1.50 1.51 1.52 | 2.00 2.10 2.20 4.00 4.10 4.20
WINDOWS | WINDOWS NT
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The information in this article applies to:
- The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++ for Windows, versions 1.5, 1.51, 1.52
- Microsoft Visual C++, 32-bit Edition, versions 2.0, 2.1, 2.2,
4.0, 4.1, 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:
- Implement the owner drawn CBitmapButton using one of the standard
procedures described in the Books Online help for the CBitmapButton
class.
- 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.
- 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();
- 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);
- Modify the declaration of the CBitmapButton member variable from step 1
so that it is now of type CMyButton.
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