wglCreateContext in C# failing but not in managed C++

Question

I'm trying to use opengl in C#. I have following code which fails with error 2000 ERROR_INVALID_PIXEL_FORMAT
First definitions:

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
public static extern IntPtr GetDC(IntPtr hWnd);

[StructLayout(LayoutKind.Sequential)]
    public struct PIXELFORMATDESCRIPTOR
    {
        public void Init()
        {
            nSize = (ushort) Marshal.SizeOf(typeof (PIXELFORMATDESCRIPTOR));
            nVersion = 1;
            dwFlags = PFD_FLAGS.PFD_DRAW_TO_WINDOW | PFD_FLAGS.PFD_SUPPORT_OPENGL | PFD_FLAGS.PFD_DOUBLEBUFFER | PFD_FLAGS.PFD_SUPPORT_COMPOSITION;
            iPixelType = PFD_PIXEL_TYPE.PFD_TYPE_RGBA;
            cColorBits = 24;
            cRedBits = cRedShift = cGreenBits = cGreenShift = cBlueBits = cBlueShift = 0;
            cAlphaBits = cAlphaShift = 0;
            cAccumBits = cAccumRedBits = cAccumGreenBits = cAccumBlueBits = cAccumAlphaBits = 0;
            cDepthBits = 32;
            cStencilBits = cAuxBuffers = 0;
            iLayerType = PFD_LAYER_TYPES.PFD_MAIN_PLANE;
            bReserved = 0;
            dwLayerMask = dwVisibleMask = dwDamageMask = 0;
        }
        ushort nSize;
        ushort nVersion;
        PFD_FLAGS dwFlags;
        PFD_PIXEL_TYPE iPixelType;
        byte cColorBits;
        byte cRedBits;
        byte cRedShift;
        byte cGreenBits;
        byte cGreenShift;
        byte cBlueBits;
        byte cBlueShift;
        byte cAlphaBits;
        byte cAlphaShift;
        byte cAccumBits;
        byte cAccumRedBits;
        byte cAccumGreenBits;
        byte cAccumBlueBits;
        byte cAccumAlphaBits;
        byte cDepthBits;
        byte cStencilBits;
        byte cAuxBuffers;
        PFD_LAYER_TYPES iLayerType;
        byte bReserved;
        uint dwLayerMask;
        uint dwVisibleMask;
        uint dwDamageMask;
    }

    [Flags]
    public enum PFD_FLAGS : uint 
    {
        PFD_DOUBLEBUFFER = 0x00000001,
        PFD_STEREO = 0x00000002,
        PFD_DRAW_TO_WINDOW = 0x00000004,
        PFD_DRAW_TO_BITMAP = 0x00000008,
        PFD_SUPPORT_GDI = 0x00000010,
        PFD_SUPPORT_OPENGL = 0x00000020,
        PFD_GENERIC_FORMAT = 0x00000040,
        PFD_NEED_PALETTE = 0x00000080,
        PFD_NEED_SYSTEM_PALETTE = 0x00000100,
        PFD_SWAP_EXCHANGE = 0x00000200,
        PFD_SWAP_COPY = 0x00000400,
        PFD_SWAP_LAYER_BUFFERS = 0x00000800,
        PFD_GENERIC_ACCELERATED = 0x00001000,
        PFD_SUPPORT_DIRECTDRAW = 0x00002000,
        PFD_DIRECT3D_ACCELERATED = 0x00004000,
        PFD_SUPPORT_COMPOSITION = 0x00008000,
        PFD_DEPTH_DONTCARE = 0x20000000,
        PFD_DOUBLEBUFFER_DONTCARE = 0x40000000,
        PFD_STEREO_DONTCARE = 0x80000000
    }

    public enum PFD_LAYER_TYPES : byte
    {
        PFD_MAIN_PLANE = 0,
        PFD_OVERLAY_PLANE = 1,
        PFD_UNDERLAY_PLANE = 255
    }

    public enum PFD_PIXEL_TYPE : byte
    {
        PFD_TYPE_RGBA = 0,
        PFD_TYPE_COLORINDEX = 1
    }

    [DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
    public static extern int ChoosePixelFormat(IntPtr hdc, [In] ref PIXELFORMATDESCRIPTOR ppfd);

    [DllImport("gdi32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
    public static extern bool SetPixelFormat(IntPtr hdc, int iPixelFormat, ref PIXELFORMATDESCRIPTOR ppfd);
[DllImport("opengl32.dll", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
    public static extern IntPtr wglCreateContext(IntPtr hDC);

And now the code that fails:

IntPtr dc = Win.GetDC(hwnd);

var pixelformatdescriptor = new GL.PIXELFORMATDESCRIPTOR();
pixelformatdescriptor.Init();

var pixelFormat = GL.ChoosePixelFormat(dc, ref pixelformatdescriptor);
if(!GL.SetPixelFormat(dc, pixelFormat, ref pixelformatdescriptor))
    throw new Win32Exception(Marshal.GetLastWin32Error());
IntPtr hglrc;
if((hglrc = GL.wglCreateContext(dc)) == IntPtr.Zero)
    throw new Win32Exception(Marshal.GetLastWin32Error()); //<----- here I have exception

the same code in managed C++ is working

HDC dc = GetDC(hWnd);

PIXELFORMATDESCRIPTOR pf;
pf.nSize = sizeof(PIXELFORMATDESCRIPTOR);
pf.nVersion = 1;
pf.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER | PFD_SUPPORT_COMPOSITION;
pf.cColorBits = 24;
pf.cRedBits = pf.cRedShift = pf.cGreenBits = pf.cGreenShift = pf.cBlueBits = pf.cBlueShift = 0;
pf.cAlphaBits = pf.cAlphaShift = 0;
pf.cAccumBits = pf.cAccumRedBits = pf.cAccumGreenBits = pf.cAccumBlueBits = pf.cAccumAlphaBits = 0;
pf.cDepthBits = 32;
pf.cStencilBits = pf.cAuxBuffers = 0;
pf.iLayerType = PFD_MAIN_PLANE;
pf.bReserved = 0;
pf.dwLayerMask = pf.dwVisibleMask = pf.dwDamageMask = 0;

int ipf = ChoosePixelFormat(dc, &pf);
SetPixelFormat(dc, ipf, &pf);

HGLRC hglrc = wglCreateContext(dc);

I've tried it on VIsta 64-bit with ATI graphic card and on Windows XP 32-bit with Nvidia with the same result in both cases.
Also I want to mention that I don't want to use any already written framework for it.

Can anyone show me where is the bug in C# code that is causing the exception?

Answer 1

Hi SeeR,

I cannot test this right now, but my first suspicion would be the structure packing. Have you tried setting the packing to 1 in the StructLayout attribute? For example:

[StructLayout(LayoutKind.Sequential, Pack=1)]

Cheers, Brian

Answer 2

Found solution.
Problem is very strange ugly and really hard to find. Somwhere on the internet I found that when you are linking opengl32.lib while compiling c++ application it must be placed before gdi32.lib. The reason for this is that (supposedly) opengl32.dll is overwriting ChoosePixelFormat and SetPixelFormat functions (and probably more :-). As I found in my c++ version, accidentally it was the case.
Heh, but how to do it in C#
After few days of searching I found that in tao framework they solved it using kernel32.dll LoadLibrary() function and loading opengl32.dll before calling SetPixelFormat

public static bool SetPixelFormat(IntPtr deviceContext, int pixelFormat, ref PIXELFORMATDESCRIPTOR pixelFormatDescriptor) {
        Kernel.LoadLibrary("opengl32.dll");
        return _SetPixelFormat(deviceContext, pixelFormat, ref pixelFormatDescriptor);
    }

So we know that opengl32.dll must be loaded before gdi32.dll, is there any other way of doing this. After while I thought that we can call some NOP function from opengl32.dll to load it. For example:

[DllImport("opengl32.dll", EntryPoint = "glGetString", CharSet = CharSet.Auto, SetLastError = true, ExactSpelling = true)]
static extern IntPtr _glGetString(StringName name);
public static string glGetString(StringName name)
{
    return Marshal.PtrToStringAnsi(_glGetString(name));
}
public enum StringName : uint
{
    GL_VENDOR = 0x1F00,
    GL_RENDERER = 0x1F01,
    GL_VERSION = 0x1F02,
    GL_EXTENSIONS = 0x1F03
}

and on the start of application, before any call to gdi32.dll I use this:

GL.glGetString(0);

Both ways solves the problem.

Answer 3

I ran into this same problem. SeeR's workaround by calling glGetString first seems to do the trick.

Answer 4

Just want to confirm that this solves it for me as well.