Draw rectangle on CView and Track using CRectTracker

This blog will be helpful for those who want to draw a rectangle using mouse dragging feature and show a re-sizing handler and also want to move a rectangle from one position to another.
 

Step 1

Open the .h header file of subclass of CView in editor.

Eg: In this example , using CDrawViewView.h header file which is subclass of CView.

Step 2

Declare a protected variable in .h file.

CRectTracker                               m_RectTracker;              // Rect Tracker
CArray<CRect, CRect&>            m_RectArray;              // Contains reference of Rect

Step 3

Declare a protected method in .h file.

bool LMouseButtonDown(CPoint point); // Method called from left mouse buton down event.
afx_msg void OnLButtonDown(UINT flags, CPoint point);
afx_msg BOOL OnSetCursor(CWnd* pWnd, UINT nHitTest, UINT message);
afx_msg void OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags);

Step 4

Open .m file such as CDrawViewView.m in editor and modify begin message map and declare message block.

BEGIN_MESSAGE_MAP(CDrawViewView, CView)
ON_WM_LBUTTONDOWN()
ON_WM_SETCURSOR()
END_MESSAGE_MAP()

Step 5

And placed following code in .m file.

  CDrawViewView::CDrawViewView()
  {
           m_RectTracker.m_rect.SetRect(-1,-1,-1,-1);
           m_RectTracker.m_nStyle = CRectTracker::resizeOutside|CRectTracker::dottedLine;
  }

     /* Method invoked to check whether user selected rectangle or not */
     bool CDrawViewView::LMouseButtonDown(CPoint point)
     {
                 bool status = false;
                 int rectCount = m_RectArray.GetCount();

                  if (rectCount <= 0)
                          return status;
                 for (int i = 0; i < rectCount; ++i)
                 {
                          CRect rect = m_RectArray[i];
                          if (rect.PtInRect(point))
                          {
                                   m_RectTracker.m_rect = rect;
                                   m_RectArray.RemoveAt(i);
                                   status = true;
                                   break;
                          }
                 }
                 return status;
           }


 void CDrawViewView::OnLButtonDown(UINT nFlags, CPoint point)
 {
     if (!LMouseButtonDown(point))
     {

           if (m_RectTracker.TrackRubberBand(this, point, true))
           {
                    CRect rect = new CRect(m_RectTracker.m_rect);
                    m_RectArray.Add(rect);
           }
     }
     else
     {
              m_RectTracker.Track(this, point, true);
              CRect rect = new CRect(m_RectTracker.m_rect);
              m_RectArray.Add(rect);
     }

  Invalidate();
  CView::OnLButtonDown(nFlags, point);


  void CDrawViewView::OnDraw(CDC* pDC)
  {
              CDrawViewDoc* pDoc = GetDocument();
              ASSERT_VALID(pDoc);
              if (!pDoc)
                    return;


              int rectCount = m_RectArray.GetCount();
              if (rectCount > 0)
              {
                       for (int i = 0; i < rectCount; ++i)
                       {
                                      CRect currentRect = m_RectArray[i];
                                      pDC->Rectangle(currentRect);
                        }
                         m_RectTracker.Draw(pDC);
                 }
      }