Reading double from dialog edit control

Question

I'm currently working on a program (for fun, this is not an assignment) that has multiple functions. I have never used Win32 prior to yesterday and so I am rather new. I used TheForger's tutorials to get started. Right now, I have a dialog form with four edit boxes on it, charge1, charge2, charge3, and distance between particles. I am getting this information and plugging it into the formula to solve for the amount of force between the particles.

When I get to the part where I am getting the data from the edit box, I am receiving 0.

Here is my current code:

case ID_SOLVE:
{
    ZeroMemory(coulombDisplay, sizeof(coulombDisplay));

    GetDlgItemText(g_hCoulombs, IDC_DISTANCE, value1, 10);
    coulombsDistance = atof(value1);

    GetDlgItemText(g_hCoulombs, IDC_CHARGE1, value2, 10);
    coulombsStrength1Base = atof(value2);

    GetDlgItemText(g_hCoulombs, IDC_CHARGE2, value3, 10);
    coulombsStrength2Base = atof(value3);

    if(coulombsDistance == 0.0)
    {
        MessageBox(NULL, "WHAT", "WHAT", MB_OK | MB_ICONEXCLAMATION);
        DestroyWindow(g_hCoulombs);
    }

    coulombsResult = (coulombsStrength1Base * coulombsStrength2Base);
    coulombsResult /= (pow(coulombsDistance, 2));
    coulombsResult *= kConstant;

    sprintf(coulombDisplay, "%g", coulombsResult);
    SendDlgItemMessage(g_hCoulombs, IDC_FORCE, WM_SETTEXT, 0, (LPARAM)(LPCSTR)coulombDisplay);
}
break;

value1 , value2 , value3 , and coulombDisplay are all char[] that have been zero'd

coulombsResult , coulombsDistance , coulombsStrength1Base , coulombsStrength2Base are all double s

The MessageBox stating "WHAT" is popping up each and every time that I run the program. I am using the multi-byte character set of VC++ 2010.

Any help would be greatly appreciated.

Answer 1

STATUS_ACCESS_DENIED has a good point. If you look at the documentation for atof you'll see that a error condition will result in 0.0 being returned. I'd recommend writing to a log file or something to see what the data is going into the atof function. I'm wondering if your allocated char buffer is big enough.

Answer 2

Try GetDlgItemTextA instead of GetDlgItemText to make sure you're getting back 8-bit characters and not 16-bit characters. A 16-bit character will usually have a zero in the upper half, and will be interpreted as an empty 8-bit string.