[RESOLVED] Problem with text in GetWindowText function

[2kaud]

HWND TextBox, Button;

A problem is here. These are initialised in WM_CREATE, but when WndProc() exits, these values are 'lost'. So when Wndproc() is entered again, these variables have unknown values (NOT the previously assigned values) - but are unlikely to be valid window handles. GetWindowText() is likely to fail (returns 0). As you aren't testing that the functions used have completed properly, you aren't handling errors. When you use a function that can fail, you always need to check for such failure. The MSDN documentation describes this. Likewise, the textSaved array isn't initialised either, so if GetWindowText() fails, then MessageBox() will display whatever happens to be at the memory locations used by textSaved - probably the garbage you are seeing displayed.

In this case, any 'easy' solution is make TextBox and Button static so that their values remain between successive calls to WndProc().

static HWND TextBox = 0, Button = 0;

A better way of coding of case 1 could be:

TCHAR textSaved[20] = {0};
int gwtstat = GetWindowTextLength(TextBox);

if (gwstat > 0)
    if ((gwstat = GetWindowText(TextBox, textSaved, gwtstat)) > 0)
        ::MessageBox(hwnd, textSaved, "Title", MB_OK);

if (gwstat == 0)
    ::MessageBox(hwnd, "Problem obtaining window text", "Title", MB_OK);

break;

Using TCHAR rather than char should enable this to work with either UNICODE or MBCS coding.