C ++获取对话框控件的位置和大小

Question

I'm using Visual Studio 2015 C++ and have a dialog box defined in an .rc-file:

IDD_SERIALCTRLDEMO_DIALOG DIALOGEX 0, 0, 313, 164
STYLE DS_SETFONT | DS_MODALFRAME | DS_FIXEDSYS | WS_POPUP | WS_VISIBLE | WS_CAPTION | WS_SYSMENU
EXSTYLE WS_EX_APPWINDOW
CAPTION "SerialCtrlDemo"
FONT 8, "MS Shell Dlg", 0, 0, 0x1
BEGIN
    LTEXT           "Serial Number:",IDC_STATIC,14,10,48,8
    COMBOBOX        IDC_COMBO_SN,66,8,48,55,CBS_DROPDOWN | CBS_SORT | WS_VSCROLL | WS_TABSTOP
    LTEXT           "Baud Rate:",IDC_STATIC,135,10,37,8
    COMBOBOX        IDC_COMBO_BR,176,8,48,55,CBS_DROPDOWN | CBS_SORT | WS_VSCROLL | WS_TABSTOP
    LTEXT           "Read:",IDC_STATIC,11,51,20,8
    PUSHBUTTON      "Open",IDC_BUTTON_OPEN,242,7,50,14
    LISTBOX         IDC_LIST_READ,11,62,23,76,LBS_SORT | LBS_NOINTEGRALHEIGHT | WS_VSCROLL | WS_TABSTOP
    EDITTEXT        IDC_EDIT_WRITE,11,34,237,14,ES_AUTOHSCROLL
    PUSHBUTTON      "Write",IDC_BUTTON_WR,252,33,46,14
    GROUPBOX        "",IDC_STATIC,7,0,294,25
    GROUPBOX        "",IDC_STATIC,7,26,296,117
    LTEXT           "",IDC_STATIC_INFO,11,150,287,8
    CONTROL         "",IDC_SENSOR,"Static",SS_BLACKRECT,41,62,256,76
END

enter code here

The control I'm interested in is the picturebox "IDC_SENSOR" (last entry), which is defined at/as 41,62,256,76. But on screen that proportions are different, probably due to the Dynamic Dialog Layout. So I want to know the exact position and size of that box whithin the dialogbox, but I cannot get those parameters.

The procedure which it is used in:

void CSerialCtrlDemoDlg::OnEventRead(char *inPacket,int inLength)
}
    int x=0;


    m_listboxRead.AddString(inPacket);      // display the incomming data in the 'Read' listbox

    CString str;                    // display the # of data's in 'Info'
    str.Format("%d bytes read",inLength);
    m_staticInfo.SetWindowText(str);

    CWnd *cWndSensor = GetDlgItem(IDC_SENSOR);  // show the fluctuation in the Picturebox 
    CDC *pDC = cWndSensor->GetDC();

    for (x = 0; x < 200; x++)
    {
        pDC->SetPixelV(x, 10, RGB(rand() % 255, 0, 0));
    }
}

The x<200 in the for-loop should be set to the width of the picturebox.

How can I get those dimensions?

I hope this is enough info(?).

Greetings, CJ.

Answer 1

The control I'm interested in is the picturebox "IDC_SENSOR" (last entry), which is defined at/as 41,62,256,76. But on screen that proportions are different, probably due to the Dynamic Dialog Layout.

Yes, that's correct. Coordinates in dialog resources are specified in DLUs (dialog units). You can convert dialog units into pixels by calling the MapDialogRect function.

But that's not really what you want to do here, because you don't want to hard-code the dialog coordinates in your code. If you change the resource file, you want your code to continue to work.

I want to know the exact position and size of that box whithin the dialogbox

What you really need is to obtain the coordinates of the control on the screen, in pixels. There are two functions specifically designed for that purpose:

• GetClientRect tells you the window's rectangle in client coordinates. For a child window, such as a control, the upper-left corner will always be (0, 0), and the lower-right corner will tell you the width and height.
• GetWindowRect tells you the window's rectangle in screen coordinates. These are "absolute" coordinates, relative to the virtual screen. Unlike the client rectangle, the window rectangle also includes the size of the window's non-client area.

You probably already know this, but the width of this rectangle is determined by subtracting its left bound from its right bound. Similarly, the height is determined by subtracting its top bound from its bottom bound. Or, if you use the MFC wrapper class, CRect (which is interchangeable everywhere with RECT , including when calling the two above functions), you can just call the Width and Height member functions.

As for your particular use-case, since you're calling GetDC on the child window itself, you're getting a client DC, and you would need client coordinates, so you would call GetClientRect . Simple. Except that your code is wrong. You are obtaining a DC and painting outside of a WM_PAINT message handler, which means that anything you paint is subject to being erased at arbitrary intervals. All drawing should be done in response to a WM_PAINT message.

A simple way of accomplishing this in your case would be to set the SS_OWNERDRAW style for your IDC_SENSOR control. This puts the parent dialog in charge of drawing the control's contents. It will receive WM_DRAWITEM messages when the child control needs to be drawn. Add an OnDrawItem handler and do your drawing in there. The DRAWITEMSTRUCT passed as a parameter will tell you the rectangle into which you should draw ( rcItem ).

Finally, I should note that SetPixelV is quite slow. If it's fast enough for you, just ignore the rest of this comment. But if drawing on the screen is really slow, then you should consider creating and caching a bitmap object. Draw into that bitmap, setting its individual pixels, and then simply blit that bitmap onto your control's device context. Accessing and manipulating the individual pixels of an offscreen bitmap is much faster.

Answer 2

I've managed to retrieve the details with GetClientRect:

void CSerialCtrlDemoDlg::OnEventRead(char *inPacket,int inLength)

    {
        int i = 0;
        int j = 0;
        int x = 0;
        int y = 0;
        int w = 100;
        int h = 50;

        RECT sensorRect;

        CWnd *cWndSensor = GetDlgItem(IDC_SENSOR);
        CDC *pDC = cWndSensor->GetDC();

        cWndSensor->GetClientRect(&sensorRect);

        x = sensorRect.left;
        y = sensorRect.top;
        w = sensorRect.right - x;
        h = sensorRect.bottom - y;


        for (i = 0; i < w; i++)    // this fills the picturebox (for test only)
        {
            for (j = 0; j < h; j++)
            {
                pDC->SetPixelV(i, j, RGB(rand() % 255, 0, 0));
            }

        }
    }

So I mark this question as answered!

I'm not quite sure if this is the 'correct' way, I'm lacking the experience for that. But it works, and then it should be fairly ok :)

Instead of drawing (directly) into the picturebox, I'm gonna use a bitmap as suggested. Thats indeed better and easier to work with.

What I now need to discover is how to update the dialogbox the proper way with that bitmap. As Cody stated such drawing should not be done whithin this routine, but handled as a separate OnDrawItem instruction. Hmm, more to learn.

Thanx and greetins, CJ