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);
}
}