Q134421: HOWTO: How to Use CBitmapButton to Resize a Bitmap to Fit a Butt

Article: Q134421
Product(s): Microsoft C Compiler
Version(s): winnt:2.0,2.1,2.2,4.0,4.1,4.2
Operating System(s): 
Keyword(s): kbcode kbBitmap kbButton kbCtrl kbMFC KbUIDesign kbVC150 kbVC200 kbVC400 kbVC420 kbGrpD
Last Modified: 06-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++ for Windows, 16-bit edition, versions 1.5, 1.51, 1.52 
   - Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 2.2, 4.0, 4.1 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
   - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
-------------------------------------------------------------------------------

SUMMARY
=======

You can override the default behavior of CBitmapButton so the bitmap sizes to
fit the button. How CBitmapButtons behave during initialization depends on which
function is used to load the bitmaps.

Function        Behavior                  When used
AutoLoad()      button sizes to bitmap    button is in dialog box

LoadBitmaps()   button remains at size    button is in non-dialog
               specified when created    window

If you want the bitmap to stretch to fit the dimensions of the button you create,
you must override these functions:

     CBitmapButton::AutoLoad()
     CBitmapButton::DrawItem()

NOTE: You need only override AutoLoad() if you call it to initialize a button.

MORE INFORMATION
================

The following steps give the necessary changes to AutoLoad and DrawItem:

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:

  a. 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
          ...
        };

  b. 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:

  a. 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
          ...
        };

  b. 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.

Additional query words: kbinf 1.50 1.51 1.52 2.50 2.51 2.52 2.00 2.10 2.20 3.00 3.10 4.00 4.10 4.20

======================================================================
Keywords          : kbcode kbBitmap kbButton kbCtrl kbMFC KbUIDesign kbVC150 kbVC200 kbVC400 kbVC420 kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:2.0,2.1,2.2,4.0,4.1,4.2
Issue type        : kbhowto

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.