XPutImage example for GTK#

x11.cs

    public static class X11
    {
        [DllImport ("libX11.so.6")]
        static extern  IntPtr XOpenDisplay(IntPtr display);
        static IntPtr Disp;
        [DllImport ("libX11.so.6")]
        static extern int XGetGeometry(IntPtr disp, IntPtr hwnd, out IntPtr root, out int x, out int y,
            out int width, out int height, out int border, out int depth);
        [DllImport ("libX11.so.6")]
        static extern  IntPtr XInitImage(ref XImage image);

        [StructLayout(LayoutKind.Sequential)]
        unsafe struct XImage
        {
            public int width, height;      
            public int xoffset;           
            public int format;        
            public IntPtr data;         
            public int byte_order;         
            public int bitmap_unit;        
            public int bitmap_bit_order;       
            public int bitmap_pad;         
            public int depth;          
            public int bytes_per_line;    
            public int bits_per_pixel;     
            public ulong red_mask;     
            public ulong green_mask;
            public ulong blue_mask;
            fixed byte fill [128];
        }
        [DllImport ("libX11.so.6")]
        static extern int XPutImage(IntPtr display, IntPtr drawable, IntPtr gc, ref XImage img,
                                        int srcx, int srcy, int destx, int desty, int width, int height);

        [DllImport ("libX11.so.6")]
        static extern IntPtr XCreateGC(IntPtr display, IntPtr drawable, ulong unused, IntPtr unused2);

        [DllImport ("libX11.so.6")]
        static extern int XFreeGC(IntPtr display, IntPtr gc);

        static void ConvertImage(ref XImage image, IntPtr data, int width, int height, int rowBytes, int bytesPerPixel)
        {
            int bitsPerPixel = bytesPerPixel * 8;
            image.width = width;
            image.height = height;
            image.format = 2;
            image.data = data;
            image.byte_order = 0;
            image.bitmap_unit = bitsPerPixel;
            image.bitmap_bit_order = 0;
            image.bitmap_pad = bitsPerPixel;
            image.depth = 24;
            image.bytes_per_line = rowBytes;// - width * bytesPerPixel;
            image.bits_per_pixel = bitsPerPixel;
            XInitImage(ref image);
        }



        static X11()
        {
            Disp = XOpenDisplay(IntPtr.Zero);
        }

        public static void GetPlatformWindowSize(IntPtr hwnd, out int w, out int h)
        {
            int border, x, y, depth;
            IntPtr root;
            XGetGeometry(Disp, hwnd, out root, out x, out y, out w, out h, out border, out depth);
        }

        public static void Draw(IntPtr hwnd, IntPtr data, int width, int height, int rowBytes, int bytesPerPixel)
        {
            XImage img = new XImage();
            ConvertImage(ref img, data, width, height, rowBytes, bytesPerPixel);
            IntPtr gc = XCreateGC(Disp, hwnd, 0, IntPtr.Zero);
            XPutImage(Disp, hwnd, gc, ref img, 0, 0, 0, 0, width, height);
            XFreeGC(Disp, gc);
        }
        
        
}
        
        
public partial class MainWindow: Gtk.Window
{
    public MainWindow()
        : base(Gtk.WindowType.Toplevel)
    {
        Build();
        DoubleBuffered = false;

    }

    [DllImport("libgtk-x11-2.0.so.0", CallingConvention = CallingConvention.Cdecl)]
    extern static IntPtr gdk_x11_drawable_get_xid(IntPtr gdkWindow);

    protected override bool OnExposeEvent(Gdk.EventExpose evnt)
    {
        int w, h;
        IntPtr hwnd = gdk_x11_drawable_get_xid(GdkWindow.Handle);
        HelloGtk.X11.GetPlatformWindowSize(hwnd, out w, out h);

        using(var bmp = new Bitmap(w, h))
        using(var g = Graphics.FromImage(bmp))
        using(var b = new LinearGradientBrush(new Point(0,0), new Point(w, h), Color.Aqua, Color.GreenYellow))
        {
            g.FillRectangle(b, new Rectangle(0, 0, w, h));

            var data = bmp.LockBits(new Rectangle(0, 0, w, h), System.Drawing.Imaging.ImageLockMode.ReadOnly, bmp.PixelFormat);
            HelloGtk.X11.Draw(hwnd, data.Scan0, data.Width, data.Height, data.Stride, 4);

            bmp.UnlockBits(data);
        }
        //X11.GetPlatformWindowSize()
        return true;


    }

    protected void OnDeleteEvent(object sender, DeleteEventArgs a)
    {
        Application.Quit();
        a.RetVal = true;
    }
}