for various functions.

I wish to capture the F5 key and the backspace key for the entire parent window, even when a child control has the focus. I can catch the two keys when the parent window has the focus and it works fine, but if a child window has the focus the main window procedure catches no such message.

I'm wondering which solution would be more efficient on memory and processing:
1) Subclassing all the child controls to catch the WM_KEYDOWN message
2) Creating a separate thread which loops GetAsyncKeyState() and see's the key press no matter what control has the focus.

Another alternative would be using a global keyboard hook, but that seems to be overdoing it, I know many anti-malware programs are set off by such actions.

Implementing solution 2 would be much easier, but I'm not sure if it would be frowned upon that I chose that over subclassing.

Have you tried building an accelerator table with these keys you want and directing it to your main window with TranslateAccelerator() in your message dispatcher?

Just check the MSG structure after TranslateMessage but before you foist it off on DispatchMessage

Quote:

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Originally Posted by CommonTater

Have you tried building an accelerator table with these keys you want and directing it to your main window with TranslateAccelerator() in your message dispatcher?

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I'm not familiar with using accelerator tables. However I just tried to implement one and have failed to make it work properly.

I'm following the procedure here: Using Keyboard Accelerators (Windows)

I've tried both loading the table from a resource and creating it at runtime, trying the F5 or F6 key. My message dispatcher is checking for keys with TranslateAccelerator(), and the callback is checking for the ID in WM_COMMAND under the low order word in wParam. I'm using Windows 7 Pro.

Maybe could you give me an example how you would use it?

And adeyblue: If you could be more specific about what I would be checking and doing with the result. Thanks.

For those wondering what the solution is:

Create a new function to call during the message loop:

Code:

---

int process_keydown(HWND hwnd, MSG* msg)
{
    if(msg->message == WM_KEYDOWN)
    {
        switch(msg->wParam)
        {
            case VK_F5:
                /* Do your stuff here */
                return 1;

            case VK_BACK:
                /* ... */
                return 1;
        }
    }

    return 0;
}

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And in the message loop:

Code:

---

while(GetMessage(&msg, NULL, 0, 0))
{
    if(!process_keydown(hwnd, &msg)) // check for any WM_KEYDOWN message
    {
          TranslateMessage(&msg);
          DispatchMessage(&msg);
    }
}

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Usually accelerator tables are processed like this...

Code:

---

while(GetMessage(&msg, NULL, 0, 0))
    {  if (!TranslateAccelerator(win,KeyBrd,&msg))
          if (!IsDialogMessage(win,&msg))
            { TranslateMessage(&msg);
              DispatchMessage(&msg); }

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You create them in your resources like this...

Code:

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HOTKEYS ACCELERATORS
{
  80, 1000, VIRTKEY
  VK_SPACE, 1001, VIRTKEY
  83, 1002, VIRTKEY
  VK_PRIOR, 1003, VIRTKEY
  VK_NEXT, 1004, VIRTKEY
  VK_LEFT, 1005, VIRTKEY
  VK_RIGHT, 1006, VIRTKEY
  VK_UP, 1007, VIRTKEY
  VK_DOWN, 1008, VIRTKEY
  49, 1009, VIRTKEY
  50, 1010, VIRTKEY
  51, 1011, VIRTKEY
  52, 1012, VIRTKEY
  VK_RETURN, 1013, VIRTKEY
  84, 1014, VIRTKEY
  88, 1015, VIRTKEY
}

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That is ... KEY, CMD, FLAGS...

Of course you have to load the accelerator table on startup...

Code:

---

HACCEL KeyBrd; 

// start accelerators
KeyBrd = LoadAccelerators(PgmInst,"HOTKEYS");

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From there... it should work...

From the example... Pressing the Space bar should result in a WM_COMMAND message with 1001 in the low word of WPARAM, sent to the window specified in TranslateAccelerators().