MFC getting mouse pointer coordinate problem

Question

I'm trying to get coordinate of the Rect (Picture control) but It's a bit glitchy.

So here're the process that I've done.

1st. made a picture control

2nd. I've earned WindowRect through GetWindowRect

// myDialogDlg.cpp

CRect m_rcDisp // (is acually in myDialogDlg.h)

BOOL myDialogDlg::OnInitDialog()
{
// IDC_PIC1 == ID of the (static) picture control
GetDlgItem(IDC_PIC1)->GetWindowRect(m_rcDisp);

...
}

3rd. I've made OnMouseMove event, and used PtInRect to make some action while mouse pointer is inside the picture control.

// myDialogDlg.cpp
void myDialogDlg::OnMouseMove(UINT nFlags, CPoint point)
{
    CString debug;
    {
        if (m_rcDisp.PtInRect(point))
        {
// my event starts
            OutputDebugString(_T("here"));
            if (m_CamTrig == CAMERA_TRIG_SW)
            {
                m_CurSor.x = point.x;
                m_CurSor.y = point.y;
                InvalidateRect(m_rcDisp, NULL);
            }
// my event ends
        }
    }
    CDialogEx::OnMouseMove(nFlags, point);
}

and... where actually PtInRect works is about here inside the red box

:( Hope I get the best answer. thx!

Answer 1

GetWindowRect returns the window dimensions in screen coordinates. WM_MOUSEMOVE reports the mouse position in client coordinates. ScreenToClient¹ can be used to translate from screen coordinates to client coordinates, making the picture control's window rectangle coordinates and hit testing function agree on a common origin.

This needs to be done whenever the picture control is moved relative to its parent dialog. If the picture control is never moved you only need to adjust the rectangle once.

This answer links to the Windows API documentation, since it's generally more informative and better maintained than the respective MFC entries. You can call either one from MFC code, though it's usually more convenient to just call into the CWnd members.

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¹ Use MapWindowPoints instead if you plan on supporting RTL and LTR layouts. See Window Layout and Mirroring for guidance.