GLArea for GtkSharp 2

GLArea.cs

using System;
using System.Runtime.InteropServices;

namespace Gtk
{
    public unsafe class GLArea : DrawingArea, IDisposable
    {
        private IntPtr display, window, visualinfo, glx_context;
        private int screen_number;
        private bool initialized = true;

        private const string libgdkx112 = "libgdk-x11-2.0.so.0";
        private const string libx11 = "libX11.so.6";
        private const string libGLX = "libGLX.so.0";

        // Gdk-X11 2
        [DllImport(libgdkx112)]
        private extern static IntPtr gdk_x11_display_get_xdisplay(IntPtr gdk_display);

        [DllImport(libgdkx112)]
        private extern static IntPtr gdk_x11_drawable_get_xid(IntPtr gdk_window);

        [DllImport(libgdkx112)]
        private extern static IntPtr gdk_x11_visual_get_xvisual(IntPtr gdk_visual);


        // GLX
        [DllImport(libGLX)]
        private extern static IntPtr glXGetProcAddress(IntPtr* func_name);

        [DllImport(libGLX)]
        private extern static bool glXIsDirect(IntPtr display, IntPtr glx_context);

        [DllImport(libGLX)]
        private extern static IntPtr glXChooseVisual(IntPtr display, int screen_numberm, ref int[] attrilists);

        [DllImport(libGLX)]
        private extern static IntPtr glXCreateContext(IntPtr x_display, IntPtr x_visualinfo, IntPtr share, bool direct);

        [DllImport(libGLX)]
        private extern static bool glXMakeCurrent(IntPtr x_display, IntPtr x_window, IntPtr glx_context);

        [DllImport(libGLX)]
        private extern static void glXSwapBuffers(IntPtr display, IntPtr drawable);

        [DllImport(libGLX)]
        private extern static void glXDestroyContext(IntPtr display, IntPtr glx_context);

        [Flags]
        internal enum GLXAttribute
        {
            TRANSPARENT_BLUE_VALUE_EXT = 0x27,
            GRAY_SCALE = 0x8006,
            RGBA_TYPE = 0x8014,
            TRANSPARENT_RGB_EXT = 0x8008,
            ACCUM_BLUE_SIZE = 16,
            SHARE_CONTEXT_EXT = 0x800A,
            STEREO = 6,
            ALPHA_SIZE = 11,
            FLOAT_COMPONENTS_NV = 0x20B0,
            NONE = 0x8000,
            DEPTH_SIZE = 12,
            TRANSPARENT_INDEX_VALUE_EXT = 0x24,
            MAX_PBUFFER_WIDTH_SGIX = 0x8016,
            GREEN_SIZE = 9,
            X_RENDERABLE_SGIX = 0x8012,
            LARGEST_PBUFFER = 0x801C,
            DONT_CARE = unchecked((int)0xFFFFFFFF),
            TRANSPARENT_ALPHA_VALUE_EXT = 0x28,
            PSEUDO_COLOR_EXT = 0x8004,
            USE_GL = 1,
            SAMPLE_BUFFERS_SGIS = 100000,
            TRANSPARENT_GREEN_VALUE_EXT = 0x26,
            HYPERPIPE_ID_SGIX = 0x8030,
            COLOR_INDEX_TYPE_SGIX = 0x8015,
            SLOW_CONFIG = 0x8001,
            PRESERVED_CONTENTS = 0x801B,
            ACCUM_RED_SIZE = 14,
            EVENT_MASK = 0x801F,
            VISUAL_ID_EXT = 0x800B,
            EVENT_MASK_SGIX = 0x801F,
            SLOW_VISUAL_EXT = 0x8001,
            TRANSPARENT_GREEN_VALUE = 0x26,
            MAX_PBUFFER_WIDTH = 0x8016,
            DIRECT_COLOR_EXT = 0x8003,
            VISUAL_ID = 0x800B,
            ACCUM_GREEN_SIZE = 15,
            DRAWABLE_TYPE_SGIX = 0x8010,
            SCREEN_EXT = 0x800C,
            SAMPLES = 100001,
            HEIGHT = 0x801E,
            TRANSPARENT_INDEX_VALUE = 0x24,
            SAMPLE_BUFFERS_ARB = 100000,
            PBUFFER = 0x8023,
            RGBA_TYPE_SGIX = 0x8014,
            MAX_PBUFFER_HEIGHT = 0x8017,
            FBCONFIG_ID_SGIX = 0x8013,
            DRAWABLE_TYPE = 0x8010,
            SCREEN = 0x800C,
            RED_SIZE = 8,
            VISUAL_SELECT_GROUP_SGIX = 0x8028,
            VISUAL_CAVEAT_EXT = 0x20,
            PSEUDO_COLOR = 0x8004,
            PBUFFER_HEIGHT = 0x8040,
            STATIC_GRAY = 0x8007,
            PRESERVED_CONTENTS_SGIX = 0x801B,
            RGBA_FLOAT_TYPE_ARB = 0x20B9,
            TRANSPARENT_RED_VALUE = 0x25,
            TRANSPARENT_ALPHA_VALUE = 0x28,
            WINDOW = 0x8022,
            X_RENDERABLE = 0x8012,
            STENCIL_SIZE = 13,
            TRANSPARENT_RGB = 0x8008,
            LARGEST_PBUFFER_SGIX = 0x801C,
            STATIC_GRAY_EXT = 0x8007,
            TRANSPARENT_BLUE_VALUE = 0x27,
            DIGITAL_MEDIA_PBUFFER_SGIX = 0x8024,
            BLENDED_RGBA_SGIS = 0x8025,
            NON_CONFORMANT_VISUAL_EXT = 0x800D,
            COLOR_INDEX_TYPE = 0x8015,
            TRANSPARENT_RED_VALUE_EXT = 0x25,
            GRAY_SCALE_EXT = 0x8006,
            WINDOW_SGIX = 0x8022,
            X_VISUAL_TYPE = 0x22,
            MAX_PBUFFER_HEIGHT_SGIX = 0x8017,
            DOUBLEBUFFER = 5,
            OPTIMAL_PBUFFER_WIDTH_SGIX = 0x8019,
            X_VISUAL_TYPE_EXT = 0x22,
            WIDTH_SGIX = 0x801D,
            STATIC_COLOR_EXT = 0x8005,
            BUFFER_SIZE = 2,
            DIRECT_COLOR = 0x8003,
            MAX_PBUFFER_PIXELS = 0x8018,
            NONE_EXT = 0x8000,
            HEIGHT_SGIX = 0x801E,
            RENDER_TYPE = 0x8011,
            FBCONFIG_ID = 0x8013,
            TRANSPARENT_INDEX_EXT = 0x8009,
            TRANSPARENT_INDEX = 0x8009,
            TRANSPARENT_TYPE_EXT = 0x23,
            ACCUM_ALPHA_SIZE = 17,
            PBUFFER_SGIX = 0x8023,
            MAX_PBUFFER_PIXELS_SGIX = 0x8018,
            OPTIMAL_PBUFFER_HEIGHT_SGIX = 0x801A,
            DAMAGED = 0x8020,
            SAVED_SGIX = 0x8021,
            TRANSPARENT_TYPE = 0x23,
            MULTISAMPLE_SUB_RECT_WIDTH_SGIS = 0x8026,
            NON_CONFORMANT_CONFIG = 0x800D,
            BLUE_SIZE = 10,
            TRUE_COLOR_EXT = 0x8002,
            SAMPLES_SGIS = 100001,
            SAMPLES_ARB = 100001,
            TRUE_COLOR = 0x8002,
            RGBA = 4,
            AUX_BUFFERS = 7,
            SAMPLE_BUFFERS = 100000,
            SAVED = 0x8021,
            MULTISAMPLE_SUB_RECT_HEIGHT_SGIS = 0x8027,
            DAMAGED_SGIX = 0x8020,
            STATIC_COLOR = 0x8005,
            PBUFFER_WIDTH = 0x8041,
            WIDTH = 0x801D,
            LEVEL = 3,
            CONFIG_CAVEAT = 0x20,
            RENDER_TYPE_SGIX = 0x8011,
            SWAP_INTERVAL_EXT = 0x20F1,
            MAX_SWAP_INTERVAL_EXT = 0x20F2,
        }


        // X11
        [DllImport(libx11)]
        private extern static void XFree(IntPtr handle);

        [DllImport(libx11)]
        private extern static IntPtr XCreateColormap(IntPtr display, IntPtr window, IntPtr visual, int alloc);

        [DllImport(libx11)]
        private extern static int XMapWindow(IntPtr display, IntPtr window);

        [DllImport(libx11)]
        private extern static void XDestroyWindow(IntPtr display, IntPtr window);

        [DllImport(libx11)]
        private extern static void XFlush(IntPtr display);


        public GLArea()
        {
            AppPaintable = true;
        }

        ~GLArea()
        {
            Dispose(false);
        }

        public override void Dispose()
        {
            GC.SuppressFinalize(this);
            Dispose(true);
            base.Dispose();
        }

        public virtual void Dispose(bool disposing)
        {
            if (disposing)
            {
                glXMakeCurrent(display, window, glx_context);
                if (display != IntPtr.Zero && window != IntPtr.Zero || glx_context != IntPtr.Zero)
                {
                    display = window = glx_context = IntPtr.Zero;
                }
                glXDestroyContext(display, glx_context);
                XDestroyWindow(display, window);
            }
        }


        public event EventHandler Initialized;
        protected virtual void OnInitialized()
        {
            if (Initialized != null)
                Initialized(this, EventArgs.Empty);
        }

        public event EventHandler RenderFrame;
        protected virtual void OnRenderFrame()
        {
            if (RenderFrame != null)
                RenderFrame(this, EventArgs.Empty);
        }

        protected override bool OnExposeEvent(Gdk.EventExpose evnt)
        {
            if (!initialized)
            {
                display = gdk_x11_display_get_xdisplay(Display.Handle);
                window = gdk_x11_drawable_get_xid(GdkWindow.Handle);

                screen_number = Screen.Number;

                int[] attributes =
                {
                    (int)GLXAttribute.RGBA,
                    (int)GLXAttribute.RED_SIZE, 8,
                    (int)GLXAttribute.GREEN_SIZE, 8,
                    (int)GLXAttribute.BLUE_SIZE, 8,
                    (int)GLXAttribute.DOUBLEBUFFER,
                    (int)GLXAttribute.USE_GL
                };

                visualinfo = glXChooseVisual(display, screen_number, ref attributes);
                glx_context = glXCreateContext(display, visualinfo, IntPtr.Zero, true);

                if (visualinfo == IntPtr.Zero)
                    XFree(visualinfo);

                XMapWindow(display, window);
                XFlush(display);

                OnInitialized();
            }
            /*else
            {
                glXMakeCurrent(display, window, glx_context);
            }*/

            glXMakeCurrent(display, window, glx_context);
            bool result = base.OnExposeEvent(evnt);
            OnRenderFrame();
            evnt.Window.Display.Sync();
            glXSwapBuffers(display, window);
            return result;
        }

        public IntPtr GetProcAddress(string func_name)
        {
            IntPtr* proc_name_ptr = stackalloc IntPtr[1];
            proc_name_ptr[1] = Marshal.StringToHGlobalAnsi(func_name);
            return glXGetProcAddress(proc_name_ptr);
        }

        public bool IsDirect
        {
            get
            {
                return glXIsDirect(display, glx_context);
            }
        }
    }
}