Need help Creating Basic Window

[zordon]

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.

#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);
}

[novacain]

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.)

[megafiddle]

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

should be

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

Also, the function

int initialize(WNDCLASS *wc, HINSTANCE hInstance)

needs a return value:

return RegisterClass(wc);

[megafiddle]

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

>>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().

[TAZIN]

Here's one way I got it to work.

// #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);
}

[megafiddle]

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

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

change to

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

In the function initialize():

RegisterClass(wc);

change to

return RegisterClass(wc);

Those are the same two changes I mentioned previously.

But also in the function initialize():

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

change to

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

[zordon]

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