getting the HWND for my own application in C

Question

since I couldn't find an answer to this question I researched a bit further into the MSDN and I found isChild(). It might give me the answer to that other question.

Now, in order to use isChild() I need to pass the HWND of the parent application that I want to check, in this case my own application. How do I get the HWND of my own application?

I don't know the title since it changes constantly so I can't use FindWindow().

Thanks

Edit:

Since it's not clear, I'll add more information: I am not creating a window. I don't have access to the creation of a window. My code is a piece of code that gets compiled together with whatever application the other programmer is coding and I have no access to how the window is created, the title or any other information. So, how do I get the HWND to the "WINDOW" of the application I am running?

Answer 1

Can't you just hold onto the handle returned from CreateWindow? If not, why not?

Answer 2

This is old for me, but IIRC you should receive the HWND as a parameter in the window proc. You can save it in a global variable somewhere in the beginning.

Answer 3

Your application doesn't have a HWND. The window does. An application may have no windows or it may have many, so there is no general function to "Get the application's HWND".

The obvious solution is just to hold on to the handle when you get it. When you create the window, a HWND is returned. Store that.

Answer 4

What about your windows class name? Is it always different on window creation? If not you could still you FindWindow().

Answer 5

Use GetTopWindow() and GetNextWindow() to walk through windows z-order.

However, don't think it is necessary, but you can use GetCurrentProcessId() and GetWindowThreadProcessId(), may be something like following will help you:

HWND FindMyTopMostWindow()
{
    DWORD dwProcID = GetCurrentProcessId();
    HWND hWnd = GetTopWindow(GetDesktopWindow());
    while(hWnd)
    {
        DWORD dwWndProcID = 0;
        GetWindowThreadProcessId(hWnd, &dwWndProcID);
        if(dwWndProcID == dwProcID)
            return hWnd;            
        hWnd = GetNextWindow(hWnd, GW_HWNDNEXT);
    }
    return NULL;
 }

Answer 6

As others have already pointed out

• In general, an application can have zero or multiple top-level windows.
• If you're creating the window yourself you can just remember the HWND somewhere.

But maybe your code is in a DLL, so you didn't actually create the top-level window yourself. So what to do?

I would suggest the following:

• Use EnumWindows to enumerate all top-level windows.
• Use GetWindowLongPtr to get the HINSTANCE for each top-level window. Compare this against the HINSTANCE of the application, which you can get using GetModuleHandle(NULL). If they're identical, you've found your main window.

Edit: Here is some code. Turns out you also have to use IsWindowVisible because there seem to be quite a few invisible "helper" windows.

HWND hwndMain;

BOOL CALLBACK EnumWindowProc(HWND hwnd, LPARAM lParam)
{
    HINSTANCE hinst=(HINSTANCE)GetModuleHandle(NULL);

    if((HINSTANCE)GetWindowLongPtr(hwnd, GWL_HINSTANCE)==hinst &&
        IsWindowVisible(hwnd))
    {
        hwndMain=hwnd;
        return FALSE;
    }
    else
        return TRUE;
}

Then in the place you want to find the window:

hwndMain=NULL;
EnumWindows(EnumWindowProc, 0);

And after this, hwndMain should contain the handle of the window, or NULL if none exists.

Using EnumWindows is a bit burdensome but is recommended over calling GetWindow in a loop because, as MSDN notes: "An application that calls GetWindow to perform this task risks being caught in an infinite loop or referencing a handle to a window that has been destroyed."

Answer 7

Presumably your code gets called by main application code, otherwise what use is it? In which case I acnnot see why your code's API cannot include some way of informing you of the handle of the application's main window.

Answer 8

You can inject a DLL in a thread who appeal user32.dll http://msdn.microsoft.com/en-us/library/ms821625.aspx