当窗口焦点不对准时，WndProc不起作用

Question

I wanted to use SendMessage to a WM_COPYDATA from a global hook dll , and then send it to my Mainwindow WndProc . WndProc only listens to procs when it is the active screen, and does not receive the message being sent by the dll when it is out of focus.

Is this a limitation of WndProc? are there better alternatives to this?

Answer 1

I found out the problem to be the HWND being used on my SendMessage call. It has to be shared by all dlls like so:

#pragma data_seg("Shared")
//our hook handle which will be returned by calling SetWindowsHookEx function
HHOOK hkKey = NULL;
HINSTANCE hInstHookDll = NULL;  //our global variable to store the instance of our DLL
HWND pHWnd = NULL; // global variable to store the mainwindow handle
#pragma data_seg() //end of our data segment

#pragma comment(linker,"/section:Shared,rws")
// Tell the compiler that Shared section can be read,write and shared

__declspec(dllexport) LRESULT CALLBACK procCharMsg(int nCode, WPARAM wParam, LPARAM lParam)
//this is the hook procedure
{
    //a pointer to hold the MSG structure that is passed as lParam
    MSG* msg;
    //to hold the character passed in the MSG structure's wParam
    char charCode;
    if (nCode >= 0 && nCode == HC_ACTION)
        //if nCode is less than 0 or nCode
        //is not HC_ACTION we will call CallNextHookEx
    {
        //lParam contains pointer to MSG structure.
        msg = (MSG*)lParam;
        if (msg->message == WM_CHAR)
            //we handle only WM_CHAR messages
        {
            SendMessage(pHWnd, WM_CHAR, (WPARAM)msg->message, (LPARAM)0); // This should now work globally
        }
    }
    return CallNextHookEx(hkKey, nCode, wParam, lParam);
}

// called by main app to establish a pointer of itself to the dlls
extern "C" __declspec(dllexport) int SetParentHandle(HWND hWnd) {
    pHWnd = hWnd;
    if (pHWnd == NULL) {
        return 0;
    }

    return 1;
}

I should have posted my code along with the problem, since little things are always pretty hard to spot alone.