Rounded Corners on Windows 11

///
/// \enum CornerPreference
/// 
enum class CornerPreference
  {
  Default    = 0, ///< Let the system decide to round window corners.
  DoNotRound = 1, ///< Never round window corners.
  Round      = 2, ///< Round corners if appropriate.
  RoundSmall = 3, ///< Round corners if appropriate (with small radius).
  };

HRESULT UpdateWindows11RoundCorners(HWND hWnd, CornerPreference cornerPreference)
  {
  typedef HRESULT(WINAPI *PFNSETWINDOWATTRIBUTE)(HWND hWnd, DWORD dwAttribute, LPCVOID pvAttribute, DWORD cbAttribute);

  // We don't build against the Windows 11 SDK so we define these ourselves. These are normally
  // defined in dwmapi.h header.

  ///
  /// \enum DWMWINDOWATTRIBUTE
  /// 
  enum DWMWINDOWATTRIBUTE
    {
    DWMWA_WINDOW_CORNER_PREFERENCE = 33
    };

  ///
  /// \enum DWM_WINDOW_CORNER_PREFERENCE
  /// 
  enum DWM_WINDOW_CORNER_PREFERENCE
    {
    DWMWCP_DEFAULT    = 0,
    DWMWCP_DONOTROUND = 1,
    DWMWCP_ROUND      = 2,
    DWMWCP_ROUNDSMALL = 3
    };

  HMODULE hDwmApi = ::LoadLibrary(_T("dwmapi.dll"));
  if (hDwmApi)
    {
    auto *pfnSetWindowAttribute = reinterpret_cast<PFNSETWINDOWATTRIBUTE>(
      ::GetProcAddress(hDwmApi, "DwmSetWindowAttribute"));
    if (pfnSetWindowAttribute)
      {
      auto preference = static_cast<DWM_WINDOW_CORNER_PREFERENCE>(cornerPreference);
      return pfnSetWindowAttribute(hWnd, DWMWA_WINDOW_CORNER_PREFERENCE, 
                                   &preference, sizeof(DWM_WINDOW_CORNER_PREFERENCE));
      }
    ::FreeLibrary(hDwmApi);
    }

  return E_FAIL;
  }

pCommandBars->GetFrameHook()->m_bAllowDwm = TRUE;