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POSDL2 OpenGL3 How to initialize SDL inside a function
 

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  1. POSDL2 OpenGL3 How to initialize SDL inside a function
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    <p>I'm experimenting with the new SDL2 beta and an OpenGL3 context, and I'm having a weird problem:</p> <p>If I run the SDL initialization code in my main() function, it works fine, but I want to have this code in a separete init_sdl() function.</p> <p>If I put the initialization code in a separate init_sdl() function, and call this function from main(), the background color is never drawn, and the program starts to madly consume all my system's resources.</p> <p>Could someone point me to a working example where SDL is initialized in a separate function? I can't seem to find one... Maybe this is not possible? I think I vaguely remember having a similar problem with SDL 1.2, but it's been a few years since I've used that, and I don't think I ever found a solution. In fact, this may be the reason I chose to switch to using SFML instead.</p> <p>I really want to use SDL2 instead of SFML because it runs on more platforms, but not being able to separate things out into small functions is a deal breaker for me. This should be easy, am I missing something obvious?</p> <p><strong>Edit:</strong></p> <p>This works:</p> <pre><code>#include &lt;iostream&gt; #include &lt;GL/glew.h&gt; #include &lt;SDL.h&gt; #define PROGRAM_NAME "SDL2 OpenGL3 Example" int main(int argc, char** argv) { SDL_Window* sdl2_window = 0; SDL_GLContext opengl3_context; SDL_Init(SDL_INIT_VIDEO); // set the opengl context version SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2); // turn on double buffering set the depth buffer to 24 bits // you may need to change this to 16 or 32 for your system SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1); SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24); // create the sdl2 window sdl2_window = SDL_CreateWindow(PROGRAM_NAME, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 512, 512, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN); // create the opengl3 context opengl3_context = SDL_GL_CreateContext(sdl2_window); GLenum status = glewInit(); if (status != GLEW_OK) { std::cerr &lt;&lt; "GLEW Error: " &lt;&lt; glewGetErrorString(status) &lt;&lt; "\n"; exit(1); } // sync buffer swap with monitor's vertical refresh rate SDL_GL_SetSwapInterval(1); // set background color glClearColor( 1.0, 0.0, 0.0, 1.0 ); while (true) { int status = 0; glClear( GL_COLOR_BUFFER_BIT ); SDL_GL_SwapWindow(sdl2_window); SDL_Event event; while (SDL_PollEvent(&amp;event)) { switch (event.type) { case SDL_KEYDOWN: break; case SDL_KEYUP: // if escape is pressed, quit if (event.key.keysym.sym == SDLK_ESCAPE) status = 1; // set status to 1 to exit main loop break; case SDL_QUIT: status = 1; break; } } if (status == 1) // if received instruction to quit break; } // delete opengl3 context, destroy sdl2 window, and shut down sdl subsystems SDL_GL_DeleteContext(opengl3_context); SDL_DestroyWindow(sdl2_window); SDL_Quit(); return 0; } </code></pre> <p>This doesn't work:</p> <pre><code>#include &lt;iostream&gt; #include &lt;GL/glew.h&gt; #include &lt;SDL.h&gt; #define PROGRAM_NAME "SDL2 OpenGL3 Example" void init_sdl(SDL_Window* sdl2_window, SDL_GLContext&amp; opengl3_context) { SDL_Init(SDL_INIT_VIDEO); // set the opengl context version SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3); SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2); // turn on double buffering set the depth buffer to 24 bits // you may need to change this to 16 or 32 for your system SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1); SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24); // create the sdl2 window sdl2_window = SDL_CreateWindow(PROGRAM_NAME, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 512, 512, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN); // create the opengl3 context opengl3_context = SDL_GL_CreateContext(sdl2_window); } int main(int argc, char** argv) { SDL_Window* sdl2_window = 0; SDL_GLContext opengl3_context; init_sdl(sdl2_window, opengl3_context); GLenum status = glewInit(); if (status != GLEW_OK) { std::cerr &lt;&lt; "GLEW Error: " &lt;&lt; glewGetErrorString(status) &lt;&lt; "\n"; exit(1); } // sync buffer swap with monitor's vertical refresh rate SDL_GL_SetSwapInterval(1); // set background color glClearColor( 1.0, 0.0, 0.0, 1.0 ); while (true) { int status = 0; glClear( GL_COLOR_BUFFER_BIT ); SDL_GL_SwapWindow(sdl2_window); SDL_Event event; while (SDL_PollEvent(&amp;event)) { switch (event.type) { case SDL_KEYDOWN: break; case SDL_KEYUP: // if escape is pressed, quit if (event.key.keysym.sym == SDLK_ESCAPE) status = 1; // set status to 1 to exit main loop break; case SDL_QUIT: status = 1; break; } } if (status == 1) // if received instruction to quit break; } // delete opengl3 context, destroy sdl2 window, and shut down sdl subsystems SDL_GL_DeleteContext(opengl3_context); SDL_DestroyWindow(sdl2_window); SDL_Quit(); return 0; } </code></pre>
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