Need help Creating Basic Window

I need help with the following. When executed know window is visible. Can someone help me, please? It is based on a tutorial from msdn. I tried to give more structure by placing some of the code into functions. The compiled and executed msdn's example and it works. Mine doesn't.

Code:

---

#ifndef UNICODE
#define UNICODE
#endif
#include <windows.h>
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
int initialize(WNDCLASS* wc, HINSTANCE hInstance);
int makeApp(HWND &hwnd, WNDCLASS wc);
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    LPSTR pCmdLine, int nCmdShow)
{
    // Declare window class for the main window
    WNDCLASS wc = {};
    HWND hwnd;
   
    // Register , create, and show window
    if(!initialize(&wc, hInstance))
        return FALSE;
    if(!makeApp(hwnd, wc))
        return FALSE;
    ShowWindow(hwnd, nCmdShow);
   
    // Declare message struct
    MSG msg;
    // Create the message loop
    while(GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg); 
    }
   
    return 0;
}
int initialize(WNDCLASS *wc, HINSTANCE hInstance)
{
 const wchar_t CLASS_NAME[]  = L"Sample Window Class";
 //wc.sytle = 0;
 (*wc).lpfnWndProc = WindowProc;
 //wc.cbClsExtra = NULL;
 //wc.cbWndEXtra = NULL;
 (*wc).hInstance = hInstance;
 (*wc).lpszClassName = CLASS_NAME;
 RegisterClass(wc);
   
}
int makeApp(HWND &hwnd, WNDCLASS wc)
{
 hwnd = CreateWindowEx(
 0,    // Optional window styles
 wc.lpszClassName,  // Window Class
 L"Learn to Program Windows", // Window Text
 WS_OVERLAPPEDWINDOW,  // Window style
 
 // Size and position
 CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
 NULL,  // Parent window
 NULL,  // Menu
 wc.hInstance,  // Instance handle
 NULL  // Additional application data
 );
 
 if(hwnd == NULL)
 {
  return 0;
 }
 else
 {
  return 1;
 }
}

LRESULT WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
 switch(uMsg)
 {
  case WM_PAINT:
            {
                PAINTSTRUCT ps;
                    HDC hdc = BeginPaint(hwnd, &ps);
               
                    // All painting occurs here, between BeginPaint and EndPaint
               
                    FillRect(hdc, &ps.rcPaint, (HBRUSH) (COLOR_WINDOW+1));
               
                EndPaint(hwnd, &ps);
                return 0;
            }
  case WM_DESTROY:
            {
                PostQuitMessage(0);
                return 0;
            }
 }
 return DefWindowProc(hwnd, uMsg, wParam, lParam);
}

---

Do you know which line fails?

Did you use GetLastError() to find out why?

>>int makeApp(HWND &hwnd, WNDCLASS wc)

HWND is a HANDLE, which is a VOID pointer. So you do not need the '&' (which is probably your problem as the assignment / validation might be failing.)

Code:

---

LRESULT WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)

---

should be

Code:

---

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)

---

Also, the function

Code:

---

int initialize(WNDCLASS *wc, HINSTANCE hInstance)

---

needs a return value:

Code:

---

return RegisterClass(wc);

---

My suggestions above aren't all of the problem. Still doesn't work after those corrections.

Quote:

---

Originally Posted by novacain

>>int makeApp(HWND &hwnd, WNDCLASS wc)

HWND is a HANDLE, which is a VOID pointer. So you do not need the '&' (which is probably your problem as the assignment / validation might be failing.)

---

Isn't that C++ syntax, for passing by reference (as opposed to passing by value or pointer)?
It's apparantly to allow makeApp() to set the value of hwnd, which was declared in WinMain().

Here's one way I got it to work.

Code:

---

// #ifndef UNICODE
// #define UNICODE
// #endif
#include <windows.h>

WNDCLASS wc = {};
HWND hwnd;
const char szNAME[]  = "Sample Window Class";

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
int initialize(WNDCLASS* wc, HINSTANCE hInstance);
int makeApp(HINSTANCE hInstance, WNDCLASS wc);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    LPSTR pCmdLine, int nCmdShow)
{
    // Declare window class for the main window
    // WNDCLASS wc = {};
    // HWND hwnd;

    // Register , create, and show window
    if(!initialize(&wc, hInstance))
      return FALSE;
    if(!makeApp(hInstance, wc))
      return FALSE;
    ShowWindow(hwnd, nCmdShow);

    // Declare message struct
    MSG msg;
    // Create the message loop
    while(GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return 0;
}

int initialize(WNDCLASS *wc, HINSTANCE hInstance)
{
    // const char szNAME[]  = "Sample Window Class";
    //wc.sytle = 0;
    (*wc).lpfnWndProc = WindowProc;
    //wc.cbClsExtra = NULL;
    //wc.cbWndEXtra = NULL;
    (*wc).hInstance = hInstance;
    (*wc).lpszClassName = szNAME;
    RegisterClass(wc);
    return (TRUE);

}

int makeApp(HINSTANCE hInstance, WNDCLASS wc)
{
    hwnd = CreateWindowEx(
          0,    // Optional window styles
          wc.lpszClassName,  // Window Class
          // szNAME,
          "Learn to Program Windows", // Window Text
          WS_OVERLAPPEDWINDOW,  // Window style

          // Size and position
          CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
          NULL,  // Parent window
          NULL,  // Menu
          wc.hInstance,  // Instance handle
          // hInstance,
          NULL  // Additional application data
);

    if(hwnd == NULL)
    {
      return 0;
    }
    else
    {
      return 1;
    }
}

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch(uMsg)
    {
      case WM_PAINT:
      {
          PAINTSTRUCT ps;
          HDC hdc = BeginPaint(hwnd, &ps);

          // All painting occurs here, between BeginPaint and EndPaint

          FillRect(hdc, &ps.rcPaint, (HBRUSH) (COLOR_WINDOW+1));

          EndPaint(hwnd, &ps);
          return 0;
      }
      case WM_DESTROY:
      {
          PostQuitMessage(0);
          return 0;
      }
    }
    return DefWindowProc(hwnd, uMsg, wParam, lParam);
}

---

Referring to zordon's code, this seems to fix it:

Code:

---

LRESULT WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)

---

change to

Code:

---

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)

---

In the function initialize():

Code:

---

RegisterClass(wc);

---

change to

Code:

---

return RegisterClass(wc);

---

Those are the same two changes I mentioned previously.

But also in the function initialize():

Code:

---

const wchar_t CLASS_NAME[]  = L"Sample Window Class";

---

change to

Code:

---

static const wchar_t CLASS_NAME[]  = L"Sample Window Class";

---

Okay, thanks everyone for the replies. I appreciate it.