DPI aware WPF application

处理在不同DPI情况下GUI显示的问题，有2个方法：

• 用 ViewBox 包一层

• 运行时转换转换像素单位

namespace Program
{
    public class pxExtension : MarkupExtension
    {
        private readonly double _len;
        public pxExtension(string len)
        {
            try
            {
                _len = double.Parse(len);
            }
            catch (Exception e)
            {
                throw new ArgumentException("pxExtension ctor argument invalid.", e);
            }
        }

        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            return ToUnits(_len);
        }

        public static double ToUnits(double desiredPixels)
        {
            double finalUnits = desiredPixels * 96 / Dpi;
            return finalUnits;
        }

        private static readonly int Dpi = DpiX;

        public static int DpiX
        {
            get
            {
                IntPtr dc = GetDC(IntPtr.Zero);
                return GetDeviceCaps(dc, LOGPIXELSX);
            }
        }
        public static int DpiY
        {
            get
            {
                IntPtr dc = GetDC(IntPtr.Zero);
                return GetDeviceCaps(dc, LOGPIXELSY);
            }
        }

        #region Win32 Interop

        [DllImport("User32.dll", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
        private static extern IntPtr GetDC(IntPtr hWnd);

        [DllImport("Gdi32.dll", CallingConvention = CallingConvention.StdCall, ExactSpelling = true)]
        private static extern int GetDeviceCaps(IntPtr hdc, int nIndex);

        private const int HORZRES = 8;
        private const int VERTRES = 10;
        private const int LOGPIXELSX = 88;
        private const int LOGPIXELSY = 90;

        #endregion
    }
}

<TextBlock Width="{local:px 50}" FontSize="{local:px 12}" Text="lalala" HorizontalAlignment="Center"/>