[RESOLVED] win32 - how center a control depending on it's parent position and size?

[Cambalinho]

i have these code for center a control depending on it's parent position and size:

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



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);
        }

the control seems been on center of screen instead been center of it's parent
both controls are forms and none are WS_CHILD.
when i create a form:

form(string caption = "", HWND parent=HWND_DESKTOP)
        {
            ++FormCount;
            if(caption=="")
                strCaption = strCaption + to_string(FormCount);
            else
                strCaption=caption;
            setParent(parent);
        }


void setParent(HWND parent=GetDesktopWindow())
        {
            if (hwnd==NULL)
            {

                WNDCLASSEX FormClass;
                char classname[20]="Form";
                sprintf(classname,"%s",strCaption.c_str());
                HINSTANCE mod = (HINSTANCE)GetModuleHandle(NULL);

                FormClass.cbSize        = sizeof(WNDCLASSEX);
                FormClass.style         = CS_DBLCLKS;
                FormClass.lpfnWndProc   = WndProcForm;
                FormClass.cbClsExtra    = 0;
                FormClass.cbWndExtra    = 0;
                FormClass.hInstance     = mod;
                FormClass.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
                FormClass.hCursor       = LoadCursor(NULL, IDC_ARROW);
                FormClass.hbrBackground = (HBRUSH)GetSysColor(COLOR_BACKGROUND);
                FormClass.lpszMenuName  = NULL;
                FormClass.lpszClassName = classname;
                FormClass.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

                // register the new window class
                RegisterClassEx(&FormClass);

                hwnd = CreateWindowEx(0,classname, strCaption.c_str(),WS_OVERLAPPEDWINDOW | WS_VISIBLE | WS_CLIPCHILDREN ,
                                  CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, parent, NULL, mod, this);

                SetLayeredWindowAttributes(hwnd, 0, 255, LWA_ALPHA);
                if (hwnd == NULL)
                    MessageBox(NULL, "Can't create the control", "error", MB_OK);
            }
            else
            {
                SetParent(hwnd,parent);
            }

            ShowWindow(hwnd, SW_NORMAL);
            InvalidateRect(hwnd,NULL,TRUE);//i add these line for fix that
            UpdateWindow(hwnd);
            clrBackColor =GetDCBrushColor(GetDC(hwnd));
            clrTextColor = GetTextColor(GetDC(hwnd));
        }

[Igor Vartanov]

The sample: HOWTO_center_window_in_parent_rect.zip

[Igor Vartanov]

void CenterInsideParent(HWND hWnd)
{
    /* start calculating in parent's coordinates */
    HWND hParent = GetParent(hWnd);
    RECT rcp, rcc;
    GetClientRect(hParent, &rcp);
    GetWindowRect(hWnd, &rcc);

    /* offset child rect to top left */
    rcc.bottom -= rcc.top; /* height */
    rcc.right -= rcc.left; /* width */
    rcc.left = rcc.top = 0;

    /* get top-left anchor */
    rcc.left = (rcp.right - rcc.right)/2;
    rcc.top = (rcp.bottom - rcc.bottom)/2;

    /* non-child to be centered in screen coordinates, not in parent's ones */
    if (!(GetWindowLong(hWnd, GWL_STYLE) & WS_CHILD))
    {
        /* adjust anchor position */
        MapWindowPoints(hParent, GetDesktopWindow(), (LPPOINT)&rcc, 1);
    }

    //MoveWindow(hWnd, rcc.left, rcc.top, rcc.right /*width*/, rcc.bottom /*height*/, TRUE);
    SetWindowPos(hWnd, NULL, rcc.left, rcc.top, 0, 0, SWP_NOSIZE | SWP_NOZORDER);
}

[Cambalinho]

void CenterInsideParent(HWND hWnd)
{
    /* start calculating in parent's coordinates */
    HWND hParent = GetParent(hWnd);
    RECT rcp, rcc;
    GetClientRect(hParent, &rcp);
    GetWindowRect(hWnd, &rcc);

    /* offset child rect to top left */
    rcc.bottom -= rcc.top; /* height */
    rcc.right -= rcc.left; /* width */
    rcc.left = rcc.top = 0;

    /* get top-left anchor */
    rcc.left = (rcp.right - rcc.right)/2;
    rcc.top = (rcp.bottom - rcc.bottom)/2;

    /* non-child to be centered in screen coordinates, not in parent's ones */
    if (!(GetWindowLong(hWnd, GWL_STYLE) & WS_CHILD))
    {
        /* adjust anchor position */
        MapWindowPoints(hParent, GetDesktopWindow(), (LPPOINT)&rcc, 1);
    }

    //MoveWindow(hWnd, rcc.left, rcc.top, rcc.right /*width*/, rcc.bottom /*height*/, TRUE);
    SetWindowPos(hWnd, NULL, rcc.left, rcc.top, 0, 0, SWP_NOSIZE | SWP_NOZORDER);
}

i can't see the form inside the screen
anotherthing: in these case i don't care if is WS_CHILD or not. the position, always, will depend on it's parent(of course if is DeskTop, then will be on screen center)

[Igor Vartanov]

i can't see the form inside the screen

Did you build and play with my sample? It creates a popup dialog that can be centered over its parent.

[Cambalinho]

Did you build and play with my sample? It creates a popup dialog that can be centered over its parent.

i'm playing with the function. and the child control it's on center. but not a control without a WS_CHILD style
i must test more the function

[Cambalinho]

please see the setParent() function. i belive here is a problem. 2 diferent controls(both forms), 1 is parent of other. but when i do:

GetParent(hWnd)

i get NULL. so heres there a problem. thats why i will always get it on center of screen, instead it's parent

[Igor Vartanov]

please see the setParent() function. i belive here is a problem. 2 diferent controls(both forms), 1 is parent of other. but when i do:

GetParent(hWnd)

i get NULL. so heres there a problem. thats why i will always get it on center of screen, instead it's parent

You are not allowed to explicitly set pop-up or overlapped window's owner. Window ownership is set only during CreateWindow or CreateDialog execution (see my sample). Once set, owner cannot be changed.

SetParent in its turn works only with windows having WS_CHILD style. That's why you get NULL parent.

[Cambalinho]

You are not allowed to explicitly set pop-up or overlapped window's owner. Window ownership is set only during CreateWindow or CreateDialog execution (see my sample). Once set, owner cannot be changed.

SetParent in its turn works only with windows having WS_CHILD style. That's why you get NULL parent.

but see the funcion in these way:

const UINT CenterCenter=0;

void CenterInsideParent(HWND hWnd, HWND parent=GetDesktopWindow(), UINT ControlPosition=CenterCenter)
{
    //getting the controls positions\size
    RECT frm,frmparent;

    //getting the parent coordenates
    //depending if is a form or the desktop\screen
    GetWindowRect(parent, &frmparent);
    //ScreenToClient(GetParent(hWnd),&frmparent);


    //getting the control coordenates
    //i have a 2nd ScreenToClient() api function for accept the RECT
    GetWindowRect(hWnd, &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;


    ScreenToClient(parent,&frm);


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

how i use it:

 CenterInsideParent(InputBox,a);

InputBox its the form that need to be re-positioned;
a its the form where InputBox is centered.
so why my function can't put the InputBox on center of the a?

[Igor Vartanov]

so why my function can't put the InputBox on center of the a?

Debugger will answer.

Besides, as I wrote in my comments, non-child window (i.e. pop-up or overlapped one) must be repositioned in screen coordinates, not parent's client coordinates.

[Cambalinho]

Debugger will answer.

Besides, as I wrote in my comments, non-child window (i.e. pop-up or overlapped one) must be repositioned in screen coordinates, not parent's client coordinates.

after some work i put it to work:

const UINT CenterCenter=0;

void CenterInsideParent(HWND hWnd, HWND parent=GetDesktopWindow(), UINT ControlPosition=CenterCenter)
{
    //getting the controls positions\size
    RECT frm,frmparent;

    //getting the parent coordenates
    //depending if is a form or the desktop\screen
    GetWindowRect(parent, &frmparent);
    //ScreenToClient(GetParent(hWnd),&frmparent);


    //getting the control coordenates
    //i have a 2nd ScreenToClient() api function for accept the RECT
    GetWindowRect(hWnd, &frm);

    //calculate the center
    LONG x;
    LONG y;
    if(parent!=GetDesktopWindow())
    {
        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 //center of screen
    {
        x=(((frmparent.right-frmparent.left)/2)) - ((frm.right-frm.left)/2);
        y=(((frmparent.bottom-frmparent.top)/2)) - ((frm.bottom-frm.top)/2);
    }


    if ((GetWindowLong(hWnd, GWL_STYLE) & WS_CHILD))
    {
        POINT a={x,y};
        ScreenToClient(parent,&a);
        x=a.x;
        y=a.y;
    }


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

and yes... i can center on screen too
thanks for all

[Cambalinho]

these calculation isn't prepared for border(the caption or arround the window), can anyone advice me?

[VladimirF]

these calculation isn't prepared for border(the caption or arround the window), can anyone advice me?

Do you want to NOT count caption and border of the parent window? Then use GetClientRect() instead of GetWindowRect().
Please note: client rectangle is always in client's coordinates.

Also please note that
frmparent.left+((frmparent.right-frmparent.left)/2)
is the same as
(frmparent.left+frmparent.right)/2

[Cambalinho]

Do you want to NOT count caption and border of the parent window? Then use GetClientRect() instead of GetWindowRect().
Please note: client rectangle is always in client's coordinates.

Also please note that
frmparent.left+((frmparent.right-frmparent.left)/2)
is the same as
(frmparent.left+frmparent.right)/2

for child controls now works fine:

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);
}

see when is 1:

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);
        }

strange the frmparent.left been less some pixles