Undo Drawing

Nelly · #1 10-May-2004, 07:24

Hi Hi,

I have a draw function which is drawing 25 rectangle on mouse click on my Scroll view, which is the main viewclass.

I have another Form view which contains some 25 Radiobuttons and Edit controls. When I click on the radio button, then click on the main, it draws the rectangle and displays the cordinate in the edit controls in the formview.

CPP / C++ / C Code:

void CMFFAView::OnDrawFeat(CDC* pDC)
{
	CMFFADoc* pDoc = GetDocument();
	ASSERT_VALID(pDoc);

	UINT pointIndex = pDoc-> m_pointIndex;

	for ( int i = 0; i < pointIndex; ++i)
	{
	CBrush brush( RGB( 0, 255, 0 ) );
	CBrush* pOldBrush = pDC->SelectObject( &brush );
	pDC-> Rectangle( pDoc->m_point[i].x-3, pDoc->m_point[i].y-3,   pDoc->m_point[i].x + 3, pDoc->m_point[i].y + 3);

	pDC->SetPixel(pDoc->m_point[i].x,pDoc->m_point[i].y,RGB(0,0,0));
	
	pDC->SelectObject( pOldBrush );

	}
}


void CMFFAView::OnLButtonDown(UINT nFlags, CPoint point) 
{
          CMFFADoc *pDoc = GetDocument();
          pDoc->m_pnt = point;
          if ( pDoc->m_pointIndex == 25 )
            {
	return;
              }
          pDoc->m_point[pDoc->m_pointIndex] = pDoc->m_pnt;
           pDoc->m_pointIndex++;

            UpdateData(FALSE);	
 
 	/**marks the document as modified or "dirty"
	Any code you write that change any document variables 
	should call SetModifiedFlag().**/
	pDoc->SetModifiedFlag(); 
	
	/**Call the OnDraw() function, where the window's display
	is redrawn with the new data.  
	Invalidate();

		
	CMainFrame* pFrame =  (CMainFrame*)::AfxGetMainWnd();
    CFeature* pView = (CFeature*) pFrame->m_WndSplitterDB.GetPane(0, 0);	
	pView->OnUpdate(this, NULL, NULL);


	CScrollView::OnLButtonDown(nFlags, point);
}

void CFeature::OnUpdate(CView* pSender, LPARAM lHint, CObject* pHint) 
{
	
  // 1 - Get the current data from our document
 CMFFADoc* pDoc = GetDocument();
 
  if (m_myRadio == 0 )
{
    m_RMouthX = pDoc->m_pnt.x - 30;
    m_RMouthY = pDoc->m_pnt.y - 30; 
    FaceFeat.Mth.XRCorner = m_RMouthX;
    FaceFeat.Mth.YRCorner = m_RMouthY;
    Undo (UndoVector);
}
    else
  if (m_myRadio == 1 )
{
    m_LMouthX = pDoc->m_pnt.x - 30;
    m_LMouthY = pDoc->m_pnt.y - 30;
    FaceFeat.Mth.XLCorner = m_LMouthX;
    FaceFeat.Mth.YLCorner = m_LMouthY;
................................
....................................			
}
// 2 - Show the current data in our controls
	UpdateData( FALSE );
}

I need to be able to undo the drawing, lets say I've click it in the wrong place, then re-click in the right position.
In other words, how can I undo the drawing of the rectangle.

Please can anyone help.....

aaroncohn · #2 10-May-2004, 14:12

Hmmm... I would have a couple of global variables that store identifiers to describe what the user just did, and what the user did before that. Or you could even make a linked list of the user's actions. Then, to undo, all you have to do is clear the screen and draw what happened last time the user did something.

Max Payne · #3 10-May-2004, 19:39

The simplest way to do this is by using stack. you push user action and just simply pop when you want undo. Are you using MFC here?? THe you should look at this article, it may help:

UndoRedo1

There more if you search the site.

Using linked list is also a fine idea, but what is important is what and how you store the user action. Redrawing it is not that hard but it could be slow..

aaroncohn · #4 10-May-2004, 21:14

I haven't learned about stacks yet, so that was my only idea, and yeah... I realized it might take up a few more cycles than are really necessary :-P

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