Creating an OpenGL context on Windows with Glew.

Tocs1001 · 2014-06-27T23:54:29

Something weird has happened. I had context creation working just fine. It worked on my desktop and my laptop and I was happily plugging along doing graphics programming. One day I attempt to build my code on my laptop again, suddenly context creation starts to fail. I don't know what has changed. My original context creation code looks like this https://gist.github.com/LordTocs/f227528a729986df9643 It's sloppy and has next to no error handling but it at least worked. It still works on my desktop and fails on my laptop. Specifically wglCreateContextAttribsARB fails. I started to modify the code in an attempt to figure out what was wrong. I added some "GetLastError()" print outs in hopes I was doing something silly and it would tell me what was wrong. Using "FormatMessage()" to change error code into readable stings. Instead of a usable error I was greeted with GetLastError() returning 3221692565. Which FormatMessage() had no idea what to do with. A quick cursory internet search lead me to a single result on the opengl forums. Which didn't yield any results. After some reading I was told not to create a forward compatible context. And that I should use wglChoosePixelFormatARB to get the appropriate pixel format. Thinking this was the issue, I tried to use this function, it didn't help. So now I'm left with this code that doesn't work and I'm very confused. void DisplayWindowsError() { LPVOID lpMsgBuf; DWORD dw = GetLastError(); FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, dw, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPTSTR)&lpMsgBuf, 0, NULL); if (lpMsgBuf) { std::cout << "Windows Error:" << dw << ": " << (char *)lpMsgBuf << std::endl; LocalFree(lpMsgBuf); } else { std::cout << "Windows Error:" << dw << ": unknown" << std::endl; } } GraphicsContext::GraphicsContext(ContextTarget &target) : Target (target) { PIXELFORMATDESCRIPTOR pfd = // pfd Tells Windows How We Want Things To Be { sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor 1, // Version Number PFD_DRAW_TO_WINDOW | // Format Must Support Window PFD_SUPPORT_OPENGL | // Format Must Support OpenGL PFD_DOUBLEBUFFER, // Must Support Double Buffering PFD_TYPE_RGBA, // Request An RGBA Format 32, // Select Our Color Depth 0, 0, 0, 0, 0, 0, // Color Bits Ignored 0, // No Alpha Buffer 0, // Shift Bit Ignored 0, // No Accumulation Buffer 0, 0, 0, 0, // Accumulation Bits Ignored 24, // 32Bit Z-Buffer (Depth Buffer) 8, // No Stencil Buffer 0, // No Auxiliary Buffer PFD_MAIN_PLANE, // Main Drawing Layer 0, // Reserved 0, 0, 0 // Layer Masks Ignored }; PixelFormat = 1; if (!(PixelFormat = ChoosePixelFormat (target.GetHDC (), &pfd))) { DisplayWindowsError(); cout << "Failed to choose pixel format." << endl; } if (!SetPixelFormat(target.GetHDC(),PixelFormat, &pfd)) { //DestroyGameWindow (); //Insert Error DisplayWindowsError(); cout << "Failed to set pixel format." << endl; } HGLRC temp; temp = wglCreateContext(target.GetHDC()); if (!temp) { //DestroyGameWindow (); //Insert Error cout << "Failed to create context" << endl; } DisplayWindowsError(); if (!wglMakeCurrent(target.GetHDC (), temp)) { //DestroyGameWindow (); cout << "Failed to make current." << endl; GLErrorCheck(); } DisplayWindowsError(); GLenum err = glewInit(); if (err != GLEW_OK) { char *error = (char *)glewGetErrorString(err); cout << "GLEW INIT FAIL: " << error << endl; } int contextattribs [] = { WGL_CONTEXT_MAJOR_VERSION_ARB, 4, WGL_CONTEXT_MINOR_VERSION_ARB, 2, #ifdef _DEBUG WGL_CONTEXT_FLAGS_ARB, WGL_CONTEXT_DEBUG_BIT_ARB, #endif 0 }; int pfattribs[] = { WGL_DRAW_TO_WINDOW_ARB, GL_TRUE, WGL_SUPPORT_OPENGL_ARB, GL_TRUE, WGL_DOUBLE_BUFFER_ARB, GL_TRUE, WGL_PIXEL_TYPE_ARB, WGL_TYPE_RGBA_ARB, WGL_COLOR_BITS_ARB, 32, WGL_DEPTH_BITS_ARB, 24, WGL_STENCIL_BITS_ARB, 8, 0 }; if (wglewIsSupported ("WGL_ARB_create_context") == 1) { unsigned int formatcount; if (!wglChoosePixelFormatARB(target.GetHDC(), pfattribs, nullptr, 1, (int *)&PixelFormat, &formatcount)) { std::cout << "Failed to find a matching pixel format" << std::endl; DisplayWindowsError(); } if (!SetPixelFormat(target.GetHDC(), PixelFormat, &pfd)) { DisplayWindowsError(); std::cout << "Failed to set pixelformat" << std::endl; } hRC = wglCreateContextAttribsARB(Target.GetHDC(), nullptr, contextattribs); if (!hRC) { DisplayWindowsError(); std::cout << "Failed to create context." << std::endl; } wglMakeCurrent(nullptr, nullptr); DisplayWindowsError(); wglDeleteContext(temp); DisplayWindowsError(); GLErrorCheck(); MakeCurrent (); } else { cout << "Failed to create context again..." << endl; } #ifdef _DEBUG glEnable(GL_DEBUG_OUTPUT); glDebugMessageCallback(dbgcallback, nullptr); #endif char *shadeversion = (char *)glGetString (GL_SHADING_LANGUAGE_VERSION); //GLErrorCheck; char *version = (char *)glGetString(GL_VERSION); //GLErrorCheck; std::cout << "Version: " << version << std::endl << "Shading Version: " << shadeversion << std::endl; glViewport (0,0,Target.GetWidth (), Target.GetHeight ()); GLErrorCheck (); SetClearColor (Color(0,0,0,0)); SetClearDepth(1000.0f); //EnableDepthBuffering (); //DisableDepthTest (); NormalBlending (); glHint(GL_POLYGON_SMOOTH_HINT, GL_NICEST); //Doesn't get Abstracted GLErrorCheck(); //glLoadIdentity (); } Gist mirror https://gist.github.com/LordTocs/9266d8c8f7e3eb9a498e If anyone knows what I'm doing wrong I'd love to know. Thanks.

Graphics and GPU Programming Programming OpenGL

Started by Tocs1001 June 26, 2014 05:57 PM

10 comments, last by swiftcoder 9 years, 10 months ago

Tocs1001

695

Author

June 27, 2014 11:46 PM

The wiki says "A forward compatible context must fully remove deprecated features in the version that it returns; you should never actually use this." It's actually bolded on wiki so I took it at face value. Perhaps the wiki is overzealous. It seems like it would be a good idea to not include deprecated features, however I suppose if somewhere down the line features I'm using became deprecated and I asked for the latest context without deprecated features I would suddenly break my program. That seems like a far out case though.

Interestingly enough if I set major to 1 and minor to 0. I get a 3.3 context. I tried updating the drivers, same results.

swiftcoder

18,997

June 27, 2014 11:54 PM

The wiki says "A forward compatible context must fully remove deprecated features in the version that it returns;you should never actually use this." It's actually bolded on wiki so I took it at face value. Perhaps the wiki is overzealous. It seems like it would be a good idea to not include deprecated features, however I suppose if somewhere down the line features I'm using became deprecated and I asked for the latest context without deprecated features I would suddenly break my program. That seems like a far out case though.

They are just paraphrasing NVidia's guidelines there. You would expect a Core context to be more efficient, given that all deprecated functionality can be removed, but in some cases a single driver implements both Core and non-Core contexts, and in the Core case, it may have to add a bunch of extra error checking to make sure you don't call non-Core functionality.

I generally recommend that you use a Core context for development, and if you feel it necessary, switch to a non-Core context for release.

Tristam MacDonald. Ex-BigTech Software Engineer. Future farmer. [https://trist.am]

Creating an OpenGL context on Windows with Glew.

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Creating an OpenGL context on Windows with Glew.

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