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Editable Flex Grid (without an Edit control)

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Editable Flex Grid: How to edit Flex grid?

Indeed there is a demo project in MSDN for VB. But there is no example for VC. There is no one to one conversion of the source from VB to VC. Even if you convert the VB project to VC, you are still left with some of the magic numbers to map correctly edit box to the grid cell. For my different views I have to always twick those magic numbers to get edit box in sync with the flexgrid cells. At the end of the article I shown the edit box approach also. If some body knows a way to eliminate those magic numbers, please let me know.

I used a different approach than using an Edit control. With this approach, I am trapping the keys and manipulating them which gives user a feeling as he is editing the grid cell directly.

This approach is very easy to use as I put all the functionality in a single class called CGrid.

Using the CGrid Class

  1. You simply need to include this class' header file in your project and declare a CGrid object.
  2. CGrid m_grid;
    
  3. Define an HWND hGrid variable in your view class.
  4. From the Flex Grid click and key press events just call the m_grid equivalent functions as follows:
  5. void CFlexGridView::OnClickMsflexgrid1() 
    {
     m_grid.OnClickGrid ();
    }
    
    void CFlexGridView::OnKeyPressMsflexgrid1(short FAR* KeyAscii) 
    {
     m_grid.OnKeyPressGrid ( KeyAscii);	
    }
    
    BOOL CFlexGridView::PreTranslateMessage(MSG* pMsg) 
    {
     if (pMsg->message == WM_KEYDOWN  
     && (pMsg->hwnd == hGrid  ) ) {
    
      switch (pMsg->wParam ) {
     
       case VK_UP : 
       m_grid.GoUp ();
       return TRUE;
     
       case VK_DOWN:
       m_grid.GoDown();
       return TRUE;
     
       case VK_LEFT : 
       m_grid.GoLeft();
       return TRUE;
     
       case VK_RIGHT: 
       m_grid.GoRight();
       return TRUE;
      }
     }		
     
     return CFormView::PreTranslateMessage(pMsg);
    }
    
    void CFlexGridView::OnInitialUpdate()
    {
     CFormView::OnInitialUpdate();
     CWnd * hwnd = GetDlgItem (IDC_MSFLEXGRID1);
     hGrid = hwnd->GetSafeHwnd ();
    }
    
Thats all for making flex grid editiable . Enjoy.

Part 2

Following is the code which is a translation of the MSDN VB code example to Visual C++.
void CGridEdit::MoveEditBox ()
{
 HDC hDC; 
 hDC = ::GetDC (NULL); 

 SetMapMode (hDC, MM_TWIPS);

 RECT rec;
 m_grid.GetWindowRect (&rec);

 int x,y,h,w;
 x =  XTwipsToPixels (rec.left) 
   + XTwipsToPixels ( m_grid.GetCellLeft () );

 y =  YTwipsToPixels (rec.top ) 
   +  YTwipsToPixels( m_grid.GetCellTop ()  );

 h = (int) XTwipsToPixels (m_grid.GetCellHeight() );
 w = (int) YTwipsToPixels(m_grid.GetCellWidth () );

 //MAGIC NUMBERS ????
 y = y + 148;    
 x = x + 27; 

 m_edit.MoveWindow  (x ,y,w,h ,TRUE); //has to be in pixels
 m_edit.BringWindowToTop ();

 m_edit.SetFocus ();	

 TransferValue (FALSE); //get the value in Editbox
}

Utility Functions

BOOL CGridEdit::TransferValue(BOOL ToGrid)
{
 CString sText;
 
 if (ToGrid) { //Transfer value to Grid from Edit Box
  GetDlgItemText (IDC_EDITBOX,sText);
  m_grid.SetText( sText );
  
 } else {
  sText = m_grid.GetText ();
  SetDlgItemText (IDC_EDITBOX,sText); 
 }

 return TRUE;
}
 
short lpx = 0;
short lpy = 0;
 
// called once to get constants
void GetDeviceConstants(void)
{
 HDC hdc = GetDC(NULL);
 
 //pixel in one logical inch
 lpx = GetDeviceCaps(hdc, LOGPIXELSX); 
 lpy = GetDeviceCaps(hdc, LOGPIXELSY);

 ReleaseDC(NULL, hdc);
}       
 
long XTwipsToPixels(long twips)
{
 if (!lpx) 
  GetDeviceConstants();

 return MulDiv(lpx, (int)twips, 1440);
 // Total pixel in Inch = Total pixel in twips/1440
}
 
long YTwipsToPixels(long twips)
{
 if (!lpy) 
  GetDeviceConstants();

 return MulDiv(lpy, (int)twips, 1440);
}  
 
long XPixelsToTwips(long pixels)
{
 if (!lpx) 
  GetDeviceConstants();

 return MulDiv(pixels, 1440, lpx);
}
 
long YPixelsToTwips(long pixels)
{
 if (!lpx) GetDeviceConstants();
  return MulDiv(pixels, 1440, lpy);
}  

Downloads

Download demo application - 16 Kb
Download demo source - 31 Kb


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