Win32 GUI : failing to create win32 GUI dialog

Question

i'm trying to create a simple dll which has a .rc file with simple dialogbox and listbox within it. i have created the resource by the help of visual studio and by use of drag and drop the controls. i have exposed a function which is intern calls DialogBox() API.

I'm dynamically loading the dll from sample windows application and calling the exposed function. dialog box creation failing with error code 126

could any one help me why it is behaving like this !?

Here is the code:

INT_PTR CALLBACK WndProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch(uMsg)
    {

    case WM_INITDIALOG:
        {
               InitCommonControls();
               PopulateList(hwndDlg);
               return TRUE;
        }
    case WM_COMMAND:
        {
          switch(wParam)
          {
          case IDOK:
              SaveSelectedItem(hwndDlg);
               EndDialog(hwndDlg,0);    
               return TRUE;
         case IDCANCEL:
               EndDialog(hwndDlg, 0);
               return TRUE;

          }

        }   
    default:
        DefWindowProc(hwndDlg, uMsg, wParam, lParam);

    }
}
HINSTANCE gInstance;

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
               LPSTR lpCmdLine, int nCmdShow) 
{
DialogBox(gInstance, MAKEINTRESOURCE(IDD_DIALOG), hwnd, WndProc);

return TRUE;
}

126 means "module could not be found". My guess is that when you call DialogBox you are passing the HINSTANCE of your program instead of the HINSTANCE of the DLL. — Stuart, Oct 09 '13 at 00:34
DialogBox(gInstance, MAKEINTRESOURCE(IDD_DIALOG1), hwnd, CListDevices::WndProc); — Raveendra M Pai, Oct 09 '13 at 12:35
Note also that you are calling `InitcommonControls()` too late. You need to call it before calling `DialogBox` because the controls on the dialog box are created *before* you get you `WM_INITDIALOG` message. — Raymond Chen, Oct 09 '13 at 14:45

David Heffernan · Accepted Answer · 2013-10-09T17:34:03.913

You never assign to gInstance and so it is default initialised to NULL. You then pass that to DialogBox.

Assign hInstance to gInstance in WinMain.

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
               LPSTR lpCmdLine, int nCmdShow) 
{
    gInstance = hInstance;
    DialogBox(gInstance, MAKEINTRESOURCE(IDD_DIALOG), hwnd, WndProc);
    return TRUE;
}

Or just do away with gInstance altogether since you don't use it anywhere else. Delete the variable and make your WinMain like this:

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
               LPSTR lpCmdLine, int nCmdShow) 
{
    DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG), hwnd, WndProc);
    return TRUE;
}

There is more code that you are omitting though because I cannot see the declaration or initialisation of hwnd. It's always best to show a complete SSCCE if possible, and it's clearly possible here.

And also take heed of Raymond's comment to the question and move the call to InitCommonControls into WinMain.

Win32 GUI : failing to create win32 GUI dialog

1 Answers1