Windows Win32 APIs: changes from win95/98/2000 to XP

I needed to code a simple http downloader, a dialog based win32 application. This application provides a simple UI to allow user to put in an URL and click a button to start downloading. Initially I also want to provide a RichEdit text area to log transactions and messages for debugging/diagnosis purpose.

I used to program win32 applications on windows 2000 platform with visual c++ 6.0, using a CmnHdr.H dialog template. This header file has some convenience macros to easily define win32 message handlers. The first problem I encountered is on Windows XP, this header file no longer works well. It can still be made to work after some modifications but the template needs adjustment. It made more sense to throw away to header file and template and just code the dialog box directly using this example code:

#define STRICT
#define WIN32_LEAN_AND_MEAN
#include 
#include "resource.h"

BOOL CALLBACK DialogProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) {
 switch (message) {
  case WM_INITDIALOG:
   return (TRUE);
  case WM_COMMAND:
   switch (wParam) {
    case IDOK:
    case IDCANCEL:
     EndDialog(hDlg, TRUE);
     return (TRUE);
     }
   break;
 }
return (FALSE);
}

int PASCAL WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
 int ReturnValue;
        ReturnValue = DialogBoxParam(NULL, MAKEINTRESOURCE(IDD_DIALOG1), NULL, DialogProc, NULL);
        return 0;
}

The 2nd problem really puzzled me. My dialogbox won't show up no matter what. DialogBox returned -1 but GetLastError returned 0. Debugging into the win32 library code quickly showed me that there is something intricately wrong and -1 is returned from win32 internals. After spending many hours to resolve this issue, I finally found the solution from the win32.programmer.ui newsgroups. The answer is an win32 API called InitCommonControlsEx. On WinXP, one must call this API to use standard controls, otherwise the syptom is exactly as I described, the dialogbox won't show up (for some people, the dialog box would show up but without controls).

References:
1. http://simplesamples.info/Windows/DlgHello.php
2. http://msdn.microsoft.com/en-us/library/bb775697(VS.85).aspx