MFC Ribbon: change icon of a button (dynamically)

Question

For CMFCRibbonBar, I want to change the icon of a button depnding on application state.

(I've dug through the code and documentation for a while, but haven't found anything helpful.)

Answer 1

I derived a class CMFCRibbonButtonEx from CMFCRibbonButton to control how the icon is being drawn. In this special case I wanted to alpha-blend a green checkmark over the original icon:

Header:

class CMFCRibbonButtonEx : public CMFCRibbonButton
{
// Construction
public:
    CMFCRibbonButtonEx();
    CMFCRibbonButtonEx(UINT nID, LPCTSTR lpszText, int nSmallImageIndex = -1, int nLargeImageIndex = -1, BOOL bAlwaysShowDescription = FALSE);
    CMFCRibbonButtonEx(UINT nID, LPCTSTR lpszText, HICON hIcon, BOOL bAlwaysShowDescription = FALSE, HICON hIconSmall = NULL, BOOL bAutoDestroyIcon = FALSE, BOOL bAlphaBlendIcon = FALSE);

// Overridden
    void SetCheck(BOOL bCheck = TRUE);
    void DrawImage(CDC* pDC, RibbonImageType type, CRect rectImage);

// Attributes
private:
    BOOL m_bChecked;

// Helper
private:
    void DrawCheckmark(CDC* pDC, int CheckmarkResourceBitmapID, RECT *r);
    void PremultiplyBitmapAlpha(HDC hDC, HBITMAP hBmp);
};  

Implementation:

CMFCRibbonButtonEx::CMFCRibbonButtonEx() : CMFCRibbonButton() { }
CMFCRibbonButtonEx::CMFCRibbonButtonEx(UINT nID, LPCTSTR lpszText, int nSmallImageIndex, int nLargeImageIndex, BOOL bAlwaysShowDescription)
    : CMFCRibbonButton(nID, lpszText, nSmallImageIndex, nLargeImageIndex, bAlwaysShowDescription) { }
CMFCRibbonButtonEx::CMFCRibbonButtonEx(UINT nID, LPCTSTR lpszText, HICON hIcon, BOOL bAlwaysShowDescription, HICON hIconSmall, BOOL bAutoDestroyIcon, BOOL bAlphaBlendIcon)
    : CMFCRibbonButton(nID, lpszText, hIcon, bAlwaysShowDescription , hIconSmall, bAutoDestroyIcon, bAlphaBlendIcon) { }
void CMFCRibbonButtonEx::SetCheck(BOOL bCheck)
{
    m_bChecked = bCheck;
}
void CMFCRibbonButtonEx::DrawImage(CDC* pDC, RibbonImageType type, CRect rectImage)
{
    CMFCRibbonButton::DrawImage(pDC, type, rectImage);
    if (type == RibbonImageLarge && m_bChecked) 
        DrawCheckmark(pDC, IDB_BIG_ICON_CHECKMARK, &rectImage);
}
void CMFCRibbonButtonEx::DrawCheckmark(CDC* pDC, int CheckmarkResourceBitmapID, RECT *r)
{
    HDC  hdc;
    CDC  *dc;
    CDC dcMem;
    CBitmap cbm;

    VERIFY(hdc = pDC->m_hDC);
    VERIFY(dc = pDC);

    dcMem.CreateCompatibleDC(dc);

    cbm.LoadBitmap(CheckmarkResourceBitmapID);
    PremultiplyBitmapAlpha(dcMem.m_hDC, cbm);
    SelectObject(dcMem.m_hDC, cbm.m_hObject);

    BLENDFUNCTION bf;
    bf.BlendOp = AC_SRC_OVER;
    bf.BlendFlags = 0;
    bf.SourceConstantAlpha = 255;
    bf.AlphaFormat = AC_SRC_ALPHA;
    ::AlphaBlend(hdc, r->left, r->top, r->right-r->left, r->bottom-r->top, dcMem, 0, 0, 32, 32, bf);

    VERIFY(dcMem.DeleteDC());
}
void CMFCRibbonButtonEx::PremultiplyBitmapAlpha(HDC hDC, HBITMAP hBmp)
{
   BITMAP bm = { 0 };
   GetObject(hBmp, sizeof(bm), &bm);
   BITMAPINFO* bmi = (BITMAPINFO*) _alloca(sizeof(BITMAPINFOHEADER) + (256 * sizeof(RGBQUAD)));
   ::ZeroMemory(bmi, sizeof(BITMAPINFOHEADER) + (256 * sizeof(RGBQUAD)));
   bmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
   BOOL bRes = ::GetDIBits(hDC, hBmp, 0, bm.bmHeight, NULL, bmi, DIB_RGB_COLORS);
   if( !bRes || bmi->bmiHeader.biBitCount != 32 ) return;
   LPBYTE pBitData = (LPBYTE) ::LocalAlloc(LPTR, bm.bmWidth * bm.bmHeight * sizeof(DWORD));
   if( pBitData == NULL ) return;
   LPBYTE pData = pBitData;
   ::GetDIBits(hDC, hBmp, 0, bm.bmHeight, pData, bmi, DIB_RGB_COLORS);
   for( int y = 0; y < bm.bmHeight; y++ ) {
      for( int x = 0; x < bm.bmWidth; x++ ) {
         pData[0] = (BYTE)((DWORD)pData[0] * pData[3] / 255);
         pData[1] = (BYTE)((DWORD)pData[1] * pData[3] / 255);
         pData[2] = (BYTE)((DWORD)pData[2] * pData[3] / 255);
         pData += 4;
      }
   }
   ::SetDIBits(hDC, hBmp, 0, bm.bmHeight, pBitData, bmi, DIB_RGB_COLORS);
   ::LocalFree(pBitData);
}

This is how I build my 'Filter' submenu with the CMFCRibbonButtonEx items:

m_pBtnFilter->RemoveAllSubItems();

int i;
for (i = 0; i < m_csaNames.GetSize(); i++)
{
    std::auto_ptr<CMFCRibbonButtonEx> apBtn(new CMFCRibbonButtonEx(ID_FILTER_BASE + i, (LPCTSTR)m_csaNames[i], m_tbiIcons.ExtractIcon(m_nIcons[i], true, NULL, true, true));
    apBtn->SetToolTipText(m_csaTooltips[i]);
    m_pBtnFilter->AddSubItem(apBtn.release());
}

I'm sure you can adapt this to the main menu buttons (and the special way you want the application state have effect on the icons) without problems.