Question

I have recently begun learning the Win32 API using this tutorial:

http://www.winprog.org/tutorial/ (though I’m using C++, not C as in the tutorial)
I’m currently experimenting with the “edit box”-function where I’m trying to compare the text written in the edit box with another line of characters.
Code:

#define IDC_MAIN_EDIT   101

Code:

case WM_CREATE:
{
    HFONT hfDefault;
    HWND hEdit;

    hEdit = CreateWindowEx(WS_EX_CLIENTEDGE, "EDIT", "", 
        WS_CHILD | WS_VISIBLE | WS_VSCROLL | WS_HSCROLL | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL, 
        0, 0, 100, 100, hwnd, (HMENU)IDC_MAIN_EDIT, GetModuleHandle(NULL), NULL);
    if(hEdit == NULL)
        MessageBox(hwnd, "Could not create edit box.", "Error", MB_OK | MB_ICONERROR);

    hfDefault = GetStockObject(DEFAULT_GUI_FONT);
    SendMessage(hEdit, WM_SETFONT, (WPARAM)hfDefault, MAKELPARAM(FALSE, 0));
}
break;
case WM_SIZE:
{
    HWND hEdit;
    RECT rcClient;

    GetClientRect(hwnd, &rcClient);

    hEdit = GetDlgItem(hwnd, IDC_MAIN_EDIT);
    SetWindowPos(hEdit, NULL, 0, 0, rcClient.right, rcClient.bottom, SWP_NOZORDER);
}
break;

Code:

bool comparison (HWND hEdit) {
LPWSTR pszText;
DWORD dwTextLength;
DWORD dwBufferSize;

dwTextLength = GetWindowTextLength(hEdit);
dwBufferSize = dwTextLength + 1;

GetWindowText(hEdit, pszText, dwBufferSize);

if(pszText == TEXT("3")) {
    return true;
}
else {
    return false;
}
}

The problem when I call the “comparison”-function is that pszText and hEdit aren’t initialized. I get why pszText isn’t and I’ve tried using the new/delete to fix it, but I don’t get it to work. I have no clue about hEdit. Am I perhaps using the GetWindowText-function wrong?
Warnings
Code:

warning C4700: uninitialized local variable ‘pszText’ used
warning C4700: uninitialized local variable ‘hEdit’ used

Run-Time Check Failure (appear when I’m using the function, and this is just one of them)
Code:

Run-Time Check Failure #3 – The variable ‘hEdit’ is being used without being initializ

Answer 1

Look into the very important concept of scope. refer this page http://www.cplusplus.com/doc/tutorial/variables/

c++ Code:

  case WM_CREATE:

  {

          HFONT hfDefault;

          HWND hEdit;



          hEdit = CreateWindowEx(WS_EX_CLIENTEDGE, "EDIT", "",

              WS_CHILD | WS_VISIBLE | WS_VSCROLL | WS_HSCROLL | ES_MULTILINE | ES_AUTOVSCROLL | ES_AUTOHSCROLL,

              0, 0, 100, 100, hwnd, (HMENU)IDC_MAIN_EDIT, GetModuleHandle(NULL), NULL);

          if(hEdit == NULL)

              MessageBox(hwnd, "Could not create edit box.", "Error", MB_OK | MB_ICONERROR);



          hfDefault = GetStockObject(DEFAULT_GUI_FONT);

          SendMessage(hEdit, WM_SETFONT, (WPARAM)hfDefault, MAKELPARAM(FALSE, 0));

      } 

The variable hEdit only exists for the duration of the block in which it’s declared, which is within the {}s for the WM_CREATE case.