Taking Screeshot of extern Window which have an OpenGL ES Window inside

Question

Im trying to capture a screenshot of a Genymotion instance which has an opengl es window inside.

The problem is that injecting a dll (hooking) to capture the framebuffer didnt work as excepted (genymotion crash, cant hook the framebuffer because i have no idea how to really hook a dll which proxy swapbuffer) and public solutions like glintercept or glproxy didnt work either (no idea how to use them). Using easyhook to inject a dll like http://spazzarama.com/2011/03/14/c-screen-capture-and-overlays-for-direct3d-9-10-and-11-using-api-hooks/ didnt work either since its opengl and not directx.

Now my goal is taking a screenshot while the screen is in background. this works well on all windows containing no opengl/directx inside.

Usually the screen keeps being black. i have found several solutions using SRCCOPY | CAPTUREBLT but this leads in a white screenshot.

Now ive tried different screenshot mechanism but all are black or white (tested on genymotion x86 with dual monitor.

I have also tried capturing the parent window of the genymotion contentwindow which means that instead of the opengl hwnd, the main window of genymotion is captured. same result. everything looks great but the opengl window keeps being black. Could anyone tell me how to hook a dll which capture the framebuffer (gDebugger could display the graphics very well) or why the screenshots are black or white?

Here are my screenshot codes.

   public Image TakeScreenshotFromHandle(IntPtr handle)
        {
            IntPtr hdcSrc = User32.GetWindowDC(handle);
            User32.RECT windowRect = new User32.RECT();
            User32.GetWindowRect(handle, out windowRect);
            int width = windowRect.Right - windowRect.Left;
            int height = windowRect.Bottom - windowRect.Top;
            IntPtr hdcDest = GDI32.CreateCompatibleDC(hdcSrc);
            IntPtr hBitmap = GDI32.CreateCompatibleBitmap(hdcSrc, width, height);
            IntPtr hOld = GDI32.SelectObject(hdcDest, hBitmap);
            GDI32.BitBlt(hdcDest, 0, 0, width, height, hdcSrc, 0, 0, GDI32.TernaryRasterOperations.SRCCOPY | GDI32.TernaryRasterOperations.CAPTUREBLT);
            GDI32.SelectObject(hdcDest, hOld);
            GDI32.DeleteDC(hdcDest);
            User32.ReleaseDC(handle, hdcSrc);
            Image img = Image.FromHbitmap(hBitmap);
            GDI32.DeleteObject(hBitmap);

            return img;

        }

   public Image TakeScreenshotFromHandle_2(IntPtr hwnd)
        {
            Clash_of_Clans_Genymotion_Bot.User32.RECT rc;
            User32.GetWindowRect(hwnd, out rc);
            Bitmap bmp = new Bitmap(rc.Right - rc.Left, rc.Bottom - rc.Top, System.Drawing.Imaging.PixelFormat.Format32bppPArgb);
            Graphics gfxBmp = Graphics.FromImage(bmp);
            IntPtr hdcBitmap = gfxBmp.GetHdc();
            User32.PrintWindow(hwnd, hdcBitmap, 0);
            gfxBmp.ReleaseHdc(hdcBitmap);
            gfxBmp.Dispose();
            bmp.Save("screenshothandle2.png");

            return bmp;
        }

Now my idea was sending alt+print button to the window and grab the clipboarded stuff, since the graphics in the clipboard shows the screenshot, but this is a horrible solution. best would be capturing the framebuffer. Does anyone have a simple example how to proxy the buffer (with injecting/hooking)?