how can i center a control by it's parent?

[Cambalinho]

heres my ScreenToClient():

void ScreenToClient(HWND WindowDestination, RECT *WindowRectangle)
{
    MapWindowPoints(NULL, WindowDestination, LPPOINT(WindowRectangle), 2);
}

and heres how i center a control:

void Center()
        {
            //getting the controls positions\size
            RECT frm,frmparent;
            
            //getting the parent coordenates
            //depending if is a form or the desktop\screen
            if(GetParent(hwnd)!=NULL)
            {
                GetWindowRect(GetParent(hwnd), &frmparent);
                ScreenToClient(GetParent(hwnd),&frmparent);
            }
            else
            {
                GetWindowRect(GetDesktopWindow(), &frmparent);
                ScreenToClient(GetDesktopWindow(),&frmparent);
            }
            
            //getting the control coordenates
            //i have a 2nd ScreenToClient() api function for accept the RECT
            GetWindowRect(hwnd, &frm);            
            if(GetParent(hwnd)!=NULL)
            {
                ScreenToClient(GetParent(hwnd),&frm);
            }
            else

            {
                ScreenToClient(GetDesktopWindow(),&frm);
            }
            
            //calculate the center
            LONG x=(frmparent.right-frmparent.left)/2 - (frm.right-frm.left)/2;
            LONG y=(frmparent.bottom-frmparent.top)/2 - (frm.bottom-frm.top)/2;
            
            //position the control
            SetWindowPos(hwnd,0,x ,y,0,0, SWP_NOSIZE |  SWP_NOZORDER);
        }

i see the control more on center of the screen, instead center of parent form :(
what i'm doing wrong?
Moderator: i can't create threads with code. 1st i need create the thread then i must edit it for add the code. please see the problem

[tath]

Children coordinates are relative to its parent (not screen), so if you create children window at 20,20 it will appear at screen parentX+20, parentY+20.

If you parent is not desktop, dont map client position to screen position with ScreenToClient.

[Cambalinho]

void CenterInsideParent(HWND hWnd, ControlPositions ControlPosition=CenterCenter)
{
    //getting the parent
    HWND parent=GetDesktopWindow();
    if (!(GetWindowLong(hWnd, GWL_STYLE) & WS_CHILD) && parent==GetDesktopWindow())
    {
        if(GetProp(hWnd, "parent")!=NULL)
            parent=(HWND)GetProp(hWnd, "parent");
    }
    else
        parent=GetParent(hWnd);

    //getting the controls positions\size
    //depending if is a child or not
    RECT frm,frmparent;

    if ((GetWindowLong(hWnd, GWL_STYLE) & WS_CHILD))
    {
        GetClientRect(parent, &frmparent);
        GetWindowRect(hWnd, &frm);
        ScreenToClient(parent,&frm);
    }
    else
    {
        GetWindowRect(parent, &frmparent);
        GetWindowRect(hWnd, &frm);
    }

    //calculate the position choosed
    LONG x;
    LONG y;
    if (parent!=GetDesktopWindow())
    {
        if(ControlPosition==0)
        {
            x=(frmparent.left+((frmparent.right-frmparent.left)/2)) - ((frm.right-frm.left)/2);
            y=(frmparent.top+((frmparent.bottom-frmparent.top)/2)) - ((frm.bottom-frm.top)/2);
        }
        else if (ControlPosition==1)
        {
            x=frmparent.left;
            y=(frmparent.top+((frmparent.bottom-frmparent.top)/2)) - ((frm.bottom-frm.top)/2);
        }

    }
    else //center of screen
    {
        if(ControlPosition==0)
        {
            x=(((frmparent.right-frmparent.left)/2)) - ((frm.right-frm.left)/2);
            y=(((frmparent.bottom-frmparent.top)/2)) - ((frm.bottom-frm.top)/2);
        }
        else if (ControlPosition==1)
        {
            x=0;
            y=(((frmparent.bottom-frmparent.top)/2)) - ((frm.bottom-frm.top)/2)+3;
        }
    }

    //position the control
    SetWindowPos(hWnd,0,x ,y,0,0, SWP_NOSIZE |  SWP_NOZORDER);
}

the child control it's on wright position. but the form isn't.
if (parent!=GetDesktopWindow())
and

 else if (ControlPosition==1)
        {
            x=frmparent.left;
            y=(frmparent.top+((frmparent.bottom-frmparent.top)/2)) - ((frm.bottom-frm.top)/2);
        }

the frmparent.left is less 3 or 4 pixels from original value. why?