Resizing Controls at run time

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Introduction

Suppose you wanted to give the user the ability to modify the size and position on a certain control? This example shows how to implement resizing controls on a dialog box as it is done when drawing controls on a dialog template or using Visual Basic at design time.

In order to accomplish this, we can use the class CRectTracker to manage all the drawing and resizing of a rectangular frame which also has (optional) 6 resize handlers (as in the image above). First thing to do is to invoke a CRectTracker and specify given coordinates:

LPRECT rect = new RECT;
CWnd* wnd = (CWnd*)(GetDlgItem(IDC_EDIT1));
wnd->GetWindowRect(rect);
ScreenToClient(rect);
m_tracker = new CRectTracker(rect,CRectTracker::dottedLine  | 
                CRectTracker::resizeOutside | 
                CRectTracker::hatchedBorder );
m_tracker->Draw(pDC);

There are two events that are needed to be taken care of:

1. SetCursor

   if (pWnd == this && m_tracker->SetCursor(this, nHitTest))
       return TRUE;

   This is done in order to draw the correct mouse cursors when floating the mouse pointer over the rectangle.

2. OnLButtonDown

   m_tracker->Track(this, point, TRUE);
   Invalidate(FALSE);
   CDC* pDC = GetDC();
   m_tracker->Draw(pDC);

   This will take care of the drawing of the rectangle with resizing it.

Once you have finished, all you have to do is draw the control with the new rectangle coordinates:

LPRECT rect = new RECT;
CWnd* wnd = (CWnd*)(GetDlgItem(IDC_EDIT1));
rect = LPRECT(m_tracker->m_rect); 
wnd->MoveWindow(rect,TRUE) ;

That's it!