[vtkusers] Re: Single/Multiple Document Examples for MFC

[Nigel Nunn]

Wrt MFC demos for Vtk 4 Sebastien BARRE wrote: 
 
> At 1/30/2002 04:08 PM, Andrew J. P. Maclean wrote: 
> 
> > I have two examples, one for a Single Document Interface 
> > (SDI) and the other for a Multiple Document Interface (MDI) 
> > using MFC. Each example has a compressed html file (about 18k) 
> > of instructions. Does anyone at Kitware want to look at it? 
> > I would suggest that they could go into the directory tree 
> > at: VTK\Examples\GUI\Win32 
> > 
> Go ahead, send them to me privately. 
 
 
Andrew's examples are a neat repackaging of the old Sample, 
and the well-crafted HTML instructions are great.  However, 
I feel the main shortcoming of the existing Sample is not 
that it splits support for Vtk over 2+1 classes, but that 
it buries the message handlers in WindowProc().  I used MFC 
at a fairly advanced level for 5 years before ever meeting 
a "WindowProc".  Those getting started with both MFC and Vtk 
might find things easier if we explicitly exposed the usual 
set of message handlers in the normal MFC way: message maps. 
 
//------------------------------------------------  
class vtkMFCRenderView : public CView 
//------------------------------------------------  
{ 
protected: 
  vtkMFCRenderView(); 
  DECLARE_DYNCREATE(vtkMFCRenderView) 
 
  vtkRenderer                    *m_Ren; 
  vtkWin32OpenGLRenderWindow     *m_RenWin; 
  vtkWin32RenderWindowInteractor *m_IRen; 
 
  // etc. 
  ... 
 
protected: 
  //{{AFX_MSG(vtkMFCRenderView) 
  afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct); 
  afx_msg void OnSize(UINT nType, int cx, int cy); 
  afx_msg BOOL OnEraseBkgnd(CDC* pDC); 
  afx_msg void OnTimer(UINT nIDEvent); 
  afx_msg void OnChar(UINT nChar, UINT nRepCnt, UINT nFlags); 
  afx_msg void OnMouseMove(UINT nFlags, CPoint point); 
  afx_msg void OnLButtonDown(UINT nFlags, CPoint point); 
  afx_msg void OnLButtonUp(UINT nFlags, CPoint point); 
  afx_msg void OnMButtonDown(UINT nFlags, CPoint point); 
  afx_msg void OnMButtonUp(UINT nFlags, CPoint point); 
  afx_msg void OnRButtonDown(UINT nFlags, CPoint point); 
  afx_msg void OnRButtonUp(UINT nFlags, CPoint point); 
  afx_msg void OnEditCopy(); 
  //}}AFX_MSG 
 
  DECLARE_MESSAGE_MAP() 
}; 
 
 
A user can have their way in the usual MFC handler, and 
when done, pass control through to vtkHandleMessage2(...); 
 
//------------------------------------------------  
void vtkMFCRenderView::OnLButtonDown(UINT nFlags, CPoint point) 
//------------------------------------------------ 
{
  if (nFlags & MK_CONTROL)
  { 
    my_pick_operation(); 
    go_wild(); 
  } 

  CallInteractor(WM_LBUTTONDOWN, (WPARAM)(UINT)(nFlags), 
                 MAKELPARAM((point.x), (point.y)));
}
 
 
CallInteractor(..) wraps the call to vtkHandleMessage2: 
 
 
//------------------------------------------------ 
LRESULT vtkMFCRenderView::CallInteractor
(
  UINT uMsg, 
  WPARAM wParam, 
  LPARAM lParam
)
//------------------------------------------------ 
{ 
  // Replaces... WindowProc(UINT, WPARAM, LPARAM) 
  // Maintain individual event handlers that pass 
  // control here. 
 
  if (m_IRen->GetInitialized()) 
  { 
    return vtkHandleMessage2(m_hWnd, uMsg, wParam, lParam, m_IRen); 
  } 
  return 0; 
} 

Of course, this highlights the problem:  many of us using 
Vtk under MFC have customised approaches to exploiting 
the power of MFC to orchestrate the wonders of Vtk  :-) 
MFC and Win32 are vast -- may be why some folks give 
up after a mere six months and start looking around for 
less [huge/magical/awesome/beautiful] solutions? 
 
thanks, 
Nigel