wxBitmap不在Mac上的wxButton中居中

class MyButton : public wxButton
{
public:
    MyButton(wxWindow* parent, wxWindowID id, const wxString& label, const wxPoint& pos, const wxSize& size)
        : wxButton(parent, id, label, pos, size)
    {
    }

private:
    void OnPaint(wxPaintEvent& event)
    {
        wxPaintDC dc(this);
        wxClientDC clientDC(this);

        // 绘制按钮的背景和边框
        dc.SetBackground(wxBrush(GetBackgroundColour()));
        dc.Clear();
        dc.DrawRectangle(GetClientRect());

        // 获取按钮的尺寸
        wxSize buttonSize = GetSize();

        // 获取wxBitmap的尺寸
        wxSize bitmapSize = m_bitmap.GetSize();

        // 计算居中显示的位置
        int x = (buttonSize.GetWidth() - bitmapSize.GetWidth()) / 2;
        int y = (buttonSize.GetHeight() - bitmapSize.GetHeight()) / 2;

        // 在按钮中居中显示wxBitmap
        clientDC.DrawBitmap(m_bitmap, x, y);
    }

private:
    wxBitmap m_bitmap;

    DECLARE_EVENT_TABLE()
};

BEGIN_EVENT_TABLE(MyButton, wxButton)
    EVT_PAINT(MyButton::OnPaint)
END_EVENT_TABLE()