Can I add a control in the ribbon bar caption?

// MmRibbonBar.h

///
/// \enum eSearchPosition
///
enum eSearchPosition
  {
  eSearchPositionTabControl = 0, ///< Next to the tab control, similar to Office 2016 products.
  eSearchPositionTitleBar, ///< In the frame hook title bar, similar to Office 365 (late 2019).
  eSearchPositionDefault = eSearchPositionTabControl
  };

#define SEARCH_MINIMUM_WIDTH XPT_DPI_X(40)
#define SEARCH_MAXIMUM_WIDTH XTP_DPI_X(220)
#define SEARCH_HEIGHT        XTP_DPI_Y(22)

...

// MmRibbonBar.cpp

CSize CMmRibbonBar::CalcDockingLayout(int nLength, DWORD dwMode, int nWidth /*= 0*/)
  {
  CXTPControl *pControlSearch = NULL;
  if (dwMode & LM_COMMIT)
    {
    pControlSearch = m_pControls->FindControl(xtpControlEdit, ID_COMMAND_SEARCH, TRUE, FALSE);
    if (pControlSearch)
      {
      if (m_searchPosition == eSearchPositionTabControl)
        {
        pControlSearch->SetVisible(TRUE);
        // Minimum width and padding.
        pControlSearch->SetWidth(SEARCH_MINIMUM_WIDTH + XTP_DPI_X(16));
        }
      else
        {
        // Hide before base calc docking layout to avoid this control effecting the size.
        pControlSearch->SetVisible(FALSE);
        }
      }
    }

  const CSize sz = CXTPRibbonBar::CalcDockingLayout(nLength, dwMode, nWidth);

  if (dwMode & LM_COMMIT)
    {
    if (pControlSearch)
      {
      // Left align the left-most right aligned edit control to the last visible tab item.
      CRect rcSearch = GetSearchControlRect(pControlSearch);

      if (IsBackstageViewVisible())
        {
        // Hide when backstage view is active.
        pControlSearch->SetVisible(FALSE);
        }
      else if (m_searchPosition == eSearchPositionTabControl)
        {
        ASSERT(pControlSearch->IsVisible());
        pControlSearch->SetWidth(rcSearch.Width());
        pControlSearch->SetRect(rcSearch);

        if (m_pControlTab && m_rcTabControl.right > rcSearch.left)
          {
          // Resize tab control.
          // Don't want overlap between the edit control and the tab control as it messes with hit testing.
          m_rcTabControl.right = rcSearch.left;
          m_pControlTab->SetRect(m_rcTabControl);
          }
        }
      else
        {
        // If there is not enough room, hide the control.
        if (rcSearch.Width() >= SEARCH_MINIMUM_WIDTH)
          {
          pControlSearch->SetRect(rcSearch);
          pControlSearch->SetVisible(TRUE);
          }
        }
      }
    }

  return sz;
  }
  
  CRect CMmRibbonBar::GetSearchControlRect(CXTPControl *pControlSearch) const
  {
  using std::min;
  using std::max;

  CRect rcControl;

  switch (m_searchPosition)
    {
    case eSearchPositionTabControl:
      {
      // Get last visible tab item.
      const CXTPTabManagerItem *pLastTabItem = NULL;
      for (int i = m_pControlTab->GetItemCount() - 1; i >= 0; --i)
        {
        const CXTPTabManagerItem *pTabItem = m_pControlTab->GetItem(i);
        if (pTabItem->IsVisible())
          {
          pLastTabItem = pTabItem;
          break;
          }
        }

      // Get next visible ribbon background control to the right of this control.
      CXTPControl *pRHSControl = NULL;
      for (int i = pControlSearch->GetIndex() + 1; i < GetControlCount(); ++i)
        {
        CXTPControl *pControl = GetControl(i);
        if (pControl &&
            pControl->IsVisible() &&
            pControl->GetFlags() & (xtpFlagRightAlign | xtpFlagRibbonTabBackground) &&
            pControl->GetID() != ID_COMMAND_SEARCH)
          {
          pRHSControl = pControl;
          break;
          }
        }

      if (pLastTabItem)
        {
        const CRect rcLastTab = pLastTabItem->GetRect();

        CRect rcClient;
        GetClientRect(&rcClient);

        int nLeft = rcLastTab.right + XTP_DPI_X(8);
        int nTop = rcLastTab.top;
        int nRight = rcClient.right - XTP_DPI_X(8);
        if (pRHSControl)
          nRight = pRHSControl->GetRect().left - XTP_DPI_X(8);
        int nBottom = rcLastTab.bottom - XTP_DPI_Y(2);

        int nSearchMinWidth = SEARCH_MINIMUM_WIDTH;
        int nSearchMaxWidth = SEARCH_MAXIMUM_WIDTH;

        int nSearchWidth = max(nSearchMinWidth, min(nSearchMaxWidth, nRight - nLeft));
        int nSearchHeight = SEARCH_HEIGHT;

        // Left align the left-most right aligned edit control to the last visible tab item.
        rcControl = CRect(nLeft,
                          nTop + (nBottom - nTop) / 2 - nSearchHeight / 2,
                          nLeft + nSearchWidth,
                          nTop + (nBottom - nTop) / 2 + nSearchHeight / 2);
        }
      }
      break;
    case eSearchPositionTitleBar:
      {
      // Get frame hook caption button.
      CXTPControl *pMinimize = m_pControls->FindControl(SC_MINIMIZE);

      // Get last visible tab item.
      const CXTPRibbonTabContextHeader *pFirstContextHeader = NULL;
      const CXTPRibbonTabContextHeader *pLastContextHeader = NULL;
      for (int i = m_pControlTab->GetItemCount() - 1; i >= 0; --i)
        {
        CXTPRibbonTab *pTab = DYNAMIC_DOWNCAST(CXTPRibbonTab, m_pControlTab->GetItem(i));
        if (pTab && pTab->IsVisible())
          {
          CXTPRibbonTabContextHeader *pContextHeader = pTab->GetContextHeader();
          if (pContextHeader)
            {
            if (!pLastContextHeader)
              pLastContextHeader = pContextHeader;
            pFirstContextHeader = pContextHeader;
            }
          }
        }

      if (pMinimize)
        {
        CRect rcMinimize = pMinimize->GetRect();
        CRect rcCaption = m_rcCaptionText;

        int nMaxSearchWidth = SEARCH_MAXIMUM_WIDTH;

        int nTop = rcMinimize.top + XTP_DPI_Y(4);
        int nBottom = rcMinimize.bottom - XTP_DPI_Y(4);
        int nLeft, nRight;
        if (pFirstContextHeader && pLastContextHeader)
          {
          // pFirstContextHeader can be equal to pLastContextHeader if only a single context is up.
          CRect rcFirstContextTab = pFirstContextHeader->m_rcRect;
          CRect rcLastContextTab = pLastContextHeader->m_rcRect;

          // Left side of context titles.
          int nLeftLeft = rcCaption.right + XTP_DPI_X(8);
          int nLeftRight = rcFirstContextTab.left - XTP_DPI_X(8);

          // Right side of context titles (preferred).
          int nRightLeft = std::max(rcCaption.right, rcLastContextTab.right) + XTP_DPI_X(8);
          int nRightRight = rcMinimize.left - XTP_DPI_X(8);

          if (nLeftRight - nLeftLeft > nRightRight - nRightLeft && 
              nRightRight - nRightLeft < nMaxSearchWidth) // Prefer right if it can fit max width.
            {
            nLeft = nLeftLeft;
            nRight = nLeftRight;
            }
          else
            {
            nLeft = nRightLeft;
            nRight = nRightRight;
            }
          }
        else
          {
          nLeft = rcCaption.right + XTP_DPI_X(8);
          nRight = rcMinimize.left - XTP_DPI_X(8);
          }

        int nSearchWidth = min(nMaxSearchWidth, nRight - nLeft);
        int nSearchHeight = SEARCH_HEIGHT;

        // Right align to the left-most caption button (minimize button).
        rcControl = CRect(nLeft + (nRight - nLeft) / 2 - nSearchWidth / 2,
                          nTop + (nBottom - nTop) / 2 - nSearchHeight / 2,
                          nLeft + (nRight - nLeft) / 2 + nSearchWidth / 2,
                          nTop + (nBottom - nTop) / 2 + nSearchHeight / 2);
        }
      }
      break;
    default:
      ASSERT(0);
    }

  return rcControl;
  }