private void UpdateLayeredWindow(Rectangle rect)
        {
            // Cache the latest size and location
            _showRect = rect;

            // Must have a visible rectangle to render
            if ((rect.Width > 0) && (rect.Height > 0))
            {
                // Draw onto a bitmap that is then used as the window display
                Bitmap memoryBitmap = new Bitmap(rect.Width, rect.Height, PixelFormat.Format32bppArgb);
                using (Graphics g = Graphics.FromImage(memoryBitmap))
                {
                    // Perform actual painting onto the bitmap
                    Rectangle area = new Rectangle(0, 0, rect.Width, rect.Height);
                    using (RenderContext context = new RenderContext(null, g, area, _renderer))
                    {
                        _renderer.RenderGlyph.DrawDragDropDockingGlyph(context, _dragData, _paletteDragDrop, PaletteDragFeedback.Rounded);
                    }

                    // Get hold of the screen DC
                    IntPtr hDC = PI.GetDC(IntPtr.Zero);

                    // Create a memory based DC compatible with the screen DC
                    IntPtr memoryDC = PI.CreateCompatibleDC(hDC);

                    // Get access to the bitmap handle contained in the Bitmap object
                    IntPtr hBitmap = memoryBitmap.GetHbitmap(Color.FromArgb(0));

                    // Select this bitmap for updating the window presentation
                    IntPtr oldBitmap = PI.SelectObject(memoryDC, hBitmap);

                    // New window size
                    PI.SIZE ulwsize;
                    ulwsize.cx = rect.Width;
                    ulwsize.cy = rect.Height;

                    // New window position
                    PI.POINT topPos = new PI.POINT(rect.Left, rect.Top);
                    // Offset into memory bitmap is always zero
                    PI.POINT pointSource = new PI.POINT(0, 0);

                    // We want to make the entire bitmap opaque
                    PI.BLENDFUNCTION blend = new PI.BLENDFUNCTION
                    {
                        BlendOp             = PI.AC_SRC_OVER,
                        BlendFlags          = 0,
                        SourceConstantAlpha = 255,
                        AlphaFormat         = PI.AC_SRC_ALPHA
                    };

                    // Tell operating system to use our bitmap for painting
                    PI.UpdateLayeredWindow(Handle, hDC, ref topPos, ref ulwsize,
                                           memoryDC, ref pointSource, 0, ref blend,
                                           PI.ULW_ALPHA);

                    // Put back the old bitmap handle
                    PI.SelectObject(memoryDC, oldBitmap);

                    // Cleanup resources
                    PI.ReleaseDC(IntPtr.Zero, hDC);
                    PI.DeleteObject(hBitmap);
                    PI.DeleteDC(memoryDC);
                }
            }
        }
        private void UpdateLayeredWindow(Rectangle rect)
        {
            // Cache the latest size and location
            _showRect = rect;

            // Must have a visible rectangle to render
            if ((rect.Width > 0) && (rect.Height > 0))
            {
                // Draw onto a bitmap that is then used as the window display
                Bitmap memoryBitmap = new Bitmap(rect.Width, rect.Height, PixelFormat.Format32bppArgb);
                using (Graphics g = Graphics.FromImage(memoryBitmap))
                {
                    // Perform actual painting onto the bitmap
                    Rectangle area = new Rectangle(0, 0, rect.Width, rect.Height);
                    using (RenderContext context = new RenderContext(null, g, area, _renderer))
                        _renderer.RenderGlyph.DrawDragDropDockingGlyph(context, _dragData, _paletteDragDrop, PaletteDragFeedback.Rounded);

                    // Get hold of the screen DC
                    IntPtr hDC = PI.GetDC(IntPtr.Zero);

                    // Create a memory based DC compatible with the screen DC
                    IntPtr memoryDC = PI.CreateCompatibleDC(hDC);

                    // Get access to the bitmap handle contained in the Bitmap object
                    IntPtr hBitmap = memoryBitmap.GetHbitmap(Color.FromArgb(0));

                    // Select this bitmap for updating the window presentation
                    IntPtr oldBitmap = PI.SelectObject(memoryDC, hBitmap);

                    // New window size
                    PI.SIZE ulwsize;
                    ulwsize.cx = rect.Width;
                    ulwsize.cy = rect.Height;

                    // New window position
                    PI.POINT topPos;
                    topPos.x = rect.Left;
                    topPos.y = rect.Top;

                    // Offset into memory bitmap is always zero
                    PI.POINT pointSource;
                    pointSource.x = 0;
                    pointSource.y = 0;

                    // We want to make the entire bitmap opaque
                    PI.BLENDFUNCTION blend = new PI.BLENDFUNCTION();
                    blend.BlendOp = (byte)PI.AC_SRC_OVER;
                    blend.BlendFlags = 0;
                    blend.SourceConstantAlpha = 255;
                    blend.AlphaFormat = (byte)PI.AC_SRC_ALPHA;

                    // Tell operating system to use our bitmap for painting
                    PI.UpdateLayeredWindow(Handle, hDC, ref topPos, ref ulwsize,
                                           memoryDC, ref pointSource, 0, ref blend,
                                           (int)PI.ULW_ALPHA);

                    // Put back the old bitmap handle
                    PI.SelectObject(memoryDC, oldBitmap);

                    // Cleanup resources
                    PI.ReleaseDC(IntPtr.Zero, hDC);
                    PI.DeleteObject(hBitmap);
                    PI.DeleteDC(memoryDC);
                }
            }
        }