HOWTO: How to Use CBitmapButton to Resize a Bitmap to Fit a Button

MORE INFORMATION

1. Implement the owner drawn CBitmapButton using one of the standard procedures described in the Books Online help for the CBitmapButton class.
2. Derive a class from CBitmapButton.
   
   NOTE: If you are using Classwizard, you can not derive directly from CBitmapButton; use a base class lower in hierarchy.
3. To override the AutoLoad member function:
   
   
   1. Include a function prototype in your CBitmapButton-derived class header (.h) file, as in this example:

            class CMyButton: public CBitmapButton
            {
              ...
            public:
              CMyButton(){};
              BOOL AutoLoad(UINT nID, CWnd* pParent);     // ADD THIS LINE
              ...
            };
      								

   2. Implement CMyButton::AutoLoad() in the .cpp file by copying the CBitmapButton::AutoLoad() function from Winbtn.cpp file in the MFC Src directory and changing the following line near the end of the function into a comment:

            // change following to a comment to prevent button resizing
            // SizeToContent();
      								

4. To override the DrawItem() member function:
   
   
   1. Include a function prototype in your CBitmapButton-derived class header (.h) file, as in this example:

            class CMyButton: public CBitmapButton
            {
              ...
            public:
              CMyButton(){};
              void DrawItem(LPDRAWITEMSTRUCT lpDIS);     // ADD THIS LINE
              ...
            };
      								

   2. Implement CBitmapButton::DrawItem() in the .cpp file by copying the CBitmapButton::DrawItem() function from Winbtn.cpp in the MFC Src directory and making these changes:
      
      Replace this code:

               pDC->BitBlt(rect.left, rect.top, rect.Width(), rect.Height(),
                   &memDC, 0, 0, SRCCOPY);
      								

      with this code:

               // determine bitmaps size for use in StretchBlt
               BITMAP bits;
               pBitmap->GetObject(sizeof(BITMAP),&bits);
               pDC->StretchBlt(rect.left,rect.top,rect.Width(),rect.Height(),
                  &memDC,0,0,bits.bmWidth, bits.bmHeight, SRCCOPY);
      								

5. Modify the declaration of the CBitmapButton member variable from step 1 so that it is now of type CMyButton.